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F. Borja - One of the best experts on this subject based on the ideXlab platform.
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millennial submillennial scale sea level fluctuations in western mediterranean during the second Highstand of mis 5e
Quaternary Science Reviews, 2011Co-Authors: C.j. Dabrio, C. Zazo, A. Cabero, J.l. Goy, T. Bardají, J. Lario, P.g. Silva, C Hillairemarcel, J A Gonzalezdelgado, F. BorjaAbstract:Abstract This paper investigates a series of small-scale, short-lived fluctuations of sea level registered in a prograding barrier spit that grew during the MIS 5e. This interglacial includes three Highstands ( Zazo et al., 2003 ) and we focus on the second Highstand, of assumed duration ∼10 ± 2 ka, given that U–Th ages do not provide more accurate data. Geometry and 3D architecture of beach facies, and thin-section petrography were used to investigate eight exposed offlapping subunits separated by seven conspicuous erosion surfaces, all interpreted as the result of repeated small-scale fluctuations of sea level. Each subunit records a relatively rapid rise of sea level that generated a gravelly shoreface with algal bioherms and a sandy uppermost shoreface and foreshore where most sand accumulated. A second range of still smaller-scaled oscillations of sea level has been deduced in this phase of sea-level fluctuation from lateral and vertical shifts of the foreshore-plunge-step-uppermost shoreface facies. Eventually, progradation with gently falling sea level took place and foreshore deposits underwent successive vadose cementation and subaerial dissolution, owing to relatively prolonged exposure. Later recovery of sea level re-established the Highstand with sea level at approximately the same elevation, and there began deposition of a new subunit. The minimum sea-level variation (fall and subsequent rise) required to generate the observed features is 4 m. The time span available for the whole succession of events, and comparison with the Holocene prograding beach ridge complex in the nearby Roquetas (Almeria) were used to calculate the periodicity of events. A millennial-suborbital time scale is suggested for fluctuations separating subunits and a decadal scale for the minor oscillations inside each subunit.
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Millennial/submillennial-scale sea-level fluctuations in western Mediterranean during the second Highstand of MIS 5e
Quaternary Science Reviews, 2011Co-Authors: C.j. Dabrio, C. Zazo, A. Cabero, J.l. Goy, T. Bardají, C. Hillaire-marcel, J.a. González-delgado, J. Lario, P.g. Silva, F. BorjaAbstract:This paper investigates a series of small-scale, short-lived fluctuations of sea level registered in a prograding\ud barrier spit that grew during theMIS 5e. This interglacial includes three Highstands (Zazo et al., 2003) and\ud we focus on the second Highstand, of assumed duration ∼10 2 ka, given that UeTh ages do not provide\ud more accurate data. Geometry and 3D architecture of beach facies, and thin-section petrography were used\ud to investigate eight exposed offlapping subunits separated by seven conspicuous erosion surfaces, all\ud interpreted as the result of repeated small-scale fluctuations of sea level.\ud Each subunit records a relatively rapid rise of sea level that generated a gravelly shoreface with algal\ud bioherms and a sandy uppermost shoreface and foreshore where most sand accumulated. A second\ud range of still smaller-scaled oscillations of sea level has been deduced in this phase of sea-level fluctuation\ud from lateral and vertical shifts of the foreshore-plunge-step-uppermost shoreface facies.\ud Eventually, progradation with gently falling sea level took place and foreshore deposits underwent\ud successive vadose cementation and subaerial dissolution, owing to relatively prolonged exposure. Later\ud recovery of sea level re-established the Highstand with sea level at approximately the same elevation,\ud and there began deposition of a new subunit. The minimum sea-level variation (fall and subsequent rise)\ud required to generate the observed features is 4 m. The time span available for the whole succession of\ud events, and comparison with the Holocene prograding beach ridge complex in the nearby Roquetas\ud (Almería) were used to calculate the periodicity of events. A millennial-suborbital time scale is suggested\ud for fluctuations separating subunits and a decadal scale for the minor oscillations inside each subunit
C.j. Dabrio - One of the best experts on this subject based on the ideXlab platform.
