Panel_14454
Panel_14454
1:15 PM
5:05 PM
1:15 p.m.
Introductory Remarks
Room 505/506/507
Panel_15746
Panel_15746
1:15 PM
12:00 AM
1:20 p.m.
Fluvially Generated Heterolithic Stratification as a Tool for Determining Process Dominance and Location in the Fluvial-Marine Transition
Room 505/506/507
By R. W. Dalrymple, C. E. Kurcinka, B. Jablonski, A. Ichaso, D. Mackay
At the mouths of rivers, and for a considerable distance inland in low-gradient settings, fluvial and tidal processes interact to create a unique suite of deposits. Most rivers display variations in discharge, and their hydrographs can be divided simplistically into two parts: the river flood when most of the sediment discharge occurs, and the longer-duration interflood period when sediment discharge is small. Tidal currents, by contrast, act throughout the year, although their strength varies on various time scales (e.g., neap-spring cycles). Most importantly, the increase in the strength of fluvial currents during river floods decreases the tidal influence by pushing the limit of tidal intrusion (and also salt-water intrusion) seaward. In the more proximal parts of the fluvial-marine transition, depositional conditions alternate between being river-dominated during river floods and tide-dominated during interflood/low-flow periods. This is commonly reflected in an alternation between coarser sandy deposits with a unidirectional seaward paleocurrent and minimal bioturbation (river-flood deposits), and finer-grained, commonly muddy, deposits in which tidal lamination and higher levels of bioturbation are present (interflood deposits). These deposits are indicative of a fluvially dominated, tidally influenced environment. In more distal areas where tidal currents are stronger, tidal lamination and/or reversed paleocurrents begin to occur in the waning-flow portion of the flood deposits, until eventually the tidal currents become strong enough to overprint the entire river-flood bed. In such settings, river-flood deposits can be cryptic, but can be marked by the coarsest sand and thickest fluid-mud beds. Bioturbation is typically more intense, but restricted, in the interflood deposits. This pattern indicates a tidally dominated, fluvially influenced environment. Considerable local variability is expected, but general trends in the character of river-flood and interflood beds are a powerful tool for determining location in the fluvial-marine transition and the nature of coastal environments at a larger scale.
At the mouths of rivers, and for a considerable distance inland in low-gradient settings, fluvial and tidal processes interact to create a unique suite of deposits. Most rivers display variations in discharge, and their hydrographs can be divided simplistically into two parts: the river flood when most of the sediment discharge occurs, and the longer-duration interflood period when sediment discharge is small. Tidal currents, by contrast, act throughout the year, although their strength varies on various time scales (e.g., neap-spring cycles). Most importantly, the increase in the strength of fluvial currents during river floods decreases the tidal influence by pushing the limit of tidal intrusion (and also salt-water intrusion) seaward. In the more proximal parts of the fluvial-marine transition, depositional conditions alternate between being river-dominated during river floods and tide-dominated during interflood/low-flow periods. This is commonly reflected in an alternation between coarser sandy deposits with a unidirectional seaward paleocurrent and minimal bioturbation (river-flood deposits), and finer-grained, commonly muddy, deposits in which tidal lamination and higher levels of bioturbation are present (interflood deposits). These deposits are indicative of a fluvially dominated, tidally influenced environment. In more distal areas where tidal currents are stronger, tidal lamination and/or reversed paleocurrents begin to occur in the waning-flow portion of the flood deposits, until eventually the tidal currents become strong enough to overprint the entire river-flood bed. In such settings, river-flood deposits can be cryptic, but can be marked by the coarsest sand and thickest fluid-mud beds. Bioturbation is typically more intense, but restricted, in the interflood deposits. This pattern indicates a tidally dominated, fluvially influenced environment. Considerable local variability is expected, but general trends in the character of river-flood and interflood beds are a powerful tool for determining location in the fluvial-marine transition and the nature of coastal environments at a larger scale.
Panel_15180
Panel_15180
1:20 PM
1:40 PM
1:40 p.m.
Large, Heterolithic Channel Fills of the Upper Permian Rangal Coal Measures, Queensland, Australia: Well-Exposed Analogues for the McMurray Formation
Room 505/506/507
By C. Fielding
The Upper Permian Rangal Coal Measures and equivalents formed during a phase of declining continental arc volcanism and active thrust loading in the complex retroarc foreland Bowen Basin of eastern Queensland, Australia. The unit, around 100 m thick in total, comprises sandstone bodies, thick heterolithic sandstone-siltstone intervals with Inclined Heterolithic Stratification (IHS), mudrocks with thin-bedded sandstones, and coal bodies up to 8 m thick. A number of large, opencut mines have provided extensive though temporary exposures of the Rangal Coal Measures, allowing an evaluation of their sedimentology and stratigraphy. In an earlier study, Fielding (1993, Sedimentary Geology, 85, 475-497) carried out a facies analysis and concluded that the depositional environment was an extensive, low-lying alluvial plain crossed by rivers that alternated between two distinct fluvial styles; 1. Moderately sinuous (< 1.5) streams that formed highly complex, heterolithic channel fills, and 2. More mobile, perhaps braided rivers that formed sheet-like sandstone bodies. In this study, a re-evaluation of the dataset is presented, and the conclusion is drawn that significant portions of the Rangal Coal Measures were likely formed in tidally-influenced rivers (estuaries) that drained the north-south Bowen Basin axially during the latest Permian. The principal lines of evidence in support of this reinterpretation are 1. abundance and diversity of IHS-filled channel forms, and abrupt lateral facies variations that indicate significant areal partitioning of sand in the formative rivers, 2. presence of abundant small-scale sedimentary structures commonly associated with tidal activity (flaser bedding, mud drapes, etc.), 3. presence of a low-diversity, sporadically distributed trace fossil suite, 4. presence of fish fossils of types that have been previously regarded as marine, and 5. bimodal to bipolar palaeocurrent distributions. Given this reinterpretation, the Rangal Coal Measures can serve as a well-exposed analogue for the internal stratal architecture and reservoir heterogeneity that is known to characterize the Cretaceous McMurray formation in the Athabasca oil sands province.
