Article

Sharp‐based, tide‐dominated deltas of the Sego Sandstone, Book Cliffs, Utah, USA

December 2001
Sedimentology 48(3):479 - 506

December 2001
48(3):479 - 506

DOI:10.1046/j.1365-3091.2001.00363.x

Authors:

Brian Willis

Chevron

Sharon Gabel

Lee College

The lower part of the Cretaceous Sego Sandstone Member of the Mancos Shale in east-central Utah contains three 10- to 20-m thick layers of tide-deposited sandstone arranged in a forward- and then backward-stepping stacking pattern. Each layer of tidal sandstone formed during an episode of shoreline regression and transgression, and offshore wave-influenced marine deposits separating these layers formed after subsequent shoreline transgression and marine ravinement. Detailed facies architecture studies of these deposits suggest sandstone layers formed on broad tide-influenced river deltas during a time of fluctuating relative sea-level. Shale-dominated offshore marine deposits gradually shoal and become more sandstone-rich upward to the base of a tidal sandstone layer. The tidal sandstones have sharp erosional bases that formed as falling relative sea-level allowed tides to scour offshore marine deposits. The tidal sandstones were deposited as ebb migrating tidal bars aggraded on delta fronts. Most delta top deposits were stripped during transgression. Where the distal edge of a deltaic sandstone is exposed, a sharp-based stack of tidal bar deposits successively fines upward recording a landward shift in deposition after maximum lowstand. Where more proximal parts of a deltaic-sandstone are exposed, a sharp-based upward-coarsening succession of late highstand tidal bar deposits is locally cut by fluvial valleys, or tide-eroded estuaries, formed during relative sea-level lowstand or early stages of a subsequent transgression. Estuary fills are highly variable, reflecting local depositional processes and variable rates of sediment supply along the coastline. Lateral juxtaposition of regressive deltaic deposits and incised transgressive estuarine fills produced marked facies changes in sandstone layers along strike. Estuarine fills cut into the forward-stepped deltaic sandstone tend to be more deeply incised and richer in sandstone than those cut into the backward-stepped deltaic sandstone. Tidal currents strongly influenced deposition during both forced regression and subsequent transgression of shorelines. This contrasts with sandstones in similar basinal settings elsewhere, which have been interpreted as tidally influenced only in transgressive parts of depositional successions.

Untangling the web of life: reconstructing spatial patterns in the palaeoenvironment, palaeoecology and taphonomy of the Western Interior Seaway

Thesis

Jan 2019

Christopher David Dean

A central goal of palaeontology is determining trends in diversity through deep time, but our un- derstanding of these patterns is hampered by bias in the fossil record, arising from taphonomic, geological and anthropogenic causes. These factors can be further exacerbated by environments which are unqiue to the past. Epicontinental seas - shallow, continent covering oceans - were common throughout the Phanerozoic and contain the majority of our available fossil record. Their unique environmental conditions have led to the suggestion that their depositional pro- cesses, palaeo-community structure and taphonomic biases could be driven by different variables than those of otherwise time-equivalent shelf margin settings. Understanding this variation in both time and space is essential for bridging the gap in understanding between these environ- ments and the modern. In this thesis, a series of case studies attempt to understand the spatial patterns in palaeoenvironment, palaeoecology and taphonomy of the Western Interior Seaway, an epicontinental sea from the late Cretaceous of North America. A new method of estimat- ing palaeobathymetry using numerical tidal modelling reports that the seaway was deeper than previously suggested in the mid-Campanian, with tides within the 'Utah Bight' amplified by resonance effects. Analysis of palaeocommunity structure reveals that palaeobiogeography of molluscan fauna varies between the Cenomanian-Turonian and the lower Campanian; the for- mer exhibits a latitudinal gradient whilst the latter shows a homogeneous central seaway. As such, previous suggestions of distinct sub-provinces of fauna can be better explained by other palaeobiogeographic patterns. Differences in sampling probability between calcitic and aragonitic molluscs at varying depths suggest that preferential aragonite bias can be expressed spatially, potentially influencing the perceived range size of aragonitic organisms due to differences in between-site preservation. These studies show that it is important to understand the inherent spatial heterogeneity of the geological record to adequately analyse diversity patterns through time.

Characteristics of a Campanian delta deposit controlled by alternating river floods and tides: the Loyd Sandstone, Rangely Anticline, Colorado, U.S.A.

Article

Dec 2019

The Campanian Loyd Sandstone Member of the Mancos Shale (Loyd) along the Rangely Anticline, Piceance Basin, Colorado, contains a series of multi-meter-thick, heterolithic, coarsening-upward successions (CUSs) with internal clinoforms comprising low-angle-dipping (< 5°), parallel-laminated sandstone beds interbedded with bioturbated flaser-wavy-lenticular bedded sandstone and siltstone. Loyd clinoforms are delta foresets composed of prodelta and delta-front deposits, including mouthbars. Many CUSs exhibit scours filled with bioturbated sandstone, or interbedded bioturbated sandstone and siltstone or mudstone representing aggradational fill of subaqueous terminal distributary channels or the migration of mouthbars into channel scours. Mud drapes on sedimentary structures and mud rip-up clasts are extremely common. A high-abundance, high-diversity, trace-fossil assemblage includes vertical, 1–4-m-deep Ophiomorpha that may penetrate multiple bedsets of parallel-laminated sandstones and highly bioturbated finer-grained interbeds. Bioturbation increases sandstone content in finer-grained interbeds, and provides sandy conduits that increase connectivity between beds. Although parallel-laminated sandstones volumetrically dominate Loyd delta clinoforms, they likely represent relatively short-term freshwater and sediment input during river flooding that produced delta-front turbidity currents. Interbedded finer-grained beds, mud-draped sedimentary structures, and the high-abundance, high-diversity trace-fossil assemblages record longer amounts of time during reduced fluvial discharge, tidal reworking of sediments, and intense bioturbation under marine salinities. Controls on the internal characteristics of the Loyd delta deposits include: 1) a high sediment influx into a relatively shallow marine basin protected from wave action during normal regression; 2) relatively short-duration, episodic freshwater and sediment discharge from distributaries that reduced salinities, deposited sand as turbidity currents, and promoted delta-front channelization; and 3) longer-duration periods of reduced discharge with deposition of finer-grained sediment, tidal reworking, and bioturbation of sediments under higher salinities. These controls combined to produce the heterolithic, highly bioturbated, river-flood delivered, and tidally modified clinoforms of the Loyd that differ from deposits typically considered to be classic examples of fluvial-flood-dominated or extensively tidally modified deltas.

Regional-scale paleobathymetry controlled location, but not magnitude, of tidal dynamics in the Late Cretaceous Western Interior Seaway, USA

Article

Nov 2019
GEOLOGY

Despite extensive outcrop and previous sedimentologic study, the role of tidal processes along sandy, wave- and river-dominated shorelines of the North American Cretaceous Western Interior Seaway remains uncertain, particularly for the extensive mid-Campanian (ca. 75–77.5 Ma) tidal deposits of Utah and Colorado, USA. Herein, paleotidal modeling, paleogeographic reconstructions, and interpretations of depositional process regimes are combined to evaluate the regional-scale (hundreds to thousands of kilometers) basin physiographic controls on tidal range and currents along these regressive shorelines in the “Utah Bight”, southwestern Western Interior Seaway. Paleotidal modeling using a global and astronomically forced tidal model, combined with paleobathymetric sensitivity tests, indicates the location of stratigraphic units preserving pronounced tidal influence only when the seaway had a deep center (~400 m) and southern entrance (>100 m). Maximum tidal velocity vectors under these conditions suggest a dominant southeasterly ebb tide within the Utah Bight, consistent with the location and orientation of paleocurrent measurements in regressive, tide-influenced deltaic units. The modeled deep paleobathymetry increased tidal inflow into the basin and enhanced local-scale (tens to hundreds of kilometers) resonance effects in the Utah Bight, where an amphidromic cell was located. However, the preservation of bidirectional, mudstone-draped cross-stratification in fine- to medium-grained sandstones requires tides in combination with fluvial currents and/or local tidal amplification below the maximum resolution of model meshes (~10 km). These findings suggest that while regional-scale controls govern tidal potential within basins, localized physiography exerts an important control on the preservation of tidal signatures in the geologic record.

Estimating paleobathymetry using numerical tidal modelling in the Cretaceous Western Interior Seaway, USA

Preprint

May 2018

The depth of shallow seas exerts a strong control on water-body mixing, sedimentation and biodiversity but evaluating bathymetry in the geological past has traditionally proven challenging. Despite an extensive sedimentologic record and long history of geologic study, accurate estimates of water depth in the Cretaceous Western Interior Seaway, USA, remain uncertain. Herein paleotidal modelling, paleogeographic reconstructions and depositional process regimes are combined to evaluate the basin physiographic controls on tidal sedimentary processes in the region of the 'Utah Bight' of the Western Interior Seaway and thereby constrain paleobathymetric estimates. Paleotidal modelling using a global and astronomically-forced tidal model and paleobathymetric sensitivity tests suggest that tides were only able to transport silt or sand in the 'Utah Bight' if the seaway had a deeper basin center (~400 m) and a deeper southern entrance (>100 m) than previously estimated. This deeper paleobathymetry increased tidal inflow into the basin and enhanced local resonance effects in the 'Utah Bight'. Maximum tidal velocity vectors suggest a dominant south-easterly ebb tide, consistent with paleocurrent measurements from the Sego Sandstone. However, the preservation of tidal cross stratification in very fine- to fine-grained sandstones implies local tidal amplification below the maximum resolution of model meshes. Tidal modelling is shown to be a useful tool for evaluating paleobathymetry in ancient epicontinental seas at scales appropriate to mesh resolution.

Fluvial to tidal transition in proximal, mixed tide-influenced and wave-influenced deltaic deposits: Cretaceous lower Sego Sandstone, Utah, USA

Article

May 2016
SEDIMENTOLOGY

Facies models for regressive, tide-influenced deltaic systems are under-represented in the literature compared with their fluvial-dominated and wave-dominated counterparts. Here, a facies model is presented of the mixed, tide-influenced and wave-influenced deltaic strata of the Sego Sandstone, which was deposited in the Western Interior Seaway of North America during the Late Cretaceous. Previous work on the Sego Sandstone has focused on the medial to distal parts of the outcrop belt where tides and waves interact. This study focuses on the proximal outcrop belt, in which fluvial and tidal processes interact. Five facies associations are recognized. Bioturbated mudstones (Facies Association 1) were deposited in an offshore environment and are gradationally overlain by hummocky cross-stratified sandstones (Facies Association 2) deposited in a wave-dominated lower shoreface environment. These facies associations are erosionally overlain by tide-dominated cross-bedded sandstones (Facies Association 4) interbedded with ripple cross-laminated heterolithic sandstones (Facies Association 3) and channelized mudstones (Facies Association 5). Palaeocurrent directions derived from cross-bedding indicate bidirectional currents which are flood-dominated in the lower part of the studied interval and become increasingly ebb-directed/fluvial-directed upward. At the top of the succession, ebb-dominated/fluvial-dominated, high relief, narrow channel forms are present, which are interpreted as distributary channels. When distributary channels are abandoned they effectively become estuaries with landward sediment transport and fining trends. These estuaries have sandstones of Facies Association 4 at their mouth and fine landward through heterolithic sandstones of Facies Association 3 to channelized mudstones of Facies Association 5. Therefore, the complex distribution of relatively mud-rich and sand-rich deposits in the tide-dominated part of the lower Sego Sandstone is attributed to the avulsion history of active fluvial distributaries, in response to a subtly expressed allogenic change in sediment supply and relative sea-level controls and autocyclic delta lobe abandonment.

A new interpretation for the Pliensbachian Cook Formation (northern North Sea) as N-S prograding tidal deltas and shelf ridges in Early Jurassic Seaway; new model of linkage to the Norwegian Sea

Article

Full-text available

Jul 2022

The Lower Jurassic Cook Formation reservoir is a hydrocarbon-prolific unit that produces from several fields in the northern North Sea. For 40 years this formation has been interpreted as a westward-prograding deltaic unit sourced from Norway. Despite numerous discoveries, exploration targeting this unit has been hampered by well failures with lack of reservoir sand, discouraging companies from further exploration of this play. During a current re-evaluation of the process sedimentology of the Norwegian offshore basins, the Cook Formation is now interpreted as the middle to distal reaches of a very large, north-to-south-oriented delta system, variably confined within the Early Jurassic Seaway running from the Norwegian Sea into the northern North Sea. The Cook Formation is a subaqueous delta built southward during regression, whereas several internal transgressive phases produced sands that were reworked as north–south-oriented, shelf tidal ridges. The tidal ridges of the Cook Formation constitute some of the best reservoirs and are elongated with stacked, well-sorted, cross-bedded sandstone sets with mudstone drapes. Both the elongate tidal sand-ridges and intervening mudstone-rich, inter-ridge zones are proven by numerous well observations and illustrated by seismic amplitudes. In contrast to earlier eastern derivation models, these new results for the depositional system of the Cook Formation better explain the Cook well successes and failures in the northern North Sea. This work also strongly suggests that the tide-dominated subaqueous delta to transgressive-ridge system of the Cook Formation is spatially linked with the time-equivalent shorelines, subaerial tidal deltas and estuaries of the Tilje Formation in the Haltenbanken region to the north. The Tilje Formation deltas built into the Early Jurassic Seaway due to rift-initiation and rift-shoulder uplift, drained southwards and spilled eventually into the northern North Sea, becoming the entirely subaqueous Cook Formation. The relatively narrow seaway enhanced the tidal currents and suppressed wave activity, resulting in Cook subaqueous delta lobes and ridges without any delta-top facies. Overall, this elongate and extensive, Pliensbachian deltaic to estuarine system of the Early Jurassic Seaway off Norway competes in scale with some of Earth's largest present-day deltas.

