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U-Pb ages of detrital zircons from Permian and Jurassic eolian sandstones of the Colorado Plateau, USA: Paleogeographic implications
Abstract
Detrital zircon grains (n=468) from eolian sandstones of Permian and Jurassic sand seas on the Colorado Plateau of southwest Laurentia fall into six separable age populations defined by discrete peaks on age–probability plots. The eolian sands include significant contributions from all Precambrian age belts of the Laurentian craton and all key plutonic assemblages of the Appalachian orogen marking the Laurentia–Gondwana suture within Pangaea. Nearly half the detrital zircon grains were derived ultimately from Grenvillian (1315–1000 Ma), Pan-African (750–500 Ma), and Paleozoic (500–310 Ma) bedrock sources lying within or along the flank of the Appalachian orogen. Recycled origins for Appalachian-derived grains, except for temporary residence of synorogenic detritus in the Appalachian foreland basin or in deformed Ouachita flysch and molasses along tectonic strike, are precluded by regional geology and known geochronology from other Laurentian sedimentary assemblages. We infer that transcontinental Permian and Jurassic river systems transported detritus of Appalachian provenance westward across the subdued surface of the Laurentian craton, for deposition as proximate sources for eolian systems feeding the ergs, on unconsolidated fluvial plains, deltas, and strandlines that lay up-paleowind along or near the Cordilleran paleoshoreline north and northeast of the Colorado Plateau. The postulated river systems headed in the remnant Appalachian orogen (Permian) or the incipient Atlantic rift belt (Jurassic), and additional transport of the Appalachian-derived detritus toward the Colorado Plateau was achieved by longshore drift of sediment southward along the Cordilleran paleoshoreline under the influence of prevailing trade winds in the Permian–Jurassic tropics. Only a quarter of the eolianite detrital zircons were derived or recycled from Mesoproterozoic (1470–1335 Ma) and younger Paleoproterozoic (1800–1615 Ma) basement of the Ancestral Rocky Mountains province adjacent to the Colorado Plateau. The final quarter of eolianite detrital zircons were derived from older Paleoproterozoic (2200–1800 Ma) and Archaean (3015–2580 Ma) basement of the Laurentian shield, or recycled from its sedimentary cover. Both Laurentian shield and Ancestral Rockies detritus may have entered the same transcontinental river systems (through tributary streams), or the same Cordilleran strandline system (by longshore drift), responsible for the delivery of Appalachian-derived sediment to positions near the Colorado Plateau ergs. As Colorado Plateau ergs received contributions from all the potential bedrock sources contiguous with Permian–Jurassic Laurentia and its orogenic–taphrogenic margins, detrital zircon studies of analogous ancient erg deposits elsewhere may help test reconstructions of Rodinia and other ancient paleocontinents by providing proxy records of the full age ranges of bedrock sources distributed across the surfaces of entire landmasses.
... By Early Jurassic time, fluvial Chinle-Dockum sedimentation was terminated by the drift of Laurentia northward into desert paleolatitudes where through-going fluvial drainages could no longer be sustained (Dickinson 2005;Dickinson and Gehrels, 2008a) (Figure 10). Despite this environmental adjustment to more arid conditions in the southwest, Dickinson and Gehrels (2003) hypothesize that farther north, transcontinental river systems were able to continue transporting sediment sourced from the Appalachian highlands up to 2,000 km westward across northern Laurentia. Ultimately, this material would redeposit as unconsolidated sediments along fluvial plans, deltas, and strandlines adjacent to a paleoshoreline just north and northeast of the Colorado Plateau region. ...
... This widespread eolianite deposition terminated only at the onset of the Late Jurassic . Remnants of these massive dune fields are preserved within formations such as the Glen Canyon and San Rafael of the Colorado Plateau, and the Aztec-Nugget sandstone of southern Nevada (Dubiel et al 1991;Rahl et al., 2003;Dickinson and Gehrels, 2003). Again, in the town of Currie, Nevada, remnant outcroppings of sand dunes show that these ergs likely stretched as far west as eastern Nevada (Stewart, 1980;Lucas and Orchard, 2007). ...
... Before Hinterland thrust highlands began to intervene, Jurassic Cordilleran arc activity contributed supplemental volcaniclastic material to the trough and parts of the Colorado Plateau region (ca. 165-145 Ma;Lawton, 1994;Dickinson and Gehrels, 2003). This incorporation of arc-derived material in units such as the Carmel Formation (ca. ...
Chapter 1: Mining Industry Challenges and the Opportunity for New Carlin Gold Discoveries
CHAPTER 2: Detrital Zircon Study of the Piñon Range, Nevada: Reassessing Eastern Nevada’s Paleozoic through Cenozoic Conglomerates Emphasizing Implications for the Elko Basin and Associated Natural Resources
CHAPTER 3: Mineralization in the Rain-Railroad District, Southern Carlin Trend, Nevada: Investigating Carlin and Intrusion-related Gold Deposit Relationships and the Influence of Paleogeography
CHAPTER 4: The Age and Petrogenesis of Igneous Rocks in the Piñon Range, Nevada: Evaluating Eocene Magmatism and the Effects on Associated High- and Low-Temperature Deposits
CHAPTER 5: New Insights into an Integrated Carlin gold Deposit Model and the Implications for Future Exploration
... The absence of these Laurentian sediments within the Stockton Formation argues for the presence of a drainage divide close to the ENAM border fault system due to paleotopography either inherited from the Appalachian orogeny and/or related to rift flank uplift. Major Appalachian topography, a regional drainage divide, and a west-flowing late Paleozoic and early Mesozoic transcontinental river system are supported by DZ U-Pb data from Triassic-Permian eolian sandstone on the Colorado Plateau (Dickinson and Gehrels, 2003). Dickinson and Gehrels (2003) argued for nearly half the eolian sand delivered to these early Mesozoic ergs originating from the Appalachian orogenic belt along the eastern Laurentia margin. ...
... Major Appalachian topography, a regional drainage divide, and a west-flowing late Paleozoic and early Mesozoic transcontinental river system are supported by DZ U-Pb data from Triassic-Permian eolian sandstone on the Colorado Plateau (Dickinson and Gehrels, 2003). Dickinson and Gehrels (2003) argued for nearly half the eolian sand delivered to these early Mesozoic ergs originating from the Appalachian orogenic belt along the eastern Laurentia margin. This Appalachian topography likely developed during the Alleghenian orogen before the onset of ENAM rifting but was accentuated by rift flank uplift in the Carnian. ...
Mesozoic rift basins of the Eastern North American Margin (ENAM) span from Florida in the United States to the Grand Banks of Canada and formed during progressive extension prior to continental breakup and the opening of the north-central Atlantic. The syn-rift strata from all the individual basins, lumped along the entire margin into the Newark Supergroup, are dominated by fluvial conglomerate and sandstone, lacustrine siltstone, mudstone, and abundant alluvial conglomerate and sandstone lithofacies. Deposition of these syn-rift sedimentary rocks was accommodated in a series of half grabens and subsidiary full grabens situated within the Permo-Carboniferous Appalachian orogen. The Mesozoic ENAM is commonly depicted as a magma-rich continental rift margin, with magmatism (Central Atlantic magmatic province [CAMP]) driving continental breakup. However, the southern portion of the ENAM shows evidence of magmatic breakup (e.g., seaward-dipping reflectors), and rifting and crustal thinning appeared to start ~30 m.y. prior to CAMP emplacement in the Jurassic. This study provides extensive new detrital zircon and apatite U-Pb provenance data to determine the provenance and reconstruct the paleodrainages of the Newark Basin during progressive rifting and magmatic breakup and the implications for the overall rift configuration and asymmetry during progressive rifting along the ENAM rift margin. Detailed new detrital zircon (N = 21; n = 3093) and apatite (N = 4; n = 559) U-Pb results from sandstone outcrop and core samples from the Newark Basin indicate a distinct provenance shift, with relatively older Carnian syn-rift strata predominately sourced from the hanging wall of the basin bounding fault in the east while relatively younger Norian strata were regionally sourced from both the hanging wall and footwall. The syn-rift strata at the Triassic-Jurassic boundary were sourced from the hanging wall before a transition to local footwall terranes. These results suggest two major provenance changes during progressive rifting—the first occurring during Carnian crustal necking and rift flank uplift as predicted by recent numerical models and the second occurring at the onset of the Jurassic due to regional and local thermal uplift during CAMP magmatism as seen along other magma-rich margins, such as the North Atlantic and the southern portion of the South Atlantic margin.
... Sedimentary provenance analysis, which integrates sedimentological and biostratigraphic data, sandstone petrography, and detrital zircon U-Pb geochronological and Hf isotopic data, has become the most effective strategy to reconstruct the original architecture and the depositional and paleogeographic framework of sedimentary basins (e.g., Dickinson and Suczek, 1979;Dickinson et al., 1983;Gehrels et al., 1995;Cawood et al., 2003;Dickinson and Gehrels, 2003). In recent decades, detrital zircon U-Pb geochronology has shown great advantages in constraining the maximum depositional timing and potential sources for sedimentary strata (Dickinson andGehrels, 2003, 2009;Sharman et al., 2018). ...
Sedimentological and geochronological data from late Paleozoic strata located between the East Junggar and Chinese Altai regions in NW China were examined, aiming to decipher the tectono-sedimentary evolution of this important tectonic boundary. Carboniferous sediments on the East Junggar side show arc-proximal depositional characteristics of the proximal Heishantou and Nanmingshui Formations and distal Beitashan and Yundukala Formations, while the Erqis complex on the Chinese Altai side is characterized by continental margin affinity. Lithological analysis revealed the dominant input of arc-related detritus for all these sequences and a uniform transition from volcaniclastic to siliciclastic components in their respective upper sections. The investigated East Junggar strata are dominated by Carboniferous zircons with positive εHf(t) values, sourced exclusively from the southerly Yemaquan-Jiangjunmiao arc domain, whereas the Erqis complex received detritus from the same arc domain but also evolved components from the northerly Chinese Altai. Combined with regional data, the examined strata are interpreted to have developed in a back-arc basin with regard to an arc that developed above the north-dipping Kalamaili subduction system. In contrast, the unmetamorphosed Lower Permian Tesibahan Formation, unconformably overlying the Erqis complex, received detritus mainly from the Chinese Altai. These sediments were deposited in an intracontinental piggyback or synformal basin following closure of the back-arc basin. The late Paleozoic sedimentation records support the interpretation that the Chinese Altai and East Junggar domains evolved from the same suprasubduction system prior to the Carboniferous rather than as independent terranes mutually juxtaposed during Permian lateral translation, as previously proposed.
... Four samples of the best-preserved felsic gneisses (charnockite, TTG, granitic gneiss, and monzogranite) of the Nyabessane granitegreenstone belt were selected for zircon U-Pb laser ablation inductively coupled plasma sector field mass spectrometry (LA-ICP-SF-MS) TTG Wiedenbeck et al., 1995) was used for correction of element fractionation as well as instrumental drift. The Peixe reference zircon (564 ± 4 Ma, Dickinson and Gehrels, 2003) was used to monitor the quality of the reduction procedures. During the analytical session, 14 analyses of Peixe zircon yielded 560.5 ± 3.4 Ma. ...
Archean granitoids played key roles in the generation and differentiation of the Archean continental crust and provide clues to understand crustal processes in the early Earth. Abundant Mesoarchean granitoids were emplaced in the Nyabessane granite-greenstone terrane (NGB), part of the Ntem Complex of the Northwest Congo Craton. They include charnockites, tonalite-trondhjemite-granodiorite (TTG), granitic and monzogranitic gneisses. Here, we present a geochemical and geochronological (zircon LA-ICP-SF-MS Usingle bondPb) study of these granitoids to determine their petrogenesis and to better constrain the crustal evolution of the Ntem Complex. Field and petrographic observations indicate that most of these granitoids underwent extensive metamorphism and deformations, associated with anatexis. Zircon Usingle bondPb dating results suggest that the charnockite, TTGs and granitic gneisses, and monzogranites have emplacement ages of 2910 ± 11 Ma, 2870–2865 Ma and 2852 ± 31 Ma, respectively. The charnockites have low SiO2 (55–58 wt%) and high Al2O3 (16–18 wt%), CaO (7–8 wt%) and MgO (~ 4.5 wt%) content with Mg# ~ 54, and exhibit magnesian, metaluminous characteristics of the Cordilleran granitoid-type formed in magmatic arc. The 2.87–2.86 Ga TTG gneisses are silica-rich (55–58 wt% SiO2), sodic (3–5 wt% Na2O, Na2O/K2O = 1–3), with HREE-depleted, and display the typical Archean medium- to low pressure TTG geochemical features groups. Their chemical compositions are characteristics of TTG-like melts derived from the partial melting of hydrated low- to high-K metabasic/thickened lower crust at various depths followed by magmatic differentiation during ascent. When compared to the TTG gneisses in the NGB, the ~2.87 Ga granitic gneisses are K-rich, and high Gd/Yb, Th/Yb, Th/Nb, Sr/Y and La/Yb ratios but lower MgO, Yb, V, Y, Cr, Ni and Sr contents, matching typical Archean hybrid and potassic granitic rocks. We propose that the granitic gneisses were derived from the intra-crustal melting of a pre-existing felsic crust. The granitic and the TTG gneisses were generated contemporaneously through the same magmatic event at ~2.87–2.86 Ga. The ~2852 Ma monzogranitic gneisses are ferroan and metaluminous rocks, and show LREE enrichment with strongly fractionated REE patterns and positive Eu anomalies. Geochemical features, together with the presence of ~2.9 Ga-old inherited zircon grains are consistent with the remelting of Mesoarchean granitoids. Considering the petrogenetic, regional geological and geochronological data, the Mesoarchean granitoid magmatism of the Ntem Complex was likely generated via complex transitional geodynamic regimes involving subduction and accretion processes.
... All uncertainties are reported as 2 standard errors. The Peixe zircon standard (ID-TIMS age 564 ± 4 Ma; Dickinson and Gehrels, 2003) was used for validation to ensure the quality of the reduction procedures. The 206 Pb/ 238 U and 207 Pb/ 235 U ages for the Peixe zircon standard across four analysis sessions were 566 ± 7 Ma and 566 ± 9 Ma, respectively. ...
The São José do Jacuípe Suite (SSJJ) comprises an association of mafic and ultramafic rocks that crops out in the northern portion of the Itabuna Salvador-Curaçá Orogen (ISCO), São Francisco Craton. They are represented by small NW-SE elongated bodies comprising metamorphosed anorthosites, leucogabbros, gabbronorites, gabbros, ferrogabbros, and subordinate pyroxenites and serpentinites. The rocks are part of an orogenic belt that comprises orthogranulites and orthogneisses of the Caraíba complex, and metasedimentary rocks of the Tanque Novo-Ipirá complex, which appear to be amalgamated into a folded mélange. Petrographical analysis of the SSJJ rocks revealed relict cumulus textures in the pyroxenites. Moreover, inclusion relationships allowed the identification of two metamorphic phases; the first phase likely occurred at amphibolite facies conditions and was overprinted by granulite facies metamorphism that represents the peak metamorphic conditions recorded by the SSJJ rocks. Analytical results for major and trace elements indicate cogeneticity between the mafic rocks, and arc-related mafic cumulate field compositions. In the geotectonic environment diagrams the rocks plot in the MORB and IAT fields, indicating an origin involving melting of different sources or magma mixing. The characteristic signature of the studied rocks is represented by negative HFSE anomalies (Nb, Ti, Zr and Hf), depletion in HREE and enrichment in LILE (Ba, Rb, and Cs), indicating their derivation from metasomatic mantle in a suprasubduction setting. These data corroborate previous isotope data that point to mildly enriched mantle sources. Incompatible trace elements signatures are similar to ophiolites generated in supra-subduction zone (SSZ) environments worldwide. New U/Pb LA-ICP-MS ages indicate igneous crystallization at 2549 ± 23 Ma and 2563 ± 13 Ma for SSJJ gabbronorites, thus indicating that they postdate the other members of the magmatic arc that formed the ISCO by 20 – 30 Ma.