The Upper Permian Rangal Coal Measures and equivalents formed during a phase of declining continental arc volcanism and active thrust loading in the complex retroarc foreland Bowen Basin of eastern Queensland, Australia. The unit, around 100 m thick in total, comprises sandstone bodies, thick heterolithic sandstone-siltstone intervals with Inclined Heterolithic Stratification (IHS), mudrocks with thin-bedded sandstones, and coal bodies up to 8 m thick. A number of large, opencut mines have provided extensive though temporary exposures of the Rangal Coal Measures, allowing an evaluation of their sedimentology and stratigraphy. In an earlier study, Fielding (1993, Sedimentary Geology, 85, 475-497) carried out a facies analysis and concluded that the depositional environment was an extensive, low-lying alluvial plain crossed by rivers that alternated between two distinct fluvial styles; 1. Moderately sinuous (< 1.5) streams that formed highly complex, heterolithic channel fills, and 2. More mobile, perhaps braided rivers that formed sheet-like sandstone bodies. In this study, a re-evaluation of the dataset is presented, and the conclusion is drawn that significant portions of the Rangal Coal Measures were likely formed in tidally-influenced rivers (estuaries) that drained the north-south Bowen Basin axially during the latest Permian. The principal lines of evidence in support of this reinterpretation are 1. abundance and diversity of IHS-filled channel forms, and abrupt lateral facies variations that indicate significant areal partitioning of sand in the formative rivers, 2. presence of abundant small-scale sedimentary structures commonly associated with tidal activity (flaser bedding, mud drapes, etc.), 3. presence of a low-diversity, sporadically distributed trace fossil suite, 4. presence of fish fossils of types that have been previously regarded as marine, and 5. bimodal to bipolar palaeocurrent distributions. Given this reinterpretation, the Rangal Coal Measures can serve as a well-exposed analogue for the internal stratal architecture and reservoir heterogeneity that is known to characterize the Cretaceous McMurray formation in the Athabasca oil sands province.
Panel_15185
Panel_15185
1:40 PM
2:00 PM
2:00 p.m.
Core Description, Markov Chain Analysis and AVO Modeling of a Lagoon/Tidal to Fluvial Transition Zone in the Cretaceous Straight Cliffs Formation, Southern Utah
Room 505/506/507
By L. Stright, K. Dworsky, C. Johnson, T. Vanorio
Tidal successions are comprised of a complex mixture of fluvial, tidal, and marine lithofacies. Subtle changes in the transition from tidal to fluvial deposits make lithofacies differentiation from subsurface wireline log and seismic reflection data problematic. Because tide-dominated and tidally-influenced reservoirs account for a significant portion of petroleum reserves, forward seismic reflection modeling coupled with a predictive facies model framework derived from rock physics measurements on cores and outcrops can lead to invaluable insights for interpreting subsurface data. The Cretaceous John Henry Member (Straight Cliffs Formation), located in the Kaiparowits Plateau of southern Utah, reveals excellent outcrops of fluvial and tidally-influenced deposits, and offers an opportunity to improve our understanding of wireline log interpretation and seismic imaging in similar subsurface petroleum reservoirs. The focus of this study is a 240 m core that captures a progradational succession from shoreface through tidally-influenced lagoon to fluvial deposits. The full spectrum of lithofacies stacking patterns present in the core is captured with a Markov Chain analysis. Benchtop measurements were performed on 1 inch core plugs (57 total; 25 from the coastal plain succession and 32 from the tidal succession) to obtain physical rock properties (Vp, Vs, density, permeability and porosity) for each lithofacies. The rock properties show a wide range of values as a direct result of the highly heterolithic nature of these deposits. Although measurements from different lithofacies are overlapping, we observe a slight offset between fluvial and tidal rock properties. To test our ability to observe the tidal to fluvial transition with seismic imaging, average rock properties for each lithofacies were used to generate synthetic seismic reflection models for different expressions of upward-fining packages documented in the core. This investigation elucidates variations in amplitude versus offset responses as a function of variable tidal influence. The number of overlapping values highlights the complications associated with interpreting these deposits in subsurface data. However, the modeling shows promise in differentiating the end member packages, along with a gradational trend for intermediate packages consistent with the sedimentology of transitioning from more marine influence to more terrestrial influence.
