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The gymnosperm pollen Shanbeipollenites proxireticulatus Schrank from the Vaca Muerta Formation (Upper Jurassic–Lower Cretaceous), Neuquén Basin, Argentina
Abstract
This study documents for the first time the occurrence of Shanbeipollenites proxireticulatus Schrank in levels of the Vaca Muerta Formation, Neuquén Basin, Argentina. It represents the first record of this species in high latitudes of the Southern Hemisphere. The Argentinian specimens are associated with useful palynostratigraphical indicators which suggest an early Valanginian age for the palynoflora yielding S. proxireticulatus. Therefore, this finding constitutes the first record from the Cretaceous. This taxon is related to the orders Cycadales/Bennettitales/Ginkgoales. During the Cretaceous in Patagonia cycads and bennettitaleans groups show marked adaptations to warm and strongly seasonal dry climate periodically influenced by volcanic activity. The paleogeographic distribution of the records of S. proxireticulatus, symmetrically located on both sides of the equator, together with its relationship with the climate zones or Biomes, suggest that the parental plants of this pollen grain thrived under warm climate and probably stressed paleoenvironmental conditions. Since the studied sample is located near 1000 m below the Intravalanginian unconformity, and older age (i.e. late Berriasian) cannot be discarded.
... The type species S. quadrangulatus Qian Lijun and Wu Jingyun (in Qian et al. 1987) was reported from the Jurassic of China. Two other species S. quadratus (Kumar) Schrank and S. proxireticulatus Schrank mainly occur in the Southern Hemisphere (Africa and Argentina: Schrank 1999Schrank , 2004Schrank , 2010Olivera et al. 2018). Schrank (2004) considered Shanbeipollenites similar to some species of Cycadopites which are proximally sculptured, but the former genus can be distinguished by its typically rhombic/quadrangular outline. ...
... The three informal dinoflagellate cyst assemblages recognized by Schrank (2005), for the same interval with Shanbeipollenites were the Rigaudella aemula-Chlamydophorella wallala assemblage from the Nerinea Bed (Oxfordian to Kimmeridgian age); the Endoscrinium attadalense-Ctenidodinium sellwoodii group assemblage from the Middle Saurian Bed (late Kimmeridgian age for this unit); the Dingodinium jurassicum-Kilwacysta assemblage from the Trigonia smeei Bed (Tithonian age). In Argentina, the only record of the genus Shanbeipollenites (S. proxireticulatus) corresponds to an early Valanginian palynoflora from the Vaca Muerta Formation, Neuqu en Basin, Argentina (Olivera et al. 2018). Related to the age of this palynoflora, Olivera et al. (2018) discussed that since the studied sample is located near 1000 m below the Intravalanginian unconformity, dated at the boundary between the early and late Valanginian Qian et al. (1987), based on the translation of Jansonius et al. (2002), S. quadratus Kumar (1987) Schrank, comb. ...
... In Argentina, the only record of the genus Shanbeipollenites (S. proxireticulatus) corresponds to an early Valanginian palynoflora from the Vaca Muerta Formation, Neuqu en Basin, Argentina (Olivera et al. 2018). Related to the age of this palynoflora, Olivera et al. (2018) discussed that since the studied sample is located near 1000 m below the Intravalanginian unconformity, dated at the boundary between the early and late Valanginian Qian et al. (1987), based on the translation of Jansonius et al. (2002), S. quadratus Kumar (1987) Schrank, comb. nov. ...
A new monosulcate species, Shanbeipollenites lagarcitensis sp. nov. is described from the Lower Cretaceous Lagarcito Formation, Sierras de Guayaguas (north-western San Luis Basin), Argentina. Shanbeipollenites lagarcitensis shares with other species of this genus a broadly ellipsoidal outline and a diagonally disposed distal sulcus. However, the new species differs from the psilate type species Shanbeipollenites quadrangulatus and from S. quadratus by the presence of sculptural elements distributed at the equatorial region, close to the opposite ends of the sulcus. The thicker wall, exine separation, much more strongly diagonal offset of the sulcus and the rugulate-verrucate sculpture with an equatorial distribution close to the opposite ends of the sulcus, distinguish this new species and expands the concept of the genus Shanbeipollenites. The presence of two separate exine layers supports its gymnosperm affinity. Furthermore, the occurrence of Shanbeipollenites lagarcitensis in the Albian Lagarcito Formation from mid–latitudes, central–western Argentina constitutes the youngest record of the genus worldwide. This new record expands the biostratigraphical range of the taxon into the Albian.
... Its record in this assemblage is the first register in our country. Interulobites lajensis mainly registered in Argentina, is another interesting taxon with a narrow biochron ranging from Late Bathonian to Hautterivian (Martínez, 2000b(Martínez, , 2002Olivera et al., 2010Olivera et al., , 2018Olivo et al., 2019). By other hand, Striatella seebergensis was previously recorded in Argentina only till Toarcian, so this mention would constitute the youngest record of this species, coincident with its latest worldwide occurrence (e.g. ...