... Vertebrate tracks and invertebrate traces can be locally abundant on and within these interdunal carbonates. Additionally, stromatolites and Miall, 2010, andothers, 2016;data after Blakey, 1994;Parrish and Peterson, 1988;Dickinson and Gehrels, 2003). microbial mat surface are quite common in some areas, including many localities within GLCA. ...
A large fallen block of Early Jurassic Navajo Sandstone located at Lake Powell, within Glen Canyon National Recreation Area, south-central Utah, displays natural casts of vertebrate tracks. The footprints occur on at least three track-bearing horizons preserved on and between stromatolitic sandstone beds. Two large, parallel trackways, plus a third, divergent trackway, on the main track layer (MTL) superficially resemble ornithopod footprints; however, they were produced by large-sized theropod dinosaurs, rather than ornithischians, and we identify these as Eubrontes.
Small coelophysoid theropod tracks (Grallator) are the most common vertebrate ichnofossils on all track-bearing horizons, with approximately 50 footprints preserved on the MTL, six on the highest surface, and three on thinner float slabs stratigraphically lower in section. An additional 12 tracks in three trackways of Anchisauripus size occur on the MTL, but they superficially resemble Kayentapus in having wider divarication angles than typical Anchisauripus. The MTL also preserves at least five closely associated tetradactyl footprints that we identify as cf. Brasilichnium. A nearby, smaller fallen block preserves distinct Batrachopus tracks, which are rare in eolian environments.
The microbial (possibly endoevaporitic) mats and stromatolitic horizons on which the animals had walked produced a distinct ichnomorphologic variation because of substrate consistency and the elastic properties of the mats, resulting in differential compaction of the bedding surfaces. Lithic compaction of the finer-grained sediments between denser, more resistant sandstone beds pre- and/or post-lithification resulted in additional deformation of the tracks, followed by natural erosion. We interpret these natural cast footprints on the MTL as possible transmitted tracks. The track-bearing, microbial-mat surfaces represent
interdunal pooling of water, probably during periods of increased precipitation and/or rising water tables during wet seasons.
... The zircon grains were identified and separated under the binocular microscope (Zeiss Stemi 2000-C) by the hand-picking method. Studies of the morphology and typology of the zircon crystals were carried out under the scanning electron microscope (JEOL JSM 6360 LV) at the Museo de La Plata according to the procedures applied by Gärtner et al. (2013) to determine the main morphological populations that are present and a preliminary provenance of the detrital sources (Dickinson and Gehrels 2003). For euhedral zircon grains, the Pupin (1980) classification was used to expand the interpretations. ...
This work focuses on the sedimentary provenance of the Villavicencio Formation of the Mendoza Precordillera and integrates the information obtained with previous work on other coeval units of the Precordillera Central of San Juan province (Gualilán Group: Talacasto and Punta Negra formations) in western Argentina. Multiproxy provenance analyses are carried out from different applied methodologies (petrography, geochemistry, morphological, and cathodoluminescence studies of detrital zircon grains, and analysis of U-Pb and Lu-Hf isotopes). The Villavicencio Formation is mostly composed of pelites and very fine-grained psammites. The major components are quartz, both monocrystalline and polycrystalline, and metamorphic lithics that associate this unit with a recycled orogen. Regarding geochemistry, the Chemical Index of Alteration (CIA) values are similar to the Post-Archean Australian Shales (PAAS), indicating a null to incipient degree of weathering. The ratios between different trace elements and rare earth elements (REEs) suggest the felsic composition of the source area. Th/U ratios differ, but a secondary uranium enrichment is inferred. The morphological analysis of the zircon grains reveals their mainly plutonic origin. The integration of U-Pb data with Lu-Hf data shows a juvenile-mantle origin in which the populations are dominantly Mesoproterozoic and ɛHf of positive values (up to 12), indicating poor differentiation. The Villavicencio Formation would be the product of deltaic deposits in which its components are dominantly from the Western Pampean Sierras associated with the Grenville orogen, assuming exhumation and erosion of the Mesoproterozoic basement. The data support the hypothesis of equivalence and correlation with the Punta Negra Formation in the Devonian depocenters of the south-central region of the San Juan Precordillera.
... The northern Rocky Mountain region contains unique outcrop belts of Neoproterozoic to Neogene magmatic rocks and the Snake River drainage includes local (first-order) to regional (third-order) drainage basins, a fundamental division proposed by Ingersoll et al. (1993). For thirty years now, DZ age distributions have produced surprisingly reproducible and useful results (e.g., Gehrels et al., 2000;Dickinson and Gehrels, 2003;Amidon et al., 2005;Perez and Horton, 2014;Thomas et al., 2017), with large scale global tectonic implications (Cawood et al., 2012;Gehrels, 2014). DZ geochronology has become standard in regional studies of sedimentary units, to the benefit of tectonic syntheses (Gehrels et al., 2011;Laskowski et al., 2013;Wissink and Hoke, 2016;Thomas et al., 2020;Mahoney et al., 2021). ...
... indicating magmatic origin [32,33]. In this study, 206 Pb/ 238 U ages are used for zircon grains younger than 1.0 Ga and 207 Pb/ 206 Pb ages for the older ones [34]. Chuzhou area: Sixty grains from sample XL02 were analyzed, but some of them were discarded for being highly discordant (Figure 3a). ...
The Yangtze Block records Neoproterozoic magmatism and sedimentation related to the breakup of Rodinia and is an important piece in the reconstruction of the supercontinent. However, the tectonic setting and position of this block in Rodinia remain a subject of debate. In the present study, we report the zircon U-Pb ages and Hf isotopic composition of zircon and geochemical and Nd-Pb isotopic compositions for meta-volcanic rocks exposed in the Zhangbaling uplift of the NE Yangtze Block. The volcanic rocks, dominated by rhyolite and dacite, belong to the calc-alkaline series and show geochemical characteristics of arc rocks. Zircon U-Pb isotopic ages show that volcanic rocks in the Xileng Formation formed at ca. 790 Ma and ca. 760–700 Ma peaking at ~740 Ma. The late-stage volcanism was widely exposed in the uplift, characterized by a temporal-spatial trend becoming younger southwards. The old volcanic rocks have low initial εNd (−11.0) and εHf (−19.7 to −8.2) values and low Pb isotopic ratios, likely indicating an origin from ancient basement rocks underneath the Yangtze Block. The younger ones, being similar to continental arc andesite in trace element compositions, have relatively high initial εNd (mostly −4.6 to 0.5) and εHf (−0.4 to 8.8) values and high Pb isotopic ratios. These isotopic features point to an origin from the partial melting of juvenile crustal rocks. Sedimentary rocks of the Xileng Formation and the overlying strata also contain numerous zircon grains of ~700 Ma to ~630 Ma. The volcanic rocks in the Zhangbaling uplift might demonstrate long-lasting subduction along the northeastern margin of the Yangtze Block, probably active until ca. 700 Ma.
... The data were reduced offline using the Iolite Software (version 2.5; Petrus and Kamber, 2012), according to the methods described by Paton et al. (2011), involving blank subtraction followed by downhole fractionation correction by comparing to the behavior of the primary reference zircon 91,500 (Wiedenbeck et al., 1995), monazite 44,069 (Aleinikoff et al., 2006) and rutile R10 (Luvizotto et al., 2009) and rutile R19 (Zack et al., 2011). The Peixe zircon (age ID-TIMS of 564 ± 4 Ma; Dickinson and Gehrels, 2003) was used as secondary reference material. The Concordia diagrams were plotted using the Software Isoplot R (Vermeesch, 2018), with no common-Pb correction considered. ...
The ultra-high pressure metamorphic rocks of the West Gondwana Orogen are the earliest evidence of deep subduction on Earth. The West Gondwana Orogen resulted from the closure of the Pharusian-Goianides Ocean in the Late Neoproterozoic, leading to the formation of the Santa Quitéria Continental Magmatic Arc (SQCMA) in NE Brazil and the Forquilha Eclogitic Zone, located on the western margin of the SQCMA, suggesting subduction from W to E. This research investigated and reports the occurrence of a coesite-bearing eclogite on the eastern margin of SQCMA, bringing new insights into the regional tectonic evolution of the West Gondwana Orogen. Although extensively retrogressed during exhumation, the coesite-bearing eclogite still records UHP conditions. The multiple stages of the pressure-temperature path were reconstructed by combining textural relationships, integrating symplectite domains in compositional maps, phase equilibrium modeling and Zr-in-rutile thermometry. The pressure peak is estimated at 35.8 ± 5.2 kbar, reached at a temperature from 700 ± 15 °C to 804 ± 15 °C. Retrogression formed symplectite and corona textures at ca. 18 kbar and 760–860 °C. Our results indicate a clockwise P-T path that is characterized by a nearly isothermal decompression associated with a slight temperature increase after the baric peak, followed by decompression and cooling. Geochronological data indicate that the UHP rocks were metamorphosed in the Brasiliano/Panafrican orogenic event during the Western Gondwana amalgamation in the Neoproterozoic. Remnants of intra-oceanic arcs were described at the SQCMA eastern margin. We propose two main tectonic models for the evolution of these rocks: i) double subduction with convergent polarities to E-SE and W-NW, which can be correlated to the scenario proposed to the Hoggar belt in NW Africa and is also supported by geophysical data, and ii) exhumation of the eclogite as a diapir in the mantle wedge.
... If regional rock type and age are spatially diverse then adjacent drainages are likely to contain variable downstream sedimentological and geochemical signatures. This allows detrital zircon U-Pb geochronology the capability to characterize bedrock sediment-source signatures for drainage networks (Figure 1; Dickinson and Gehrels, 2003;Gehrels et al., 2011). In the southeastern United States, regional drainage networks commonly have headwater regions in the southern Appalachian thrust belt and traverse through Mesozoic-Cenozoic eastern Gulf Coastal Plain strata. ...
The Mississippi, Tennessee, Mobile, and Apalachicola drainages provide unique detrital-zircon age spectra that can be used to differentiate Mesozoic and Cenozoic networks in the eastern Gulf Coastal Plain. Results show that a spatial trend in sediment provenance persists from the Cretaceous to the Oligocene, where a southern Appala-chian eastern Blue Ridge and Inner Piedmont signature is present to the southeast and an Appalachian foreland and western Blue Ridge signature is present to the northwest. These end member signatures correlate to results from the modern Tennessee and Apalachicola drainages. A modern Mobile River age spectrum is established in the Miocene and indicates southeastward divide migration of the paleo-Tennessee drainage and incorporation (capture) of the Tallapoosa River from the paleo-Apalachicola drainage. Cretaceous strata exhibiting a paleo-Apalachicola River signature also contain a high abundance (10-23%) of metamorphic zircons compared to foreland derived strata and the paleo-Tennessee signature (1-6%). When detrital-zircon results are filtered to only include metamorphic grains the age spectrum shows a major peak at 361 Ma alongside smaller peaks at 410 Ma and 328 Ma. The 361 Ma and 328 Ma peaks correlate to Acadian and Neoacadian metamorphism documented by zircon U-Pb and garnet Sm-Nd ages in the eastern Blue Ridge province. A 410 Ma peak is cautiously correlated to the eastern Blue Ridge and Inner Piedmont as well. This study demonstrates how detrital-zircon geochronology from passive margin deposits record drainage network evolution and capture the complete history of an orogenic system over small stratigraphic intervals.
... Sediment sources for Jurassic ergs originate from palaeorivers traversing the continental interior sourcing and transporting material from the Appalachian orogenic belt and the Ancestral Rocky Mountains (Blakey 1994, Dickinson & Gehrels 2003. Towards the end of the Jurassic Period, the Ancestral Rocky ...
The sedimentology, controls and efficiency of central erg environments are well-constrained, however marginal relationships are less understood and often under-represented. The Moab Member of the Curtis Formation is a well-exposed, laterally continuous example of the preserved sediments of an aeolian erg system deposited along a marine margin. It comprises the Upper Jurassic deposits found on the Colorado Plateau, a 380,000km 2 area in the Four Corners region of the Western United States. The Moab Member provides an excellent opportunity to study the controls upon aeolian dune fields with increasing proximity to the coastal marine margin. Lateral relationships within the Curtis Formation preserve spatial interactions between systems, temporal interactions are represented by the vertical transition from the Moab Member into the overlying Summerville Formation. This work provides an understanding and analysis of both the sequence-stratigraphical scale and the element scale interactions between dune and contemporaneous sedimentary deposition.
Results from fieldwork carried out in the Canyonlands Section of the Colorado Plateau provided extensive data in the form of sedimentary logs, Spectral Gamma Ray (SGR) data and drone photogrammetry. The collation of these individual data sets enabled a basin wide analysis and the construction of sedimentary models providing a context for the deposition of the Moab Member and its contemporaneous environments.
The results identify a significant change in the sedimentology and geometry of the erg system towards the marine margin. Establishing the morphologies of this system and its interactions with the surrounding environments enabled the identification of 'pulses' linked to small scale sea-level fluctuations. When considered within the wider framework of basin sea-level fluctuations identified from shallow marine deposits, which preserved allocyclic signals, these smaller scale events provide a more in-depth characterisation of sequence stratigraphy in the area and hence document the behaviour of the aeolian-marine margin through a transgressive-regressive cycle.
... Due to the well-documented tectonic history and a wellformed backbone of prior work (Willis, 1999;Dickinson and Gehrels, 2003;DeCelles, 2004;Dickinson and Gehrels, 2009a,b;Laskowski et al., 2013; and references therein), we can draw meaningful linkages to likely source terranes. Mesozoic-aged grains constitute a vast majority of all recovered ages from all three bulk samples, and of this, an overwhelming majority fall between the Cenomanian and Turonian respectively (±89.8e100.5 Ma). ...
... The application of multiple provenance techniques attenuates the uncertainties from chemical weathering or sediment recycling (Nie et al., 2012). The pattern fluctuations potentially record secular changes from the sedimentary flux into the Araripe Basin and also the shifts in the composition of the sources (e.g., Dickinson and Gehrels, 2003;Dickinson et al., 2009). This analysis corroborates the interpretation of the Araripe Basin provenance evolution during the Mesozoic, reflecting changes in topography, tectonics and climate. ...
This study presents UPb dating of detrital zircons from sandstones of the Araripe basin (NE Brazil) assisting in the reconstruction of the Mesozoic paleogeography. In particular, we focus in the seaway connection between the Proto-Atlantic ocean and this intracontinental basin in northwest Gondwana.The new UPb age spectra of detrital zircon grains from the pre-Jurassic and Mesozoic clastic sequences of the Araripe Basin, along with paleocurrent, stratigraphic and structural data, demonstrate a significant change in provenance during the LaterLater Jurassic to mid-Cretaceous. Six distinct provenance patterns are identified in the sequences, which may reflect the rapid evolution of the paleogeographic scenarios during tectono-sedimentary history of the northwest Gondwana rift-related basins throughout the onset to the opening of the Atlantic Ocean. Here, we propose an alternative model for paleogeography of the northwest Gondwana. In the Later Jurassic, the main source of terrigenous clastics to the Araripe Basin was the Paleozoic-Triassic sedimentary rocks of the Parnaíba Basin, which formed a prominent barrier to separate the Araripe Basin from the Mesozoic units of the Parnaíba Basin. In the mid-Aptian, erosion led to the retraction of the Parnaíba Paleozoic sedimentary units to the west, as the Precambrian terranes from the Borborema Province, to the northwest, became the main source for the Araripe Basin. The rapid rifting evolution show that the Rio Salgado Belt, from NE region, became topographically depressed, potentially initiating a link between the Araripe and the Potiguar basins. During late-Aptian, the Araripe Basin probably connected to the Proto-Equatorial Atlantic Ocean from the northeast, through the Potiguar Basin and associated grabens on the north. The present paleogeographical reconstruction may explain the occurrence of warm water adapted Tethyan fauna in the Araripe Basin, more plausible than previous hypothesis of a connection to Proto-South Atlantic Ocean.