Tidal successions are comprised of a complex mixture of fluvial, tidal, and marine lithofacies. Subtle changes in the transition from tidal to fluvial deposits make lithofacies differentiation from subsurface wireline log and seismic reflection data problematic. Because tide-dominated and tidally-influenced reservoirs account for a significant portion of petroleum reserves, forward seismic reflection modeling coupled with a predictive facies model framework derived from rock physics measurements on cores and outcrops can lead to invaluable insights for interpreting subsurface data. The Cretaceous John Henry Member (Straight Cliffs Formation), located in the Kaiparowits Plateau of southern Utah, reveals excellent outcrops of fluvial and tidally-influenced deposits, and offers an opportunity to improve our understanding of wireline log interpretation and seismic imaging in similar subsurface petroleum reservoirs. The focus of this study is a 240 m core that captures a progradational succession from shoreface through tidally-influenced lagoon to fluvial deposits. The full spectrum of lithofacies stacking patterns present in the core is captured with a Markov Chain analysis. Benchtop measurements were performed on 1 inch core plugs (57 total; 25 from the coastal plain succession and 32 from the tidal succession) to obtain physical rock properties (Vp, Vs, density, permeability and porosity) for each lithofacies. The rock properties show a wide range of values as a direct result of the highly heterolithic nature of these deposits. Although measurements from different lithofacies are overlapping, we observe a slight offset between fluvial and tidal rock properties. To test our ability to observe the tidal to fluvial transition with seismic imaging, average rock properties for each lithofacies were used to generate synthetic seismic reflection models for different expressions of upward-fining packages documented in the core. This investigation elucidates variations in amplitude versus offset responses as a function of variable tidal influence. The number of overlapping values highlights the complications associated with interpreting these deposits in subsurface data. However, the modeling shows promise in differentiating the end member packages, along with a gradational trend for intermediate packages consistent with the sedimentology of transitioning from more marine influence to more terrestrial influence.
Panel_15179
Panel_15179
2:00 PM
2:20 PM
2:20 p.m.
Estuarine Facies Within Incised Valley Fill Systems, Mt. Garfield Formation, Book Cliffs, Colorado
Room 505/506/507
By R. Bell, D. Kamola
Incised valley fills (IVF) are complex features which complicate the interpretation of stratal successions. The Upper Cretaceous Mt. Garfield Formation, exposed near Grand Junction, Colorado, consists of shallow marine sandstones truncated by numerous sequence boundaries and contains multiple incised valleys. These valley fills are often nested and show significant lateral variability. When nested, facies successions alone are not distinct enough to distinguish individual valleys. Some IVF are dominantly nonmarine/fluvial with numerous coal beds and paleosols. Other IVF have a strong tidal signature: evidence for tidal influence include multiple reactivation surfaces, double mud drapes, flaser/wavy/lenticular bedding, heterolithic bedding and tidal bundles. Field study of IVF at the facies level yields a detailed sequence stratigraphic analysis at the parasequence scale. Parasequences are traced from canyon to canyon to determine lateral and down dip extent of facies. Valley fills which show tidal dominance contain numerous estuarine facies associations: tidally influenced channel-fill sandstones, estuarine deltas, coals/mires, paleosols and migrating tidal bars/burrowed sandstones interpreted as estuarine floor deposits. Individual facies average 5 to 7 meters in thickness. This is interpreted to reflect accommodation steps during sea level rise of 5 to 7 meters. Some facies have limited lateral extent (coals, tidally influenced channel-fill sandstones) and are aerially restricted within individual valley fill, while other facies are correlated over a distance of kilometers (estuarine floor deposits, estuarine deltas) and seen in multiple canyons. The IVF facies can be partitioned into high energy and low energy/protected depositional settings. Estuarine floor deposits contain meter-scale tidal bars which indicate the velocity of the tidal currents within the estuary were significant. Other estuarine facies, such as the estuarine deltas, were deposited in a more protected part of the estuary. Estuarine deltas are upward coarsening successions and rarely show large scale cross stratification. These heterolithic deposits are thinly bedded, contain flaser/wavy/lenticular bedding and have double mud drapes within finer grained interbeds. These deltas are abundant in the IVF but are not a dominant sub-environment in modern estuaries. Other estuarine floor deposits are mud dominated and highly burrowed, and were deposited in a protected setting.
Incised valley fills (IVF) are complex features which complicate the interpretation of stratal successions. The Upper Cretaceous Mt. Garfield Formation, exposed near Grand Junction, Colorado, consists of shallow marine sandstones truncated by numerous sequence boundaries and contains multiple incised valleys. These valley fills are often nested and show significant lateral variability. When nested, facies successions alone are not distinct enough to distinguish individual valleys. Some IVF are dominantly nonmarine/fluvial with numerous coal beds and paleosols. Other IVF have a strong tidal signature: evidence for tidal influence include multiple reactivation surfaces, double mud drapes, flaser/wavy/lenticular bedding, heterolithic bedding and tidal bundles. Field study of IVF at the facies level yields a detailed sequence stratigraphic analysis at the parasequence scale. Parasequences are traced from canyon to canyon to determine lateral and down dip extent of facies. Valley fills which show tidal dominance contain numerous estuarine facies associations: tidally influenced channel-fill sandstones, estuarine deltas, coals/mires, paleosols and migrating tidal bars/burrowed sandstones interpreted as estuarine floor deposits. Individual facies average 5 to 7 meters in thickness. This is interpreted to reflect accommodation steps during sea level rise of 5 to 7 meters. Some facies have limited lateral extent (coals, tidally influenced channel-fill sandstones) and are aerially restricted within individual valley fill, while other facies are correlated over a distance of kilometers (estuarine floor deposits, estuarine deltas) and seen in multiple canyons. The IVF facies can be partitioned into high energy and low energy/protected depositional settings. Estuarine floor deposits contain meter-scale tidal bars which indicate the velocity of the tidal currents within the estuary were significant. Other estuarine facies, such as the estuarine deltas, were deposited in a more protected part of the estuary. Estuarine deltas are upward coarsening successions and rarely show large scale cross stratification. These heterolithic deposits are thinly bedded, contain flaser/wavy/lenticular bedding and have double mud drapes within finer grained interbeds. These deltas are abundant in the IVF but are not a dominant sub-environment in modern estuaries. Other estuarine floor deposits are mud dominated and highly burrowed, and were deposited in a protected setting.