The basal succession of the Lajas Formation at Trasandino section, Arroyo Covunco area, constitutes an excellent example of proximal prodelta facies cut by sediment-waves formed during a complete acceleration-deceleration hyperpycnal discharge cycle. The main outcome of this contribution was to present a new studied locality in which the Lajas Formation outcrops. Nine mudstones and fine-grained heterolites levels deposited during the waning stage, were sampled to palynological analysis. The recovered assemblages are dominated by sporomorphs, which are characterized by a great diversity of the trilete spores. Among them, is interesting to highlight the first mention of Manumia variverrucata and the extension of the last occurrence of Striatella seebergensis until to Callovian in Argentina. Based on selected key taxa a Late Bathonian–Callovian age is proposed for the Lajas Formation at the Trasandino section in this area. The Trasandino section spore assemblages show the greatest similarity with the Arroyo Covunco section spore associations when they are compared with the Lajas Formation of other studied localities. The endemic development of certain types of bryophyte (sensu lato) spores, e.g. Taurocusporites quattrocchiensis, was favored by locally humid conditions inferred at the Arroyo Covunco area. Large abundance of phytoclasts, sporomorphs and fresh-water algae characterize the recovered organic matter suggesting a high input of continental organic particles to the basin, as the result of fluvial-derived density discharges. Three palynofacies type (PT) had been identified which allow to evaluate the hydrodynamic characteristics of the flow, taking into account the differential buoyancy of the opaque particles. The large amount of equidimensional opaque particles recognized at the PT-B, characterizes the beginning of the deceleration phase of the flow and the abundance of blade-shape opaque particles, identified in the PT-A, point out a deposition from the final buoyant plume of hyperpycnal flow. The PT-C shows transitional features between these two conditions.
The perforated Pediastrum Meyen s.l. species are recorded for the first time in the basal levels of the Tithonian Vaca Muerta Formation, extending its first stratigraphical record to ages as old as Late Jurassic times. Based on the ecological requirements of Pediastrum simplex var. clathratum and P. simplex var. biwaense, the previously warm paleoclimatic conditions suggested by the Late Jurassic of Neuquén Basin, are reinforced. The co-occurrence of the different mechanisms that interacted during the transport, accumulation, and early diagenesis of these sediments and their organic content would have allowed for the excellent preservation of the Pediastrum Meyen s.l. species.
Since the publication of four compilations issued between 2012 and 2019, 93 further published contributions on Triassic, Jurassic and earliest Cretaceous (Berriasian) dinoflagellate cysts from Africa, North America, South America, the Arctic, Australasia, East Europe, West Europe, the Middle East and Russia have been discovered in the literature, or were issued in the last 12 months (i.e. between February 2018 and January 2019). Of these, 55 were published during 2018 and 2019, making this period a very productive one. These studies are mostly on the Late Triassic and Early Jurassic of Europe. All the 93 items are listed herein with digital object identifier (doi) numbers where available, as well as a description of each item as a string of keywords. Publications on West Europe comprise 31.2% of the total, and items on Africa, the Arctic, Australasia, East Europe and Russia are also significant (15.1%, 6.5%, 7.5%, 9.7% and 14.0% respectively). The least well-represented regions are North America, South America and the Middle East (2.2%, 1.1% and 1.1% respectively).
The Late Jurassic to Early Cretaceous Tendaguru Beds (Tanzania, East Africa) have been well known for nearly a century for their diverse dinosaur assemblages. Here, we present sedimentological and palaeontological data collected by the German-Tanzanian Tendaguru Expedition 2000 in an attempt to reconstruct the palaeo-ecosystems of the Tendaguru Beds at their type locality. Our reconstructions are based on sedimentological data and on a palaeoecological analysis of macroinvertebrates, microvertebrates, plant fossils and microfossils (ostracods, foraminifera, charophytes, palynomorphs). In addition, we included data from previous expeditions, particularly those on the dinosaur assemblages.
The environmental model of the Tendaguru Beds presented herein comprises three broad palaeoenvironmental units in a marginal marine setting: (1) Lagoon-like, shallow marine environments above fair weather wave base and with evidence of tides and storms. These formed behind barriers such as ooid bar and siliciclastic sand bar complexes and were generally subject to minor salinity fluctuations. (2) Extended tidal flats and low-relief coastal plains. These include low-energy, brackish coastal lakes and ponds as well as pools and small fluvial channels of coastal plains in which the large dinosaurs were buried. Since these environments apparently were, at best, poorly vegetated, the main feeding grounds of giant sauropods must have been elsewhere. Presumably, tidal flats and coastal plains were visited by dinosaurs primarily during periods of drought. (3) Vegetated hinterland. Vegetation of this environment can only be inferred indirectly from plant material transported into the other depositional environments. Vegetation was dominated by a diverse conifer flora, which apparently formed part of the food source of large herbivorous sauropods. Evidence from various sources suggests a subtropical to tropical palaeoclimate, characterised by seasonal rainfall alternating with a pronounced dry season during the Late Jurassic. In Early Cretaceous times, sedimentological and palaeontological proxies suggest a climatic shift towards more humid conditions.