... Sedimentary provenance studies have made ample use of U-Pb zircon geochronology by comparing detrital zircon population ages with those of potential source rocks (e.g. Dickinson and Gehrels 2003;Chen et al. 2019). However, this technique provides an incomplete picture of provenance because of differential zircon fertility (Moecher and Samson 2006;Dickinson 2008a) and its refractory character through multiple sedimentary cycles (Fedo et al. 2003;Andersen et al. 2016). ...
Sandstone petrography, zircon and apatite U-Pb geochronology, and apatite geochemistry of Early Cretaceous siliciclastic turbidites interbedded with basalt (Chivillas Formation) in the southern Sierra Madre Oriental, Mexico, indicate local provenance from westerly basement sources. Three main detrital populations were observed in both the zircon and apatite geochronology: Meso–Neoproterozoic, Carboniferous–Permian, and Early Cretaceous. Apatite Sr/Y vs light rare earth element discrimination diagrams indicate that most Precambrian grains have affinity with high-grade metamorphic rocks and most Phanerozoic grains with igneous rocks. These results are consistent with derivation from exposed crystalline sources within the Acatlán-Oaxacan block including the Grenvillian Oaxacan Complex, the East Mexico Arc, and the Early Cretaceous continental arc. The compositional disparities observed in individual samples reflect differences in source of individual turbiditic flows comprising the Chivillas Formation. We surmise that various rivers from the northern and southern Acatlán-Oaxacan block drained into the basin during the Early Cretaceous. Furthermore, detrital apatite fission-track analyses of Chivillas sandstones yielded mostly 42–40 Ma ages (Eocene) that post-date the shortening of the Mexican orogen in the southern Sierra Madre Oriental. Thermal models calculated based on track lengths indicate rapid exhumation of Chivillas rocks at 46–36 Ma, which is the time of the development of the Tehuacán Valley and reactivation of the Oaxaca Fault System as a normal fault.
... This hypothesis was inspired by the scarcity of Grenville DZ in the western GOM , and these Grenville DZ were thought to have been transported a long distance. These grains were first delivered to the western marine margin of Pangea by transcontinental fluvial systems during the Pennsylvanian, then blown southeastward by trade winds to the Colorado Plateau during Permian to Jurassic times (Dickinson & Gehrels, 2003) and finally transported to the GOM by fluvial systems during the Miocene . ...
Abstract Detrital zircon (DZ) geochronology has become a popular tool in provenance studies during the past two decades. However, similar zircon crystallization ages from different source regions greatly hamper interpretation of sediment dispersal and recycling processes. The Alleghenian‐Ouachita‐Marathon (AOM) foreland and vicinity in North America is a typical region, in that some dominant DZ age groups could come from both the southern Appalachians in the eastern United States and the Gondwanan terranes in Mexico. In this study, we present 1045 new DZ U‐Pb ages and 81 DZ core‐rim age pairs in lower Permian sandstone in the Permian Basin and Miocene sandstone in the eastern Gulf of Mexico (GOM). These new data were integrated with published DZ single U‐Pb age and core‐rim ages from syn‐ and postorogenic strata in the Permian Basin, Marathon foldbelt, southern Appalachian foreland basin, and eastern GOM to interpret the sediment‐dispersal models in the AOM foreland and eastern GOM. Our models show that during the Leonardian Stage, sediments derived from the Appalachians were first delivered to the US midcontinent and then recycled to the Permian Basin; during the Miocene, sediment from the Appalachians fluxed to the eastern GOM, with no longshore mixing from the western GOM. These models based on the integration of single U‐Pb and core‐rim ages are consistent with published results that used other methods, including zircon single U‐Pb age, zircon Hf isotopic data, zircon (U‐Th)/He age, sedimentology, and stratigraphy. Our results demonstrate that although some limitations exist, zircon core‐rim age is a powerful tool, adding an extra constraint on the interpretation of sediment‐dispersal systems. This tool is particularly applicable to the postorogenic stage, during which the sediment pathways are more complicated because of the dominant input from distal sources. Insights gained in this study imply that this novel strategy of using core and rim ages could be integrated with other methods to better understand sediment dispersal.
... Zircon U-Pb isotope ratios were measured using a 193 nm ArF excimer laser ablation system (Cetac/Photon Machines) coupled to a Nu Plasma inductively coupled plasma mass-spectrometer (LA-ICP-MS) at the University of California, Santa Barbara. Data were calibrated using the zircon reference materials GJ1 (601.7 ± 1.3 Ma; Jackson et al., 2004), Plešovice (337.13 ± 0.37 Ma; Sláma et al., 2008), 91,500 (1062Wiedenbeck et al., 1995), and Peixe (564 ± 4 Ma; Dickinson and Gehrels, 2003). Data reduction was performed using Iolite software (Paton et al., 2010(Paton et al., , 2011 and no correction for common Pb to LA-ICP-MS data was done to the total Pb content and its isotopic composition; histogram Kernel Density Estimation (KDE) plots were made using DensityPlotter (Vermeesch, 2012). ...
Paleogeography is critical as a backdrop for environmental changes, yet the Paleoproterozoic configuration of Archean cratons remains controversial. The Snowy Pass Supergroup (SPS), a Paleoproterozoic succession on the SE Wyoming craton (Medicine Bow Mountains, MBM), has been correlated with the Huronian Supergroup (HS) of the Superior craton, suggesting deposition in the same basin, and indicating that these cratons were adjoined in the Paleoproterozoic Superia supercraton. We present U-Pb volcanic and detrital zircon data for the underlying Phantom Lake Metamorphic Suite (PLMS), SPS, and Snowy Pass Group (SPG; Sierra Madre, SM) and U-Pb zircon ages for two mafic sills and Baggot Rocks granite. The PLMS contains a statistically significant mode of ca. 2.45 Ga zircon dates in the SM; zircons of this age also occur in one to two grain quantities in the PLMS in the MBM. The Baggot Rocks granite and Colberg Metavolcanics of the PLMS also yielded the ca. 2.45 Ga U-Pb zircon ages, indicating the early Paleoproterozoic age for this suite and the ca. 2.45 Ga extensive, rift-related mafic magmatism on the southern margin of the Wyoming craton, allowing correlation with the basal HS units of the Superior craton. Zircon age spectra for lithostratigraphically correlative units on the Wyoming and Superior cratons show strikingly similar, primarily Archean patterns, which, along with paleocurrent directions, establish provenance of both cratons for the shared basin; ca. 2.55 and 2.3 Ga modes are common for the uppermost formations. Fine-grained siliciclastic rocks throughout the SPS yield similar TDM and εNd ages as well as μ and κ values to the HS, further supporting similar provenance for the two supergroups. Mafic sills in the MBM yielded U-Pb zircon dates of 2220 ± 8 Ma and 2094.3 ± 1.6 Ma that closely correspond to the age of the Nipissing mafic intrusions in the HS and the Cauchon Lake dikes in the NW Superior craton. Correlation between the HS and SPS breaks down in the upper SPS at the Nash Fork Formation, which bears detrital zircon age modes at ca. 2.2 and 2.1 Ga, whereas deposition of the HS terminated before ca. 2.22 Ga when the Nipissing dikes intruded and shortly after a ca. 2.31 Ga volcanic event recorded by the Gordon Lake and Bar River formations. The matching detrital zircon dates to a globally unique, ca. 2.3 Ga, mode first appeared in the Lookout Schist of the SPS and steadily decreased up-section through the upper SPS, pointing to a similar volcanic source. Maximum depositional ages for the uppermost formations of the SPS and SPG, the purportedly correlative Nash Fork and Slaughterhouse formations, are at 2081 ± 10 Ma and 2334 ± 20 Ma, respectively. The former detrital zircon mode corresponds to that recorded by the basal Animikie basin units (Denham Formation of the Mille Lacs Group in MN and East Branch Arkose of the Dickinson Group, MI) and are linked to rifting, breakup, and ultimate separation of the Wyoming and Superior cratons at ca. 2075 Ma.
... Antler highlands is synonymous with ''Antler orogenic belt.'' Modified from Dickinson and Gehrels (2003) and Stevens et al. (2015). ...
The Late Permian to earliest Triassic Sonoma orogeny has long been envisioned as the result of an arc-continent collision that closed the Havallah oceanic basin, creating the Golconda allochthon, which was emplaced eastward onto the western edge of the continental margin along the Golconda thrust. Critical reevaluation of available stratigraphic, biostratigraphic, and structural data raise some fundamental issues with this scenario, including: (1) The Golconda allochthon experienced multiple phases of deformation both older and younger than the Sonoma orogeny; (2) the tectonostratigraphic successions in the Golconda allochthon record a disrupted depositional history; (3) these punctuated events and unconformities are mirrored by simultaneous punctuated tectonic disruptions of the adjacent continental margin; (4) some of the lithotectonic units within the Golconda allochthon have clear ties to a magmatic arc. These observations indicated that the Havallah basin did not originate as a simple, post-Antler orogeny rift basin, nor is the Mediterranean model for opening of a basin a solution to the initiation of this basin. Instead they imply a more complex paleogeography for the Havallah basin. The Late Permian–earliest Triassic closure of the Havallah basin did result in the development of the Golconda allochthon sensu stricto, but final emplacement of the Golconda allochthon was likely an Early–Middle Jurassic event.
... Despite plenty of local works deciphering mainly metamorphic (P/T) conditions (see Krist et al. 1992;Bezák et al. 1993 for a review) only a few papers deal with the geochemistry and lithology of the Western Carpathians crystalline basement (WCCB) in detail can be used to decipher their provenance (Hovorka and Méres 1991;Ivan et al. 2001;Méres 2005). Detrital zircon geochronology permits insights into the tectonic and geochronological evolution of source terrains, which may be unknown, and the testing of paleogeographic reconstructions and/or terrane derivations and paleotectonic linkages of various tectonostratigraphic units (Dickinson and Gehrels 2003;Friend et al. 2003;Linnemann et al. 2007. The aim of this contribution is to present new detrital zircon U-Th-Pb data, and together with available lithological, metamorphic and magmatic data to discuss the possible provenance of the Western Carpathians units as a part of the European Variscides within the Lower Paleozoic microcontinent puzzle. ...
The Western Carpathians crystalline basement recorded common indications of the Cadomian/Avalonian basement precursors. There the pre-Mesozoic basement of the Tatric Unit was studied with respect to its lithological, structural, metamorphic and age characteristics. The obtained data proves that this basement is made of two different rock complexes—the older Lower Étage (Cambrian to Silurian) showing high-grade metamorphic evolution, and the younger Upper Étage (Upper Silurian to Devonian) presenting low-grade metamorphism and younger stage of development. First representative U–Th–Pb detrital zircon data from metamorphosed siliciclastics from the Tatric Unit of the Western Carpathians indicate a general dominance of Neoproterozoic—mainly Ediacaran source rocks. The latter are interpreted to have been located at the Cadomian arc supplied mostly from the Saharan Metacraton. Combined with less frequent Archean and Paleoproterozoic zircon populations a common Gondwanan provenance derived from reworked West African Craton is proposed for part of the samples. However, some samples contain Mesoproterozoic detrital zircons what is typical for the Avalonian microcontinent. The studied metamorphic rocks are interpreted to originate from the Rheic Ocean and also partly from the Rheno-Hercynian basin. Indeed, significant differences in the metamorphic evolution of both metamorphic rock assemblages suggest their present juxtaposition and or their thrusting during the Late Devonian to Carboniferous (Visean) Variscan subduction/collision processes.
... Data from Smith and McConnaughey (1999) and McConnaughey and Smith (2000). aeolian processes may be another factor in long-scale zircon transport across the shelf (Garzanti et al., 2015) and can be abundant in wind-blown deposits (Dickinson & Gehrels, 2003). However prevailing winds on the Bering Sea shelf are generally toward the east-northeast (Field et al., 1981), but vary seasonally (Danielson et al., 2012). ...
Abstract Continental shelves serve as critical transfer zones in sediment‐routing systems, linking the terrestrial erosional and deep‐water depositional domains. The degree to which clastic sediment is mixed and homogenised during transfer across broad shelves has important implications for understanding deep sea detrital records. Wide continental shelves are thought to act as capacitors characterised by transient sediment storage during sea‐level rise and sediment remobilisation during sea‐level fall. This study attempts to test the hypothesis that sea‐level lowstand yields more efficient and direct sediment transfer from fluvial sources to deep sea sinks compared to highstand when sediment is sequestered and mixed on the shelf. This hypothesis is tested by evaluating U‐Pb and Lu‐Hf detrital zircon provenance trends along the vast Bering Sea shelf and deep‐marine Beringian continental margin. Presented here are 5884 U‐Pb ages and 402 Lu‐Hf analyses from 30 samples to characterise the provenance of modern to Pleistocene sediment across the Bering Sea region. Both forward and inverse numerical mixture modelling was used to estimate the abundance of distinct fluvial sources in shelfal and deep‐water deposits. These results demonstrate that sediment in the Bering Sea is derived from a mixture of regional fluvial sources, but that the Yukon River is the primary detrital source for sediment throughout the region. Although Yukon River signatures are abundant in all basin samples, the relative proportions of Yukon River versus other sources vary spatially across the shelf. A comparison of Holocene and surficial sediment with Pleistocene deposits shows that sediment across the shelf and in the deep sea remains well‐mixed between climate states. Thus, detrital provenance signatures in deep‐marine deposits outward of broad transfer zones are likely to represent mixtures of fluvial sources regardless of sea level.
... In between the starting and end standard suites, a group of 6-8 analyses (depending on the number of total zircon crystals picked for each sample) including one Peixe and one FC5z immediately followed by 4-6 unknowns were analyzed successively until all zircons from the same sample have been measured. Peixe, with an accepted ID-TIMS value of 564 ± 4 Ma (Dickinson and Gehrels, 2003), was used as the primary calibration standard and FC5z with an accepted ID-TIMS value of 1099.0 ± 0.6 Ma (Paces and Miller, 1993) as a secondary standard. We conducted one shot per zircon crystal. ...