Depositional architecture of sub-aqueous part of a tide-dominated delta and its palaeogeographic implications: Laisong Formation (Barail Group), Indo-Myanmar Ranges, western Manipur

Article

Full-text available

Jun 2022

In western Manipur, India, a ~765 m thick dominantly fine-grained succession of the Late Eocene–Early Oligocene Laisong Formation, constituted of siltstone-silty-shale heterolithic units at its lower part and thickly bedded sandstones in the upper part, allowed documentation of subaqueous part of a tidal delta. The abundant incidence of features including lenticular, wavy bedding, starved ripple trains, syn-sedimentary deformation, reactivation and erosional surfaces, double-mud drapes, tangential bottom set contact, rip-up mud clasts bear tell-tale evidence in favour of tidal modulations. Furthermore, a prominent thickening- and coarsening-up progradational facies stacking motif is correlated as signature for tide-dominated delta. From process-based facies and facies succession analysis, five different sub-aqueous environments of delta were delineated which include prodelta, terminal distributary channel, distal delta front, proximal delta front sheet and proximal delta front lobe in order of stratigraphic superposition. The river-fed sediments were extensively reworked by accentuated tidal currents in an embayed coastline, developed along a narrow, elongated ocean basin bordered by the Indian plate on its west and Burmese micro-plate in the east. A local-scale subsidence and sea-level rise is inferred as trigger for the Laisong tidal delta development in the backdrop of its Late Eocene–Early Oligocene time frame that otherwise witnessed large-scale growth of east Antarctic ice sheet and regional scale fall in sea-level.

The Midway to Carrizo Succession in the Southeastern Texas Gulf Coast: Evolution of a Tidally-Influenced Coastline.

Article

Full-text available

Sep 2020

The Midway to Carrizo succession in the southeastern Texas Gulf Coast: Evolution of a tidally-influenced coastline

Deposition and preservation of fluvio‐tidal shallow‐marine sandstones: A re‐evaluation of the Neoproterozoic Jura Quartzite (western Scotland)

Article

Jan 2020

The 2 to 5 km thick, sandstone‐dominated (>90%) Jura Quartzite is an extreme example of a mature Neoproterozoic sandstone, previously interpreted as a tide‐influenced shelf deposit and herein re‐interpreted within a fluvio‐tidal deltaic depositional model. Three issues are addressed: (i) evidence for the re‐interpretation from tidal shelf to tidal delta; (ii) reasons for vertical facies uniformity; and (iii) sand supply mechanisms to form thick tidal‐shelf sandstones. The predominant facies (compound cross‐bedded, coarse‐grained sandstones) represents the lower parts of metres to tens of metres high, transverse fluvio‐tidal bedforms with superimposed smaller bedforms. Ubiquitous erosional surfaces, some with granule–pebble lags, record erosion of the upper parts of those bedforms. There was selective preservation of the higher energy, topographically‐lower, parts of channel‐bar systems. Strongly asymmetrical, bimodal, palaeocurrents are interpreted as due to associated selective preservation of fluvially‐enhanced ebb tidal currents. Finer‐grained facies are scarce, due largely to suspended sediment bypass. They record deposition in lower‐energy environments, including channel mouth bars, between and down depositional‐dip of higher energy fluvio‐ebb tidal bars. The lack of wave‐formed sedimentary structures and low continuity of mudstone and sandstone interbeds, support deposition in a non‐shelf setting. Hence, a sand‐rich, fluvial‐tidal, current‐dominated, largely sub‐tidal, delta setting is proposed. This new interpretation avoids the problem of transporting large amounts of coarse sand to a shelf. Facies uniformity and vertical stacking are likely due to sediment oversupply and bypass rather than balanced sediment supply and subsidence rates. However, facies evidence of relative sea level changes is difficult to recognise, which is attributed to: (i) the areally extensive and polygenetic nature of the preserved facies, and (ii) a large stored sediment buffer that dampened response to relative sea level and/or sediment supply changes. Consideration of preservation bias towards high‐energy deposits may be more generally relevant, especially to thick Neoproterozoic and Lower Palaeozoic marine sandstones. This article is protected by copyright. All rights reserved.

Architecture and preservation in the fluvial to marine transition zone of a mixed‐process humid‐tropical delta: Middle Miocene Lambir Formation, Baram Delta Province, north‐west Borneo

Article

Apr 2019

The interaction of river and marine processes in the fluvial to marine transition zone fundamentally impacts delta plain morphology and sedimentary dynamics. This study aims to improve existing models of the facies distribution, stratigraphic architecture and preservation in the fluvial to marine transition zone of mixed‐process deltas, using a comprehensive sedimentological and stratigraphic dataset from the Middle Miocene Lambir Formation, Baram Delta Province, north‐west Borneo. Eleven facies associations are identified and interpreted to preserve the interaction of fluvial and marine processes in a mixed‐energy delta, where fluvial, wave and tidal processes display spatially and temporally variable interactions. Stratigraphic successions in axial areas associated with active distributary channels are sandstone‐rich, comprising fluvial‐and wave‐dominated units. Successions in lateral, or interdistributary, areas, which lack active distributary channels, are mudstone‐rich, comprising fluvial‐dominated, tide‐dominated and wave‐dominated units, including mangrove swamps. Widespread mudstone preservation in axial and lateral areas suggests well‐developed turbidity maximum zones, a consequence of high suspended‐sediment concentrations resulting from tropical weathering of a mudstone‐rich hinterland. Within the fluvial to marine transition zone of distributary channels, interpreted proximal–distal sedimentological and stratigraphic trends suggest: (i) a proximal fluvial‐dominated, tide‐influenced subzone; (ii) a distal fluvial‐dominated to wave‐dominated subzone; and (iii) a conspicuously absent tide‐dominated subzone. Lateral areas preserve a more diverse spectrum of facies and stratigraphic elements reflecting combined storm, tidal and subordinate river processes. During coupled storm and river floods, fluvial processes dominated the fluvial to marine transition zone along major and minor distributary channels and channel mouths, causing significant overprinting of preceding interflood deposits. Despite interpreted fluvial–tidal channel units and mangrove influence implying tidal processes, there is a paucity of unequivocal tidal indicators (for example, cyclical heterolithic layering). This suggests that process preservation in the fluvial to marine transition zone preserved in the Lambir Formation primarily records episodic (flashy) river discharge, river flood and storm overprinting of tidal processes, and possible backwater dynamics. This article is protected by copyright. All rights reserved.

Geological inheritance and its role in the geomorphological and sedimentological evolution of bedrock-hosted incised valleys, Lake St Lucia, South Africa

Article

Apr 2019

Outcrop analysis and facies model of an Upper Permian tidally influenced fluvio-deltaic system: Northern Sydney Basin, SE Australia

Article

Full-text available

Mar 2019
GEOL MAG

An integrated study of sedimentological, sequence-stratigraphic and palaeodispersal analysis was applied to the Upper-Permian clastic sedimentary succession in the Northern Sydney Basin, Australia. The succession is subdivided into fifteen facies and three facies associations. The facies associations are further subdivided into eight sub-facies associations. The sedimentary evolution involves progradation from delta-front to delta-plain to fluvial depositional environments, with a significant increase in sediment grain size across the unconformable contact that separates the deltaic from the overlying fluvial system. In contrast to the delta front that is wave/storm- and/or river-influenced, the delta plain is significantly affected by tides, with the impact of tidal currents decreasing up-sequence in the delta plain. The general lack of wave-influenced sedimentary structures suggests low wave energy in the delta plain. The abrupt termination of the tidal impact in the fluvial realm relates to the steep topographic gradients and high sediment supply, which accompanied the uplift of the New England Orogen. The sequence-stratigraphic framework includes highstand (deltaic forest and topset) and lowstand (fluvial topset) systems tracts, separated by a subaerial unconformity. In contrast to most of the mud-rich modern counterparts, this is an example of a sand-rich tidally influenced deltaic system, developed adjacent to the source region. This investigation presents a depositional model for tidal successions in regions of tectonic uplift and confinement.

Regional Controls On Depositional Trends In Tidally Modified Deltas: Insights From Sequence Stratigraphic Correlation and Mapping of the Loyd And Sego Sandstones, Uinta And Piceance Basins of Utah and Colorado, U.S.A.

Article

Jul 2016

Conditions for deposition of tidally influenced facies are most commonly associated with transgression; however, tidal influence can also be observed in regressive deposits. Herein we present a regional study that correlates the Loyd and Sego sandstones across the Uinta–Piceance basins, an area rich in both outcrop and subsurface data. Variable energy conditions in these tidally modified deltas result in a complex arrangement of facies and environments, making it difficult to correlate sequence stratigraphic surfaces. We highlight the controls, including tectonics, eustasy, and sediment supply, on depositional environments and sand distribution in these regressive tidally modified deposits. Five environments of deposition (EOD) were identified from a combination of vertical and lateral facies trends and stratal geometries found in outcrops and core. EODs were assigned unique well-log signatures and identified, correlated, and mapped in subsurface logs and outcrop from the Uinta to the Piceance Basin. From a proximal to distal position along shorelines these EODs are: 1) coastal-plain channels and floodplains, 2) tidally influenced valley fills, 3) tidally modified deltas, 4) delta front, and 5) open marine. The regional distribution and stacking of these environments were used to identify ten flooding surfaces and map nine genetic sequences: two in the Loyd Sandstone, four in the lower Sego Sandstone, and three in the upper Sego Sandstone.

Subtidal to intertidal deposits in a mixed clastic-carbonate epicontinental seaway, the Windy Hill Sandstone and Upper Sundance Formation (Oxfordian), Wyoming, U.S.A.

Article

Jul 2023

Oxfordian deposits in northern Colorado and Wyoming, USA preserve proximal, intertidal, clastic, coastal deposits and distal, offshore to nearshore, subtidal bioclastic facies that accumulated during a forced regression of the Jurassic epeiric Sea. This contrasts with the common association between tidal deposits, carbonate facies, and rising sea level common to many depositional models of mixed clastic/carbonate systems. Ichnology, sedimentology, and architecture of these deposits were documented along a 460 km outcrop transect to test previous depositional interpretations and decipher the mechanisms driving the change from proximal, siliciclastic, intertidal flats to distal, bioclastic, subtidal macroforms. In southeastern Wyoming, the Windy Hill Sandstone (WH) is composed of very fine, SiO2-dominated, intertidal facies that truncate offshore to lower shoreface, storm-dominated deposits of the Redwater Shale Member (RS) of the Sundance Fm. Eolian and small fluvial systems delivered sand to the coastline after subaerial erosion reworked it from older, uplifted Jurassic strata onshore. The regional and time-transgressive J-5 unconformity separating the WH from the RS is readily identifiable using ichnological and sedimentological criteria. In the Wind River and Bighorn basins to the north, the Upper Sundance Fm (USF) is time-equivalent to the WH but is composed of glauconitic, silt-prone sandstone and meter to decimeter-scale, bioclastic, cross-bedded sandstone bodies. The abundance of molluscan shell material and limited volume of siliciclastic sediment in the geographically widespread outcrops suggests that nearby, marine shoals were the source of the coarse-grained material. Bioclastic, cross-stratified sandstone bodies represent two architectural elements: 1) coarsening-upward bodies with seaward-dipping foresets arranged into complexes bound by seaward-directed bounding surfaces interpreted to represent subtidal compound dunes and 2) landward- and laterally accreting tidal inlet fills composed of meter-scale, landward-accreting bodies with some landward-directed current ripples. The presence of transgressive tidal inlets supports previous interpretations that the WH and USF record high frequency transgressions superimposed on a tectonically-driven forced regression.

Coastal response to global warming during the Paleocene-Eocene Thermal Maximum

Article

Jun 2023
PALAEOGEOGR PALAEOCL

Tide-dominated deltas responding to high-frequency sea-level changes, Pre-Messinian Rifian Corridor, Morocco: Reply

Article

Aug 2021

Stratigraphy and sedimentary evolution of a modern macro‐tidal incised valley: An analogue for reservoir facies and architecture

Article

Full-text available

Jul 2021

Incised valley fills are complex as they correspond to multiple sea-level cycles which makes interpretation and correlation of stratigraphic surfaces fraught with uncertainty. Despite numerous studies of the stratigraphy of incised valley fills, few have focused on extensive core coverage linked to high fidelity dating in a macro-tidal, tide-dominated settings. For this study nineteen sediment cores were drilled through the Holocene succession of the macro-tidal Ravenglass Estuary in north-west England, UK. A facies and stratigraphic model of the Ravenglass incised valley complex was constructed, to understand the lateral and vertical stacking patterns relative to the sea-level changes. The Ravenglass Estuary formed in five main stages. First, incision by rivers (ca 11,500 to ca 10,500 yrs BP) cutting through the shelf during lowstand, which was a period of fluvial dominance. Secondly, a rapid transgression and landward migration of the shoreline (10,500 to 6000 yrs BP). Wave action was dominant, promoting spit formation. The third stage was a highstand at ca 6000 to ca 5000 yrs BP, creating maximum accommodation and the majority of backfilling. The spits narrowed the inlet and dampened wave action. The fourth stage was caused by a minor fall of sea-level (ca 5000 to ca 226 yrs BP), which forced the system to shift basinward. The fifth and final stage (226 yrs BP to present) involved the backfilling of the River Irt, southward migration of the northerly (Drigg) spit and merging of the River Irt with the Rivers Esk and Mite. The final stage was synchronous with the development of the central basin. As an analogue for ancient and deeply buried sandstones, most of the estuarine sedimentation occurred after transgression, of which the coarsest and cleanest sands are found in the tidal inlet, on the foreshore and within in-channel tidal bars. The best-connected (up to 1 km) reservoir-equivalent sands belong to the more stable channels.