Die Tendaguru-Schichten von Tansania in Ostafrika (Oberjura bis Unterkreide) sind als Lagerstätte oberjurassischer Dinosaurier seit nahezu einem Jahrhundert weltweit bekannt. Anhand von sedimentologischen und paläontologischen Daten, die während der Deutsch-Tansanischen Tendaguru Expedition 2000 im Typus-Gebiet der Tendaguru-Schichten gewonnen wurden, werden Paläo-Ökosysteme rekonstruiert. Grundlage der Rekonstruktionen sind die Auswertung sedimentologischer Daten sowie die paläo-ökologische Analyse von Makroinvertebraten, Mikrovertebraten, pflanzlichen Fossilien und Mikrofossilien (Ostrakoden, Foraminiferen, Charophyten, Palynomorphen). Darüber hinaus werden Informationen über Dinosaurier berücksichtigt, die bei früheren Expeditionen gewonnen wurden.
Das hier vorgestellte Ablagerungsmodell der Tendaguru-Schichten umfaßt drei Teilbereiche eines randlich marinen Sedimentationsraumes, die wie folgt gekennzeichnet werden können: (1) Lagunen-artige, marine Flachwasserbereiche, die oberhalb der Schönwetter-Wellenbasis lagen und unter deutlichem Einfluß von Gezeiten und Stürmen standen. Sie waren vom offenen Meer durch Barrieren, wie Ooidbarren und siliziklastischen Sandbarrenkomplexen, getrennt und wiesen einen leicht schwankenden Salzgehalt auf. (2) Ausgedehnte Wattgebiete und flache Küstenebenen. Dort befanden sich niedrig-energetische, brackische Strandseen und Teiche sowie Tümpel und kleinere Flußrinnen, in denen die großen Dinosaurier eingebettet wurden. Da diese Lebensräume bestenfalls dürftig bewachsen waren, müssen die Nahrungsquellen und der eigentliche Lebensraum der riesigen Sauropoden anderswo gelegen haben. Vermutlich wurden die Wattgebiete und Flachküsten von Dinosauriern vorrangig in den Trockenzeiten aufgesucht. (3) Bewachsenes Hinterland. Die Vegetation dieses Lebensraumes kann nur indirekt aus Pflanzenresten erschlossen werden, die in die anderen Ablagerungsraume transportiert wurden. Die Vegetation wurde von einer diversen Koniferenflora dominiert, die zumindest teilweise die Nahrungsgrundlage der großen, herbivoren Sauropoden bildete. Sedimentologische und paläontologische Indikatoren sprechen für ein subtropisches bis tropisches Klima wahrend der späten Jurazeit mit einem jahreszeitlichen Wechsel von Regenfällen und ausgeprägten Trockenzeiten. In der frühen Kreidezeit deutet sich ein Wechsel zu starker humiden Bedingungen an.
doi:10.1002/mmng.20020050103
A well-preserved, diverse sporomorph flora of over 60 species has been found in Cores 120-750B-12W through -14R from the Southern Kerguelen Plateau. Analysis of the flora indicates that the terrestrial sediments overlaying the basaltic basement are late Early Cretaceous in age. Ranges of the sporomorphs in other parts of Gondwana and the morphology and paucity of angiosperm pollen grains confine the age of this section to the early to possibly early middle Albian. The Albian palynomorph assemblages in Hole 750B are composed primarily of fern spores and podocarpaceous pollen, and show most similarity to those from southern Australia. Changes in the flora through time reflect the successional vegetation changes on barren volcanic islands. The climatic conditions were probably cool to temperate and humid. -from Authors
Groebericeras bifrons Leanza is described from the Chacao Formation of central Mendoza and the Lo Valdés Formation of central Chile. The species appears limited to the Argentiniceras noduliferum Zone, which is traditionally placed in the lower Berriasian. Spanish records of Groebericeras appear to be younger (Hoedemaeker, 1982), while Groebericeras from Iraq were placed in the late Berriasian by comparison with the Spanish records (Howarth, 1992).
The revision of the stratigraphy of the Cerro Bayo in the Bajo Grande area (Argentinean Patagonia) and the new 206Pb/238U age of 116.85 ± 0.26 Ma constrain the dating of the Baqueró flora, one of the most abundant Aptian floras of southern Gondwana. This flora, preserved in the Baqueró Group, represents an extinct biome that flourished ca. 118 Ma ago and was affected by increasing regional volcanism during the subsequent four millions years. The outcrops of the Cerro Bayo are characterized by fluvio-lacustrine deposits divided into three facies associations that include nine lithofacies. The first palynological record for the locality confirms the correlation of the lower part of the outcrops with the Anfiteatro de Ticó Formation (the oldest unit of the Baqueró Group). The new radiometric age and stratigraphy support recognition of the Bajo Tigre Formation (the middle unit of the Baqueró Group) in the area and date the earliest stage in angiosperm diversification in southern South America. Stratigraphic relationships among the Baqueró, Chubut and Divisadero groups are briefly discussed.