The Coastal Complex (CC) and Bay of Islands Complex (BOIC) represent two supra-subduction zone (SSZ) forearc ophiolitic assemblages of different ages within the Taconic Humber Arm Allochthon of the Western Newfoundland Appalachians. To further constrain age relationships between the CC and BOIC and earliest initiation of Iapetus subduction, we acquired LA-ICP-MS U-Pb zircon ages for eleven plagiogranites sampled along strike of the CC belt. These ages combined with three prior legacy ages establish an age range of 514.3-502.7 Ma for the six CC plagiogranite plutons. The oldest precise ca. 514.3 Ma CC pluton age represents the oldest Taconic arc-related plutonic activity yet documented in Western Newfoundland and provides a minimum age for the intruded CC ophiolite basement and initiation of westerly vergent subduction within the peri-Laurentian Iapetus Ocean. This confirms the Early Cambrian CC mafic-ultramafic basement is significantly older than the juxtaposed SSZ BOIC, which formed by later rifting of the CC forearc along younger forearc spreading center in the Late Cambrian by ca. 488.3 Ma. After subduction initiation a prolonged early period CC forearc silicic magmatism lasted at least ∼11.6 Ma until ca. 502.7 Ma, a range consistent with age spans of magmatism in modern juvenile forearcs. We also reinvestigated the Central Newfoundland Twillingate Granite batholith thought to be one of the earliest major felsic batholiths formed within the adjacent juvenile arc massif of the Notre Dame Subzone, part of the same peri-Laurentian arc. We determined a precise 3-sample composite age of 504.3 ± 1.8 Ma that signals the formation of earliest Notre Dame arc edifice developed by Middle Cambrian. It overlaps the end-stage CC forearc plagiogranite magmatism and places a minimum mid-Cambrian age constraint on intruded ophiolitic arc tholeiitic and boninitic pillow lavas of the Sleepy Cove and correlated Lushs Bight volcanics, suggesting basement continuity with the CC.
... Basal layer characteristics have been previously ascribed as evidence of friction-reducing processes, and the formation and evolution of the basal layer may play an important role in the mechanics of translation (e.g., Anders, Aharonov, & Walsh, 2000). Zircon U/Pb geochronology is a standard methodology for provenance studies (e.g., Dickinson & Gehrels, 2003;Freiburg, Holland, Malone, & Malone, 2020;Johnson & Winter, 1999;Malone, Craddock, Stein, Stein, & Malone, 2020). ...
Formation and evolution of the basal layer in large landslides has important implications for processes that reduce frictional resistance to sliding. In this report, we show that zircon geochronology and tectonic provenance can be used to investigate the basal layer of the gigantic scale Markagunt gravity slide of Utah, USA. Basal layer and clastic injectite samples have unique tectonic chronofacies that identify the rock units that were broken down during emplacement. Our results show that basal material from sites on the former land surface are statistically indistinguishable and formed primarily by the breakdown of upper plate lithologies during sliding. Decapitated injectites have a different tectonic chronofacies than the local basal layer, with more abundant lower plate derived zircons. This suggests clastic dikes formed earlier in the translation history from a structurally deeper portion of the slide surface and a compositionally different basal layer before being translated to their current position.
... Detrital zircon U-Pb age dating and Hf isotopic composition, as robust provenance proxies, are widely used in paleogeographic reconstruction (e.g., Dickinson and Gehrels, 2003;Fedo, 2003;Miller et al., 2006;Meinhold et al., 2013;Hu et al., 2015;Iaccheri and Bagas, 2020). In Sedimentary Geology 434 (2022) 106144 and Metcalfe (2013)) and detrital zircon samples locations. ...
The Baoshan, Tengchong, Lhasa, South Qiangtang, and Sibumasu terranes were part of Gondwana prior to rifting and drifting from the northern margin since the Early Permian. However, paleopositions of these terranes during the late Paleozoic remain controversial, which hinders better understanding the tectonic evolution of the Paleo-Tethys and glacier distribution patterns on eastern Gondwana during the late Paleozoic ice age. As robust provenance indicators, detrital zircon U-Pb dating and Hf isotope signatures have been widely utilized in paleogeographic reconstruction. Here, we collected a total of 8209 detrital zircon U-Pb ages and 1606 zircon Hf isotopic values from Paleozoic strata of northeastern Gondwana. These data are utilized to evaluate their paleopositions relative to Australian and Indian Gondwana through semi-quantitative data analysis. Our new paleogeographic model indicates that the South Qiangtang, Baoshan, and part of Sibumasu were outboard of the northern margin of Indian Gondwana during the Paleozoic, whereas the Lhasa and Sumatra terranes were located along the northern margin of Australia. Based on provenance shifts of late Paleozoic glaciogenic sedimentary rocks in northeastern Gondwana, two main ice sheets are hypothesized to have developed during the late Paleozoic. This study further confirms the model of a multicenter glacier distribution pattern on Gondwana during the late Paleozoic ice age from a perspective of provenance.
... Plotting made use of the detritalPy program by Sharman et al. (2018) using an optimized, fixed bandwidth for the age populations that applies the algorithm of Shimazaki and Shinomoto (2010). Pie charts for each geographic location show the proportion of grain ages that fall within prescribed age bins corresponding to primary zircon sources for North America (Table 2; Dickinson and Gehrels, 2003;Dickinson and Gehrels, 2008;Gehrels et al., 2011;Laskowski et al., 2013;Blum et al., 2017). Identification of specific source lithologies was performed through comparison with known age spectra of Mesozoic and Paleozoic strata exposed along the margins of the Bighorn Basin (May et al., 2013) binned by tectonostratigraphic assemblage as well as the ages of crystalline basement in the region (Gast et al., 1958;Frost and Fanning, 2006). ...
This Special Paper focuses on the evolution of the crust of the hinterland of the orogen during the orogenic cycle, and describes the evolution of the crust and basins at metamorphic core complexes. The volume includes a regional study of the Sevier-Laramide orogens in the Wyoming province, a regional seismic study, strain analysis of Sevier and Laramide deformation, and detrital zircon provenance from the Pacific Coast to the foreland between the Jurassic and the Eocene.
... Furthermore, these zircon concentrations were analyzed for combined U-Pb and Lu-Hf isotopic data. As a consequence of long transport and reworking during a sedimentary cycle, zircon morphologies are greatly affected (Dickinson and Gehrels, 2003). The occurrence of zircon grains displaying different morphologies within a sedimentary rock might indicate derivation from a mixture of sources rather than a single sediment contribution. ...
This paper explores the sedimentary provenance of the Silurian to Devonian siliciclastic successions in the Central region of the San Juan Precordillera, in central-western Argentina. The comprehensive provenance analysis of the Tambolar Formation (upper Silurian), Talacasto Formation (Lower Devonian) and Punta Negra Formation (Lower-Middle Devonian) from the San Juan River section is based on petrography, detrital zircon analyses and combined U–Pb and Lu–Hf isotopic data. Modal composition of the three units here studied shows an evolution trend from quartzose recycled, mixed, to transitional arc. Detrital zircon morphologies indicate derivation from dominantly plutonic and metamorphic sources with little evidence of transportation. The most representative detrital zircon U–Pb age populations are Famatinian (middle Cambrian - Devonian), Pampean–Brazilian (Tonian - lower Cambrian), and Grenvillian (Ectasian - Stenian) cycles derived rocks. Hf isotopes determined mainly in Mesoproterozoic detrital zircons reflect a juvenile mantle source during crystallization, with less significant inputs from those with a crustal and recycled crust origin. Results from this work are compared to data from outcrops of the same units developed in the North-Central region of the Precordillera, presented in previous works. Provenance proxies provide insights regarding the correlation of probably equivalent units deposited in other foreland basins within the Cuyania terrane, such as the Villavicencio Formation (Mendoza Precordillera), Río Seco de los Castaños and La Horqueta Formations (San Rafael Block). The K–S test suggests a low correlation between the units studied at the San Juan River and the equivalent outcrops exposed towards the central and northern parts of the San Juan Precordillera, as well as with the known records of the Río Seco de los Castaños and La Horqueta Formations of the San Rafael Block. In contrast, the samples from the Villavicencio Formation show a high correlation with the sample from the Punta Negra Formation, indicating a possible common sediment source. The broad variations of U–Pb detrital age pattern distributions observed between Silurian and Devonian successions throughout the Precordillera and the San Rafael Block point to provenance shifts linked to variability in east-to-west sediment dispersal patterns within an axial peripheral foreland basin. Fluctuations in the sedimentary composition are ascribed to the differential exhumation rate of source rocks and a progression from a convergent tectonic setting in the San Rafael block towards a coeval collisional environment in the Precordillera. The Silurian - Early Devonian foreland basin is tectonically linked to the Ocloyic Orogen that resulted from the collision of Cuyania terrane to the Western margin of Gondwana. Source rocks were most likely located within the Mesoproterozoic basement of Cuyania, exhumed during the Middle Devonian as a response to the approximation of Chilenia.
The Klamath Mountains Province of Northern California and southern Oregon, USA, consists of generally east-dipping terranes assembled via Paleozoic to Mesozoic subduction along the western margin of North America. The Klamath Mountains Province more than doubled in mass from Middle Jurassic to Early Cretaceous time, due to alternating episodes of extension (e.g., rifting and formation of the Josephine ophiolite) and shortening (e.g., Siskiyou and Nevadan events). However, the tectonic mechanisms driving this profound Mesozoic growth of the Klamath Mountains Province are poorly understood. In this paper, we show that formation of the Condrey Mountain schist (CMS) of the central Klamath Mountains Province spanned this critical time period and use the archive contained within the CMS as a key to deciphering the Mesozoic tectonics of the Klamath Mountains Province. Igneous samples from the outer CMS subunit yield U-Pb zircon ages of ca. 175–170 Ma, which reflect volcanic protolith eruptive timing. One detrital sample from the same subunit contains abundant (~54% of zircon grains analyzed) Middle Jurassic ages with Paleozoic and Proterozoic grains comprising the remainder and yields a maximum depositional age (MDA) of ca. 170 Ma. These ages, in the context of lithologic and thermochronologic relations, suggest that outer CMS protoliths accumulated in an outboard rift basin and subsequently underthrust the Klamath Mountains Province during the Late Jurassic Nevadan orogeny. Five samples of the chiefly metasedimentary inner CMS yield MDAs ranging from 160 Ma to 130 Ma, with younger ages corresponding to deeper structural levels. Such inverted age zonation is common in subduction complexes and, considering existing K-Ar ages, suggests that the inner CMS was assembled by progressive underplating over a >10 m.y. timespan. Despite this age zonation, age spectra derived from structurally shallow and deep portions of the inner CMS closely overlap those derived from the oldest section of the Franciscan subduction complex (South Fork Mountain schist). These relations suggest that the inner CMS is a composite of South Fork Mountain schist slices that were sequentially underplated beneath the Klamath Mountains Province. The age, inboard position, and structural position (i.e., the CMS resides directly beneath Jurassic arc assemblages with no intervening mantle) of the CMS suggest that these rocks were emplaced during one or more previously unrecognized episodes of shallow-angle subduction restricted to the Klamath Mountains Province. Furthermore, emplacement of the deepest portions of the CMS corresponds with the ca. 136 Ma termination of magmatism in the Klamath Mountains Province, which we relate to the disruption of asthenospheric flow during slab shallowing. The timing of shallow-angle subduction shortly precedes that of the westward translation of the Klamath Mountains Province relative to correlative rocks in the northern Sierra Nevada Range, which suggests that subduction dynamics were responsible for relocating the Klamath Mountains Province from the arc to the forearc. In aggregate, the above relations require at least three distinct phases of extension and/or rifting, each followed by an episode of shallow-angle underthrusting. The dynamic upper-plate deformation envisioned here is best interpreted in the context of tectonic switching, whereby slab steepening and trench retreat alternate with slab shallowing due to recurrent subduction of buoyant oceanic features.
Facies of the Permian Lyons Sandstone are described and interpreted based on analyses of 23 cores from Larimer and Weld counties, Colorado. Here, the Lyons Sandstone consists of very fine-to medium-grained sandstone with minor silt and mudstone interbeds. The unit has five recurrent siliciclastic facies that can be grouped into two facies associations (FA). FA1 consists of (1) high-angle, cross-laminated sandstone (Facies 1; interpreted as eolian dune remnants); (2) low-angle, cross-laminated and horizontally laminated sandstone (Facies 2; interdune); and (3) chaotically bedded to folded sandstone (Facies 3; lower dune flanks). FA2, in contrast, is mainly (4) wavy-to irregularly laminated silty sandstone (Facies 4; wet to damp interdune); and (5) massive to wavy-laminated silt-rich mudstone (Facies 5; ponded water areas between dunes) with minor amounts of high-angle, cross-laminated sandstone (Facies 1) and low-angle, cross-laminated and horizontally laminated sandstone (Facies 2). FA1 is hypothesized to have been produced in an eolian system akin to those that might exist in the dune-dominated portion of an erg, whereas FA2 was deposited in the intermittently wet portion of this eolian system, perhaps along erg margins or in flat dune-adjacent settings that were impacted by the water table. Isopach data suggests that the study area is on the fringe of a larger Lyons system that spans > 100,000 km 2 , and was deposited close to the Ancestral Rockies-a paleogeography consistent with deposition in erg to erg-margin paleoenvironments. Detrital zircon populations from nearby Colorado Front Range outcrops and from 12 correlative eolian units are dominated by small, well-rounded Paleoproterozoic and Mesoproterozoic grain populations that are remarkably similar between units, signaling a well-mixed system that also received an influx of distally sourced sediment from the Appalachian orogen. Detrital zircon-based maximum depositional ages of the Lyons Sandstone and its equivalents are internally consistent with deposition of the unit during the latest Artinskian to Kungurian.
Source-to-sink evolution of a basin is a key to understand sedimentary processes, especially in a complex regional
orogenic setting. Detrital zircon populations can be traced from their primary sources to their depositional settings. The resulting interpretations are enhanced by calculation of the adjacent orogen's paleoaltimetry, which
provides additional insights into paleogeography. In this study, we present a combined methodology which
aims to reconstruct source-to-sink evolution by the analysis of detrital zircon age distribution in sandstones,
together with the calculation of paleo-elevation of surrounding orogens based on the chemical compositions of
coeval magmatic rocks. We test the method using detrital zircon U–Pb geochronological data sets from the Triassic Songpan–Ganzi basin in central China, combined with whole-rock geochemical data from intermediatecomposition magmatic rocks in adjacent crustal blocks. Application of the combined methodology supports a
syn-collisional basin model for the formation of the Triassic Songpan-Ganzi basin in preference to a continental
back-arc basin. The clastic sediments, mainly deep-marine turbidites, accumulated in a remnant Paleotethyan
Ocean that was surrounded by the converging North China Block, South China Block, East Kunlun Orogenic
Belt and the Qiangtang Block. The North China Block and the North Qaidam Block were major proto-sources of
detrital zircons to the basin, contributing on average 12 % and 15 %, respectively. Triassic magmatic rocks in
the East Kunlun and Qiangtang regions were major sources of igneous zircons, up to 68 % for the former and
up to 56 % for the latter. Despite being located at a calculated elevation of ca. 4000 m, the Qinling Orogenic Belt
contributed only ca. <10 % of the zircons, mostly restricted to the eastern depocenter of the basin. In contrast,
supply from the North Qiangtang Block, despite its calculated lower elevation (1000–3000 m), accounts for 2–
10 % of the detrital zircons in the basin, suggesting high erosion rates of this block. The minimal supply of zircons
from the South China Block, restricted to 3–6 % in the central and western depocenters, is inconsistent with the
zircon abundances predicted in the alternative back-arc basin model of the Songpan–Ganzi basin
Late Cretaceous to Eocene Laramide basement–involved shortening fragmented the Sevier and Mexican foreland basins. This resulted in a major drainage reorganization in response to the emerging topography of Laramide basement–cored uplifts and Mexican inverted Border rift basins. This study presents new depth-profile detrital zircon U-Pb data (3679 ages from 28 samples) from Upper Cretaceous–Eocene fluvial strata of the Tornillo basin in west Texas to determine sedimentary provenance and reconstruct sediment dispersal through the U.S.-Mexico border region. Detrital zircon U-Pb data are dominated by Hauterivian–Coniacian (130–87 Ma; ~20%) and Coniacian–Ypresian (87–52 Ma; ~30%) ages that represent Cordilleran and Laramide arc magmatism, respectively. Subordinate age groups are Paleoproterozoic–Mesoproterozoic (1900–1300 Ma; ~12%), Ectasian–Tonian (1300–900 Ma; ~8%), Tonian–Pennsylvanian (900–300 Ma, ~10%); Permian–Triassic (300–200 Ma; ~8%), and Jurassic–Early Cretaceous (200–130 Ma; ~11%). Detrital zircon maximum depositional ages provide new constraints on the chronostratigraphic framework of the Tornillo Group, the stratigraphic nature of the Cretaceous-Paleogene boundary, and the stratigraphic level of the Paleocene–Eocene thermal maximum. Depth-profile core-rim age pairs yielded Paleoproterozoic–Mesoproterozoic and Jurassic cores with Cretaceous–Paleogene rims, which represent zircons derived from Laramide magmatic rocks that intruded Yavapai-Mazatzal basement and Cordilleran-Nazas magmatic rocks. Zircon grains with Ectasian–Tonian cores and Paleozoic rims likely represent Appalachian-derived and/or Coahuila terrane zircons recycled from the inverted Mesozoic Bisbee basin and Chihuahua trough. These results demonstrate that fluvial strata in the Tornillo basin were sourced from Laramide and Cordilleran magmatic rocks, Yavapai-Mazatzal basement, and recycled Mexican Border rift sedimentary rocks in the southwest United States and northern Sonora, and these sediments were delivered via a large (>103-km-long), axial-trunk river. Additional recycled detritus from Mexican Border rift sedimentary rocks in the Chihuahua fold belt was delivered via transverse tributaries. This drainage reconstruction indicates that the Tornillo river flowed along an inversion-flank drainage corridor adjacent to topography formed by the inverted Mexican Border rift. Therefore, inherited Mexican Border rift architecture represented a first-order control on sediment routing to the Tornillo basin.