Panel_15178
Panel_15178
2:20 PM
2:40 PM
2:40 p.m.
Relating Modern Analogs and Process-Based Facies Models to Ancient Deposits: A Mixed-Energy Estuary From the Cretaceous Straight Cliffs Formation, Southern Utah
Room 505/506/507
By J. Mulhern, C. Johnson, L. Stright
Process-based facies models for estuaries and deltas are largely derived from modern analogs, and generally depict end-member energy settings. It is unclear how applicable these models are to interpretations of the rock record, particularly in more complex mixed-energy estuarine, deltaic, and tidal environments. Such ambiguity reflects the difficulty in understanding preservation potential, the close temporal and stratigraphic interplay between end-member systems, and a general knowledge gap for both modern and ancient high-energy, sand-rich tidal settings. Differences in the temporal and physical scales of observation between modern and ancient examples pose a challenge to analog studies and their application to subsurface reservoirs. This research presents a detailed assessment and model for outcrops of a mixed-energy (wave- and tide-dominated) estuary from the Cretaceous Straight Cliffs Formation, southern Utah, with specific modern analog comparisons. Along a 1,200 m-wide, 60 to 120 m-thick section, cm-scale measured sections, petrography, and photos are used to document vertical and lateral facies changes. The estuary consists of three depositional units (DU): (1) a lowermost interval, 20–30 m thick, of tidal bars and marsh deposits composed of carbonaceous shales and coals; (2) a middle interval, 50–80 m thick, with channelized tidally-influenced bayhead delta / tidally-dominated delta deposits; and (3) an uppermost interval, 30–50 m thick, of landward-stepping barrier island strata. A combination of modern analogs show the evolution of the estuary. The system began similar to the North Carolina coast at Cape Hatteras (DU1). As the estuary filled it looked more like Winyah Bay, South Carolina (DU2). The capping barrier island strata could be similar to Big Sarasota Pass, Florida or the East Friesian Islands, Germany (DU3). This study highlights areas for improvement in the modern to ancient to reservoir analog workflow, particularly in mixed-energy systems. For example, we illustrate the difficulties in distinguishing between bayhead and tidal deltas in outcrop, despite the importance of such distinctions for both sequence-stratigraphic and reservoir interpretations. Overall, detailed facies characterization and predictive 3-D geobody analysis does elucidate key recognition criteria for the mixed-energy system, including the preservation of both tide and wave energy indicators, tidal packages, and barrier island facies.
Process-based facies models for estuaries and deltas are largely derived from modern analogs, and generally depict end-member energy settings. It is unclear how applicable these models are to interpretations of the rock record, particularly in more complex mixed-energy estuarine, deltaic, and tidal environments. Such ambiguity reflects the difficulty in understanding preservation potential, the close temporal and stratigraphic interplay between end-member systems, and a general knowledge gap for both modern and ancient high-energy, sand-rich tidal settings. Differences in the temporal and physical scales of observation between modern and ancient examples pose a challenge to analog studies and their application to subsurface reservoirs. This research presents a detailed assessment and model for outcrops of a mixed-energy (wave- and tide-dominated) estuary from the Cretaceous Straight Cliffs Formation, southern Utah, with specific modern analog comparisons. Along a 1,200 m-wide, 60 to 120 m-thick section, cm-scale measured sections, petrography, and photos are used to document vertical and lateral facies changes. The estuary consists of three depositional units (DU): (1) a lowermost interval, 20–30 m thick, of tidal bars and marsh deposits composed of carbonaceous shales and coals; (2) a middle interval, 50–80 m thick, with channelized tidally-influenced bayhead delta / tidally-dominated delta deposits; and (3) an uppermost interval, 30–50 m thick, of landward-stepping barrier island strata. A combination of modern analogs show the evolution of the estuary. The system began similar to the North Carolina coast at Cape Hatteras (DU1). As the estuary filled it looked more like Winyah Bay, South Carolina (DU2). The capping barrier island strata could be similar to Big Sarasota Pass, Florida or the East Friesian Islands, Germany (DU3). This study highlights areas for improvement in the modern to ancient to reservoir analog workflow, particularly in mixed-energy systems. For example, we illustrate the difficulties in distinguishing between bayhead and tidal deltas in outcrop, despite the importance of such distinctions for both sequence-stratigraphic and reservoir interpretations. Overall, detailed facies characterization and predictive 3-D geobody analysis does elucidate key recognition criteria for the mixed-energy system, including the preservation of both tide and wave energy indicators, tidal packages, and barrier island facies.
Panel_15184
Panel_15184
2:40 PM
3:00 PM
Panel_15747
Panel_15747
3:00 PM
12:00 AM
3:25 p.m.