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millennial submillennial scale sea level fluctuations in western mediterranean during the second Highstand of mis 5e
Quaternary Science Reviews, 2011Co-Authors: C.j. Dabrio, C. Zazo, A. Cabero, J.l. Goy, T. Bardají, J. Lario, P.g. Silva, C Hillairemarcel, J A Gonzalezdelgado, F. BorjaAbstract:Abstract This paper investigates a series of small-scale, short-lived fluctuations of sea level registered in a prograding barrier spit that grew during the MIS 5e. This interglacial includes three Highstands ( Zazo et al., 2003 ) and we focus on the second Highstand, of assumed duration ∼10 ± 2 ka, given that U–Th ages do not provide more accurate data. Geometry and 3D architecture of beach facies, and thin-section petrography were used to investigate eight exposed offlapping subunits separated by seven conspicuous erosion surfaces, all interpreted as the result of repeated small-scale fluctuations of sea level. Each subunit records a relatively rapid rise of sea level that generated a gravelly shoreface with algal bioherms and a sandy uppermost shoreface and foreshore where most sand accumulated. A second range of still smaller-scaled oscillations of sea level has been deduced in this phase of sea-level fluctuation from lateral and vertical shifts of the foreshore-plunge-step-uppermost shoreface facies. Eventually, progradation with gently falling sea level took place and foreshore deposits underwent successive vadose cementation and subaerial dissolution, owing to relatively prolonged exposure. Later recovery of sea level re-established the Highstand with sea level at approximately the same elevation, and there began deposition of a new subunit. The minimum sea-level variation (fall and subsequent rise) required to generate the observed features is 4 m. The time span available for the whole succession of events, and comparison with the Holocene prograding beach ridge complex in the nearby Roquetas (Almeria) were used to calculate the periodicity of events. A millennial-suborbital time scale is suggested for fluctuations separating subunits and a decadal scale for the minor oscillations inside each subunit.
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Millennial/submillennial-scale sea-level fluctuations in western Mediterranean during the second Highstand of MIS 5e
Quaternary Science Reviews, 2011Co-Authors: C.j. Dabrio, C. Zazo, A. Cabero, J.l. Goy, T. Bardají, C. Hillaire-marcel, J.a. González-delgado, J. Lario, P.g. Silva, F. BorjaAbstract:This paper investigates a series of small-scale, short-lived fluctuations of sea level registered in a prograding\ud barrier spit that grew during theMIS 5e. This interglacial includes three Highstands (Zazo et al., 2003) and\ud we focus on the second Highstand, of assumed duration ∼10 2 ka, given that UeTh ages do not provide\ud more accurate data. Geometry and 3D architecture of beach facies, and thin-section petrography were used\ud to investigate eight exposed offlapping subunits separated by seven conspicuous erosion surfaces, all\ud interpreted as the result of repeated small-scale fluctuations of sea level.\ud Each subunit records a relatively rapid rise of sea level that generated a gravelly shoreface with algal\ud bioherms and a sandy uppermost shoreface and foreshore where most sand accumulated. A second\ud range of still smaller-scaled oscillations of sea level has been deduced in this phase of sea-level fluctuation\ud from lateral and vertical shifts of the foreshore-plunge-step-uppermost shoreface facies.\ud Eventually, progradation with gently falling sea level took place and foreshore deposits underwent\ud successive vadose cementation and subaerial dissolution, owing to relatively prolonged exposure. Later\ud recovery of sea level re-established the Highstand with sea level at approximately the same elevation,\ud and there began deposition of a new subunit. The minimum sea-level variation (fall and subsequent rise)\ud required to generate the observed features is 4 m. The time span available for the whole succession of\ud events, and comparison with the Holocene prograding beach ridge complex in the nearby Roquetas\ud (Almería) were used to calculate the periodicity of events. A millennial-suborbital time scale is suggested\ud for fluctuations separating subunits and a decadal scale for the minor oscillations inside each subunit
Eric C. Potter - One of the best experts on this subject based on the ideXlab platform.
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Sequence-stratigraphic controls on complex reservoir architecture of Highstand fluvial-dominated deltaic and lowstand valley-fill deposits in the Upper Cretaceous (Cenomanian) Woodbine Group, East Texas field: Regional and local perspectives
AAPG Bulletin, 2009Co-Authors: William A. Ambrose, Robert G. Loucks, Tucker F. Hentz, Florence Bonnaffé, L. Frank Brown, Fred P. Wang, Eric C. PotterAbstract:An analysis of 31 whole cores (1600 ft, 490 m) and closely spaced wireline logs (500 wells) penetrating the Lower Cretaceous (Cenomanian) lower Woodbine Group in the mature East Texas field and adjacent areas indicates that depositional origins and complexity of the sandstone-body architecture in the field vary from those inferred from previous studies. Heterogeneity in the lower Woodbine Group is controlled by Highstand, fluvial-dominated deltaic depositional architecture, with dip-elongate distributary-channel sandstones pinching out over short distances (typically 500 ft [150 m]) into delta-plain and interdistributary-bay siltstones and mudstones. This Highstand section is truncated in the north and west parts of the field by a thick (maximum of 140 ft [43 m]) lowstand, incised-valley-fill succession composed of multistoried, coarse-gravel conglomerate and coarse sandstone beds of bed-load fluvial systems. In some areas of the field, this valley fill directly overlies distal-delta-front deposits, recording a fall in relative sea level of at least 215 ft (65 m). Correlation with the Woodbine succession in the East Texas Basin indicates that these Highstand and lowstand deposits occur in the basal three fourth-order sequences of the unit, which comprises a maximum of 14 such cycles. Previous studies of the Woodbine Group have inferred meanderbelt sandstones flanked by coeval flood-plain mudstones and well-connected, laterally continuous sheet sandstones of wave-dominated deltaic and barrier-strand-plain settings. This model is inappropriate, and a full assessment of reservoir compartmentalization, fluid flow, and unswept mobile oil in East Texas field should include the Highstand, fluvial-dominated deltaic and lowstand valley-fill sandstone-body architecture.