Calcareouos nannofosils, duration and origin of limestone-marl cycles (Late Jurassic, Neuquén Basin). A nannofossil association corresponding to Zone NJ20b was defined in the rhythmically interbedded limestones and marls of the Los Catutos Member, Vaca Muerta Formation. It confirmed the Late Middle Tithonian age, previously assigned on the basis of ammonites, to the beds which crop out in the locality of Zapala, Neuquén Province, Neuquén Basin. The stratigraphical resolution of the nannoflora was no better than that of the ammonite fauna, but a good correlation between zones can be established. This represents a powerful and useful tool for future biostratigraphical studies in the Neuquén Basin. On the basis of the ammonite and nannofossil zones, a period of 1 my was estimated for the deposition of the 25 m thick sequence of limestones and marls. From these data a high sedimentation rate (5 m/ka on average) was calculated. As a consequence, the duration of the individual limestone-marl cycles is about 20 ka on average, in good agreement with the precession period of the earth axis. Thus, rhythmic changes in sedimentation would be related to climatic changes driven by orbital forcing.
Eight palynological samples from a broad geographical range of the upper part of the Morrison Formation have yielded a rich palynoflora of over 100 morphospecies of bryophytes, lycophytes, sphenophytes, ferns, and seed plants. In striking contrast to Morrison megafloras, conifers are dominant throughout the palynoflora, with ferns diverse but subordinate; other components are uncommon to rare. Palynofloras display increased taxic diversity and increased spore abundance and diversity northward, accompanied by reduction in frequency of the probable xerophytic conifer family Cheirolepidiaceae, suggesting a moisture-driven latitudinal diversity gradient. Facies and taphonomic biases preclude extrapolation to the regional flora and climate from these data, but the palynological data suggest that coniferous trees with an understory of ferns comprised the predominant vegetation overall, alongside more heterogeneous riparian and wetland vegetation, during later Morrison times.
The Andean Cordillera has been considered a simple model of a mountain chain; but detailed analyses of its geologic evolution
show a more complex history. Ouring the early Paleozoic, the southwestem margin of the Gondwana continent was near the westem side of the present~day Sierras Pampeanas of Argentina. The site of the present Precordillera was a carbonate platform, facing an ocean to the west, which separated a microcontinental block, the Chilenia terrane, from the rest of Gondwana. This ocean basin was consumed along an astward~dippingsubduction z¿ne below the Sierras Pampeanas during the Late Devonian, when Chilenia moved eastward and was accreted to the Gondwana continental margin. A new subduction zone was then formed at the west side of the accreted terrane, leaving a large accretionary prism at the site of the present Chilean Coastal Range. A late Paleozoic-early Mesozoíc magma tic are, consisting of a belt of granitoids and ~elated rhyolitic volean k rocks, developed in this accretionary prism and in the adjacent continental terrane.
Lateral growth of the continental margin~ended in the Paleozoic, and in the early Mesozoic a magmatic are and associated backarc
basins were developed on the late Paleozoic basement. Subsequent subduction erosion or strike-slip faulting eliminated large pieces of the Paleozoic forearc assemblages. In northem Chile, these processes reached a maximum, resulting in formation of a Jurassic magmatic are at the present~day continental margin.
The outstanding fea tu re of che Mesozoic evolution of the Andes of Chile and Argentina is a tectonic segmentation characterized
by differences in che geologic evolution, changes in che nature of backarc basins, differences in structural style, and behavior of
related magmatic ares of the various segments. As a consequence of these differences, the following well~defined segments have been recognized:
SegmentA (lat. 21 °·27 °S) hada Jurassic-Early Cretaceous magmatic are, preserved in the present Coastal Range ofNorthem
Chile, toche east of which was che Tarapacá basin, an ensialic, extensional, backarc basin that became filled with carbonate and
clastic sediments.
Segment B (lat. 27 °-35 °S) also hada Jurassic magmatic are along the Coastal Range. In the Early Cretaceous the backarc basin evolved into an "aborted" marginal basin where large volumes of andesitic and basaltic volcanic rocks were erupted and which interfinger eastward with the carbonate and clastic sedimerits of a narrow shelf (Aconcagua platform) along the stable continental edge.
Segment C (la t. 35 o ~40 °S) hada magma tic are, which remairied stationary from che Jurassic to the present, a long che m a in axis of the Cordillera Principal; toche east was the Jurassic-Cretaceous Neuquén basin, an extensive and deep ensialic foreland basin.
Segment D (lat. 41 °~49 °S) was characterized by an oscillatory magmatic are and only minor extension behind the are during the
Jurassic and Early Cretaceous.