Petrographic and detrital zircon U-Pb analysis of modern beach sands and river sands from major catchments in northeastern Mexico draining to the Gulf of Mexico provides evidence for a minimum of 650 km of littoral sand transport southward from the mouth of the Rio Grande at the Mexico-U.S. border to the central part of the state of Veracruz, Mexico. Principal tracers of Rio Grande sand include: (1) quartzose composition that contrasts with lithic compositions of sand in eastern Mexico rivers and (2) detrital zircon ages with Mesoproterozoic modes at 1.8−1.5 Ga and 1.4 Ga, age groups that are typical of basement and derivative sediment of the SW United States but are uncommon to rare in Mexican river catchments. In contrast, abundant Miocene and younger grains in beach sands of Veracruz indicate primary sediment derivation from active and recently active volcanoes in the Trans-Mexican volcanic belt in central Mexico. A proportional decrease in sand of Rocky Mountain provenance with distance southward along the coast from the mouth of the Rio Grande and absence of Miocene and younger zircon grains in beaches north of rivers draining the Trans-Mexican volcanic belt indicate net littoral sand transport southward along the eastern coast of Mexico, demonstrating that wintertime shoreline-parallel surface currents rather than north-directed summertime currents dominate sediment transfer. Sand samples of Tamaulipas beaches in northeastern Mexico commonly have equal or higher proportions of U.S.-derived Mesoproterozoic zircon grains than are present in river bar sand of the lower Rio Grande and the Rio Grande delta, and thus require that littoral processes rework and incorporate coastal dune and beach sands of northeastern Mexico that are enriched in predam Rio Grande sediment. Implied coastal erosion may be related to Holocene transgression or interruption of sediment supply to the coastal sediment transport system by dams in the Rio Grande drainage basin. Such coastal erosion is impacting long-term shoreline stability and viability of the littoral environment.
Intermontane deserts are an important type of arid‐climate sedimentary system. Although rare at present, the sedimentary records of intermontane deserts reveal their widespread development in past greenhouse periods, and they might develop in the near future in response to ongoing global warming. Determination of the provenance of sand supplied for the construction of intermontane deserts is important to gain improved understanding of the potential impact of future climate on environmental evolution in arid and semi‐arid regions. During the Cretaceous, a typical intermontane desert developed in the Xinjiang Basin, south‐east China. In this study, the origin, spatial variability, and transport pathways of both aeolian and alluvial–fluvial sediments in the Xinjiang intermontane desert are investigated by analyses of bulk‐rock petrography and detrital‐zircon U–Pb geochronology. These results demonstrate that the sand in the Xinjiang intermontane desert succession was mainly of extraneous origin and wind‐derived. The nearby South China Block and South China Magmatic Belt were primary sources, and the 1000 km distant western margin of Yangtze Block was an important secondary source. During the Late Cretaceous, the westerlies were stronger in the northern than in the southern hemisphere with doubled wind speeds. In such a climatic context, the results herein suggest that the ultra‐long‐distance aeolian sediment transport was likely further enabled by two factors: (i) the strengthening of intermittent westerly winds during short‐lived glacial episodes; and (ii) the presence of a low‐relief corridor that served as a transport pathway from source to sink.
Lithic and quartz arenites of the Central Appalachian Basin deposited by late Paleozoic Laurentian fluvial systems are widely interpreted to be sourced by recycling of late Precambrian and early Paleozoic clastic sequences in the Appalachian Orogen. U-Pb and (U-Th)/He age distributions for detrital-zircon and Th-Pb age distributions for detrital-monazite, detrital-zircon and monazite textures (including detrital diagenetic monazite, which prove recycling), sandstone petrology, heavy-mineral abundances, and other detrital proxies are all accounted for by the following: 1) lithic arenite is directly sourced from late Neoproterozoic metasediments in the proximal Appalachian fold and thrust belt via transverse drainages, 2) the late Neoproterozoic sediments were recycled from early Neoproterozoic, post-Grenvillian clastic sequences, 3) Cambrian quartz arenites along the Laurentian margin were recycled from Neoproterozoic sequences with local cratonic input, 4) although dominated by sediment of ultimate Grenvillian age, quartz arenites require ∼ 40% of Paleoproterozoic and Archean input, interpreted to be recycled from late Neoproterozoic to Devonian clastic sequences of the northern Appalachians and/or southern (Scottish–Irish) Caledonides in the distal reaches of a longitudinal drainage system. Ordovician to Mississippian clastic sequences and their metamorphosed equivalents in the Appalachian crystalline core were also likely sediment sources. Quartz arenite does not result from mixing of lithic arenite with other sources because of differences in textural and compositional maturity, and in heavy-mineral characteristics. Input from the Laurentian craton, commonly cited as the source for Paleoproterozoic and Archean detrital zircon in the eastern Laurentian clastic systems, is untenable here because of: 1) the presence of Paleozoic monazite derived from Appalachian Neoproterozoic and early Paleozoic metasediments, 2) abundant detrital chromite, and 3) abundant Paleozoic detrital muscovite. Multiple recycling explains all observed sedimentologic and mineralogic characteristics of the two lithic types. Incorporation of published detrital-zircon data for Paleozoic to modern clastic sequences in eastern Laurentia reveals that Grenville-age zircons experienced at least five and potentially ten recycling events since entering the clastic system in the Neoproterozoic. Recycling also explains the abundance of quartz pebbles in conglomerates of the quartz-arenite lithofacies, and the range of detrital-muscovite 40Ar/39Ar ages in quartz arenites of the Appalachian Basin.
The Resende Basin (Eocene–Oligocene) is a continental taphrogenic structure associated with the Continental Rift of Southeast Brazil and includes the Itatiaia and Acácias members. While the sediment provenance of the Itatiaia member is known, such knowledge regarding the Acácias Member is lacking. This work studies U–Pb ages and Lu–Hf data analyzed by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) in detrital zircons to investigate the sandstone provenance of the Acácias Member. The results suggest that Acácias Member rocks are composed predominantly of Neoproterozoic sources (60%), significant Paleoproterozoic sources (34%), and smaller contributions from Mesoproterozoic (4%) and Archean (2%) sources. The orthogneisses of the Juiz de Fora and Quirino complexes and the metasedimentary rocks of the Andrelandia Complex and Paraíba do Sul were probably the source rocks of Archean and Paleoproterozoic materials. The metasedimentary Embú Complex may be the source of Mesoproterozoic sediments, and the granitoid bodies located south of the Resende Basin (namely, the Rio Turvo granitoid) were important Neoproterozoic origins. No Late Cretaceous ages were found in the 611 analyzed zircons, suggesting that the extensional process that originated in the basin occurred before the Itatiaia alkaline intrusions. In addition, other causes for the lack of zircon grains with the age of alkaline intrusive rocks (Morro Redondo ≈ 72–70 Ma; Itatiaia ≈ 70 Ma) is related to the basin location with a structural high. This feature could have prevented the alkaline detritus from the Itatiaia and Morro Redondo intrusive bodies from reaching the study area and restricted the supply of sediments from a fluvial system with tributaries on the northern edge. In conclusion, the U–Pb ages in the detrital zircons obtained in this work reveal that the sediments of the Resende basin were tectonically driven. Interpretations of tectonic environments that affected sediment deposition require a thorough understanding of this basin stratigraphy and factors that partitioned the sedimentary processes, such as the directions of currents and the presence of structures.
An enigmatic transition from the storm‐dominated, offshore to lower shoreface deposits of the Redwater Shale Member (Sundance Formation) to the overlying mixed tidal and aeolian Windy Hill Sandstone (Morrison Formation) in the Oxfordian of the North American Western Interior has long been a source of intrigue. Previously proposed drivers include the progradation of a large, tide‐dominated delta onto a storm‐dominated shelf, a complete reorganisation of the basin's hydrodynamics and climate, or the development of a regional unconformity (termed the J‐5). In south‐eastern Wyoming, the Redwater Shale is characterised as an offshore to distal shoreface deposit with glauconitic siltstones and sandstones punctuated by coquinoid and sandy tempestites and hosting a Cruziana Ichnofacies. The Windy Hill Sandstone, a time‐transgressive, sand‐rich, intertidal succession with classic Pteraichnus and stressed Skolithos Ichnofacies, sharply overlies the Redwater Shale and records an abrupt basinward shift in facies that accompanied at least tens of metres of sea‐level fall. New, detailed sedimentological, ichnological and architectural data collected across this transition in the study area provide fresh insights into the depositional history of these units and demonstrates the existence locally of a composite J‐5 unconformity. The unconformity developed as tectonically driven, prograding shoreline trajectories of the Redwater Shale gave way to degrading trajectories of the Windy Hill Sandstone, leading to a forced regression and formation of a regressive surface of marine erosion. The sharp juxtaposition of intertidal flat facies (Pteraichnus Ichnofacies) directly upon offshore to lower shoreface deposits (Cruziana Ichnofacies) is the key to recognising the unconformity and proves the value of the previously underutilised ichnological data.
The Guadalcazar is located in the Mesa Central (MC) province, which is mainly composed of granitic rocks and is known for its metallogenetic. The granitic rocks contain complex Sn-Hg-Ag-F mineralization and were emplaced during Eocene to Oligocene. However, the source, origin, and evolution of magma and the tectonic setting of this magmatic area have never been explained. In this study, we have conducted petrology, whole-rock geochemistry, and U–Pb zircon geochronology on granitic rocks from the Guadalcazar to constrain the petrogenesis and tectonic environment. LA-ICP-SF-MS zircon U–Pb dating shows that the Guadalcazar granite was emplaced ca. 31 Ma. These rocks are characterized by high (SiO2) contents (64–75 wt%), low CaO (0.28–1.78 wt%), with relatively high (FeOt)adj/(FeOt + MgO) values ranging from 0.90 to 0.98. The geochemical diagrams of SiO2 vs [(FeOt)/(FeOt + MgO)] and SiO2 vs [(Na2O + K2O) − CaO] show the ferroan and mostly alkali-calcic nature of these rocks. The granite shows an A2-type affinity and is strongly peraluminous, with ASI (molar Al2O3/[CaO + Na2O + K2O]) values of 1.13 to 2.60. These granitic rocks are characterized by enrichments in rare earth elements (REE) and high field strength elements (HFSE), and depletion in Ba, Nb, Sr, Ti, and Eu. These features suggest that these A-type granites were derived from the metasedimentary rocks and evolved through extensive fractional crystallization. The multidimensional discrimination diagrams showed a continental rift or within-plate setting. By combining previous and new data, we proposed a new magmatic evolution model that supports an extension during ca. 34–28 Ma in the Guadalcazar, central Mexico.
Archean and Paleoproterozoic granitoids with different geochemical affinities are widely distributed in the basement of high-grade metamorphic rocks of the Bacajá Domain, which consists of Rhyacian granite-greenstone terrain with Archean-Siderian fragments, one of which is in the southeastern Amazonian Craton. Understanding the diversity of these rocks in the geological record is essential to improve the evolution of knowledge of the Amazonian Craton. Thus, this work presents petrographic, geochemical, and geochronological (U-Pb LA-ICP-MS in zircon) data on granitoids of the São José Complex, Canaã Granite, Sant’Ana Granodiorite and Uirapuru Granite, that occur in the northwestern of the Bacajá Domain. São José Complex is composed of biotite tonalites and granodiorites slightly peraluminous from medium to high-K, magnesian and I-type affinities. One U-Pb zircon age was obtained at 2502 ± 6 Ma, which may represent a subduction magmatism in pre-collisional stage arc environment prior to the Transamazonian Orogeny, formed from the melt of Archean crustal sources and amphibolitic rocks. The granitoids like Canaã Granite, Sant’Ana Granodiorite and Uirapuru Granite are composed of weakly metaluminous to peraluminous monzogranites, granodiorites with subordinate tonalites and syenogranites, with high SiO2 and K2O contents and high-K calc-alkaline to shoshonitic affinities, of ferroan I-type and A-type. The age of 2124 ± 7 Ma was obtained for the Sant’Ana Granodiorite, which may indicate its formation in syn- to post-collisional environments related to magmatic episodes of the Transamazonian Orogeny. The granodiorite was crystallized from partial melt of crustal sources derived from intermediate rocks such as tonalites and psammitic gneisses that occur in the region.
The basin type of the Junggar Basin changed during the Permian, but the time constraint of the tectonic evolution remains unclear. Besides, the fan deltas developed in the Permian in the Mahu Sag in the northwestern of the oil-rich basin. However, the provenances of the sedimentary systems remain unclear. Based on petrology and detrital zircon U-Pb ages, this study investigates the source-to-sink systems evolution and tectonics implications. Abundant lithic clasts in sandstones with low compositional and textural maturity imply proximal sources. The dating results showed a dominant peak (310–330 Ma) and a secondary peak (400–440 Ma) in the northern Mahu Sag, only one peak at 295–325 Ma in the central Mahu Sag, several peaks at 270–350 Ma in the southern Mahu Sag, and multiple peaks at 370–450 Ma in the Zhongguai Uplift. Thus, the north-western Junggar Basin was divided into four major source-to-sink systems, with adjacent central West Junggar as the main provenance and northern and southern West Junggar as the secondary provenance. The proportion of sediment supply from the southern and northern West Junggar is higher during the Middle-Late Permian. It suggests that the source-to-sink systems show inheritance and evolve from a single provenance into a complex provenance, indicating the uplift of West Junggar. The tectonic inversion may occur early in the Middle Permian and the response to tectonic activity is stronger in the southern West Junggar than in the northern West Junggar.