Thomas C Brachert - One of the best experts on this subject based on the ideXlab platform.
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lowstand carbonates Highstand sandstones
Sedimentary Geology, 2003Co-Authors: Thomas C Brachert, M H Forst, Joao Pais, Paulo Legoinha, John J G ReijmerAbstract:The sedimentary facies, sediment dynamics and sequence architecture of modern high-energy shelves in the mid and high latitudes are largely governed by wave abrasion processes. Cool-water carbonates may form there, if the influx and/or net accretion of siliciclastics is kept at a minimum. Little dilution of the carbonate produced in situ is generally promoted by a wide “epicontinental” shelf, subdued topography of the adjacent mainland, the predominance of limestone outcrops, and an arid climate. The aforementioned requirements are rarely met, and thus will automatically lead to the formation of mixed siliciclastic–cool-water carbonates. Such an example is found in the Early to Mid-Miocene Lagos-Portimao Formation (Algarve, S-Portugal), which formed on a narrow high-energy shelf of the Atlantic Ocean that was bounded by a mountain range. The sediments of the formation consist of fossiliferous sandstone (FS), shell beds, and rhodolith blankets. Along strike, the stratification of the formation is monotonous for tens of kilometres and well exposed in coastal cliffs, whereas no outcrops of dip sections exist. The bulk skeletal composition of the sediments is typical for the warm-temperate climatic zone: various endo- and epibenthic bivalves, bryozoans, coralline algae, echinoderms, gastropods, and large foraminifers (Heterostegina). In some very rare beds, a few isolated, not framework-forming specimens of zooxanthellate corals (Porites, Tarbellastrea) indicate temporally elevated surface water temperatures close to the lower threshold of the coral reef ecosystem. In sandstones, the fauna is well preserved and burrowing bivalves are commonly found in life position. In limestone beds, the state of preservation of the grains ranges from intact to disintegrated and abraded specimens. We infer an accumulation of the shell beds through winnowing of fine materials (siliciclastic sand and carbonate mud) at wave abrasion depth and concentration of calcareous skeletons associated with the subsequent attraction of new epibiota in a complex shell bed. The vertical alternation of fossiliferous sandstone and shell beds, and in-phase variations of the “Photo Index” (photic biota vs. bryozoans) and “Bryozoan Index” (bivalves vs. bryozoans) is envisaged to document variations of water depth (and sea level). Sandstone units built up when wave abrasion depth (WAD) rose above the sea floor during TST (and early HST), whereas the shell beds formed during LST when the WAD for sand intersected with the sea floor. Clastic sediments were probably brought on the outer shelf during early transgression, and by longshore currents. Sea-level signatures inferred in the mixed siliciclastic–cool-water carbonate shelf setting of S-Portugal therefore significantly deviate from conventional concepts of carbonate sequence stratigraphy, which were developed for flat-topped platforms. Successful interpretations of ancient mixed sequences must therefore take into consideration the processes of production, concentration and accretion of the carbonate sediments.