When Is a Barrier Island Not an Island? When It Is Preserved in the Rock Record

Article

Full-text available

Feb 2021

Existing barrier island facies models are largely based on modern observations. This approach highlights the heterogeneous and dynamic nature of barrier island systems, but it overlooks processes tied to geologic time scales, such as multi-directional motion, erosion, and reworking, and their expressions as preserved strata. Accordingly, this study uses characteristic outcrop expressions from paralic strata of the Upper Cretaceous Straight Cliffs Formation in southern Utah to update models for barrier island motion and preservation to include geologic time-scale processes. Results indicate that the key distinguishing facies and architectural elements of preserved barrier island systems have very little to do with “island” morphology as observed in modern systems. Four facies associations are used to describe and characterize these barrier island architectural elements. Barrier islands occur in association with backbarrier fill (FA1) and internally contain lower and upper shoreface (FA2), proximal upper shoreface (FA3), and tidal channel facies (FA4). Three main architectural elements (barrier island shorefaces, shoreface-dominated inlet fill, and channel-dominated inlet fill) occur independently or in combination to create stacked barrier island deposits. Barrier island shorefaces record progradation, while shoreface-dominated inlet fill records lateral migration, and channel-dominated inlet fill records aggradation within the tidal inlet. Barrier islands are bound by lagoons or estuaries and are distinguished from other shoreface deposits by their internal facies and outcrop geometry, association with backbarrier facies, and position within transgressive successions. Tidal processes, in particular, tidal inlet migration and reworking of the upper shoreface, also distinguish barrier island successions. In sum, this study expands barrier island facies models and provides new recognition criteria to account for the complex geometries of time-transgressive, preserved barrier island deposits.

A stratigraphic example of the architecture and evolution of shallow water mouth bars

Article

Nov 2020

Improved understanding of mouth bar morphodynamics, and the resulting stratigraphic architectures, is important for predicting the loci of deposition of different sediment fractions, coastal geomorphic change and heterogeneity in mouth bar reservoirs. Facies and architectural analysis of exceptionally well‐exposed shallow water (ca 5 m depth) mouth bars and associated distributaries, from the Xert Formation (Lower Cretaceous), of the Maestrat Basin (east‐central Spain), reveal that they grew via a succession of repeated autogenic cycles. An initial mouth bar accretion element forms after avulsion of a distributary into shallow standing water. Turbulent expansion of the fluvial jet and high bed friction results in rapid flow deceleration, and deposition of sediment in an aggradational to expansional bar‐form. Vertical bar growth causes flattening and acceleration of the jet. The accelerated flow scours channels on the bar top, which focuses further expansion of the mouth bar at individual loci where the channels break through the front of the mouth bar. Here, new mouth bar accretion elements form, downlapping and onlapping against a readily recognizable surface of mouth bar reorganization. Vertical growth of the new mouth bar accretion elements causes flattening and re‐acceleration of the jet, leading to channelization, and initiation of the next generation of mouth bar accretion elements. Thus the mouth bar grows, until bed‐friction effects cause backwater deceleration and superelevation of flow in the feeding distributary. Within‐channel sedimentation, choking and upstream avulsion of the feeding channel, results in mouth bar abandonment. In this study, mouth bars are formed of at least two to three accretion elements, before abandonment happened. The results of this study contrast with the notion that mouth bars form by simple vertical aggradation and radial expansion. However the architecture and facies distributions of shallow water mouth bars are a predictable product of intrinsic processes that operate to deposit them.

Tidal estuarine deposits of the transgressive Naturita Formation (Dakota Sandstone): San Rafael Swell, Utah, U.S.A.

Article

Aug 2020

Thin tidal estuarine deposits of the Naturita Formation (0–23 m) of the San Rafael Swell record the initial flooding of the Cretaceous Western Interior Seaway, Utah, and capture the transition from inland fluvial systems to fully marine conditions over a time period of 5 My or less. A tide-dominated estuarine environment is favored due to the combined presence of mud and/or carbonaceous drapes on ripples and dunes, bidirectional flow indicators, sigmoidal cross-stratification, herring-bone cross-stratification, and bimodal paleocurrent measurements. Facies associations are arranged in a predictable manner. Locally at the base of the Naturita Formation, tidally influenced fluvial channel deposits are present. These are overlain by tidal bars, including subtidal bars and intertidal point bars. Overlying the tidal bars are sand-flat and mud-flat deposits as well as bedded coal and carbonaceous mudstone that represents a supratidal setting in the estuary. The Formation can be capped by a thin transgressive lag composed of shell debris, and/or pebbles, that marks the final transition into the fully marine Tununk Shale Member of the overlying Mancos Shale. Lateral relationships between estuaries and adjacent paleohighs shed light on the influence of foreland-basin tectonics on the location and preservation of tide-dominated estuaries. Estuarine and shoreface deposits are absent along the eastern flank of the San Rafael Swell and eastward for more than 80 km. This zone of nondeposition or erosion is coincident with the location of the forebulge in the developing foreland basin, implying that growth of the forebulge prohibited the development of, or enhanced the later erosion of, estuarine deposits. Conversely, enhanced accommodation in the transition into the foredeep depozone allow the preservation of tide-dominated estuarine deposits along the western flank of the San Rafael Swell. Additionally, the possibility of a pre-Laramide tectonic history for the San Rafael Swell is indicated by a distinct lack of Naturita Formation deposits in an area that is coincident with the modern-day axis of the anticline. Overall, the Naturita records the initial flooding of the Western Interior Seaway in the San Rafael Swell region and provides an excellent case study of the deposits that are laid down in a transgressive system that passes from coastal-plain to offshore deposits.

Quantifying the stratigraphic and spatial facies distribution in an ancient mixed-influence delta

Article

Feb 2019

Analysis of the sedimentology and stratigraphic architecture of tightly spaced three dimensional outcrops reveals that the Turonian (Upper Cretaceous) Wall Creek Member of the Frontier Formation in the western Powder River Basin, Wyoming, USA, is not composed of one continuous coarsening upward succession but of a complex stacked delta system containing three distinct sequences (S1-S3), each with a unique facies distribution and architectural heterogeneity. The basal sequence S1 consists of a fluvial dominated delta with two distinct lobes. These lobes are spatially constrained to the northeastern study area and show a rapid facies transition from trough crossbedded mouthbar deposits to lower delta front turbidites. Low angle clinoforms suggest a low accommodation setting with main sediment transport to the south. The middle S2 sequence is common throughout the study area and contains an abundance of storm-derived deposits, including hummocky cross stratification, suggesting the transition to a wave and storm-dominated delta setting. Sediment transport is largely to the south controlled by wind induced shear stresses. Lastly, heterolithic trough crossbedded sandstones with flaser bedding and abundant thin mudstones and rip-up clasts are characteristic for sequence S3. These deposits are interpreted as tidal bars in a tidal influenced delta. Quantitative evaluation of facies in the Wall Creek Member sequences shows that the dimensions and connectivity (baffle or barrier competence) of fine-grained thin beds varies systematically within the three delta types. The S1 fluvial delta is largely composed of laterally continuous delta front turbidites with continuous fine-grained thin beds (mean length 21.1 m or 69.2 ft, max length 83.9 m or 275.2 ft) separating individual sandstone beds. Conversely, abundant bioturbation and intense scouring by storms results in high amalgamation of sandy beds in sequence S2 and a limited length of fine-grained thin beds (mean 8.5 m or 27.9 ft) in the wave-dominated delta sequence. Tidally influenced deposits of sequence S3 are largely composed of heterolithic trough crossbedded sandstones and mudstones with low bioturbation, resulting in an intermediate fine-grained thin bed deposit (mean 12.1 m or 39.7 ft).

Characterization of effective permeability in heterolithic, distal lower-shoreface sandstone reservoirs: Rannoch Formation, Brent Group, UK North Sea

Article

Nov 2018

Facies characterisation of a shallow-water deltaic succession: the Upper Jurassic Wagad Sandstone Formation of Kachchh, western India

Article

Full-text available

Aug 2018

Ancient deltaic facies are difficult to differentiate from tidally influenced shallow-marine facies. The Wagad Sandstone Formation of the Wagad Highland (eastern Kachchh Basin) is typified by offshore and deltaic facies with sedimentary characteristics that represent different conditions of hydrodynamics and related depositional processes. The study area, the Adhoi Anticline, constitutes a ~154-m-thick, shale-dominated sequence with progressive upward intercalations of bioturbated micritic sandstone and quartz arenite. Two thick Astarte beds (sandy allochemic limestone), with an erosional base and gravel blanketing, illustrate tidal amplification and high-energy stochastic events such as storms. Sedimentological characteristics document three depositional facies: an offshore, shale-dominated sequence prograding to proximal prodeltaic micritic sandstone and quartz arenite with sandy allochemic limestones, further prograding to mouth bars and abandoned channel deposits. The Wagad Sandstone Formation displays depositional environmental conditions that are dissimilar from those of coeval deposits in Kachchh sub-basins as well as on regional and global scales. This is attributed to a reactivation of the Kachchh Mainland and South Wagad faults which resulted in detachment and uplift of the Wagad block which then experienced prograding deltaic conditions.

Spatial and Temporal Evolution of Coastal Depositional Systems and Regional Depositional Process Regimes: Campanian Western Interior Seaway, U.S.A.

Article

Aug 2018

This paper provides a critical review and regional synthesis of Late Cretaceous shallow-marine deposits along part of the western margin of the Western Interior Seaway of North America, which contains the most extensively documented outcrop-based studies of siliciclastic coastal depositional systems in the world. The results of this synthesis are presented in the form of paleogeographic maps (covering present-day New Mexico, Utah, Colorado, and Wyoming, USA) for five timeslices in the Campanian. These maps are used to evaluate the spatial and temporal evolution of regional depositional process regimes along a large (> 1000 m) stretch of coastline. The evolution of regional depositional process regimes is linked to tectonic and paleoceanographic controls on the Western Interior Seaway, which enables the results of this synthesis to be applied to prediction of depositional process regimes in other, less intensively studied basins. Six gross depositional environments have been mapped for each timeslice: (1) alluvial to coastal-plain sandstones; (2) coastal-plain coals, mudstones, and sandstones; (3) shoreline sandstones; (4) marine mudstones; (5) gravity-flow siltstones and sandstones; and (6) marine marls and chalk. Shoreline sandstones in each timeslice are interpreted in further detail using documented evidence for the three principal classes of depositional process (wave, tidal, and fluvial) and published reconstructions of coastal morphology, which is widely considered to reflect depositional process regime. Based on these interpretations, shoreline sandstones are assigned to five categories of depositional process regime: (1) regressive wave-dominated shorefaces and delta fronts; (2) regressive river-dominated delta fronts; (3) regressive mixed tide- and wave-influenced delta fronts; (4) regressive tide-dominated delta fronts; and (5) transgressive barrier islands, back-barrier lagoons, and estuaries. The accuracy of and uncertainty in classification of depositional process regime are critically evaluated. Additionally, stratal thickness and sediment routing pathways have been interpreted in order to assess the impact of tectonic and paleoceanographic controls on spatial and temporal changes. In all of the evaluated shallow-marine successions, thin tide-influenced intervals were deposited in back-barrier and lagoon systems associated with net-transgressive shorefaces and estuaries. However, it is notable that all preserved tide-dominated and tide-influenced regressive deltaic systems are located along the northern margin of the ''Utah Bight,'' a tectonically related embayment that had a pronounced expression during the middle Campanian. The southern margin of the embayment, and coastlines to the north, are conspicuously more wave-dominated, which supports their exposure to a larger wave fetch. In contrast, the northern margin of the embayment was relatively wave-protected. It is concluded that tidal range was amplified due to resonance of the principal semidiurnal tide in the strongly embayed geometry of the middle Campanian Utah Bight.

Quantifying Mixed-Process Variability In Shallow-Marine Depositional Systems: What Are Sedimentary Structures Really Telling Us?