Architecture and Rock Typing of Coal-Bearing Successions in Late Carboniferous Fluvio-Deltaic Deposits (Southeast Kentucky, USA)
Room 505/506/507
By A. LeCotonnec, A. Moscariello, D. Ventra, E. Bracinni, S. Greb, F. LaFont
The exploration of coal-bearing reservoirs for both conventional and unconventional hydrocarbon resources, has increased the interest in similar fluvial/estuarine successions worldwide. In this context, Eastern Kentucky offers excellent outcrop analogues for Carboniferous fluvial-dominated deltaic where facies associations, depositional environments and sequence-stratigraphic patterns can be observed in detail. Extensive roadcuts and a vast database of well/core data (coal and gas exploration), available at the KGS (Kentucky Geological Survey) make the Eastern Kentucky an great field laboratory for studying sedimentology and stratigraphy in coal-bearing successions. The middle Pennsylvanian Pikeville and Hyden Formations are very well exposed along the US highways 23 and 119 in Pike County (SE Kentucky). The local stratigraphy is well known thanks to numerous studies focused on very extensive Pennsylvanian coal beds, used as stratigraphic markers for outcrop correlation. Both formations were deposited in a foredeep basin during the building of the Appalachian orogeny located ot the East. Fluvio-deltaic systems prograded toward west and northwest across the basin, subject to periodic transgressions driven by high-amplitude glacio-eustatic base-level changes during the Late Palaeozoic Gondwanan glaciation. In this paper we present the observations from several outcrops in the Pikeville Formation. They were logged at 1:20 scale and densely sampled for rock-typing analysis including automated petrography with QEMSCAN. In the Pikeville Formation, successions are generally formed by vertically stacked, erosively based transgressive depositional sequences with thickness varying from a few meters to a few tens of meters. The studied sedimentary interval consists mostly of three main architectural elements: (1) river-dominated valley fills with frequent tidally-influenced deposition; (2) transitional sediments of coastal to marginal-marine environments, including coalbeds; (3) extensive marine shales, locally intercalated with prograding mouth-bar deposits. The vertical stacking of this facies form fourth-order sequences, which are grouped into third-order sequences bounded by the extensive marine shales. A series of closely spaced logs, integrated with the available subsurface datasets, will be used to derive detailed geo-cellular 3D facies and architectural models of coal-bearing succession, with the aim to link rock properties to sequence-stratigraphic system tracts.
The exploration of coal-bearing reservoirs for both conventional and unconventional hydrocarbon resources, has increased the interest in similar fluvial/estuarine successions worldwide. In this context, Eastern Kentucky offers excellent outcrop analogues for Carboniferous fluvial-dominated deltaic where facies associations, depositional environments and sequence-stratigraphic patterns can be observed in detail. Extensive roadcuts and a vast database of well/core data (coal and gas exploration), available at the KGS (Kentucky Geological Survey) make the Eastern Kentucky an great field laboratory for studying sedimentology and stratigraphy in coal-bearing successions. The middle Pennsylvanian Pikeville and Hyden Formations are very well exposed along the US highways 23 and 119 in Pike County (SE Kentucky). The local stratigraphy is well known thanks to numerous studies focused on very extensive Pennsylvanian coal beds, used as stratigraphic markers for outcrop correlation. Both formations were deposited in a foredeep basin during the building of the Appalachian orogeny located ot the East. Fluvio-deltaic systems prograded toward west and northwest across the basin, subject to periodic transgressions driven by high-amplitude glacio-eustatic base-level changes during the Late Palaeozoic Gondwanan glaciation. In this paper we present the observations from several outcrops in the Pikeville Formation. They were logged at 1:20 scale and densely sampled for rock-typing analysis including automated petrography with QEMSCAN. In the Pikeville Formation, successions are generally formed by vertically stacked, erosively based transgressive depositional sequences with thickness varying from a few meters to a few tens of meters. The studied sedimentary interval consists mostly of three main architectural elements: (1) river-dominated valley fills with frequent tidally-influenced deposition; (2) transitional sediments of coastal to marginal-marine environments, including coalbeds; (3) extensive marine shales, locally intercalated with prograding mouth-bar deposits. The vertical stacking of this facies form fourth-order sequences, which are grouped into third-order sequences bounded by the extensive marine shales. A series of closely spaced logs, integrated with the available subsurface datasets, will be used to derive detailed geo-cellular 3D facies and architectural models of coal-bearing succession, with the aim to link rock properties to sequence-stratigraphic system tracts.
Panel_15151
Panel_15151
3:25 PM
3:45 PM
3:45 p.m.