The Resende Basin (Eocene-Oligocene) is a continental taphrogenic structure associated with the Continental Rift of Southeast Brazil and includes the Itatiaia and Acácias members. While the sediment provenance of the Itatiaia member is known, such knowledge regarding the Acácias Member is lacking. This work studies U-Pb ages and Lu-Hf data analyzed by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) in detrital zircons to investigate the sandstone provenance of the Acácias Member. The results suggest that Acácias Member rocks are composed predominantly of Neoproterozoic sources (60%), significant Paleoproterozoic sources (34%) and smaller contributions from Mesoproterozoic (4%) and Archean (2%) sources. The orthogneisses of the Juiz de Fora and Quirino complexes and the metasedimentary rocks of the Andrelandia Complex and Paraíba do Sul were probably the source rocks of Archean and Paleoproterozoic materials. The metasedimentary Embú Complex may be the source of Mesoproterozoic sediments, and the granitoid bodies located south of the Resende Basin (namely,the Rio Turvo granitoid) were important Neoproterozoic sources. No Late Cretaceous ages were found in the 301 analyzed zircons, suggesting that the extensional process that originated in the basin occurred before the Itatiaia alkaline intrusions. In addition, other causes for the lack of zircon grains with the age of alkaline intrusive rocks (Morro Redondo ≈72-70 Ma; Itatiaia ≈70 Ma) may have been related to the basin location with a structural high that could have prevented the alkaline detritus from the Itatiaia and Morro Redondo intrusive bodies from reaching the study area and restricted the supply of sediments from a fluvial system with tributaries on the northern edge. In conclusion, the results of this work reveal that U-Pb ages in detrital zircons reveal a tectonic-driven of the Resende basin sediments. In this way, interpretations of tectonic environments that affected sedimentation require a thorough understanding of the lithological units that compose the basin stratigraphy and factors such as the directions of currents and the presence of structures that compartmentalized sedimentary processes.
We report new coupled zircon U-Pb age and Hf isotope data, along with whole-rock Hf-Nd isotope data for 20 samples from the Priest River and Clearwater complexes—Neoarchean and Paleoproterozoic basement exposures in northern Idaho, northwest Laurentia. The new zircon data reveal two well-defined periods of magmatism at ∼ 2.66 and ∼ 1.86 Ga in each complex, with no evidence of any intervening or older magmatic events. Positive zircon initial εHf values of the Neoarchean rocks (+1 to +3) indicate juvenile magmas derived from a depleted mantle source. The Paleoproterozoic rocks, in both complexes, share a much wider range of initial zircon εHf values (−7 to +6) which suggests magmas derived from a depleted mantle source intruded and assimilated pre-existing Neoarchean continental crust. The shared age and isotope compositions in the Priest River and Clearwater complexes suggest that the two complexes likely belong to a single crustal block—the Clearwater block.
Based on these new zircon U-Pb ages and Hf isotopic data of the Neoarchean and Paleoproterozoic rocks, the Clearwater block is shown to be distinct from the nearby Wyoming Province, the Medicine Hat block, and components of the Great Falls tectonic zone. We also report new zircon Hf isotope data for the ∼ 1.58 Ga Laclede orthogneiss in the Clearwater block, which along with published U-Pb and Hf isotope constraints, support a paleogeographic connection between the Gawler craton, East Antarctica, and northwestern Laurentia during ∼ 1.9 Ga to ∼ 1.6 Ga. Comparison with other examples of co-existing Neoarchean and Paleoproterozoic igneous rocks present in other continents suggests that the global record of 2.7–2.5 Ga magmatism often represents new crustal additions from a depleted mantle reservoir. The record of 2.0–1.7 Ga rocks also represent additions of juvenile magma, but with significantly larger contributions from pre-existing continental crust. In many cases the 2.0–1.7 Ga crust preserved on Earth today was added during the assembly of the supercontinent Nuna.
Depositional models for retroarc foreland basin systems commonly imply a direct link between thrust belt dynamics and sediment supply, despite documented complexity between orogen‐transverse and orogen‐parallel (axial) sediment routing systems. Previous detrital zircon provenance studies from the Straight Cliffs Formation in the Kaiparowits Plateau of southern Utah indicate primary axial source areas to the south (Mogollon Highlands), and southwest (Cordilleran magmatic arc), with relatively minor transverse input from the Sevier fold‐thrust belt to the west. Complementary data from 32 new samples are presented to investigate whether these trends persist in correlated strata from sections most proximal to the active fold‐thrust belt, as well as strata proximal to the Mogollon Highlands. This study aims to improve statistical robustness through higher‐n datasets (>300 analyses/sample) and addresses the possibility of recycling of zircon grains from strata in the exhumed Sevier fold‐thrust belt. Based on this provenance dataset, we infer that orogen‐transverse deposition was mainly limited to the most proximal sections (within ~75 km of the fold‐thrust belt), but included episodic distribution across the foredeep that was associated with distinct intervals of widespread amalgamated sand and gravel sheet deposits. In contrast, more distal parts of the foredeep record long‐distance fluvial transport (>400 km) of zircons from the active Cordilleran magmatic arc as well as Yavapai‐Mazatzal basement rocks in central Arizona (the Mogollon Highlands). Paleogeographic reconstructions suggest the apex of a large basin‐axial fluvial system may have been located at the structural syntaxis between the Sevier fold‐thrust belt and western margin of the Mogollon Highlands. This interpretation is supported by detrital zircon data presented here, thus extending the possibility that the Paleogene “California River” may have existed by at least Late Cretaceous time. Ultimately, these data point to extrabasinal controls on sediment supply, which was largely decoupled from flexural accommodation controls in this archetype retroarc foreland basin.
The Rupnica geosite, a key locality of the UNESCO-protected Papuk Geopark in northern Croatia, is well-known for an excellent exposure of columnar jointing in volcanic rock. This rock is defined as an albite rhyolite that comprises almost pure albite phenocrysts within a fine-grained matrix composed of microphenocrysts of albite, quartz and devitrified volcanic glass. Primary accessory minerals are clinopyroxene, apatite, zircon and magnetite. Haematite, apatite and anatase were found as inclusions in zircon. The albite rhyolite is characterized by a highly siliceous, peraluminous, oxidized (ferroan), dry, alkali-calcic to alkalic composition, with low CaO, MgO, and MnO contents and high FeOT/(FeOT+MgO) ratios. Normalized trace element contents display positive anomalies of K, Pb, and Zr as well as negative anomalies of Nb, P, Ti, Ba and Eu, together with an enrichment of light rare-earth elements (REE) relative to heavy REE. Zircon from the rhyolite of Rupnica is characterized by ratios of Th/U=1.13 and Zr/Hf=55 and contents of HfO2=1.04 wt. % typical for an early-stage igneous zircon crystallized from a dry high-temperature magma in a deep magma chamber. Apatite REE patterns show enrichment of light REE over heavy REE and a pronounced Eu anomaly, typical for apatite from granitoids formed in an oxidizing environment. The magma is of A-type and was generated at high temperatures at 800–900 °C by partial melting of lower- to mid-crustal rocks. The age of the albite rhyolite of Rupnica is Late Cretaceous at 80.8±1.8 (2σ) Ma, according to U-Pb dating of zircon, coeval with geochemically similar igneous rocks of Mt. Požeška Gora and Mt. Kozara within the Sava Zone.
Abstract
The age and provenance of the Norphlet Formation in south Texas and its
stratigraphic relationship with the Louann Salt is documented for the first time
using new detrital zircon U-Pb geochronological data. Nine samples from the Hockley
salt diapir and four deep wells (three in south Texas, one offshore México) yielded 1001
zircon ages and eight age populations; most important are: Neoproterozoic (900-541
Ma), Cambrian-Middle Mississippian, and arc-related Middle to Late Mississippian-
Permian-Triassic and Triassic-Jurassic, the latter two representing the first evidence of
Nazas and Guerrero arc extrusive volcanism reaching south Texas. Statistical analyses
of these data and published zircon ages support the interpretation that these age
populations reflect the dominance of peri-Gondwanan sources, especially the
Yucatán/Maya Block and Coahuila terrane, though Laurentian sources likely contribute
to specific populations.
The maximum depositional age of upper Norphlet Formation sandstones
is 165.5 ± 1.5 Ma (Callovian). These upper sandstones are separated from lower
Norphlet sandstones by an unconformity spanning 1.5 – 5 Myr; the lower sandstones
are interbedded with halite of the Louann Salt, and may be as old as Bathonian. These
new data may be of regional significance when applied to future models of the Jurassic
evolution of the Gulf of Mexico.
This is a comprehensive inventory of paleontological resources in Grand Canyon-Parashant National Monument.
A review of the geology of the upper Paleozoic succession in the Sverdrup Basin, including tectonic setting, volcanics, stratigraphy, lithofacies, diapirs, reefs, etc. based in large part on authors' field work; subsurface and seismic data from corporations and published literature.
Outcrops in Cañones de la Peregrina and de Caballeros near Ciudad Victoria, Tamaulipas, México, consist of the Grenville-age (1,018 Ma) Novillo gneiss. The second overlying strata are composed, in ascending order, of: (1) the Cañón de Caballeros Formation (Silurian) consisting of conglomerate, silicic volcanic arenite, limestone, and sandstone and siltstone; (2) the Vicente Guerrero Formation (Lower Mississippian), consisting of quartz and lithic arenite, siltstone, and shale; (3) the El Aserradero Rhyolite (Mississippian, a 334 ± 39-Ma U-Pb zircon age); (4) the unconformably overlying Del Monte Formation (Lower and Middle Pennsylvanian), consisting of bioclastic grainstone, sandstone, and limy sandstone; (5) the Guacamaya Formation (Lower Permian), consisting of turbiditic siltstone and sandstone rich in volcanic detritus; and (6) unconformably overlying Jurassic and Cretaceous conglomerate, limestone, siltstone, and sandstone. The Cañón de Caballeros and the Vicente Guerrero Formation are each about 100 m thick; the Del Monte Formation, about 200 m thick; and the Guacamaya Formation, about 1,260 m thick. An extensive fauna of brachiopods, gastropods, trilobites, and corals from the Silurian Cañón de Caballeros Formation has been assigned to the European Province of the North Atlantic Region, a non-North American fauna. The Silurian fauna is similar to that in the allochthonous West Avalonia terrane in eastern coastal North America, to fauna in Venezuela, and to fauna in northwest Africa, Europe, the British Isles, and Scandinavia. The Silurian fauna in the Ciudad Victoria area is most similar to fauna in the Cordillera de Mérida in Venezuela. The original distribution of the fauna of the European Province appears to have been along the South American-northwest Africa margin of the supercontinent Gondwana, and at that time, adjacent Baltica, and separate from the Laurentian (ancestral North American) continent. This pattern suggests that the Ciudad Victoria Silurian strata were derived from somewhere along this margin of Gondwana (most likely near Venezuela) and were transported tectonically to their present position near ancestral North America. The emplacement of the Ciudad Victoria rocks against ancestral North America probably took place in the late Paleozoic. Mississippian igneous and deformational events noted in the Paleozoic succession near Ciudad Victoria and in the southern United States may indicate the initial events of this tectonic activity. The rocks of the Ciudad Victoria area were apparently rifted from South America and left in their position near ancestral North America when South America separated from Laurentia during the Mesozoic break-up of the supercontinent Pangea.
These dunes formed with a variable vegetation cover, and display a gradient of former mobility with greatest mobility in the driest part of the dunefield. The dune sands were largely derived from alluvium, although foraminifera in the sands indicate a contribution from the Arabian Sea. As today, sand moved in response to the southwest monsoon in summer. Evidence from archaeological sites, radiocarbon and thermoluminescence dating shows that the dunes were accumulating from at least 20 000 BP and were stable by the middle to late Holocene. The continuation of dune construction into the Holocene distinguishes the Thar from other mid-latitude dunefields. -after Authors
Neoproterozoic fluvial quartzarenites from the Shaler Group on Victoria Island in the western Canadian Arctic yield a diverse suite of detrital zircons. U-Pb ages from single zircons fall into three modes: Archean (3.01-2.62 Ga), Paleoproterozoic (1.97-1.84 Ga), and Meso proterozoic (1.64-1.03 Ga). Particularly intriguing is the unusually high proportion (50%) of the Mesoproterozoic mode, as the nearest exposed source is the Grenville structural province, ˜3000 km southeast of Victoria Island. Unimodal northwest paleocurrents, obtained from cross-bedding, are compatible with a southeasterly provenance. These data, supported by sedimentological evidence from the Shaler Group and from correlative strata in the northwestern Canadian Cordillera, imply the existence of a large, perennial river system flowing north-westward from the Grenville orogen. An analogy with the Llanos drainage basin in Venezuela and Colombia is proposed on the basis of similar geography, climate, and sedimentation. These data also provide a maximum age for the Shaler Group (basal Reynolds Point Formation) of about 1.11 Ga.
Mature quartz-rich sandstone interbedded with Mesozoic magmatic-arc strata in southern Arizona has been previously considered correlative with the eolian Pleinsbachian to Toarcian Navajo Sandstone on the Colorado Plateau. New U-Pb zircon data from the Mount Wrightson Formation in the Santa Rita Mountains and from the strata of Cobre Ridge in the Pajarito Mountains and in the Arivaca area in southern Arizona support the hypothesis that sand derived from the Navajo Sandstone probably did gain access to the magmatic arc and further indicate that sands extending from younger eolian units on the Colorado Plateau are probably present as well. -from Authors
North American Ordovician strata record a large shift in their neodymium isotopic composition ( ) at around Nd period before orogenic sources became dominant. We conclude from this that, superimposed on a general westward regional shift in sediment sources with time, there were also complex local effects involving multiple (unmixed) sediment sources that persisted long after the initial pulse of orogenic material arrived. The combined "simultaneous" nature of the isotopic shift, an Ordovician sea-level high stand, and the emergence of the Appalachian-Taconian- Caledonian orogenic belt as a primary sediment source, leads us to conclude that by 450 Ma, seafloor south of North America was being supplied by well-mixed, isotopically homogeneous sediment delivered from uplifted fold-thrust belts and foreland basins of the Appalachian Taconian highlands. U-Pb detrital zircon ages from bracketing sandstone units reinforce the Nd evidence for a complete changeover in provenance between 465 Ma (abundant Archean-age zircons) and 440 Ma (no Archean-age zircons) in the Ouachita region.
(A) Allegheny region, by Henry L. Berryhill, Jr (B) Gulf Coast region, by Eleanor J. Crosby (C) West Texas Permian basin region, by Steven S. Oriel, Donald A. Myers, and Eleanor J. Crosby (D) Northeastern New Mexico and Texas-Oklahoma Panhandles, by George H. Dixon (E) Oklahoma, by Marjorie E. MacLachlan (F) Central Midcontinent region, by Melville R. Mudge (G) Eastern Wyoming, eastern Montana, and the Dakotas, by Edwin K. Maughan (H) Middle Rocky Mountains and northeastern Great Basin, by Richard P. Sheldon, Earl R. Cressman, Thomas M. Cheney, and Vincent E. McKelvey (I) Western Colorado, southern Utah, and northwestern New Mexico, by Walter E. Hallgarth (J) Arizona and western New Mexico, by Edwin D. McKee (K) West Coast region, by Keith B. Ketner References cited (284pp) This professional paper is a supplementary volume to "Paleotectonic Maps of the Permian System" by McKee, Oriel, and others (1967), published by the U.S. Geological Survey as Miscellaneous Geologic Investigations Map I-450. The I-450 publication consists of 20 plates isopach and lithofacies maps, cross sections to accompany the maps, and interpretive and environmental maps and a summary of available geological information on each part of the Permian Period, an interpretation or reconstruction of Permian history, and brief discussions of environment, tectonics, and other significant features. The present volume explains and documents the maps and conclusions presented there. This study of the Permian System was made by 15 geologists, who were individually responsible for coverage of 18 regions. These authors are: Henry L. Berryhill, Jr. • Walter E. Hallgarth • Vincent E. McKelvey • Thomas M. Cheney • Keith B. Ketner • Melville R. Mudge • Earl R. Cressman • Marjorie E. MacLachlan • Donald A. Myers • Eleanor J. Crosby • Edwin K. Maughan • Steven S. Oriel • George H. Dixon • Edwin D. McKee • Richard P. Sheldon The Permian System of the 18 regions is described in 11 chapters. Each chapter presents an analysis of the basic data used, points out significant trends, and presents an interpretation, as well as alternative explanations where each occur, for the region concerned. The chapters and accompanying illustrations were coordinated and assembled by E. J. Crosby, E. D. McKee, W. W. Mallory, E. K. Maughan, and S. S. Oriel. Descriptive and documentary data are organized according to region, from east to west, and according to chronological sequence. Each chapter discusses, in order, rocks that underlie the Permian, the several intervals or divisions of the Permian (from oldest to youngest (table 1, in pocket)), and, finally, the rock units that directly overlie the Permian. Stratigraphic problems, the nature of contacts, trends in thickness and lithology, possible sources of sediment, environments of deposition, and paleotectonic implications of each interval are treated in that order.