SegmentE (49 °-56 °S) hadan ocean-floored backarc basin (Magallanes marginal basin) developed to the east of a magma tic are in the Early Cretaceous. Subsequent middle Cretaceous closure caused formation of a metamorphic core complex along the foreland edge of the marginal basin.
The Andean region experienced severe deformation during the middle to Late Cretaceous, and the diverse segments reacted in
different ways, showing conspicuous differences in the pattems of folding and faulting from one segment to another. The Andean
Cordillera of Chile and Argentina was again segmented during the Miocene, resulting in the present-day morphotectonic pattem
that apparently is controlled by processes such as plate convergence velocities and inclination of the Benioff zone. These processes determined the distribution of the late Cenozoic volcanism, c~used uplift of the Altiplano and che Sierras Pampeanas of Argentina, and brought about the final tectonic changes of the geological ~nd morphological provinces now recognized in the Andean region.
The boundaries of the T ertiary segments differ slightly from those of the Mesozoic, but undoubtedly the features of each were determined by the previous segmentation.
Se presentan los primeros estudios bioestratigráficos de detalle y análisis U-Pb en circón del Miembro Huncal de la Formación Vaca Muerta, cuenca Neuquina. La asociación de nanofósiles reconocida en el perfil analizado permite asignarle una edad berriasiana a partir de la primer aparición de Cruciellipsis cuvillieri. La presencia y abundancia del género Micrantholithus sugiere condiciones de baja salinidad, asociados a ambientes marginales afectados por la entrada de agua dulce. Los amonites presentes (“Thurmanniceras” discoidal, Pseudoblanfordia australis y Cuyaniceras sp.) también indican una edad berriasiana para el Miembro Huncal. Las edades de los circones detríticos demuestran áreas fuente caracterizadas por un basamento ígneo-metamórfico y no desde el arco volcánico andino contemporáneo. Sobre la base de los resultados obtenidos se postula que los depósitos del Miembro Huncal podrían haberse originado como turbiditas extra-cuencales con aporte detrítico predominante desde áreas ubicadas en los bordes sur y oriental de la cuenca. El análisis regional sugiere que estos depósitos arenosos con slumps podrían correlacionarse con depósitos equivalentes en el subsuelo neuquino.
This monograph describes 73 species and 1 subspecies of precisely dated Trigoniidae from the Lower Jurassic (Liassic) to the Upper Cretaceous (Maastrichtian) of western central Argentina. These are classified into 14 subfamilies. Ten new species and one new subspecies are established. Comments on the Family Trigoniidae, as well as taxonomic considerations, stratigraphic occurrence, and facies relationships of the described species are presented. With the new taxonomy proposed here, the trigoniids have a much greater temporal resolution than previously thought, especially at the species level. -from Authors
A study of spores and pollen assemblages from vertebrate fossil localities in the nonmarine Otway and Strzelecki Groups, Victoria, has shown that the localities in Otway Group sediments are of late Aptian- early Albian age (Crybelosporites striatus Subzone of Dettmann & Playford 1969) and the localities of the Strzelecki Group of Valanginian - Aptian age (Cyclosporites hughesii Subzone of Dettmann & Playford 1969). This age determination is dependent on the isochronicity of spore-pollen zones across eastern Australia. -Authors
New data from the palynomorph assemblage with angiosperm pollen grains found in lacustrine sediments belonging to the terminal part of the D-129 Formation are herein presented. The fossiliferous section is included in the uppermost part of a thick lacustrine stratigraphic unit, which is widely distributed in the subsurface of the productive San Jorge Gulf Basin. The presence of the paleoequatorial marker Tucanopollis crisopolensis (Regali) in the studied sediments is emphasized and biostratigraphic as well as biogeographic aspects are discussed. Based on the information provided by the fossil record, a late Barremian?/early Aptian age is suggested for the end of the great-lake episode in the present district.
The Cañadón Asfalto Formation, Cañadón Asfalto Basin, Patagonia, Argentina, is interpreted as fluvial-lacustrine deposits. A palynological study of the lower and middle parts of the unit, at the Cañadón Lahuincó and Cañadón Caracoles sections, Cerro Cóndor Depocentre Chubut province, northwestern Patagonia, Argentina is presented. The quantitative composition of the palynofloras is characterised by the dominance of pollen produced by the conifer families Cheirolepidiaceae (Classopollis) and Araucariaceae (mainly Araucariacites and Callialasporites), suggesting that warm-temperate and relatively humid conditions under highly seasonal climate prevailed during the depositional times of the unit. The abundance of Botryococcus supports the presence of a shallow lake with probably saline conditions. Five palynomorph ecogroups (PEGs) were recognised: upland, lowland, riverside, coastal lake and aquatic. The ecological requirements of the different plant families forming the PEGs enable the inference of a sub-tropical palaeoclimate for the Cañadón Asfalto region during late Early Jurassic to mid Middle Jurassic, which is consistent with the ‘seasonally dry (winterwet)’ biome.