Variation in Stacking Style of Delta-Estuary Couplets and Associated Deep-Marine Fans: An Example From the Eocene Central Basin of Spitsbergen
Room 505/506/507
By A. Folkestad, E. P. Johannessen, R. Steel
The Eocene of the Central Basin of Spitsbergen shows a series of eastward building clinothems deposited in a foreland basin. This basin was formed by a westerly active fold and thrust-belt which also acted as provenance area for these shallow-marine sand-wedges. Some of these shallow-marine wedges prograded onto the shelf, whereas some of them reached the shelf-edge and have associated deep-marine sand-lobes. Three of these clinothems have been studied with focus on depositional environment, lateral facies variations, internal stacking pattern and shoreline trajectory pattern. All of them show a regressive deltaic to transgressive estuary/tidal couplet. Internally, there are clear differences between the three clinothems in terms of the style of the regressive deltaic part and the transgressive estuary part. The deltaic parts range from a) fluvial and punctuated mass-flow style; b) wave reworked and delta front collapse style; and c) mixed tide and fluvial influenced delta. The transgressive parts of the clinothems show a variation of the thickness of estuary sandstones and coastal plain fines developments conditioned on the degree of aggradation. Previous studies of these Eocene clinothems have interpreted the associated deep-marine sand-lobes as due to: a) sea-level fall with shelf-incision and basinward movement of the deltaic system beyond the shelf-break; b) high sediment-supply mechanism as hyperpycnal flow within shelf-edge deltas feeding the basin-fans during sustained flow; and c) having a narrow shelf that easily gets prograded across with high sediment supply. On individual basis each of these clinothems can be interpreted with these mechanisms above. However, it is interesting to see how the shape and size of each clinothem has a direct effect on the next clinothem that occurs above. As a clinothem consist of a dominant muddy part, the mud-volume can be stored: at the shelf-edge and expand the width of the shelf, on the shelf and building up the shelf height or even be stored more landward within the lagoonal and coastal areas, starving the shelf. This study show how a volumetrically-limited clinothem enables the next clinothem above, to easily cross the shelf and feed sediments down the shelf slope from a fluvial delta. The two following clinothem faced a wider shelf that first gave a wave-dominated delta and finally a mixed tidal and fluvial delta capped by an estuary.
The Eocene of the Central Basin of Spitsbergen shows a series of eastward building clinothems deposited in a foreland basin. This basin was formed by a westerly active fold and thrust-belt which also acted as provenance area for these shallow-marine sand-wedges. Some of these shallow-marine wedges prograded onto the shelf, whereas some of them reached the shelf-edge and have associated deep-marine sand-lobes. Three of these clinothems have been studied with focus on depositional environment, lateral facies variations, internal stacking pattern and shoreline trajectory pattern. All of them show a regressive deltaic to transgressive estuary/tidal couplet. Internally, there are clear differences between the three clinothems in terms of the style of the regressive deltaic part and the transgressive estuary part. The deltaic parts range from a) fluvial and punctuated mass-flow style; b) wave reworked and delta front collapse style; and c) mixed tide and fluvial influenced delta. The transgressive parts of the clinothems show a variation of the thickness of estuary sandstones and coastal plain fines developments conditioned on the degree of aggradation. Previous studies of these Eocene clinothems have interpreted the associated deep-marine sand-lobes as due to: a) sea-level fall with shelf-incision and basinward movement of the deltaic system beyond the shelf-break; b) high sediment-supply mechanism as hyperpycnal flow within shelf-edge deltas feeding the basin-fans during sustained flow; and c) having a narrow shelf that easily gets prograded across with high sediment supply. On individual basis each of these clinothems can be interpreted with these mechanisms above. However, it is interesting to see how the shape and size of each clinothem has a direct effect on the next clinothem that occurs above. As a clinothem consist of a dominant muddy part, the mud-volume can be stored: at the shelf-edge and expand the width of the shelf, on the shelf and building up the shelf height or even be stored more landward within the lagoonal and coastal areas, starving the shelf. This study show how a volumetrically-limited clinothem enables the next clinothem above, to easily cross the shelf and feed sediments down the shelf slope from a fluvial delta. The two following clinothem faced a wider shelf that first gave a wave-dominated delta and finally a mixed tidal and fluvial delta capped by an estuary.
Panel_15186
Panel_15186
3:45 PM
4:05 PM
4:05 p.m.
Controls on the Morphodynamics and Stratigraphic Architecture of Compound Dunes and Point Bars on the Open-Coast Macrotidal Flat in Gyeonggi Bay, West Coast of Korea
Room 505/506/507
By K. Choi, J. Jo
Simple and compound dunes are developed on the intertidal tributary channel and channel bank of Yeochari macrotidal flat in Gyeonggi Bay, west coast of Korea. Dunes are asymmetrical with the majority of their steeper lee faces and master bedding surfaces dipping toward ebb current direction. Dunes consist of cross-bedded medium to coarse sands with a coarsening-up textural trend, which overlie channel bank comprised of sand flat and mud flat facies and channel point bars composed of various channel facies including fluid muds and channel lags. Four-year long morphodynamic observations revealed that simple dunes on the tributary channel migrate seaward as fast as 1.5-2 m per day. In contrast compound dunes on the southern channel bank migrate either landward or seaward at much slower rates of 2-3 m per month. Despite greater current speeds on the channel bank, smaller tidal asymmetry leads compound dunes to migrate relatively slowly. In the case of intense wave activity, however, compound dunes seem to migrate at a noticeable rate. Compound dunes continued to shift their location over point bars toward northern channel bank as tributary channel migrates back and forth. Concurrent migration of compound dunes and channels produced a complicated stratigraphic architecture consisting of fining-upward point-bar succession overlain by coarsening-up compound-dune succession with master bedding surfaces dipping nearly opposite to those of point-bar succession. Tidal asymmetry, wave intensity and migration of tributary channel are seen to exert an important control on the stratigraphic architecture of compound dunes and point bars in the intertidal environment.