Thick sequences of Lower Jurassic rhyolitic and andesitic volcanic rocks in several mountain ranges of southern Arizona contain interbedded quartzarenites. Locally up to 250 m thick, these sandstone lenses, composed of well-sorted and well-rounded quartz grains, commonly contain large-scale cross-stratification and are considered to be eolian sand deposits. The eolian sands were blown up against the continental side of the Early Jurassic volcanic arc that trended northwest-southeast across the southwestern margin of the North American continent and/or plate at that time. Paleocurrent data suggest southerly eolian transport of the sands from the Colorado Plateau area. Correlation of these sandstones with the Lower Jurassic Navajo and Aztec Sandstones is indicated by the pa eocurrent data as well as radiometric dating of the interbedded volcanics. Eolian sand transport southward across central Arizona in the Early Jurassic indicates that the Mogollon highlands either did not then exist, or were merely low, discontinuous inselbergs on a broad back-arc ramp, more appropriately called the Mogollon slope.
Provenance interpretations can be used in conjunction with other evidence to test alternate paleogeographic and paleotectonic reconstructions. Where crustal blocks have moved as parts of mobile lithospheric plates, detritus transported from one block to another may record the times during which the two blocks were adjacent. Where orogenic belts are deeply eroded, sediment shed into nearby basins may record the former existence of rock masses removed by erosion from orogenic highlands.
Sediments derived from different types of provenance terrane display contrasting petrofacies, but petrofacies of mixed provenance are common because dispersal paths connecting sediment sources to basins of deposition may be complex. Consequently, the geodynamic relations of different types of sedimentary basins as revealed by their overall morphology, structural relations, and depositional systems do not predict reliably the nature of the petrofacies that some basins contain. Adequate evaluation of sedimentary linkages between varied provenances and basins requires improved understanding of regional paleo-geomorphology and an integrated view of global sediment dispersal.
Sediment dispersal is controlled by distributions of continental blocks and oceanic basins with margins of varying tectonic character, diverse climatic regimes related to paleolatitude and to changing patterns of seas and land-masses, configurations of subduction zones and associated orogenic belts, and locations of large rivers draining highlands and traversing lowlands. Conceptual models that integrate megageomorphology with paleotectonics are thus needed to infer past global patterns of sediment dispersal.
At present, the sinuous world rift system is an interconnected network of linked segments, and the two principal orogenic belts follow portions of two great circles. If the present is a key to the past, these relationships afford potential means to predict the arrangement of continental blocks, oceanic basins, drainage systems, and dispersal paths associated with global paleotectonic regimes. Provenance studies of selected sedimentary assemblages can be used to test reconstructions.
The Lower Permian (Leonardian) Yeso and correlative formations in New Mexico consist of 100 to 600+ m of marine and nonmarine siliciclastic, carbonate, and evaporite rocks deposited during the waning stage of the Ancestral Rocky Mountain deformational event. During "early" Yeso time, the north-central and northwestern parts of the state were occupied by small, ephemeral streams and an eolian dune field, respectively, while an eolian sand sheet spread across the west-central part of the state and loess mantled part of northeastern New Mexico. Marine carbonate deposition predominated in the Delaware and Pedregosa basins in the southeastern and southwestern parts of the state, respectively, while north of the Delaware Basin, on the Northwest Shelf, shoreline and shallow-marine siliciclastic, carbonate, and evaporite sediment was deposited and eolian sand and silt periodically spread to the edge of the Delaware Basin. During "medial" Yeso time, shoreline and shallow-marine lithofacies were deposited in all but the northernmost part of the state, while during "late" Yeso time, an eolian sand sheet prograded southward into west-central New Mexico. The major basement-cored uplifts of the Ancestral Rocky Mountains were worn down and onlapped during early Leonardian time and there is little evidence for differential subsidence of basins previously active in late Pennsylvanian and Wolfcampian time. Transgression, regression, and subsequent transgression in Leonardian time are indicated in the Yeso and overlying Glorieta and San Andres formations, while a climate more arid than during the earlier Wolfcampian age promoted widespread eolian and evaporite deposition in early Leonardian time.
Quartzose sandstones of latest Silurian to middle Devonian form the basal part of four unconformity-bounded, carbonate-dominated shelf successions of the Alberta Basin in the Rocky Mountains of northeastern British Columbia - the Muncho-McConnell, Stone, Dunedin and Slave Point formations. Twenty-nine single grain analyses from four different samples yielded a distinctive suite of U-Pb ages that are indistinguishable regardless of paleogeographic setting and closely match the ages of basement terranes that underlie the Peace River Arch in the autochthon to the east. These data support derivation of sediments of both basinal and shelf association from the same source: the emergent Peace River Arch area to the east. Alternatively, to account for the northeasterly-directed paleocurrents, Dunedin-equivalent quartzose sandstones of the basinal association could have been derived from the west and acquired their detrital zircon provenance signature by recycling pre-Devonian sandstones. -from Authors
The Neoproterozoic Cadomian orogenic belt of the North Armorican Massif, France, records the amalgamation of calc-alkaline magmatic-arc complexes and marginal basin successions along an active plate margin peripheral to the Gondwanan craton. Subduction-related magmatism and associated tectonothermal activity spans the period ca. 700-540 Ma. The Cadomian orogen is divided into tectonic units that were amalgamated at a late stage in the orogeny, mainly as a result of strike-slip displacements. There is no evidence for major crustal thickening and associated high-pressure metamorphism. It is therefore unlikely that Cadomian orogenesis resulted from continent-continent collision. Mesozoic-Cenozoic active plate margins such as the Andes and the East Indies that are characterized by prolonged periods of ocean-continent convergence may provide appropriate analogies for the evolution of the Cadomian orogen. Tectonic processes within such active plate margin settings are controlled by various parameters, including dip of the subducting slab, angle of plate convergence, and convergence velocity across the subduction zone. The tectonic and magmatic evolution of the Cadomian belt was likely controlled by combinations of these factors.
The Armorican Massif north of the North Armorican Shear Zone mainly comprises rocks emplaced and tectonized during the Late Proterozoic Cadomian orogeny. As these rocks were only weakly affected by later Variscan events, this is one of the few regions where it is possible to study the Pan African basement of Europe. Three domains are distinguished: Saint-Brieuc/Trégor, Saint-Malo/Guingamp and Mancellian, of which only the first two are fully exposed in northern Brittany. The Saint-Brieuc/Trégor Domain consists mainly of metamorphosed magmatic and sedimentary units and includes remnants of an old "Icartian" basement (ca. 2 Ga) in its northern part. Published and new geochronological data show that this domain experienced at least four different magmatic events between 750 Ma and 580 Ma. Local outcrops of trondhjemitic gneiss dated between 746 Ma and 656 Ma, and associated basic rocks, attest to early arc-type magmatism. Around 620(?)-615 Ma intermediate to acidic high-K calc-alkaline lava and plutonic rocks were emplaced in the north; the geochemical and isotopic data suggest the involvement of an old enriched crustal source in the magma genesis. Between ca. 615 Ma and 588 Ma, two types of volcanic suite were produced. (a) Basic to intermediate rocks with continental tholeiite affinities were emplaced probably between 610 Ma and 615 Ma and at ca. 588 Ma. These suites include many intermediate to acidic rocks of tholeiitic to calc-alkaline affinity, which trace-element modeling suggests were derived from the basic magma by fractional crystallization and assimilation of crust. (b) At ca. 610 Ma, basic lavas with arc-affinities were emplaced. Variable incompatible element ratios between the two suites suggest derivation from different mantle sources. Basic to intermediate plutonic massifs were emplaced at 595 Ma and 581 Ma; some gabbroic rocks dated at 581 Ma show geochemical characteristics of plagioclase cumulates. A direct relationship between magmatism and a subduction process for the period 620-581 Ma can be postulated for the basic rocks with arctholeiitic affinity and for part of the 595 Ma old pluton. The Saint-Malo/Guingamp Domain is composed of low-grade metasediments, mica schist, leucogranite and well-developed migmatite and anatexite. Few isotopic ages exist for this domain. A new crystallization age of 555 ± 16 Ma for the Cancale granite (east of the Baie de Saint-Brieuc) is consistent with an earlier date of 540 Ma for the neighboring migmatite and anatexite. Two episodes of progressive deformation and metamorphism have been distinguished within the Cadomian domain. At 580-570 Ma, the Saint-Brieuc/Trégor Domain was affected by low-pressure to medium-pressure metamorphism and a pervasive deformation that accommodated broadly north to south shortening; no nappe stacking is indicated within the domain. During this event, an upper amphibolite facies metagabbro unit was uplifted along the southern edge of the Saint-Brieuc/Trégor Domain. This major tectonic contact (Main Cadomian Shear Zone) has a thrust component, but little is known of its kinematics at ca. 580-570 Ma. A major sinistral transcurrent event at 550-540 Ma is clearly evident east of the Baie de Saint-Brieuc, synchronous with crystallization of the migmatite and anatexite. West of the bay, we consider the sinistral kinematics to have been partly accommodated by local west-northwest-directed reverse shearing and suggest that the North Armorican Shear Zone was active during this event as a major zone of sinistral strike slip. Local extension is evident within the migmatite and leucogranite of the western part of the Saint-Malo/Guingamp Domain. Its age is not known, but it is likely to have been active just after the main deformation of the Saint-Brieuc/Trégor Domain. No high-pressure metamorphic assemblages have been reported in the French Cadomian belt, consistent with the lack of evidence of thrust nappe stacking. We conclude, therefore, that in northern Brittany, no significant thickening occurred during the Cadomian collision.
We collected 35 sandstones and metasandstones for analysis of detrital zircons from Paleozoic and Triassic strata in suspect terranes of northern Nevada and northern California that represent five generic petrofacies: subarkose eroded from uplifted continental basement, quartzarenite (matrix-poor and matrix-rich subfacies) derived from cratonal sources, quartzolithic (quartz-rich, chert-rich, and quartzolithic-volcaniclastic subfacies) derived from recycled orogenic sources, volcaniclastic from volcanic arc structures, and volcanoplutonic from a dissected magmatic arc. Precambrian ages of dominant detrital zircons in the subarkose petrofacies (exclusively Harmony Formation of Cambrian age) and in most samples of the lower to middle Paleozoic quartzarenite petrofacies in the Roberts Mountains allochthon, the Shoo Fly Complex, and the Yreka terrane reflect a provenance in northern Laurentia or a continental block other than Laurentia. Samples from the lower part of the Vinini Formation in central Nevada are the only examples of the quartzarenite petrofacies yielding zircon populations that could have been derived from adjacent southwestern segments of Laurentia. Dominantly Grenville-age zircons in subordinate quartzose sandstones from the mainly subarkosic Harmony Formation suggest derivation from farther south along the Cordilleran continental margin. Zircons in the quartzolithic petrofacies were largely recycled into varied Paleozoic-Mesozoic overlap assemblages and successor basins, including the Havallah sequence of the Golconda allochthon, from older sedimentary sources in lower to middle Paleozoic strata of underlying or nearby terranes. Phanerozoic zircons in the upper Paleozoic to lower Mesozoic volcaniclastic petrofacies of the Sierran-Klamath belt reflect sources in coeval or older volcanic arc assemblages, with homogeneous age populations in each sample. Latest Precambrian and Grenville-age zircons in the volcanoplutonic petrofacies (one sample from the Sierra City mélange) reflect sources in a magmatic arc that was not part of the Cordilleran miogeoclinal margin. The close correlations between petrofacies compositions and the age spectra of detrital zircon populations provide significant and consistent constraints for interpretations of regional tectonic history, the two datasets jointly offering more interpretive insight than either affords alone.
The Nashoba Block, the northern portion of the Putnam-Nashoba terrane, is a fault-bounded fragment of Late Proterozoic to early Paleozoic crust located in eastern Massachusetts. The Marlboro and Nashoba gneisses of the Putnam-Nashoba terrane are composed of a sequence of mafic, intermediate, and felsic volcanic, volcanogenic, and probable plutonic rocks. This sequence was intruded by plutons ranging in composition from granite to gabbro. Major and trace element data for the Marlboro and Nashoba gneisses and some of the granitic plutons are consistent with formation in a calc-alkaline arc setting; some of the later granitic plutons are probably the result of crustal anatexis. The gabbroic plutons are slightly alkaline. U-Pb zircon age determinations for the Marlboro and Nashoba gneisses indicate ages ranging from 584 ± 8 to 425 ± 2 Ma, but most are in the range 473 to 430 Ma. These ages indicate that significant arc volcanism occurred during Late Ordovician and Silurian time in an ocean basin separating Laurentia and Avalonia as Avalonia progressed toward its eventual collision with and accretion to Laurentia. A metamorphic and deformational event, interpreted to record the docking of the Putnam-Nashoba terrane (volcanic arc) with Laurentia as the Boston-Rhode Island terrane (Avalonian fragment) impinged upon it, is constrained by a 425 ± 3 Ma monazite age for the Fish Brook gneiss and the ca. 390 Ma ages of the Straw Hollow diorite and Salem gabbro-diorite. These mildly alkaline mafic plutons, which intrude the Putnam-Nashoba terrane and the Boston-Rhode Island terrane, respectively, are members of a group of roughly contemporaneous intrusions that yield ages from 430 ± 5 to 385 ± 10 Ma. The ages and chemical similarity of these intrusions support the interpretation that the two terranes were proximal to each other by Early Silurian to Late Devonian time. The 360 ± 9 Ma syntectonic, peraluminous Andover Granite and the 349 ± 4 Ma calc-alkaline phase of the Indian Head Hill granite indicates additional igneous activity in Early Mississippian time. Later metamorphism of rocks of the Putnam-Nashoba terrane was presumably due to changing pressure-temperature conditions during oblique overthrusting and subsequent unroofing of the Putnam-Nashoba terrane during tectonic shuffling of the accreted Nashoba and Boston-Rhode Island terranes outboard of the Laurentian margin during the approach and collision of Gondwana. An important event was the migmatization of the Fort Pond and Beaver Brook members of the Nashoba gneisses about 340 Ma.