Leaves are a plant's direct means of interacting with the atmosphere, and their morphology is often attuned to and reflects prevailing environmental conditions. Although better-understood and documented for angiosperms (or 'flowering plants'), non-angiosperms also exhibit a phytogeographic pattern linked most strongly to the evaporation/precipitation ratio, a relationship often reflected in their foliar morphologies. We have used this to interpret Jurassic terrestrial climate conditions along a spectrum defined by climate-sensitive lithological end-members such as evaporites and coals. Global climate zones, or biomes, were determined by exploring the foliar morphology/climate relationship using multivariate statistical analysis. Jurassic plant productivity and maximum diversity was concentrated at mid latitudes, where forests were dominated by a mixture of ferns, cycadophytes, sphenophytes, pteridosperms and conifers. Low-latitude vegetation tended to be xeromorphic and only patchily forested, represented by small-leafed forms of conifers and cycadophytes. Polar vegetation was dominated by large-leafed conifers and ginkgophytes which were apparently deciduous. Tropical everwet vegetation was, if present at all, highly restricted. Five main biomes are recognised from the data: seasonally dry (summerwet or subtropical), desert, seasonally dry (winterwet), warm temperate and cool temperate. Their boundaries remained at near-constant palaeolatitudes while the continents moved through them (south, in the case of Asia, and north, in the case of North America). Net global climate change throughout the Jurassic appears to have been minimal. The data-derived results are compared here with a new climate simulation for the Late Jurassic. The use of more detailed palaeogeography and palaeotopography has improved the overall data/model comparisons. Major discrepancies persist at high latitudes, however, where the model predicts cold temperate conditions far beyond the tolerance limits indicated by the plants. Nevertheless, our approach at 2 least enables direct comparison of global palaeoclimate interpretations from both a data and model perspective, and indicates future research directions.
Palynostratigraphy of the Tithonian-Hauterivian interval, West-Central Neuquén Basin, Argentina]. A preliminary approach to a zonal definition for the Tithonian-Hauterivian interval of the West-Central Neuquén Basin is presented. The limits of the zone as well as the first and last appearance data of index species are located. There were recognized the Dichadogonyaulax culmula, Aptea notialis and Microcachryidites antarcticus zones for the Late Tithonian-?Early Berriasian. Due to the great abundance of Callialasporites and the absence of Cyclusphaera, Zone 1 (Late Berriasian-?Early Valanginian) is correlated with the Callialasporites-Contignisporites-Staplinisporites Zone of Patagonia Austral. It was recognized the Cyclusphaera psilata-Classopollis Zone associated with Celyphus rallus, Leiosphaeridia and Leiofusa among others for the Late Valanginian (Zone 2). Taking into account the terrestrial-marine relationships, paleoenvironmental conditions for the studied interval are discussed.
This paper deals with the facial changes of the marine beds of Upper Jurassic (Tithonian) and Lower Cretaceous (Berrasian) age, in the area located between Loncopué (S 37° 55') and Picún Leufú (S 39° 13') in the province of Neuquén, Argentina. Eight stratigraphic sections were investigated as well as its paleontological contents, being as follows, from north to south: 1) Camino a Pichaihue, Huncal area. 2) Cerrito de la Ventana, Trahuncurá area. 3) Cajón de Almaza, Loncopué area. 5) Mallín Quemado, Vaca Muerta area. 6) Cerro Caracoles, Zapala area. 7) Picún Leufú, junction between route 40 and P. Leufú creek area, and 8) Cerro Lotena, Barda Negra area.
In the stratigraphical sequence two different formations are recognised, in ascending order: The Vaca Muerta Formation Weaver, 1931 emended H. Leanza, 1972 (= Vaca Muerta and Quintuco Formations) and the Picún Leufú Formation n. nom.
The Vaca Muerta Formation is essentially composed by bituminous black shales and subordinate thin bedded dark limestones, fine grained sandstones and calcareous concretions. The Picún Leufú Formation is characterized by whitish and greenish calcareous sandstones and masives whitish limestones.
The ammonite fauna revealed that the contact between these two formations is heterochronic, cutting obliquely the time lines.
Near the border of the basin, the Vaca Muerta Formation only comprises the Lower Tithonian, while the superposed Picún Leufú Formation is of Upper Middle and Upper Tithonian age. Towards of interior of the basin, the Vaca Muerta Formation embraces the whole Tithonian, Berriasian, and the lowermost Valanginian. In the same direction, the Picún Leufú Formation gradually decreases in thickness and finally disappears, being laterally replaced by the Vaca Muerta Formation.