Article

Oct 2017
J Sediment Petrol

Interpreting the whole range of fluvial, wave, and tidal interactions recorded in shallow-marine, coastal successions can be challenging. The complexity arises because sedimentary structures produced by all three processes can be fully or partially preserved in the same stratal packages, and many of these structures are not diagnostic of a specific process.We therefore need an improved method of capturing the internal facies complexity that characterizes mixed-process coastal systems. We propose a new methodology that assigns a percentage or probability to the likelihood for a bed or stratal unit to be formed by wave (w), tide (t), and fluvial (f) processes via a library of sedimentary structures and their non-unique generating processes. The library was generated through an intensive literature review of ancient, modern, and physical experiment works; the total frequency of association of each structure to each process (wave, tidal, fluvial) is used to calculate the percentage values. Each bed or bedset can be characterized by a specific structure or multiple structures (taking also into account lateral variations). Percentage values of wave/tide/fluvial processes of various structures can be averaged to create a final compound process probability for each bed. Vertical integration of process probability for individual beds in a rock succession creates probability graphs. This methodology has been tested on a 15-meters thick parasequence of the Jurassic Las Lajas Fm., Argentina, and on sedimentary logs of the Cretaceous lower Sego Sandstone, USA, and it is seen to efficiently couple classical facies analysis and surficial-process studies to quantify process variability in ancient systems. Additionally, we assessed the likelihood of association of sedimentary structures not only to hydrodynamic processes but also to depositional sub-environments, through a collection of published sedimentary logs (in modern and ancient deposits) from various basins worldwide. The methodology presented here better quantifies changing process dominance through time, improves the prediction of depositional environment evolution, and helps future studies that aim at a quantification of process variability.

Paleocene-Eocene Stratigraphy and Paleontology of East-Central Texas: Wilcox Group-Claiborne Group-Jackson Group Guidebook.

Conference Paper

Full-text available

Sep 2016

Time-space variability of paralic depositional environments: emphasis on barrier island preservation and paleomorphodynamics

Thesis

Dec 2016

Julia Mulhern

Paralic depositional environments link terrestrial and marine settings and include a variety of environments such as deltas, lagoons, estuaries, barrier islands, tidal deltas, and strand plain shorelines. Influenced by both terrestrial and marine processes, these settings are complex and variable, which both limits and favors their preservation over various timescales through an interplay of deposition, motion, reworking, and ravinement. This dissertation addresses paralic depositional environments with analysis of both modern and ancient examples. An unusually thick succession of marine, paralic, and nonmarine strata from the Cretaceous of southern Utah (John Henry Member, Straight Cliffs Formation) is documented, with a focus on regressive-transgressive cycles and evolution of this part of the Western Interior Seaway, including controls on accommodation and sediment supply. This outcrop analysis leads to a detailed inquiry into barrier island systems, which is addressed by facies models and recognition criteria for three types of barrier island expressions. Databases of modern barrier islands (mapped in Google Earth) and ancient examples from the literature were assembled to further investigate links and disconnects between modern and ancient systems. This analysis is a first step toward developing paleomorphodynamic relationships to predict barrier island dimensions. It also highlights the uncertainty surrounding comparisons between modern and ancient barrier islands, which stems from the complexity of controls on modern barrier island motion and morphology. Additional analysis of the modern database challenges a long-held assumption in coastal geomorphology, which suggests that barrier island shape is a function of tidal range and wave height. Based on shape parameters applied to 702 mapped barrier islands and spits, I determine that tidal range and wave height control <10% of barrier island morphology. Substantial complexity exists in the other 90% of controlling factors, justifying the need for future studies that test the relationship between modern and ancient barrier island systems.

Identifying autogenic sedimentation in fluvial-deltaic stratigraphy: Evaluating the effect of outcrop-quality data on the compensation statistic

Article

Full-text available

Dec 2016

Stratigraphy preserves an extensive record of Earth-surface dynamics acting over a range of scales in a variety of environments. To take advantage of this record, we first must distinguish depositional patterns that arise due to intrinsic (i.e. autogenic) landscape dynamics from sedimentation that results from changes in climate, tectonic, or eustatic boundary conditions. The compensation statistic is a quantitative tool that has been used to estimate scales and patterns of autogenic sedimentation in experimental deposits; it has been applied to a few outcrop studies, but its sensitivity to data limitations common in natural deposits remains unconstrained. To explore how the compensation statistic may be applied to outcrop data, we evaluate the sensitivity of the tool to stratigraphic datasets limited in extent and resolution by subsampling an autogenic experimental deposit to create pseudo-outcrop-scale datasets. Results show that for datasets more than three-times thicker than a characteristic depositional element (e.g., channel or lobe), the compensation statistic can be used reliably constrain the maximum scale of autogenic sedimentation even for low-resolution datasets. Additionally, we show that autogenic sedimentation patterns may be characterized as persistent, random, or compensational using the compensation statistic when datasets are high-resolution. We demonstrate how these measurements can be applied to natural datasets with comparative case studies of two fluvial and two deltaic outcrops. These case studies show how the compensation statistic can provide insight into what controls the maximum scale of autogenic sedimentation in different systems and how landscape dynamics can produce organized sedimentation patterns over long timescales.

Tidally influenced shoal water delta and estuary in the Middle Jurassic of the Søgne Basin, Norwegian North Sea: Sedimentary response to rift initiation and salt tectonics

Article

Full-text available

Jun 2016

Recent studies in the Middle Jurassic Bryne and Sandnes formations, primary reservoirs in several fields across the Norwegian and Danish North Sea, show the widespread occurrence of tidal-influenced and tide-dominated deposits. Aalenian–Bajocian Bryne cores reflect deposition by a shoal water, tidally influenced delta onto a low wave energy tidal platform (both supratidal and intertidal) that probably occupied the majority of the Søgne Basin, a narrow rift system connected to the Central and Danish graben and transgressed from an open-marine basin, possibly located to the south. At the Bathonian–Callovian boundary, a new phase of rifting and progressive salt movements led to the deposition of the upper Bryne and Sandnes formations within an 80–100 km long composite estuarine valley. Basin tilting to the south and continued transgression resulted in tidal deltas that offlap the northern margin of the basin. The basin was fully transgressed by the end of the Callovian. From the Late Bathonian onwards, differential tectonic movements along the broadly interconnected Middle Jurassic rift basins led to a change in the transgression direction from south to north, with an open-marine basin located in the Central and Viking graben.

Deflection of the progradational axis and asymmetry in tidal seaway and strait deltas: Insights from two outcrop case studies

Article

Jun 2016

Deltas represent the major sediment source for tectonically-confined, tide-dominated seaways or straits. Modern examples show how alongshore tidal currents are able to modify the impinging delta shape, generating asymmetrical coastal plains, deflected delta-fronts and elongate sandbanks. Seaway or strait deltas become tide-influenced or tide-dominated, assuming physical attributes, which can depart from classical models. Ancient deltas in seaways and straits can also reveal unexpected facies stacking and stratigraphies, which can be misinterpreted or attributed to different depositional settings. In this paper, two ancient analogues of deltas which prograded into elongate basins dominated by amplified tidal currents are presented. A common element in these deltas is the progressive upward change in the dominant process of sediment dispersion recorded in the delta facies. Early stages of progradation are dominated by river and wave influenced lithofacies, whereas late deltaic advancements occur with dominance of tidal current circulation on the delta-fronts and consequent morphologies deflected/elongate in the direction of the tidal flow. This study provides the basis for a preliminary stratigraphic framework for the depositional style of such type of deltas. The studied deposits also suggest analogies with the spatial distribution of many hydrocarbon reservoirs investigated along the margins of confined, narrow-linear basins and whose interpretation is still debated.

Facies model for a coarse-grained, tide-influenced delta: Gule Horn Formation (Early Jurassic), Jameson Land, Greenland

Article

Full-text available

Feb 2016
SEDIMENTOLOGY

Tide-dominated deltas have an inherently complex distribution of heterogeneities on several different scales, and are less well-understood than their wave- and river-dominated counterparts. Depositional models of these environments are based on a small set of ancient examples, and are therefore immature. The Early Jurassic Gule Horn Formation is particularly well-exposed in extensive sea-cliffs from which a 32 km long, 250 m high virtual outcrop model has been acquired using helicopter-mounted lidar. This dataset, combined with a set of sedimentological logs, facilitate interpretation and measurement of depositional elements and tracing of stratigraphic surfaces over seismic-scale distances. The aim of this paper is to use this dataset to increase the understanding of depositional elements and lithologies in proximal, unconfined, tide dominated deltas from the delta plain to prodelta. Deposition occurred in a structurally controlled embayment, and immature sediments indicate proximity to the sediment source. The succession is tide-dominated but contains evidence for strong fluvial influence and minor wave-influence. Wave-influence is more pronounced in transgressive intervals. Nine architectural elements have been identified, and their internal architecture and stratigraphical distribution has been investigated. The distal parts comprise prodelta, delta front and unconfined tidal bar-deposits. The medial part is characterized by relatively narrow, amalgamated channel-fills with fluid mud-rich bases and sandier deposits upwards, interpreted as distributary channels filled by tidal bars deposited near the turbidity maximum. The proximal parts of the studied system are dominated by sandy distributary channel and heterolithic tidal-flat deposits. The sandbodies of the proximal tidal channels are several kilometres wide, and wider than exposures in all cases. Parasequence boundaries are easily defined in the prodelta to delta front environments, but are difficult to trace into the more proximal deposits. This article illustrates the proximal-to-distal organization of facies in unconfined tide-dominated deltas, and shows how such environments react to relative sea-level rise. doi: 10.1111/sed.12270

Depositional and provenane record of the Paleogene transition from foreland to hinterland basin evolution during Andean orogenesis, northern Middle Magdalena Valley basin, Colombia

Article

Full-text available

Mar 2011

The Central Cordillera and Eastern Cordillera of the northern Andes form the topographic flanks of the north-trending Magdalena Valley Basin. Constraining the growth of these ranges and intervening basin has implications for Andean shortening and the transformation from a foreland to hinterland basin configuration. We present sedimentological, paleocurrent, and sandstone petrographic results from Cenozoic type localities to provide insights into the tectonic history of the northern Middle Magdalena Valley Basin of Colombia. In the Nuevo Mundo Syncline, the mid-Paleocene transition from marine to nonmarine deposystems of the Lisama Formation corresponds with a paleocurrent shift from northward to eastward transport. These changes match detrital geochronological evidence for a contemporaneous shift from cratonic (Amazonian) to orogenic (Andean) provenance, suggesting initial shortening-related uplift of the Central Cordillera and foreland basin generation in the Magdalena Valley by mid-Paleocene time. Subsequent establishment of a meandering fluvial system is recorded in loweremiddle Eocene strata of the lower La Paz Formation. Eastward paleocurrents in mid-Paleocene through uppermost Eocene fluvial deposits indicate a continuous influence of western sediment source areas. However, at the upper middle Eocene (w40 Ma) boundary between the lower and upper La Paz Formation, sandstone compositions show a drastic decrease in lithic content, particularly lithic volcanic fragments. This change is accompanied by a facies shift from mixed channel and overbank facies to thick, amalgamated braided fluvial deposits of possible fluvial megafans, reflecting changes in both the composition and proximity of western sediment sources. We attribute these modifications to the growing influence of exhumed La Cira-Infantas paleohighs in the axial Magdalena Valley, features presently buried beneath upper EoceneeQuaternary basin fill along the western flank of the Nuevo Mundo Syncline. In uppermost Eocene strata of the lower Esmeraldas Formation, paleocurrents show a sharp reversal from eastward to dominantly westward transport that persisted into the Neogene. The Esmeraldas also records a change to more-distal, floodplain-dominated deposition of finer sediments. These adjustments are interpreted to reflect burial of the La Cira-Infantas highs and onset of Eastern Cordillera exhumation, resulting in a transition from foreland to hinterland basin conditions in the Magdalena Valley. The lack of significant variation in sandstone compositions suggests a bulk-rock compositional similarity between the La Cira-Infantas paleohighs (subsurface Magdalena Valley) and the Eastern Cordillera. Collectively, the data presented here refine previous thermochronologic and provenance studies and suggest that major uplift-induced exhumation in the Central Cordillera and Eastern Cordillera commenced by the mid-Paleocene and latest Eocene, respectively.

A tale of two end members: Tidal deposits in a semi‐arid, low subsidence, open coastal setting versus a high runoff, high subsidence, restricted environment

Article

Full-text available

Apr 2024

Jurassic and Palaeocene tidal deposits of the epeiric Western Interior Sea in Wyoming, USA, differ significantly due to their contrasting climates and tectonic, geographic and depositional settings. Tidally generated, cross‐bedded sandstone bodies contained by incisions are common to both settings and can potentially be uncritically attributed to marine flooding of fluvial systems. Key differences in lithology, ichnology and relationships with surrounding sediment reveal fundamentally different depositional settings, however. The Jurassic system occupied a low accommodation, semi‐arid environment, with geographically open shorelines as relative sea‐level fell, creating an unconformable contact with the underlying, storm wave‐dominated shelf and shoreface deposits. Siliciclastic, intertidal flats formed adjacent to coastal aeolian and fluvial environments during brief turnarounds from the degradational (forced regressive) to aggradational and retrogradational (transgressive) system tract. Basinward of these environments, metre to decimetre‐scale cross‐bedded, bioclastic, subtidal compound dunes and tidal inlet complexes accumulated in areas of minimal clastic flux and within incisions created by submarine tidal currents. By contrast, the Palaeocene tidal systems formed in a high accommodation, subtropical setting, as rising sea levels forced the fluvial to marine transition zone landward and flooded coastal swamps, forming geographically irregular, back‐barrier complexes and tidally influenced fluvial systems. High volumes of siliciclastics, terrigenous organic material and freshwater were delivered by the rivers and created physicochemical stress on the marine embayments. Sandy tidal flat deposits accumulated in lagoons and interdistributary bays, but unlike the Jurassic examples, they do not mark a turnaround from the falling stage to the transgressive system tract. The potential preservation window for tidalites is significantly greater vertically in the aggradational to retrogradational setting than in the degradational system due to greater accommodation. The preservation window is vertically smaller, but areally greater in the Jurassic, forced regressive system because of basinward enhancement of tidal currents driven by complex palaeobathymetry caused by tectonic activity of local pre‐Laramide uplifts.