New evidence consisting, in part, of sand features visible on Landsat imagery of desert regions, and surface wind data from well-equipped weather stations, supports suggestions that geologically significant quantities of sand are blown long distances across modern deserts by wind action. Analyses of regional trends in direction and potential amounts of sand drift indicate that some present-day eolian sand seas are in zones of low total effective (sand-moving) wind energy along the general direction of sand drift in any particular region. These zones in which drifting sand can accumulate to form sand seas are created by interactions of topography and wind regime, or by changes in climate along the direction of sand drift. -from Authors
Siliciclastic strata of Triassic age that are exposed in the Rocky Mountains have been sampled for isotopic studies in order to determine their provenance. Sm-Nd analyses of whole rock shale and sandstone samples from northeast British Columbia and the Bow Corridor of western Alberta are isotopically homogeneous with εNd values of -6.7 to -10.5 at the time of deposition. These values are part of a distinct isotopic provenance signature that characterizes the Devonian through Jurassic of the miogeocline of western Canada and thus the sources of Triassic sediments are part of a larger provenance signature within the miogeocline. These isotopic data do not support sediment derivation from the exposed Canadian Shield and our present working model is that most of the sediment is detrital material reworked from the Innuitian (Ellesmerian) clastic wedge. No evidence has been found in the Nd data to suggest that magmatic arc rocks of Triassic age to the west of the miogeocline (e.g., Quesnellia) made any contribution to the sediment record. U-Pb geochronology of detrital zircons from Triassic sandstones in the Pine Pass and Kananaskis areas are dominated by Precambrian grains with only a few Silurian grains. Comparison with detrital zircons dated from the Devonian Ellesmerian clastic wedge of Arctic Canada show a similar pattern and strengthen the contention that sedimentary strata of the western miogeocline were derived from reworking of Innuitian clastic strata which must have been formerly more widespread and covered the Canadian Shield.
The Suwannee terrane in northeastern Florida contains a group of calc-alkaline volcanic rocks (basaltic andesites to rhyolites) with elemental and isotopic signatures indicative of eruption within a continental arc environment. Uranium-lead zircon geochronology indicates a crystallization age of 552 ± 8 Ma for a dacite from this sequence; this is equivalent to crystallization ages of 551 Ma determined for samples of Osceola granite in central Florida but is younger than a 625 ± 2 Ma age determined for a granodiorite in the northwestern Suwannee terrane (southern Alabama). Suwannee terrane magmatism is generally coeval with magmatism in the Avalon and Carolina terranes as well as with Neoproterozoic orogenic events in West Africa and northern South America. The Sm-Nd depleted mantle model ages for Suwannee terrane volcanic rocks range from 1040 Ma to 1580 Ma with initial eNd values of +1.1 to -4.1, suggesting the magmas were derived from lithosphere of similar composition to that of the Grenville orogenic belt, although evidence also exists for Archean basement within an adjacent portion of the Suwannee terrane to the south.
This paper summarizes the stratigraphic and structural styles of Sverdrup basin rocks, interprets those styles and the chronology of events in the form of a model of basin evolution, and examines hydrocarbon prospects in the light of that model. Because of deep burial, widespread and long-lasting mafic intrusion, and subsequent great uplift, hydrocarbon prospects in the eastern and central parts of the basin are significantly less attractive than in the western part, where source rocks are not widely intruded, and evaporite migration (halokinesis) developed some structures that were not subsequently breached.
U-Pb zircon ages have been determined for several Late Proterozoic igneous units near Boston, Massachusetts, in the Avalon Zone of southeastern New England. Crystallization ages are 599 ± 1 Ma for the Westwood Granite, 596 ± 2 Ma for rhyodacite from the Mattapan Volcanic Complex and 589 ± 2 Ma for quartz diorite, which intrudes the Westwood Granite. These results together with published ages from granites of the Dedham Granite, the Esmond-Milford plutonic suite, and granitic gneisses in Massachusetts and Rhode Island fix Avalonian arc magmatism in southeastern New England between ca. 625 and 589 Ma, an interval diachronous with respect to sub-duction-related plutonism and volcanism in other northern Appalachian Avalonian terranes.
It is generally agreed that significant portions of the Appalachian and Cordilleran orogenic belts in North America are composed of accreted terranes. Despite limited exposure, the geological and geochemical studies of Proterozoic supracrustal successions in southwestern North America suggest that much of this region also comprises accreted terranes that were added to North America during the Early and Middle Proterozoic. Similar terranes were accreted to Archean crust in Scandinavia at about the same time. Several terms have been used for the segments of continental crust associated with continental accretion, and because they may be used in different ways in this chapter, it is important to define the terms. “Terrane” follows the conventional usage of Jones et al. and Coney (1989) and refers to a fault-bounded segment of continental crust with a distinctive assemblage of rocks and a tectonic history different from surrounding terranes. A “superterrane” (or composite terrane) results from the amalgamation of two or more terranes prior to final accretion with a continent, and an “overlap assemblage” is an assemblage of supracrustal rocks that overlaps older terrane boundaries.
U-Pb geochronologic analyses have been conducted on 205 individual detrital zircon grains from Cambrian through Devonian sandstones of the Roberts Mountains allochthon in central Nevada. These strata were tectonically emplaced onto the Cordilleran margin during the mid-Paleozoic Antler orogeny, but their original depositional settings and provenance have been controversial. Our data, combined with previous detrital zircon studies, define four different age signatures for the eugeoclinal strata: (1) 690-7 15 and 1065-1350 Ma grains in a minor group of sandstones in the Upper Cambrian(?) Harmony Formation, (2) 1745-1790, 1820-1860, and 2595-2700 Ma grains for most of the Harmony Formation, (3) 1410-1445, 1665-1690, and 1705-1740 Ma grains for lower Middle Ordovician sandstones of the Vinini Formation, and (4) 1020-1045, 1815-1860, 1905-1940, and 2645-2740Ma ages for lower Upper Ordovician sandstones in the Vinini, Valmy, Snow Canyon, and McAfee Formations, for the Silurian Elder Sandstone, and for the Devonian Slaven Chert. Comparison of these data with the detrital zircon reference for the Cordilleran miogeocline and with ages of basement provinces in cratonal North America indicates that sandstones in the lower Vinini and parts of the Harmony Formations were derived from 1.0-1.3, ∼1.43, and 1.6-1.8 Ga provinces of southwestern North America. In contrast, most older and younger units contain few grains of the appropriate ages to have come from the southwestern part of North America, and instead have strong similarities with the Peace River arch region of western Canada. We propose that detritus in most of the Harmony Formation was shed from off-shelf basement rocks exposed along the Canadian continental margin, perhaps as a western continuation of the Peace River arch or as extensional fault blocks. In contrast, detritus in the lower Upper Ordovician through Devonian strata is interpreted to have been recycled from platformal strata exposed along the flanks of the Peace River arch. Transport of the detritus is interpreted to have been largely via turbidity currents flowing in offshelf basins or trenches, rather than by longshore currents on the shelf. These provenance links provide new insights into the paleodispersal history along the Cordilleran margin, and indicate that sandstones of the Roberts Mountains allochthon received detritus from, and therefore accumulated near, western North America.
Devonian-Mississippian Antler and Permian-Triassic Sonoma orogenic trends are oriented northeast-southwest across Nevada and California at high angles to the Mesozoic- Cenozoic Cordilleran margin. The Roberts Mountains (Antler) and Golconda (Sonoma) allochthons of central Nevada were thrust over the miogeoclinal continental margin as accretionary prisms assembled and emplaced by episodic slab rollback toward the southeast during subduction downward to the northwest beneath an evolving offshore system of frontal and remnant magmatic arcs facing toward the continent. Diachronous Devonian and Permian arc assemblages forming superposed stratigraphic successions in the eastern Klamath Mountains and northern Sierra Nevada record alternating episodes of eruptive activity and dormancy along parallel but separate arc structures within the offshore island arc complex. Deformed lower Paleozoic rocks forming the substratum of the Klamath-Sierran arc assemblages display imbricated thrust panels shingled in a structural pattern indicative of southeast vergence within a regional accretionary prism that included the Roberts Mountains allochthon at its leading edge. Thrust emplacement of the Roberts Mountains allochthon over the miogeoclinal belt temporarily arrested subduction, to allow deposition of the Havallah sequence between the deformed continental margin and an offshore system of remnant island arcs. Renewed subduction and slab rollback emplaced the accretionary prism of the Golconda allochthon composed of the deformed Havallah sequence. Antler-Sonoma tectonic elements were truncated on the southwest by a sinistral late Paleozoic to earliest Mesozoic transform fault, which established the northwest-southeast trend of the California continental margin and displaced the miogeoclinal Caborca block southward into Mexico.
U-Pb geochonologic analyses have been conducted on 648 individual detrital zircon grains from Paleozoic and Triassic strata of western Nevada and northern California. These strata belong to several distinct terranes that are fault bounded and potentially displaced from their sites of origin. The analyses have been conducted in an attempt to provide additional constraints on where these terranes may have formed in relation to each other and to western North America. This paper provides background information that is essential to each of the accompanying chapters presenting detrital zircon data. Main components include (1) an outline of the general tectonic evolution of the region, (2) an overview of the detrital zircon reference for western North America, with a new quantitative analysis of the data that make up this reference, (3) a detailed discussion of the analytical methods used in analyzing detrital zircon grains in our laboratories, and (4) an assessment of the various biases and interpretations involved in this type of study.
The quartzose Cedar Mesa, DeChelly, and White Rim Sandstone Members of the Cutler Formation in Utah and Arizona contain abundant brown tourmaline and have low zircon/zircon+tourmaline ratios. In contrast, Cutler arkoses to the east which had as a source the Uncompahgre uplift in Colorado and New Mexico, are almost devoid of brown tourmaline and generally have high zircon/zircon+tourmaline ratios. Seemingly the quartzose members did not have an Uncompahgre source. The heavy mineral suites of the Cedar Mesa, DeChelly, White Rim, and Utah "Coconino" appear to be quite similar to each other and probably had a common source. This source was somewhere north of the Uncompahgre uplift as evidenced by prevalent southward-directed cross-bed dips in the White Rim. The cross-bed dips are subparallel to the White Rim strand line and represent a postulated longshore-current origin. Cross-bed dips in the Cedar Mesa, consistently from the northwest, that is, from out-to-sea, and cross-bed dips in the DeChelly, generally from the northeast, that is, from the Uncompahgre uplift, reflect only a final phase of transport and are unrelated to direction of source.
The Cambrian Adams Argillite and the Devonian Nation River Formation are two sandstone-bearing units within a remarkably complete Paleozoic stratigraphic section in east-central Alaska. These strata, now foreshortened and fault-bounded, were originally contiguous with miogeoclinal strata to the east that formed as a passive-margin sequence along the northwestern margin of the North American continent. Seventy-five detrital zircon grains from the Adams Argillite and the Nation River Formation were analyzed in an effort to provide constraints on the original sources of the grains, and to generate a detrital zircon reference for miogeoclinal strata in the northern Cordillera. Thirty-five single zircon grains from a quartzite in the Adams Argillite yield dominant age clusters of 1047-1094 (n = 6), 1801-1868 (n = 10), and 2564-2687 (n = 5) Ma. Forty zircons extracted from a sandstone in the Nation River Formation yield clusters primarily of 424-434 (n = 6), 1815-1838 (n = 6), 1874-1921 (n = 7), and 2653-2771 (n = 4) Ma. The Early Proterozoic and Archean grains in both units probably originated in basement rocks in a broad region of the Canadian Shield. In contrast, the original igneous sources for mid-Protcrozoic grains in the Adams Argillite and ∼ 430 Ma grains in the Nation River Formation are more difficult to identify. Possible original sources for the mid-Proterozoic grains include: (1) the Grenville Province of eastern Laurentia, (2) the Pearya terrane along the Arctic margin, and (3) mid-Proterozoic igneous rocks that may have been widespread along or outboard of the Cordilleran margin. The ∼ 430 Ma grains may have originated in: (1) arc-type sources along the Cordilleran margin, (2) the Caledonian orogen, or (3) a landmass, such as Pearya, Siberia, or crustal fragments now in northern Asia, that resided outboard of the Innuitian orogen during mid-Paleozoic time.
Distinct groupings of late Neoproterozoic tectonomagmatic and depositional events at 760 Ma, 685-670 Ma, 635-590 Ma and 590-545 Ma are recognized within the peri-Gondwanan margin of the Newfoundland Appalachians. This pre-Iapetan orogenic activity resulted in amalgamation of distinctive tectonic packages prior to deposition of a shale-rich platformal cover of terminal Neoproterozoic to Early Ordovician age, east of the Appalachian central mobile belt. The late Neoproterozoic successions chronicle, in part, the development of segments of a larger peri-Gondwanan orogenic system that was dispersed prior to, and variously reworked during, the protracted evolution of the southern Iapetus Ocean. The oldest orogenic events yet identified in the Newfoundland Avalonian belt occurred at and prior to 760 Ma and are manifest by the accumulation of submarine mafic volcanic rocks, the emplacement of oceanic gabbros, and the associated deposition of unique clastic and carbonate olistostromes. As early as 685 Ma, arc-related volcanic and associated arc-root plutonic complexes of felsic to intermediate composition developed along the orogenic belt in an overall contractional environment. These complexes, which are preserved together with amphibolite gneisses and associated intrusive rocks, were inhomogeneously deformed and then uplifted prior to the onset of widespread (635-590 Ma) volcanism, marine sedimentation, and coeval calc-alkaline plutonism, the products of which were deposited upon or emplaced into the 685-670 Ma basement. Locally, pre-600 Ma rocks have been inhomogeneously deformed prior to a complex volcanic, plutonic, and structural event (590-545 Ma), partly extensional and partly contractional in nature, during which the classical Ediacaran-bearing and younger sedimentary successions of the Avalonian belt accumulated. Diverse tectonic elements that evolved prior to the Cambrian were variably dispersed at several times, perhaps most significantly during late Neoproterozoic orogenesis. Pronounced terminal Neoproterozoic and early Paleozoic tectonothermal events were recorded on the inboard Iapetan margin of the belt, while elsewhere, terminal Neoproterozoic through Cambro-Ordovician platformal sediments were deposited, in most cases without apparent hiatus. These contrasting peri-Gondwanan terranes were reamalgamated and again dispersed during complex transpressional orogenesis of Silurian age related to closure of the Iapetus Ocean, and ensuing collision of Gondwanan and Laurentian elements of the Appalachian orogen.
Eolian and subaqueous cross-strata cannot be distinguished reliably by many commonly cited criteria. They can, however, generally be distinguished by the characteristics of their component types of stratification, which represent processes of sorting and transport of the grain population on dunes. Eolian dune stratification types consist of grainflow cross-strata, grainfall laminae, and wind ripple-generated climbing translatent strata . Some of these types, especially translatent strata, have characteristics unique to the eolian realm. These same stratification types are found to compose some ancient cross-strata, and their occurrence confirms the eolian interpretations of pans of the Entrada (Jurassic), Navajo (Triassic-Jurassic), and Galesville (Cambrian) Formations, as well as revealing emergent islands in the Curtis Formation (Jurassic), previously considered to be totally marine in origin. Stratification types show a characteristic distribution on modern eolian dunes and differ in their relative abundances and structure on dunes of differing size and kind. These same relations allow some estimates of the type, shape, and original height of ancient dune deposits, as well as influencing the occurrences of surface features such as tracks and tipple forms. The geological record of stratification types and other dune features is greatly affected, however, by the extent of the post-depositional truncation of dunes.
Regional tectonic analysis suggests that the entire Cordilleran
continental margin, from Nevada to the Yukon, underwent contractional
orogeny involving emplacement of deep basinal, submarine-fan, and mafic
volcanic strata over autochthonous continental margin strata during Late
Devonian to Mississippian time (Antler orogeny). Displaced
parautochthonous strata are present from Nevada to east-central British
Columbia, and perhaps within the Yukon-Tanana terrane of Yukon and
eastern Alaska. Manifestations of the orogenic event in the northern
Cordillera are preserved primarily by normal faults and related coarse
clastic strata of the Selwyn basin. We propose that these features
formed due to flexural extension during foreland deformation, rather
than mid-Paleozoic rifting or transtension.