This paper deals about ammonites succession and age of the Jurassic-Cretaceous boundary beds of the Neuquén and Mendoza basin, between southern parallels 35° and 40°, in west central Argentina. Twenty seven stratigraphic sections were investigated, comprising the Vaca Muerta formation and synchronics (Carrín Curá, Picún Leufú, Mulichinco formations, and Mendoza formation with is members Vaca Muerta, Chachao an Cienegüitas). The aes of this formations in certains places of the basin in correspondence with the analysed is established. An ammonites zonation based on former works complemented by an ages key that lets direct transport to the stratigraphic sections is employed. In this way, the evolution of each one of the formational units recognised is fixed, showing that these units basically respond to lithofacies according with is relative position within the basin and in wich its limits ussually cuts obliquely the time line. In the Jurassic-Cretaceous boundary it has not been observed a lithologic change that makes evident the passage from one System to another.
New age of the base of the Chubut Group at the Cerro Solo uranium reservoir, Chubut Province.
This paper analyzes the lithological characteristics of the uranium mineralization host rocks from Cerro Solo reservoir, corresponding to the lower member of the Los Adobes Formation, basal unit of the Chubut Group in its northern sector. The angiosperm pollen association there recovered is analyzed. According with this analysis, an early Albian age for the pollen association is established, that determines a younger age than that considered until now for the beginning of deposition of the Chubut Group sediments at the Cerro Solo reservoir depocentre.
The Tendaguru Beds, southeastern Tanzania, have yielded two palynological assemblages of Kimmeridgian to Tithonian age: (1) the Anapiculatisporites-Densoisporites-Trisaccites assemblage from the Middle Saurian Beds and (2) the Barbatacysta-Pareodinia assemblage from the overlying Smeei Beds. A third assemblage with Rhizophagites and rare angiosperm pollen from the Upper Saurian Beds is contaminated by recent and subrecent material.
The Anapiculatisporites-Densoisporites-Trisaccites assemblage is characterized by the presence of freshwater algae (Ovoidites), pteridopyhtic-bryophytic spores and gymnosperm (conifer) pollen, with Classopollis as the most abundant element. Among the rare elements of this assemblage is the questionable dinoflagellate Mendicodinium? quadratum, possibly a Kimmeridgian-Tithonian marker. The miospores show palaeobiogeographic links to Southern Gondwana, especially Madagascar, Australia, Argentina and India. Deposition of this assemblage took place in an aquatic environment with strong palynological influx from a terrestrial source and questionable marine influence.
The Barbatacysta-Pareodinia assemblage contains a considerable number of dinoflagellates suggesting deposition in a marine environment. The terrestrially-derived miospores are impoverished and dominated by conifer pollen, while pteridophytic-bryophytic spores form a very subordinate element or are absent.
Die Tendaguru-Schichten, Südost-Tansania, haben zwei palynologische Assoziationen, deren Alter als Kimmeridge bis Tithon interpretiert wird, geliefert. Die Anapiculatisporites-Densoisporites-Trisaccites-Assoziation stammt aus den Mittleren Saurierschichten, und die Barbatacysta-Pareodinia-Assoziation charakterisiert die darüberlagernden Smeei-Schichten. Eine dritte Vergesellschaftung mit Rhizophagites und seltenen Angiospermen-Pollen aus den Oberen Saurierschichten ist durch rezentes bis subrezentes Material kontaminiert.
Die Anapiculatisporites-Densoisporites-Trisaccites-Assoziation ist durch die Anwesenheit von Süßwasser-Algen (Ovoidites), Pteridophyten-Bryophyten-Sporen und Gymnospermen-Pollen (Koniferen) gekennzeichnet mit Classopollis als dem häufigsten Element. Zu den seltenen Elementen dieser Assoziation gehört der fragliche Dinoflagellat Mendicodinium? quadratum, der möglicherweise als leitend für das Kimmeridge-Tithon angesehen werden kann. Die Miosporen zeigen paläobiogeographische Verbindungen nach Südgondwana, besonders nach Madagaskar, Australien, Argentinien und Indien. Das Ablagerungsmilieu dieser Assoziation war aquatisch mit starker Zufuhr von terrigenem Material, während mariner Einfluß fraglich ist.
Die Dinoflagellaten-führende Barbatacysta-Pareodinia-Assoziation wurde in einem marinen Milieu gebildet, in dem die Zufuhr terrigener Palynomorphe reduziert und im wesentlichen auf Koniferen-Pollen beschränkt war, während Pteridophyten-Bryophyten-Sporen nur sehr untergeordnet vorkommen oder ganz fehlen.
doi:10.1002/mmng.1999.4860020113
The cycads are remnants of a flora that dominated the terrestrial ecosystems across the Mesozoic Era. The stem record of fossil cycads is scanty, with seventeen genera described around the world. From them, eight come from Argentina (Triassic to Paleogene strata), and actually six from the Cretaceous of Patagonia. In this research, we present a new fossil trunk of cycad from Upper Cretaceous beds of Patagonia. The good preservation of the permineralized stem allows to make detailed descriptions and comparisons and, accordingly, support the erection of a new taxon, Zamuneria amyla gen. et sp. nov. This new taxon possesses characters that fit with the Encephalarteae (e.g., columnar stem with persistent leaf bases and cataphylls, a wide pith, medullary vascular bundles, mucilage canals and idioblasts, a polyxylic vascular cylinder). Some
features present in Zamuneria are discussed, such as the great development of parenchyma tissues with a marked amount of specialized cells (idioblasts), probably related with some protective function. Furthermore, the presence of cycads during the deposition of the Mata Amarilla Formation allows inferring climatic conditions, as well as a greater diversity of Encephalarteae in South America reinforces the endemic
conditions for this group for the Cretaceous of southern continents.