Sedimentary facies and stratigraphy of the campanian-maastrichtian taloka formation, southeastern Iullemmeden Basin, Nigeria

Article

Jan 2023

Prediction of shoreline–shelf depositional process regime guided by palaeotidal modelling

Article

Full-text available

Oct 2021
EARTH-SCI REV

Ancient shoreline–shelf depositional systems are influenced by an unusually wide array of geological, biological and hydrodynamic processes, with sediment transport and deposition primarily determined by the interaction of river, wave (including storm) and tidal processes, and changes in relative sea level. Understanding the impact of these processes on shoreline–shelf morphodynamics and stratigraphic preservation remains challenging. Numerical modelling integrated with traditional facies analysis provides an increasingly viable approach, with the potential to quantify, and thereby improve understanding of, the impact of these complex coastal sedimentary processes. An integrated approach is presented here that focuses on palaeotidal modelling to investigate the controls on ancient tides and their influence on sedimentary deposition and preservation – one of the three cornerstones of the ternary process classification scheme of shoreline-shelf systems. Numerical tidal modelling methodology is reviewed and illustrated in three palaeotidal model case studies of different scales and focus. The results are synthesised in the context of shoreline–shelf processes, including a critique and modification of the process-based classification scheme. The emphasis on tidal processes reflects their global importance throughout Earth’s history. Ancient palaeotidal models are able to highlight and quantify the following four controls on tidal processes: (1) the physiography (shape and depth) of oceans (1000s km scale) determines the degree of tidal resonance; (2) the physiography of ocean connections to partly enclosed water bodies (100–1000s km scale) determines the regional-scale flux of tidal energy (inflow versus outflow); (3) the physiography of continental shelves influences shelf tidal resonance potential; and (4) tides in relatively local-scale embayments (typically 1–10s km scale) are influenced by the balance of tidal amplification due to funnelling, shoaling and resonance effects versus frictional damping. In deep time, palaeogeographic and palaeobathymetric uncertainty can be accounted for in palaeotidal models by performing sensitivity analyses to different scenarios, across this range of spatial scales. These tidal process controls are incorporated into an updated predictive decision tree for determining shoreline–shelf process regime in terms of the relative interaction of wave, fluvial and tidal processes. The predictive decision tree considers the effects of basin physiography, shelf width and shoreline morphology on wave, fluvial and tidal processes separately. Uncertainty and ambiguity in applying the widely used three-tier process classification scheme are reduced by using the decision tree in conjunction with a proposed two-tier classification of process regime that is limited to primary and secondary processes. This two-tier classification scheme is illustrated in the three case studies, showing how integration of numerical modelling with facies analysis of the preserved stratigraphic record improves confidence in prediction of tide-influenced shoreline-shelf process regimes. Wider application of this approach will further improve process-based classifications and predictions of modern and ancient shoreline–shelf systems.

Sedimentology and Stratigraphy of an Upper Permian Sedimentary Succession: Northern Sydney Basin, Southeastern Australia

Article

Full-text available

Jun 2021

This study integrates sedimentological and stratigraphic insights into the Upper Permian sedimentary rocks of the Wittingham, Tomago and Newcastle Coal Measures in the Northern Sydney Basin, Australia. Facies analysis documented fifteen facies that belong to seven facies associations. These facies associations correspond to different depositional environments and sub-environments including prodelta, delta-front, upper, lower delta-plain and fluvial. The stratigraphic development points to a shallowing upward trend and is reflected with fluvial deposits sitting on top of the deltaic deposits. The fluvio-deltaic contact is represented by an unconformity and displays an upward increase in sediment caliber. The delta front is mainly controlled by wave, storms- and/or river currents, even though the contribution of tides also occurs in the form of sedimentary structures that suggest tidal influence. In contrast, prodelta and delta-plain are significantly modulated by tidal currents. The impact of tides in the delta plain is fading away upward and therefore, the upper delta plain is much less impacted compared to the lower delta plain. The low abundance of wave ripples suggests that the wave action was not very important in the delta plain. Steep topographic gradients and increased sediment input are suggested, based on the limited or absent evidence of tides in the fluvial realm, related to the growing New England Orogen. In sequence stratigraphic terms, the deltaic system accumulated during highstand normal regression, while the deposition of the overlying fluvial system occurred during lowstand normal regression. The two systems are separated by a subaerial unconformity developed during an intervening forced regression. Short periods of transgression are inferred from the presence of higher frequency cycles in the delta-front.

Predicting shoreline depositional process regimes using insights from palaeotidal modelling

Preprint

Aug 2020

This review demonstrates the benefit of numerical tidal modelling, calibrated by integrated comparison to the preserved stratigraphic record, and offers a refined classification and prediction of shoreline process regimes. Wider and consistent utilisation of these concepts, and numerical simulations of other depositional processes, will further improve process-based classifications and predictions of modern and ancient shoreline systems.

Sedimentary Architecture of Storm-Influenced Tidal Flat Deposits of the Upper Mulichinco Formation, Neuquén Basin, Argentina

Article

Full-text available

Jul 2020

This study reports on the Lower Cretaceous upper Mulichinco Formation in the Neuquén Basin, west-central Argentina. The studied succession comprises shallow marine strata, deposited in a mixed wave and tidal flat environment where ebb-tidal currents dominated. We describe mixed storm- and tide-influenced deposits within progradationally stacked high-frequency sequences and discuss process interaction, sediment dispersal, and preservation potential. These storm and tidal deposits mix spatially on bed, bedset, and sequence scales, suggesting multi-scale process interactions. The study investigates a 12-km-long continuous outcrop, oriented sub-parallel to the paleocoastline. The succession comprises subtidal flat and meandering tidal channel complexes, with interbedding and interfingering of storm and tidal deposits. The tidal deposits are widespread and comprise moderately sorted sandstones with bimodal paleocurrent directions, single and double mud drapes, reactivation surfaces, and inclined heterolithic stratification. Varying bimodal paleocurrent directions suggest that the paleocoastline was irregular, consisting of both protrusions and bays. Storm deposits are mainly found erosively interbedded with subtidal flat sandstones, and exhibit decimeter-thick, well-sorted hummocky and swaley cross-stratified sandstones. These storm deposits show systematic lateral variations in abundance, from dominant to absent, which are linked to subtle variations in water depth along the irregular paleocoastline. As the tidal deposits are widespread across the study area, and with no significant facies change, the varying dispersal of storm-influenced deposits is considered a product of wave refraction, with converging and diverging wave energy at interpreted positions of coastal protrusions and embayments, respectively. Consequently, the irregular paleocoastline morphology caused spatial variability in wave impact and controlled preservation of interbedded storm and tidal deposits at the coastal protrusions while facilitating complete tidal remobilization of sediments in the embayments. With no evidence for fluvial influence, ebb-tidal currents are considered as the main drivers for sediment dispersal onto the subtidal flat, through the meandering tidal channels.

Marine Fazies

Chapter

Jan 2019

Andreas Schäfer

Die marine Fazies ist abhängig von der Strukturbildung des Kontinents, von dessen Bereitstellung von Sedimenten, von der Exposition der Küste gegenüber einem Ozean, Schelfmeer oder Nebenmeer. Sie ist eingebunden in den großregionalen Klimaraum, der detritisch-siliciklastische Sedimentation in höheren Breiten und biogen-karbonatische Sedimentation in niederen Breiten begünstigt. Schließlich wird sie erheblich modifiziert vom Einfluss der Gezeitenamplitude, die sehr verschiedene Wasserstände bringen kann.

The Unconformity That Isn’t: A Sequence-Stratigraphic Reinterpretation of the J-5 Unconformity and the Redwater–Windy Hill–Morrison Transition in Wyoming, USA

Article

Apr 2020

Differentiating Amalgamated Parasequences in Deltaic Settings Using IchnologyAn Example from the Upper Turonian Wall Creek Member of the Frontier Formation, Wyoming

Chapter

Jan 2007

Depositional facies and the sequence stratigraphic control of a mixed‐process influenced clastic wedge in the Cretaceous Western Interior Seaway: The Gallup System, New Mexico, USA

Article

Sep 2019

Depositional facies have been hypothesized to be linked to sequence stratigraphic positions. Also, shoreline systems are built by mixed processes, including rivers, storms, fair‐weather waves and tides. Resolving the complexity of shoreline deposition requires detailed quantitative facies analysis with particular attention to heterolithic successions. In this study, 71 sections in a 130 km long outcrop belt of the Cretaceous Gallup Formation in the north‐west of the San Juan Basin were measured. Five major facies associations were identified using sedimentological and iconological interpretations, including offshore shelf, non‐deltaic shoreline sandstones, deltas, coastal bayline and fluvial. Each facies association also comprises subordinate facies. Depositional facies interpretations are placed in a high‐resolution sequence stratigraphic framework that allows for reconstructions of the palaeogeography of individual parasequence sets that demonstrate temporal and spatial evolution of facies associations and depositional processes. The results show that the Gallup is a mixed‐process‐controlled depositional system with fair‐weather and storm wave dominance, river influence and tide‐effect, contrasting with previous interpretations of a solely fair‐weather wave‐dominated environment. Depositional processes and the resultant facies change with sequence stratigraphic positions in response to relative sea‐level changes – particular facies only deposited in certain systems tracts. Distinction and transition between non‐deltaic shorefaces and wave‐dominated deltas have also been documented in this study. Non‐deltaic shorefaces are characterized by homogeneous sandstones with a wide‐range bioturbation index and the absence of mudstones. Wave‐dominated deltas are subject to river influence and contain prodelta facies. This study shows the importance of detailed facies analysis with high‐resolution sequence stratigraphic control using outcrops for documenting sedimentary processes of shallow marine shoreline systems.

Deltaic sedimentary environments in the Niger Delta, Nigeria

Article

Aug 2019
J AFR EARTH SCI

This study is focused on the geomorphology of surface sedimentary environments contained in the fluvial, tidal and wave-dominated areas of the Niger Delta. GIS techniques applied to high-quality Landsat and SPOT images were used to identify and map landforms and processes, as well as quantitatively characterise their metrics and spatial distribution. A detailed analysis shows that the extent of the Niger Delta is 70,000 km², contrary to previous publications that reported 75,000 km². The delta has also been remapped and classified into mega sedimentary environments: the upper deltaic plain is 69% of the total extent, while the lower deltaic plain and delta front are 25% and 6% respectively. Other subunits were distinguished and mapped within the upper deltaic plain such as fluvial channels, point bars, braid bars, oxbow lakes, and other lakes. Tidal channels, beaches and spits were identified in the lower deltaic plain and delta front. The geometries of these sedimentary bodies (landforms) appear to be relatively scale-invariant, thus meaning that from the measurement of some dimensional parameters (e.g. the length) it is possible to estimate all others (e.g. the width and overall extent). This is an aspect of great relevance in subsurface analyses where it is often difficult to predict the extent of sedimentary bodies. The correlation between channel width and length (r² = 0.9), is the strongest relationship found between sedimentary body metrics.

Facies and the Architecture of Estuarine Tidal Bar in the Lower Cretaceous Mcmurray Formation, Central Athabasca Oil Sands, Alberta, Canada

Article

Full-text available

May 2019

In this study, data obtained from the Lower Cretaceous McMurray Formation in the central Athabasca Oil Sands, northeastern Alberta, Canada, are examined and used to establish the architecture of stacked fluvial and estuarine tidal bar deposits. A total of 13 distinguishable facies (F1–F7, F8a–F8b, and F9–F13) corresponding to stacked fluvial and estuarine deposits are recognized. These facies are then reassembled into four facies associations: fluvial deposits, tidal flat, tidal bar complex, and tidal bar cap. Of these, the lower fluvial deposits show a highly eroded channel lag and tidal influences in the cross-stratified sand and wavy interbeds. The fluvial deposits pass upwards into upper tidal-dominated tidal flats and a massive homogeneous tidal sand bar complex. Very thick tidal-influenced facies (F8a–F8b, up to 22 m) caused by semi-diurnal and semi-lunar cycles are also observed in tidal flats. Based on studies of the facies and facies associations, a three-dimensional (3-D) architecture model is finally established and used to analyze the internal distribution of the stacked fluvial and estuarine deposits. This is the first time that a 3-D model of the paleo-estuary tidal bar has been constructed. The results of this study will assist future research analyzing the architecture of stacked fluvial and estuarine deposits.