Simple and compound dunes are developed on the intertidal tributary channel and channel bank of Yeochari macrotidal flat in Gyeonggi Bay, west coast of Korea. Dunes are asymmetrical with the majority of their steeper lee faces and master bedding surfaces dipping toward ebb current direction. Dunes consist of cross-bedded medium to coarse sands with a coarsening-up textural trend, which overlie channel bank comprised of sand flat and mud flat facies and channel point bars composed of various channel facies including fluid muds and channel lags. Four-year long morphodynamic observations revealed that simple dunes on the tributary channel migrate seaward as fast as 1.5-2 m per day. In contrast compound dunes on the southern channel bank migrate either landward or seaward at much slower rates of 2-3 m per month. Despite greater current speeds on the channel bank, smaller tidal asymmetry leads compound dunes to migrate relatively slowly. In the case of intense wave activity, however, compound dunes seem to migrate at a noticeable rate. Compound dunes continued to shift their location over point bars toward northern channel bank as tributary channel migrates back and forth. Concurrent migration of compound dunes and channels produced a complicated stratigraphic architecture consisting of fining-upward point-bar succession overlain by coarsening-up compound-dune succession with master bedding surfaces dipping nearly opposite to those of point-bar succession. Tidal asymmetry, wave intensity and migration of tributary channel are seen to exert an important control on the stratigraphic architecture of compound dunes and point bars in the intertidal environment.
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A Potential High-Latitude Signature on a Cretaceous Paleopolar Coastal Plain: Flashiness Evidenced by Recurring Facies, Sedimentary-Pedogenic Structures and Isotopic Trends in the Prince Creek Formation of Arctic Alaska During a Greenhouse
Room 505/506/507
By P. P. Flaig, P. McCarthy, A. Fiorillo, D. vanderKolk, S. SalazarJaramillo, C. suarez
The Prince Creek Fm (Maastrichtian) of Alaska, deposited at 80-85° north paleolatitude, preserves an Arctic paleopolar Greenhouse ecosystem. We suggest that distinctive, recurring facies and sedimentary-pedogenic structures coupled with isotopic trends are evidence of a high-latitude signature on this low-gradient, muddy coastal plain. Strata record deposition in meandering trunk channels, meandering-fixed distributaries, and associated floodplains. Crevassing was common and splay complexes make up the bulk of sandy deposits. Inclined heterolithic stratification (IHS) and carbonaceous root traces are found in all channels. Although IHS is interpreted to record tidal-influence, ubiquitous roots on all IHS may also evidence a flashy system with regular discharge fluctuations. Entisols-Inceptisols are drab-colored and contain carbonaceous material and Fe-oxide depletion coatings indicating waterlogging and anoxia, consistent with a high water table. Fe-oxide mottles, ferruginous segregations, bioturbation, and illuvial clay coatings indicate recurring oxidation and periodic drying-out of soils. These compound-cumulative soils experienced repeated wetting and drying, with soil formation repeatedly interrupted by alluviation. Common pedogenic illite/smectite in ash-rich Prince Creek soils also suggest weathering and alternating wetting-drying. Bonebeds on floodplains exhibit a recurring facies pairing consistent with deposition by viscous hyperconcentrated flows. We suggest that exceptional discharge events, generated by seasonal snowmelt in the nearby Brooks Range increased suspended sediment concentrations and generated recurring, erosive hyperconcentrated flows. Hyperpycnites have also been identified in prodelta deposits of the genetically-linked shallow-marine sediments of the Schrader Bluff Fm. Stable oxygen isotope analysis of dinosaur tooth enamel and pedogenic siderite suggest that d18O depleted water ingested by dinosaurs, and meteoric water from siderite, result from increased rainout linked to increased latent heat transfer to the poles, an intensified hydrological cycle, and snowmelt. d18O and d13C values from authigenic aragonite in brackish-water invertebrates likely record seasonal fluctuations attributed to drainage from high altitude freshwater sources. We interpret these characteristics to record a seasonally flashy system, which is the high-latitude signature in the Prince Creek Fm likely driven by the paleopolar light and temperature regime.
The Prince Creek Fm (Maastrichtian) of Alaska, deposited at 80-85° north paleolatitude, preserves an Arctic paleopolar Greenhouse ecosystem. We suggest that distinctive, recurring facies and sedimentary-pedogenic structures coupled with isotopic trends are evidence of a high-latitude signature on this low-gradient, muddy coastal plain. Strata record deposition in meandering trunk channels, meandering-fixed distributaries, and associated floodplains. Crevassing was common and splay complexes make up the bulk of sandy deposits. Inclined heterolithic stratification (IHS) and carbonaceous root traces are found in all channels. Although IHS is interpreted to record tidal-influence, ubiquitous roots on all IHS may also evidence a flashy system with regular discharge fluctuations. Entisols-Inceptisols are drab-colored and contain carbonaceous material and Fe-oxide depletion coatings indicating waterlogging and anoxia, consistent with a high water table. Fe-oxide mottles, ferruginous segregations, bioturbation, and illuvial clay coatings indicate recurring oxidation and periodic drying-out of soils. These compound-cumulative soils experienced repeated wetting and drying, with soil formation repeatedly interrupted by alluviation. Common pedogenic illite/smectite in ash-rich Prince Creek soils also suggest weathering and alternating wetting-drying. Bonebeds on floodplains exhibit a recurring facies pairing consistent with deposition by viscous hyperconcentrated flows. We suggest that exceptional discharge events, generated by seasonal snowmelt in the nearby Brooks Range increased suspended sediment concentrations and generated recurring, erosive hyperconcentrated flows. Hyperpycnites have also been identified in prodelta deposits of the genetically-linked shallow-marine sediments of the Schrader Bluff Fm. Stable oxygen isotope analysis of dinosaur tooth enamel and pedogenic siderite suggest that d18O depleted water ingested by dinosaurs, and meteoric water from siderite, result from increased rainout linked to increased latent heat transfer to the poles, an intensified hydrological cycle, and snowmelt. d18O and d13C values from authigenic aragonite in brackish-water invertebrates likely record seasonal fluctuations attributed to drainage from high altitude freshwater sources. We interpret these characteristics to record a seasonally flashy system, which is the high-latitude signature in the Prince Creek Fm likely driven by the paleopolar light and temperature regime.