Resumen
With the aim to know pollen dispersal of Araucaria angustifolia (Bert.) O. Kuntze from a cluster of "parana pine" orchards, through a NE-SW transect of 40 km, following the dominant winds direction during the last bloom, five samples by "fluxage" Cour method were obteined. Results have demonstred that Araucaria pollen have a very scarce capacity for long distances transport. This is in accordance with some structural and morphological pollen characters as big size, exineless structure and citoplams volume, which have not optimal transport conditions. More studies of Araucaria pollination are necesary in order to establish the constancy of these results and the incidence on it of the annual climatic variations.
Taphonomic analysis was performed on palynological samples of marine successions from the Cuyo Group of the Neuquén Basin. The group comprises the Los Molles and Lajas Formations (Middle Jurassic) and represents the first major marine depositional episode after the configuration of the basin. A total of 21 outcrop samples from five sections, located in the central-western part of the basin, were analyzed. The palynological counts of each sample were carried out taking into account the preservation state of the palynomorphs, which was mainly influenced by two parameters: their intrinsic properties and the environmental depositional conditions. Four main deterioration types (corrosion, degradation, mechanical damage, and concealment by authigenic minerals) and their six combinations were identified. The growth of pyrite crystals within the palynomorphs was strongly influenced by the exine structure, being dominant in bisaccate pollen grains. Mechanical damage appears to be the most important deterioration type, reflecting the highly dynamic conditions of shelfal marine environments. The term Palynotaphofacies (Pt) was proposed to characterize a sedimentary rock yielding palynological associations with distinctive preservational features. Three palynotaphofacies have been recognized: Pt-1 (tidal-influenced environments) is characterized by the highest percentage of deteriorated forms, reflecting either intermittent exposure to weathering or intense reworking. Pt-2 shows the highest percentage of well-preserved palynomorphs associated with rapid burial due to a high sedimentation rate and it comes from the delta-front facies of fluvial-dominated deltas. Finally, Pt-3 was identified in samples of prodelta hyperpycnites with a wide predominance of terrigenous components and it is characterized by the coexistence of well-preserved and deteriorated palynomorphs.
The Berriasian–Aptian succession in the Neuque´n Basin is mainly marine in the lower part and non-marine in the upper portion. A detailed ammonite zonation is presented for the Berriasian–?Early Barremian interval. While some ammonite taxa are endemic, others are widely distributed and there are several levels where correlation can be suggested with the ‘standard’ stages and zones of the Tethyan Mediterranean area. Several nannofossil bioevents are recognized, and these provide evidence for correlation with Tethyan areas.
Correlations suggested by both groups are reasonably consistent. Berriasian–Aptian palynomorphs include both terrestrial and marine forms. Several terrestrial assemblages can be recognized, but the marine forms are mainly long-ranging taxa, especially in the Agrio Formation.
Spores that can be referred in the family Gleicheniaceae are described. They belong to the genera Gleicheniidites, Clavifera and Ornamentifera, Their variety suggests that the family was well represented in Patagonia during the early Cretaceous.
A flora of dispersed spores, pollen grains, and algal microfossils is recorded from subsurface equivalents of the Koonwarra Fossil Bed as cored in Mines Department of Victoria Leongatha Bore Nos 10 and 16 in the Gippsland Basin, Victoria. The palynomorphs are moderately well preserved and are considered to derive from diverse bryophytes, lycopods, ferns, and gymnosperms, together with fungi and an early angiosperm. The algal microflora comprises colonial and filamentous green and possibly blue-green forms. Qualitative and quantitative analyses indicate a regional rainforest vegetation characterized by podocarpacean-araucariacean conifers, ginkgophytes and/or pentoxylaleans, together with ferns and pteridosperms. A cool temperate, humid climate is indicated. The palynological and megafloral data are complementary, and largely compatible, in vegetational reconstruction. The spore-pollen assemblages are attributable to the upper part of the Cyclosporites hughesii Subzone. This implies a ?Barremian-Aptian age for the Koonwarra Fossil Bed on the basis of the subzone's occurrence in faunally dated marine sequences of the Eromanga and Surat Basins. Taxonomically, the playnoflora comprises 5 algal and 56 spore- pollen species. Retitriletes douglasii is newly instituted; and Trichotomosulcites Couper 1953, the senior synonym of Trisaccites Cookson & Pike 1954, is formally emended. Additionally, several recycled Permian/Triassic forms are recorded.-from Author