The Ichnological and Sedimentological Signature of a Late Paleozoic, Postglacial Marginal-Marine and Shallow-Marine, Tidally Influenced Setting: The Wudayhi Member of the Nuayyim Formation (Unayzah Group) in the Subsurface of Central and Eastern Saudi Arabia

Article

Sep 2018

Sedimentation in the Nuayyim Formation across subsurface central and eastern Saudi Arabia has been chiefly ascribed to continental sedimentary environments. However, a number of levels in this formation show evidence for marginal-marine and shallow-marine sedimentation. This paper documents trace-fossil faunas and sedimentological characteristics from these facies and presents a regional depositional model for the Wudayhi Member that confirms the presence of shallow-marine sedimentary environments. Marginal-marine and shallow-marine sedimentation in the Wudayhi Member includes estuarine deposits and upper-shoreface through lower-shoreface deposits. They are reflective of several transgressive-regressive (T-R) cycles in an overall shoaling-upwards, tidally influenced progradational succession that exhibit mixed-process (wave-, tide-, and fluvially-influenced) depositional environments. The succession displays an overall upward decrease in bioturbation intensity with elements of an impoverished proximal expression of the Cruziana Ichnofacies at the base in proximal- and distal- lower-shoreface deposits (Facies 5-6), passing into an impoverished expression of the Skolithos Ichnofacies in upper-shoreface deposits (Facies 4). Therein, Facies 5 records storm-influenced sedimentation and includes hummocky cross-stratification (HCS), combined-flow ripples, cross-lamination, and ichnofossils that alternate between storm-related and fair-weather assemblages. An overall reduction in both the diversity of ichnogenera and the intensity of burrowing across the shoreface profile, an apparent lack of middle-shoreface deposits, and the occurrence of storm-wave-generated structures interspersed with tidally generated structures in the center and southeast of the study area are interpreted as tidal modulation, suggesting macrotidal conditions at the time of sediment deposition. Estuarine sedimentation includes coal deposits (Facies 1), tidal flats (Facies 2), and fluvio-tidal deposits (Facies 3) that overlie the succession, and display a stressed, impoverished mixture of traces with facies-crossing elements of the Skolithos and Cruziana Ichnofacies in the north and northwest of the study area. Sedimentation took place on a broad and sandy, partially restricted shelf, chiefly influenced by tidal currents that was variably fluvially influenced. The interplay of the aforementioned processes results in a complex architecture that is traceable, based on the sedimentological and ichnological content. Colonization by bioturbating infauna exhibiting elements of an overall impoverished Skolithos and Cruziana Ichnofacies in the Wudayhi Member is interpreted to be related to sea-level rise, with regional transgression induced by the melting of glacier ice following the Late Carboniferous to Early Permian glaciation that affected southern Gondwana. Subsequently, as the Arabian Plate migrated northwards, isostatic rebound concomitant with increased tectonism associated with the Neotethys propagating into the Arabian Peninsula caused regional regression responsible for the progradational sequence presented herein in the Early to Middle Permian. Trace-fossil associations and ichnofacies presented in this paper are significant, because they provide evidence for marginal-marine and shallow-marine tide- and storm-influenced processes in the Unayzah Group during deposition of the Wudayhi Member of the Nuayyim Formation. Furthermore, it establishes a framework than can be linked to fully marine coeval deposits southeastern of the Arabian Peninsula into Oman.

Tectonic controls on Late Cretaceous sediment provenance and stratigraphic architecture in the Book Cliffs, Utah

Article

May 2018

Middle-late Campanian strata of the Book Cliffs, Utah, USA, archive three clastic wedges of the North American Cordilleran foreland basin east of the Sevier fold and thrust belt. Variations in wedge geometries provide an opportunity to evaluate controls on foreland basin stratigraphic architecture. There is a significant increase in eastward progradation rate from the Lower to Upper Castlegate Sandstone, followed by a decreased progradation rate in the overlying Bluecastle Tongue and Price River Formation. Rapid progradation during deposition of the Upper Castlegate Sandstone has been attributed to increased sediment supply due to either rapid exhumation of the Sevier fold and thrust belt or introduction of a new sediment source. Rapid progradation has also been attributed to a reduction in basin subsidence due to intraforeland Laramide uplifts or a change in the locus of dynamic subsidence. We test these hypotheses by documenting temporal and spatial changes in the detrital zircon U-Pb age spectra attributable to changes in sediment dispersal patterns, changes in orogenic belt configuration, and/or major tectonic episodes. Mixture modeling of relative contributions from potential source areas indicates a mixed contribution of thrust-belt, northern, and southern sources during rapid progradation. The introduction of multiple sources is likely due to a northward propagation of exhumation in the thrust belt coeval with introduction of axially-sourced detritus in the medial-distal foreland basin. The northward propagation of exhumation culminated with exhumation in the Charleston-Nebo Salient and Uinta Uplift north of the Book Cliffs and may point to a common cause for these phenomena. Mixture modeling points to a change to a dominant southern source during slower progradation in the overlying strata. The return to slower progradation is coeval with a decrease in thrust-belt derived detritus and transition to a dominant southern-source contribution. Transition to a dominantly axial fluvial system during this interval is consistent with a northeastward migration of the regional depocenter. Migration of subsidence and exhumation can be attributed to dynamic subsidence and uplift associated with the northeastward subduction of the Conjugate Shatsky Rise oceanic plateau beneath the Book Cliffs area. Rapid progradation observed during deposition of the Upper Castlegate Sandstone was controlled by a combination of increased sediment supply due to increased exhumation in the Sevier thrust belt and introduction of multiple sources.

Depositional evolution of a progradational to aggradational, mixed-influenced deltaic succession: Jurassic Tofte and Ile formations, southern Halten Terrace, offshore Norway

Article

Feb 2017
MAR PETROL GEOL

Predicting the hydrodynamics, morphology and evolution of ancient deltaic successions requires the evaluation of the three-dimensional depositional process regime based on sedimentary facies analysis. This has been applied to a core-based subsurface facies analysis of a mixed-energy, clastic coastal-deltaic succession in the Lower-to-Middle Jurassic of the Halten Terrace, offshore mid-Norway. Three genetically related successions with a total thickness of 100–300 m and a total duration of 12.5 Myr comprising eight facies associations record two initial progradational phases and a final aggradational phase. The progradational phases (I and II) consist of coarsening upward successions that pass from prodelta and offshore mudstones (FA1), through delta front and mouth bar sandstones (FA2) and into erosionally based fluvial- (FA3) and marine-influenced (FA4) channel fills. The two progradational phases are interpreted as fluvial- and wave-dominated, tide-influenced deltas. The aggradational phase (III) consists of distributary channel fills (FA3 and FA4), tide-dominated channels (FA5), intertidal to subtidal heterolithic fine-grained sandstones (FA6) and coals (FA7). The aggradational phase displays more complex facies relationships and a wider range of environments, including (1) mixed tide- and fluvial-dominated, wave-influenced deltas, (2) non-deltaic shorelines (tidal channels, tidal flats and vegetated swamps), and (3) lower shoreface deposits (FA8). The progradational to aggradational evolution of this coastal succession is represented by an overall upward decrease in grain size, decrease in fluvial influence and increase in tidal influence. This evolution is attributed to an allogenic increase in the rate of accommodation space generation relative to sediment supply due to tectonic activity of the rift basin. In addition, during progradation, there was also an autogenic increase in sediment storage on the coastal plain, resulting in a gradual autoretreat of the depositional system. This is manifested in the subsequent aggradation of the system, when coarse-grained sandstones were trapped in proximal locations, while only finer grained sediment reached the coastline, where it was readily reworked by tidal and wave processes.

TIDES AND DELTAIC MORPHODYNAMICS

Conference Paper

Jan 2016

Piret Plink-Bjorklund

Tide-dominated and tide-influenced deltas are not widely recognized in the ancient record, despite the numerous modern and Holocene examples, including eight of the twelve modern largest deltas in the world, like the Ganges–Brahmaputra, Amazon, Chang Jiang, and Irrawadi. Tide-dominated or -influenced deltas are assumed to be more common in inner-shelf or embayment settings, because wave energy is expected to be higher and tidal energy lower in outer shelf and shelf-edge. However, there are ancient examples of tide-influenced shelf-edge deltas, indicating that the controls on tidal morphodynamics in deltas are not yet well understood. This paper asks the following questions: (1) How do tides influence delta deposition, beyond creating tidal facies? (2) Does tidal reworking create specific geometries in delta clinoforms? (3) Does tidal reworking change progradation rates of deltas? (4) Is significant tidal reworking restricted to inner-shelf deltas only? (5) What are the conditions at which deltas may be tide-influenced or -dominated at the shelf edge? (6) What are the main morphodynamic controls on the degree of tidal reworking? The paper utilizes a dataset of multiple ancient and modern deltas, situated both on the shelf and shelf edge. We show that beyond the commonly recognized shore-perpendicular morphology and the recognizable tidal facies, there are changes in delta clinoform morphology, morphodynamics of delta lobe switching, delta front progradation rates, and the nature of the delta plain. Strong tidal influence is here documented to promote subaqueous, rapid progradation of deltas, by efficiently removing sediment from river mouth and thus reducing mouth bar aggradation and fluvial delta plain construction rates. The delta front clinoforms become gentler and longer. Tide-dominated deltas tend to maintain a funnel shape and show low lobe switching rates. The funnel and thus river mouth position is further stabilized by fine-grained sediment accumulation on marginal tidal flats due to the flood current sediment transport. All these effects weaken as the deltas prograde to the shelf edge, due to the loss of vertical (and lateral) restriction and tidal amplification. Here significant tidal reworking is restricted to topographic irregularities.

Facies and architecture of unusual fluvial–tidal channels with inclined heterolithic strata

Chapter

Full-text available

Dec 2015

The sedimentary facies and architecture of Late Campanian fluvial–tidal channels and channel belts of the Neslen Formation are described from the Floy area of the upper Book Cliffs in northeastern Utah using outcrop data. Vertical sedimentary sections in multiple closely spaced canyons, combined with photomosaics and LIDAR data, describe in detail the deposits over an area of about 3 km by 2 km.

Sedimentary Facies

Chapter

Jun 2013

Safiya M Hassan

An outcrop investigation of Moghra Formation (Lower Miocene, Burdigialian age) was carried out in northwestern Egypt. Eighteen detailed sedimentary measured sections, located slightly obliquely to the depositional strike were described. Emphasis was placed on lithofacies variations, interpretations of depositional settings and a depositional model was constructed. In the study area, The Moghra Formation, some 260 m thickn, consists of eight lithofacies associations: (1) Tide-influenced fluvial channel deposits; (2) Flat laminated sandflat deposits; (3) Outer estuary sand bar deposits (Tidal Channel and Tidal Bars); (4) Tidal flat deposits; (5) Bioturbated fossiliferous shelf sandstones; (6) Bioturbated fossiliferous shelf carbonates; (7) Coarsening upward deltaic deposits; and (8) Fining upward channel deposits. These eight lithofacies associations are grouped into three main depositional environments: (1) Transgressive tide-dominated estuaries, (2) Open Shelf and (3) Regressive tide-dominated deltas.

Morphology and sedimentology of an emergent fjord-head Gilbert-type delta: Alta delta, Norway

Article

Full-text available

Jan 1990

Process framework for describing the morphologic and stratigraphic evolution of deltaic depositional system

Article

Full-text available

Jan 1975

William E. Galloway

Offshore tidal deposits: sand sheet and sand bank facies

Chapter

Full-text available

Jan 1982

Incised valleys and backstepping deltaic deposits in a foreland-basin setting, Torres Strait and Gulf of Papua, Australia

Chapter

Full-text available

Jan 1994

Peter Townsend Harris

The Fly River of Papua New Guinea presently discharges approximately 6,500 m3/s and carries an estimated sediment load of 85 million tonnes/a to the continental shelf of southern Papua New Guinea, at the northern end of Australia's Great Barrier Reef; the area is thus a major carbonate/siliciclastic transition zone. The River has constructed a tidally dominated "funnel-shaped" estuary together with an offshore prograding delta in which prodelta sediments are accreting at rates of up to 0.1 m/a. During the last glacial lowering of sea level, base level for the fluvial system was lowered and numerous channels were cut into the Pleistocene flood-plain deposits of the continental shelf. The valleys thus formed are seen in bathymetric and seismic sections, incised up to 60 m below the level of surrounding seabed. They are found concentrated within a 20-25 km wide zone which divides siliciclastic and carbonate deposits and which extends along part of the present day Papua New Guinea coastline and eastwards into the Gulf of Papua; they do not extend across the adjacent Torres Strait area located further southwest. During the subsequent Holocene transgression, many of these valleys were back-filled by the landward retreating fluvial system. High-resolution boomer seismic profiles show valleys infilled with fluvial cut and fill deposits and overlain by prograding deltaic sediments which overfill the valleys. Some valleys, however, are only partially infilled with sediment and are presently scoured and maintained by strong tidal currents. In such "tidally-scoured" cases, the relict deltaic units are truncated and overlain by a thin veneer of Holocene sediment as determined from core samples.

Hummocky Cross-Stratification and Megaripples: A Geological Double Standard?