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Facies Architecture and Its Implications: Oligocene Carbonera Fm., Llanos Foreland Basin, Colombia
Room 505/506/507
By S. Ghosh, L. Suarez, F. Parraga, M. Ruiz, J. Vargas
Oligocene strata In the Llanos basin, comprise 4 units: lower, and upper Early Oligocene, and lower and upper late Oligocene. Each unit contains a couplet of thick basal sand-rich subunit and an upper shaly one. The objective here is to characterize the temporal-spatial variation of the productive Oligocene sands, specially the upper Early Oligocene one (C7), in context of foreland development and sea level oscillations. This unit hosts heavy oil reservoirs in the Rubiales and other fields. Analysis of 118 wells, 16 seismically calibrated regional transects, and 45 maps, helped to document regional facies variation in the Oligocene strata. Thickening of the Oligocene from proximal east to distal west coincided with a progressively finer granulometry westward. Significantly thick blocky proximal reservoir sands, including some incised valley fill deposits, in the east, pass laterally into finer facies toward west. The sand unit of Early Oligocene (C7) shows thickness variation across the area; the thickest basal sands (upto 400’ thick) with minor shaly intercalations occur as a belt closer to the eastern border near Guyana shield, whereas a thinner belt (upto 200’ thick) occurs westward. Further west, the 200’ sandy belt laterally passes into a silty shale facies containing only a few thin sand beds. Our upper Early Oligocene gross depositional environment (GDE) map shows 3 facies belts, broadly paralleling the lithofacies variation mentioned above. The two C7 sand belts are mainly of fluvial origin, whereas its coeval westerly shalier unit varies from proximal brackish to restricted marine outward. The Oligocene units show a marked easterly back-stepping character in all basin-transverse sections. Oligocene 0’ line distribution map reveals that following initial lower Early Oligocene regression, 3 succeeding Oligocene intervals experienced progressive eastward marine incursions coinciding with stacked retrogradational sandy units. MFS-related shales of sand/shale couplets, provide seals for the C7 sand reservoirs westward. However, hydrodynamic factors were responsible for entrapment of oil in easternmost C7 reservoirs lacking effective seals. Punctuated Oligocene uplift of the Eastern Cordilleras likely triggered the cyclic marine transgressions in the foreland basin. The significance of this study is that it provides an understanding of the temporal spatial distribution of the productive Oligocene sands in relation to seal, source rock and entrapment.
Oligocene strata In the Llanos basin, comprise 4 units: lower, and upper Early Oligocene, and lower and upper late Oligocene. Each unit contains a couplet of thick basal sand-rich subunit and an upper shaly one. The objective here is to characterize the temporal-spatial variation of the productive Oligocene sands, specially the upper Early Oligocene one (C7), in context of foreland development and sea level oscillations. This unit hosts heavy oil reservoirs in the Rubiales and other fields. Analysis of 118 wells, 16 seismically calibrated regional transects, and 45 maps, helped to document regional facies variation in the Oligocene strata. Thickening of the Oligocene from proximal east to distal west coincided with a progressively finer granulometry westward. Significantly thick blocky proximal reservoir sands, including some incised valley fill deposits, in the east, pass laterally into finer facies toward west. The sand unit of Early Oligocene (C7) shows thickness variation across the area; the thickest basal sands (upto 400’ thick) with minor shaly intercalations occur as a belt closer to the eastern border near Guyana shield, whereas a thinner belt (upto 200’ thick) occurs westward. Further west, the 200’ sandy belt laterally passes into a silty shale facies containing only a few thin sand beds. Our upper Early Oligocene gross depositional environment (GDE) map shows 3 facies belts, broadly paralleling the lithofacies variation mentioned above. The two C7 sand belts are mainly of fluvial origin, whereas its coeval westerly shalier unit varies from proximal brackish to restricted marine outward. The Oligocene units show a marked easterly back-stepping character in all basin-transverse sections. Oligocene 0’ line distribution map reveals that following initial lower Early Oligocene regression, 3 succeeding Oligocene intervals experienced progressive eastward marine incursions coinciding with stacked retrogradational sandy units. MFS-related shales of sand/shale couplets, provide seals for the C7 sand reservoirs westward. However, hydrodynamic factors were responsible for entrapment of oil in easternmost C7 reservoirs lacking effective seals. Punctuated Oligocene uplift of the Eastern Cordilleras likely triggered the cyclic marine transgressions in the foreland basin. The significance of this study is that it provides an understanding of the temporal spatial distribution of the productive Oligocene sands in relation to seal, source rock and entrapment.
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