Article

Full-text available

Jan 1983

It is difficult to account for either modern hummocky megaripples or ancient hummocky cross-stratification as responses to purely oscillatory flows. Combined-flow curents are the typical response of most modern shelves and epicontinental seas to storms and presumably were so in the past. Hummocky cross-stratified beds are generally too thick (20-80cm) to be accounted for by in-situ resuspension: they are more likely to have been deposited by combined-flow currents in areas where these currents were experiencing a downstream velocity decrease and sediment deposition throughout much of the storm's duration.-from Authors

Lowstand Deltas in the Frontier Formation, Powder River Basin, Wyoming, U.S.A.: Implications for Sequence Stratigraphic Models

Article

Full-text available

Feb 2001
AAPG BULL

Deposits of lowstand deltas formed on the floor of the Cretaceous Interior seaway of North America are found in the Cenomanian, lower Belle Fourche Member of the Frontier Formation, central Wyoming. Sandstones located in similar distal basin locations, hundreds of kilometers basinward of highstand shoreline deposits, form important hydrocarbon reservoirs isolated within marine shales, but interpretation of their origin has been highly controversial. The distribution, geometry, and internal facies of these sandstones are documented by an extensive outcrop study and regional subsurface correlations to develop genetic facies models for these deposits. This integrated record of lithofacies, ichnofacies, palynofacies, paleocurrent data, bedding relationships, and isolith maps incorporates observations from nearly 100 measured outcrop sections and about 550 subsurface well logs. Four episodes of sediment progradation and subsequent transgression each left behind gradually upward-coarsening deltaic sandstones that have eroded tops. These deltaic sandstones have a lobate to elongate geometry, basinward-dipping internal clinoform bedding, radiating paleocurrents, a low to moderate degree of shallow-marine burrowing, and show variable wave influence and tidal influence on deposition. Delta plain, paralic, and nonmarine facies have been eroded from the top of deltaic successions. Erosion surfaces capping progradational deltaic successions are the only stratal discontinuities that can be mapped regionally, and they appear to record transgressive ravinement enhanced over areas of structural uplift, compared with lowstand surfaces of erosion, which record the bypass of sediments basinward. Low accommodation during lowstands left little room for sandstones to stack vertically, and successive episodes of delta progradation were offset along strike. More tide-influenced delta deposits formed within shoreline embayments defined by the topography of older wave-influenced delta lobes and subtle syndepositional deformation of the basin floor. Standard sequence stratigraphic terminology is difficult to use in broad lowstand systems like the Frontier Formation because sandstones do not show simple vertical stacking patterns, major stratal discontinuities can form by processes other than lowstand fluvial erosion, and minor syndepositional deformation of the basin floor exerts a first-order influence on depositional and sediment preservation patterns. Although many basin-distal sandstones have been interpreted to be deposits of offshore bars, shelf-isolated valley fills, and stranded shorelines, the Frontier Formation examples documented here suggest that many of these deposits may be top-eroded deltas formed where rivers delivered sediment to lowstand coastlines. The external geometry and internal heterogeneities of hydrocarbon reservoirs found in these types of deposits reflect processes active on the low accommodation deltaic shoreline, even in cases where subsequent ravinement has significantly truncated the deposits during transgression.

Architecture and sequence stratigraphy of a Late Neogene incised valley at the shelf margin, Southern Celtic Sea

Article

Full-text available

Mar 1999

Valleys on the outer Celtic Sea shelf were cut and filled during the late Pliocene/early Pleistocene. The Kaiser valley is one of several valleys forming an anastomosed network. The main valley, di- rected 208 (Azimuth true N), is 50 m deep and . 10 km wide. It is connected to the parallel Dompaire and Parsons valleys by several 120- 1408 directed incisions of lesser width and depth. Analyzed by mean of very high-resolution seismic data, the Kaiser valley is interpreted as containing a compound fill consisting of eight erosionally based depo- sitional sequences. A typical sequence comprises two facies: (1) fluvial channels at the base, which represent lowstand to early transgressive deposits; and (2) onlapping transgressive bay-fill deposits that are lo- cally interbedded at the top with isolated small channels attributed to flood tidal deltas. The erosional bases of the fluvial facies correspond to sequence boundaries. These are interpreted to result from relative sea-level falls. Successive fluvial and bay-fill facies are separated by flat erosional surfaces of high acoustic amplitude, which extend laterally across the entire composite valley, locally beveling sequence boundaries and creating terraces on the valley walls. These flat facies contacts are interpreted as bay ravinement surfaces produced by waves in an es- tuarine setting. The larger-scale stacking pattern of the depositional sequences defines a progradational-retrogradational trend, in which the lowest sequence is mainly constituted by fluvial channel deposits, whereas upper sequences display mostly bay-fill facies. The sequences are related to fifth-order glacioeustatic fluctuations, whereas their pro- gradational-retrogradational trend reflects fourth-order eustatic vari- ations and/or rapid tectonic tilting of the area, as indicated by the presence of two incision orientations. The preservation of the system took place during a third-order sea-level rise, and was favored by sub- sidence of the margin, leading to its present occurrence down to

Depositional systems in Wilcox Group (Eocene) of Texas and Their Relation to Occurrence of Oil and Gas

Article

Full-text available

Jan 1967

Regional investigation of the lower part of the Wilcox Group in Texas in outcrop and subsurface indicates seven principal depositional systems. These include: (1) Mt. Pleasant Fluvial System developed updip and in outcrop north of the Colorado River; (2) Rockdale Delta System, present primarily in subsurface, chiefly between the Guadalupe and Sabine Rivers; (3) Pendleton Lagoon-Bay System in outcrop and subsurface largely on the southern flank of the Sabine Uplift; (4) San Marcos Strandplain-Bay System, occurring in outcrop and subsurface mainly on the San Marcos Arch; (5) Cotulla Barrier Bar System in subsurface of South Texas; (6) Indio Bay-Lagoon System developed updip and in outcrop of South Texas, and (7) South Texas Shelf System, an extensive system entirely within subsurface of South Texas. The Rockdale Delta System, consisting of large lobate wedges of muds, sands, and carbonaceous deposits, is the thickest and most extensive of the lower Wilcox depositional systems. It grades updip to the thinner terrigenous facies of the Mt. Pleasant Fluvial System. Deposits of the Rockdale Delta System were the source of sediments redistributed by marine processes and deposited in laterally adjacent marine systems. Delineation of depositional systems and, more specifically, delineation of component facies of the various systems, permits establishment of regional oil and gas trends which show relationship of producing fields and distribution of potentially producing trends.

Sequence Stratigraphy of Ramp-Setting Strand Plain SuccessionsThe Gallup Sandstone, New Mexico

Chapter

Jan 1995

Stratigraphy and Facies Architecture of Parasequences with Examples from the Spring Canyon Member, Blackhawk Formation, Utah

Chapter

Jan 1995

High-Frequency Sequence Stratigraphy and Paleogeography of the Kenilworth Member, Blackhawk Formation, Book Cliffs, Utah, U.S.A.

Chapter

Jan 1995

Sequence Stratigraphy of Turonian–Santonian Strata, Kaiparowits Plateau, Southern Utah, U.S.A.Implications for Regional Correlation and Foreland Basin Evolution

Chapter

Jan 1995

High-Frequency Sequence Stratigraphy and Facies Architecture of the Sego Sandstone in the Book Cliffs of Western Colorado and Eastern Utah

Chapter

Jan 1991

John C. Van Wagoner

Sequence Stratigraphy and Marine to Nonmarine Facies Architecture of Foreland Basin Strata, Book Cliffs, Utah, U.S.A.

Chapter

Jan 1995

John C. Van Wagoner

Miocene Deltaic Sedimentation, Louisiana Gulf Coast1

Chapter

Doris Malkin Curtis

Siliciclastic Sequence Stratigraphy in Well Logs, Cores, and Outcrops: Concepts for High-Resolution Correlation of Time and Facies

Book

Jan 1990

Incised-Valley SystemsOrigin and Sedimentary Sequences

Book

Jan 1994

Variation in sand body types on the eastern Bering Sea epicontinental shelf.

Article

Jan 1982

The eastern epicontinental shelf of the Bering Sea is characterized by variations in river and glacial sediment supply, wave energy, tidal range (microtidal to mesotidal), and tidal, geostrophic, and storm-induced currents. These factors, combined with the effect of the Holocene rise in sea level, have resulted in the formation of a complex assemblage of generally linear sand bodies of similar morphology anad lithology, but different origins. The sand bodies are large features found from the present shoreline to tens of kilometers offshore, in water depths up to 50m. -from Authors

Bedforms of the Tana River, Norway

Article

Apr 1970

John David Collinson

The greater part of the water and sediment discharge in the Tana River takes place in the weeks following the ice break-up and flood. During this time the river discharge changes rapidly with an overall falling tendency. Sand is transported as large, ripple-like bedforms, linguoid bars, though a whole hierarchy of bedforms can be recognised. These range from permanent islands and banks through side bars, linguoid bars, dunes and ripples. It is possible that there is a continuous size gradation between linguoid bars and dunes. Super- imposition of dunes on the backs of linguoid bars, which has previously been used as a criterion for their separation into distinct classes of structure, is only found on exposed or shallowly submerged bars and is rarer on deeply submerged bars, suggesting that the dunes are a response to the lower water stage. During the falling stages of the river, the bedforms are modified by a combination of falling stage currents, waves and wind activity. Flow is concentrated between bars which may be eroded or may grow by lateral accretion. Wave activity tends to lower the slip face angles of the linguoid bars, to concentrate heavy minerals and to build small beach features. Excavation shows that ripples and dunes produce small and large scale trough cross-bedding respectively while the frontal parts of linguoid bars show tabular planar cross-bedded sets interbedded with ripple cross-laminated units. Ripple morphology may be preserved undisturbed below linguoid bar foresets, this pattern probably representing an early falling stage modification when the bars were still avtice but the separation eddies in their lees were much reduced. Lateral accretion on the sides of linguoid bars, wave erosion surfaces and reactivation structures due to a rise in water stage can all be recognised in the internal structures.

Tidal sand sheets of the late Albian Joli Fou-Kiowa-Skull Creek marine transgression, Western Interior Seaway of North America

Article

Jan 1991

I. Banerjee

Subsurface facies analysis of the Lower Cretaceous hydrocarbon-bearing Basal Colorado Sandstone in the Cessford and Countess fields of southern Alberta, Canada, reveals a tidal sand sheet facies (100 km × 30 km × 10 m) displaying cross-stratification, mud couplets, tidal bundles and reactivation surfaces. The Basal Colorado Sandstone was deposited in the Western Interior Seaway as a basal transgressive unit during the Joli Fou transgression (Kiowa-Skull Creek equivalent, earliest Late Albian). This sandstone overlies tidal flat-lagoon-coastal swamp sediments of the Mannville Group and underlies open marine shales of the Joli Fou Formation. -from Author

Seismic stratigraphy and global changes in sea level, 2, the depositional sequence as a basic unit for stratigraphie analysis

Article

Jan 1977

On one mechanism forming linear sand banks. Estuarine

Article

Jan 1982

J.M. Huthnance

Facies Models: Response to Sea-Level Change

Article

Jan 1992

Rhythmic Linear Sand Bodies Caused by Tidal Currents

Article

Jan 1963
AAPG BULL

Theodore Off

Wave- and storm-dominated shallow marine systems

Article

Jan 1992

Stratigraphy of a North Sea Tidal Sand Ridge

Article

Jan 1992

The East Bank ridges are considered to have formed during the early Holocene around 9000 YBP and are now moribund. One ridge is characterized by two stacked, slightly coarsening-upward sequences of fine, well-sorted terrigenous sand. Bioturbation characterizes the top of the sequence with fine laminations and small-scale, ripple cross-strata scattered throughout. Heavy minerals are diverse and increase in abundance upward. -from Authors

Mechanics of Sediment Transport

Article

Jan 1977

M.S. YALIN

CONTENTS: FUNDAMENTALS, MECHANICAL PROPERTIES OF THE FLOW, DIMENSIONLESS EXPRESSION OF THE TWO-PHASE PHENOMENON, THE BEGINNING OF SEDIMENT TRANSPORT, SEDIMENT TRANSPORT RATE, DISTRIBUTION OF SUSPENDED LOAD, SAND WAVES, FRICTION FACTOR.

SEA-LEVEL CONTROLS ON THE FACIES ARCHITECTURE OF THE TRINITY/SABINE INCISED-VALLEY SYSTEM, TEXAS CONTINENTAL SHELF

Chapter

Jan 1994

Offshore tidal deposits: sand sheet and sand bank facies

Chapter

Jan 1982

A. H. Stride

Sand deposits are the most significant products of strong modern offshore tidal current activity. The high porosity of these modern sands implies that their fossil analogues could be economically significant as reservoir rocks. Around the British Isles the associated tidal current gravels are usually only a few centimetres thick but as yet have been little studied. The associated muds are up to about 30 m thick and are potentially much more extensive than sands or gravels because of the large areas of continental shelf with relatively weak tidal currents. However, as shown below, mud deposits are much less of an indicator of tidal current sedimentation than the sands and gravels, and will not be treated in detail.

High-frequency sequence stratigraphy and facies architecture of the Sego Sandstone in the Book Cliffs of western Colorado and eastern Utah

Article

Jan 1991

J.C. Van Wagoner

Geological Association of Canada

Article

Jan 1998

Sharp-based shoreface sequences and "offshore bars' in the Cardium Formation of Alberta: their relationship to relative changes in sea level

Article

Jan 1988

A. Guy Plint

Reveals two types of shelf-to-shoreface sequences: 1) gradational-based sequences that steadily coarsen upward from thin-bedded, wave-rippled sandstone and mudstone through hummocky cross-stratified (HCS) sandstone and mudstone into mud-free, swaley cross-stratified (SCS) sandstone capped by a root bed, and 2) sharp-based sequences that consist of SCS sandstone which, near the base, may contain large mudstone intraclasts, sharply overlying thin-bedded sandstone and mudstone. -from Author

Horizontal turbulence and alternate bars

Article

Feb 1992

Tidal depositional systems Facies models: Response to sea-level change: Waterloo, Ontario

Article

Jan 1992

Robert W Dalrymple

Facies, facies models and modern stratigraphic concepts

Article

Jan 1992

R.G. Walker

High-frequency sequence stratigraphy and paleogeography of the Kenilworth Member, Blackhawk Formation, Book Cliffs, Utah, USA

Article

Jan 1995

Shallow-marine strata within the Campanian Kenilworth Member were examined from their updip to downdip depositional limits. Sandstones of the Kenilworth Member are interpreted to comprise parts of two high-frequency sequences. A sequence boundary occurs within the Kenilworth and separates the highstand systems tract of an older sequence from the lowstand and transgressive systems tracts of a younger sequence. The magnitude of the relative sea level fall that occurred within the Kenilworth is estimated to be about 20 m, based on the amount of fluvial channel incision observed at the sequence boundary. Five wave-dominated shoreline parasequences were recognized, each with a north-south to northwest-southeast paleoshoreline orientation. The oldest four parasequences are part of the highstand systems tract. Above the sequence boundary at the top of the highstand, fluvial channel systems incise older shoreface deposits. In a basinward direction, lowstand deltaic sediments are present above the sequence boundary. -from Authors

Sequence stratigraphy of Turonian-Santonian strata, Kaiparowits Plateau, southern Utah, USA: implications for regional correlation and foreland basin evolution

Article

Jan 1995

Outcrops of Turonian through Campanian strata in the Kaiparowits Plateau of southern Utah provide an opportunity to examine both shallow-marine and continental strata within the context of unconformity-bounded depositional sequences. This approach provides insights to the evolution of the strata within the plateau as well as regional chrono- and lithostratigraphic relationships within the southwestern Colorado Plateau. Five unconformity-bounded depositional sequences are recognised. These sequences are defined by regional surfaces of erosion that juxtapose amalgamated fluvial deposits over shoreface, alluvial plain, or coal-bearing strata and reflect an abrupt basinward shift in facies tracts. Recognizing cycles of base-level change has allowed observations in the Kaiparowits Plateau to be extended across a broad region. Recognition of the relationship between sedimentary architecture and position within a sequence has resulted in a model that allows the geometry and interconnectedness of sedimentary facies to be predicted within the context of parasequence stacking patterns. -from Authors

Wave- and storm-dominated shallow marine systems

Article

Jan 1992

A. Guy Plint

Forced regressions in a sequence stratigraphic framework: Concepts, examples, and exploration significance

Article

Jan 1992
AAPG BULL

Sequence stratigraphic concepts suggest that stratal geometries develop and are largely controlled by changes in relative sea level. On the shelf, low-stand deposits, which form during falls and subsequent stillstands of relative sea level, can be recognized by the presence of an unconformity at the base, the isolated and basinward position relative to the previous shoreline, and the abrupt seaward translation of shallow-water and shoreline facies into the basin across an unconformity surface. This seaward translation of facies and shoreline regression in a response to relative sea level lowering is termed a "forced regression'. Certain shelf sands, previously interpreted as offshore or mid-shelf sand bodies, can be reinterpreted as stranded lowstand shorelines associated with forced regressions. This alternative interpretation has economic significance insofar as it suggests different subsurface correlations and reservoir geometries. Examples of forced regression are described. -from Authors

Stratigraphy and facies architecture of parasequences with examples from the Spring Canyon Member, Blackhawk Formation, Utah

Article

Jan 1995

Outcrop examples from the Spring Canyon Member document parasequence expression. Both wave-dominated shoreface sandstone and river-dominated deltaic sandstone exist laterally in the marine portion of the same parasequence. Both are terminated by a flooding event marked by a rapid landward shift in facies, with no transgressive lag. A number of marginal marine and nonmarine subenvironments exist laterally within the same parasequence. The parasequence boundary provides a temporal framework to link the genetically related subenvironments, allowing reconstruction of the entire depositional system, as opposed to evaluation of outcrops as isolated systems or facies. Continuous coal seams occur immediately beneath parasequence boundaries and are markers used to trace parasequence boundaries from nonmarine sections into the marine. -from Authors

Experiments on bed configurations in fine sands under bidirectional purely oscillatory flow, and the origin of hummocky cross- stratification

Article

Jan 1990
J Sediment Petrol

There was no net aggradation during the runs, but a deposit was synthesized by taking a time series of sidewall bed profiles during a run in which large 3D ripples developed from an initially plane bed and changed irregularly in size and position as they grew toward equilibrium, and then plotting the profiles one above the previous with a constant upward increment. The resulting stratification is strikingly similar to much hummocky cross-stratification in ancient sandstones. This suggests that some hummocky cross-stratification is generated during sediment fallout from strong purely oscillatory flows at moderate to long oscillation periods as large 3D oscillatory-current bed forms develop from a planar bed during strong but waning flow. -from Authors

Sequence stratigraphy of ramp-setting strand plain successions: the Gallup Sandstone, New Mexico

Article

Jan 1995

The Gallup Sandstone of northwestern New Mexico is a NE-prograding clastic wedge of late Turonian to earliest Coniacian age that pinches out about in the middle of the San Juan basin. Paleoenvironmental and sequence stratigraphic studies indicate that the Gallup is dominated by strand plain successions (tongues) that prograded across a gently dipping ramp during repeated episodes of relative sea level fall. These episodes were superimposed on a long-term (about 1.2 m.y.) phase of relative sea level rise that controlled the overall forestepping and aggradational stacking pattern of the tongues. Outcrop studies present incontrovertible evidence, for at least three of the Gallup tongues, that two concurrent erosional surfaces formed during sea level falls in this ramp setting. The sequence boundary climbs stratigraphic section from landward to seaward and becomes a conformity near the position of the lowstand shoreline. -from Authors

Sequence stratigraphy and marine to nonmarine facies architecture of foreland basin strata, Book Cliffs, Utah, USA: Reply

Article

Jan 1995
AAPG BULL

J. C. Van Wagoner

The Desert Member of the Blackhawk Formation and the Castlegate Sandstone in the Book Cliffs of Utah and Colorado were analyzed to develop a model of sequence stratigraphy and facies architecture in foreland basins. Stratal architecture of these rocks is controlled by two regionally extensive surfaces of incision and subaerial exposure interpreted as major sequence boundaries, and at least six surfaces of incision and subaerial exposure with more limited lateral extent, interpreted as minor sequence boundaries. Based on parasequence stacking patterns, position of sequence boundaries, and facies associations, the Desert Member and Castlegate Sandstone have been divided into sequences with durations of 200 000 to 300 000 yr. Sequence boundaries and systems tracts within the Desert and Castlegate can be continuously traced in both outcrop and subsurface, moving updip from the marine to totally nonmarine parts of the system. These relationships are used to develop an integrated model for nonmarine sequence stratigraphy applicable to the subsurface elsewhere. -from Author

Depositional facies of high-energy beach-to- offshore sequence: comparison with low-energy sequence.

Article

Jan 1981

A study of the nearshore zone and continental shelf of a high-energy coast was made in the Ventura-Port Hueneme area of California during the summer of 1974 to investigate depositional facies characteristics and compare them with similar facies from a low-energy coastal setting. Analysis of box cores, can cores, and vibracores permits recognition of three principal zones; nearshore, transition and offshore. Comparison of the results of this study with a previous description of a low-energy beach-to-offshore sequence at Sapelo Island, Georgia, indicates that the principal difference is that the California facies are significantly thicker than their Georgia counterparts. This difference is in direct response to the role of higher wave energy on the California coast.-from Authors.

Bedforms of The Tana River, Norway

Article

John David Collinson

Sequence, parasequence and intra-parasequence architecture of the Grassy Member, Blackhawk Formation, Book Cliffs, Utah, USA

Chapter

Jan 1995

The upper Campanian Grassy Member of the Blackhawk Formation, Mesa Verde Group, Utah, consists of two high-frequency, unconformity-bounded sequences within the upper part of the Blackhawk Formation highstand sequence set. Within the Grassy Member, the degree of shelf erosion in outcrop appears far less significant than that associated with type 1 sequence boundaries described from the stratigraphically higher Desert Member and Castlegate Formation. There appears to be a hierarchy of unconformities bounding sequences within the Blackhawk Formation recording progressively larger basinward shifts of facies tracts and greater amounts of shelf incision with time. It is suggested that the shoreface evolved from a prograding strand plain into a barrier island prior to formation of the parasequence flooding surface. -from Authors

The Interaction between Channel Geometry, Water Flow, Sediment Transport and Deposition in Braided Rivers

Article

Jan 1993

J.S. Bridge

Using information from recent detailed field and laboratory studies of the geometry, flow and sedimentary processes in braided rivers of simple geometry, in single river bends, in channel confluences, and using some theoretical reasoning, it has been possible to construct fully 3D qualitative and quantitative models of braided river deposits. These models can be used to provide sophisticated quantitative interpretations of palaeochannel geometry, hydraulics and migration, as illustrated by comparison with some particularly well described examples of ancient braided river deposits. -from Author

Evolution of subtidal sandbanks in Moreton Bay, Eastern Australia

Article

Jan 1992
MAR GEOL

Vibrocores, current meter data, boomer seismic profiling and sidescan sonar data provide an insight into the processes governing the formation of subtidal linear sandbanks in Moreton Bay, Australia. Bedforms observed on sidescan sonar images are predominantly 10–20 m wavelength dunes with flood-oriented slip faces within the section of the sandbank field studied. The sandbanks separate mutually evasive ebb- and flood-dominant sand transport pathways. Rates of sand transport, calculated from the current meter data, are greatest during flood tides, flowing between the interval low-low to high-high water (mixed tidal regime). Subordinate, ebb-directed transport is insignificant by comparison, which facilitates the preservation of flood-oriented foreset beds in high energy depositional settings (i.e. sandbank crests). Sediment peels obtained from cores indicate that foreset beds are preserved only in deposits of the sandbank crests; trough deposits show bioturbation.14C dating establishes that sandbanks located further away from Moreton Island were formed prior to 3 k.y. B.P. and that the banks have not been rebuilt since this time. In contrast, material obtained up to 380 cm beneath the surface in sandbanks located inshore are of modern age, showing that these banks undergo regular rebuilding. The formation of linear sandbanks in Moreton Bay is mainly a consequence of the infilling of the bay mouth with sand delivered via littoral drift along the adjacent coastline.

Tectonic control of nested sequence architecture in the Castlegate Sandstone (Upper Cretaceous), Book Cliffs, Utah

Article

Jul 1996
J Sediment Res B Stratigr Global Stud

The Castlegate Sandstone at its type section, Price Canyon, near Price, Utah, encompasses a single stratigraphic sequence spanning approximately 5 m.y. It includes a sandstone member corresponding to a low stand systems tract, consisting of braided-fluvial sheet sandstones, and a mudstone member, in which shales are more abundant and some evidence of tidal influence is present. The authors suggest that the origin of the sequences is related to flexural loading and intraplate stress on two time scales. The main 5 m.y. sequence reflects regional tectonism, with the sandstone member developing at a time of slow subsidence, and the mudstone member reflecting a higher long-term subsidence rate. The higher-order sequences nested within the third-order sequence east of Trail Canyon are interpreted as a basinal response to episodes of crustal shortening on a 10âµ yr time scale. This study amplifies the model of Posamentier and Allen (1993a), in which ramp-type foreland basins are divided into areas of rapid and slow subsidence (Zones A and B). They postulate that these zones migrated basinward and landward in response to variations in long-term subsidence rate, and can be mapped by reference to the distribution of Type 1 sequence boundaries in the higher-order sequences.

Sequence Stratigraphy and Facies Model of an Incised Valley Fill: The Gironde Estuary, France

Article

Jan 1993

The Gironde estuary was formed by the Holocene drowning of a fluvial valley incised during the Wuerm global sea-level fall. A depositional sequence accumulated in the valley during the eustatic lowstand, the Holocene rise, and the post-Holocene highstand. The sequence comprises a diverse assemblage of lithofacies that can be grouped into lowstand, transgressive, and highstand systems tracts. The objective of this paper is to describe the facies and stratal architecture of this incised-valley fill, and to propose a sequence-stratigraphic model for incised-valley fills in this type of mixed tide- and wave-influenced coastal setting. this study is based on a compilation of the abundant core, borehole, and hydrological data published by a number of authors. The valley fills forms regionally elongated belts of channelized sandstones and are the subject of considerable interest because they furnish potentially important new hydrocarbon play concepts.

Sharp‐based, tide‐dominated deltas of the Sego Sandstone, Book Cliffs, Utah, USA

Abstract

No full-text available

Recommended publications

Fluvial to tidal transition in proximal, mixed tide-influenced and wave-influenced deltaic deposits:...

Facies, Backwater Limits, and Paleohydraulic Analysis of Rivers in a Forced-regressive, Compound Inc...

Sharp-based, tide-dominated, delta deposits of the Sego sandstone, Book Cliffs, Utah

Top-Truncated, Structurally-Confined Lowstand Deltas