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sedimentary model and high frequency cyclicity in a mediterranean shallow shelf temperate carbonate environment uppermost miocene agua amarga basin southern spain
Sedimentology, 1996Co-Authors: Jose M Martin, Juan C Braga, Christian Betzler, Thomas C BrachertAbstract:Uppermost Tortonian to lower Messinian temperate carbonates crop out in the Agua Amarga Basin (SE Spain). They consist of four units. The lower three units can be tentatively assigned to the lowstand systems tract of a fourth-order sequence, constituting in turn the lowstand (‘megatrough unit’), transgressive (‘breccia unit’) and Highstand (‘bedded unit’) stages of a higher-order cycle. All these materials were deposited in a small pull-apart basin related to the sinistral Carboneras strike-slip fault system. The best represented is the bedded unit (up to 25 m thick), which consists of bioclastic, bryozoan/bivalve-dominated calcarenites/calcirudites with abundant fragments of echinoids, barnacles, benthic foraminifers, coralline algae, brachiopods and solitary corals. Facies trends within this unit are roughly arranged in an E‐W direction, with the coastline to the north of the basin. The depositional model is that of a gentle ramp with prograding beaches and shoals in its higher parts. Seaward of the shoals was the ‘factory area’, where most organisms lived and maximum carbonate production took place. From this area some of the skeletons were washed landwards by waves and/or currents during storms and incorporated into the shoals and beaches, and others moved downslope along the ramp as mass-flows, accumulating to form the ‘fan-bedded zone’. The factory-area and fan-bedded sediments intercalate five well-defined, thick beds of calcarenites/fine-grained calcirudites. They show bar morphologies (single or amalgamated), or make up sand-waves with very consistent tabular cross-bedding pointing landwards. These beds formed in a very shallow, wave/current-influenced, coastal environment. The bars and sand waves in the fan-bedded zone developed during lowstands, while those located higher up in the ramp interbedded with the factory facies are related to transgressive stages. Prograding beaches, shoals, factory facies and fan-bedded layers developed during the Highstands. Net skeletal production occurred mainly during the Highstands. Sediment-accretion values of these sediments are similar to those of present and ancient shallow-marine, temperate carbonates considering that the whole bedded unit was deposited in a 100 000-year interval (equivalent to the short eccentricity cycle). The five cycles inside the bedded unit would therefore correspond to the c. 20 000-year precession cycles of the Milankovitch band.
Robert M Deconto - One of the best experts on this subject based on the ideXlab platform.
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miocene to recent ice elevation variations from the interior of the west antarctic ice sheet constraints from geologic observations cosmogenic nuclides and ice sheet modeling
Earth and Planetary Science Letters, 2012Co-Authors: Sujoy Mukhopadhyay, Robert P Ackert, Allen Pope, David Pollard, Robert M DecontoAbstract:Abstract Observations of long-term West Antarctic Ice Sheet (WAIS) behavior can be used to test and constrain dynamic ice sheet models. Long-term observational constraints are however, rare. Here we present the first constraints on long-term (Miocene–Holocene) WAIS elevation from the interior of the ice sheet near the WAIS divide. We use geologic observations and measurements of cosmogenic 21 Ne and 10 Be in bedrock surfaces to constrain WAIS elevation variations to 65 m above present-day ice levels at the Ohio Range occur only rarely during brief ice sheet Highstands, consistent with the observed cosmogenic nuclide data. Furthermore, the model's prediction that Highstand elevations have increased on average since the Pliocene is in good agreement with the cosmogenic nuclide data that indicate the highest ice elevation over the past 5 Ma was reached during the Highstand at 11 ka. Since the simulated cosmogenic nuclide concentrations derived from the model's ice elevation history are in good agreement with our measurements, we suggest that the model's prediction of more frequent collapsed-WAIS states and smaller WAIS volumes during the Pliocene are also correct.
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West Antarctic Ice Sheet elevations in the Ohio Range: Geologic constraints and ice sheet modeling prior to the last Highstand
Earth and Planetary Science Letters, 2011Co-Authors: Robert P Ackert, Sujoy Mukhopadhyay, David Pollard, Robert M Deconto, Aaron E. Putnam, Harold W. BornsAbstract:Abstract Knowledge of the timing and extent of past West Antarctic Ice Sheet (WAIS) elevation changes provides insight to the WAIS response to sea level and climate forcing, as well as constraints for ice sheet models. Trimlines and erratics indicate that maximum ice elevation at the Ohio Range, located near the WAIS divide, was 125 m above the present ice surface and was reached at ~ 10 ka. However, 3 He and 10 Be exposure ages of most granitic erratics and supra-glacial boulders in adjacent blue ice areas are older than the last Highstand and provide constraints on earlier interior WAIS elevation changes. Although diffusive loss of 3 He occurs in quartz, an excellent correlation between 3 He and 10 Be concentrations in samples up to 400 ka is observed in the Ohio Range, demonstrating the utility of 3 He measurements in Antarctic quartz. The correlation is used to calculate “equivalent 10 Be exposure ages” from the larger 3 He data set. The exposure ages occur in distinct clusters 10–20 ka, 70–80 ka, 130–140 ka and 180–190 ka that we relate to pulses in the emergence of englacial debris in localized blue ice ablation areas. A combined ice sheet/ice shelf model predicts that WAIS elevations near the Ohio Range have varied only ~ 125 m over the last 200 kyr with Highstands at ~ 10 ka and ~ 130 ka, in good agreement with observations of trimlines and peaks in the exposure age distribution at the Ohio Range. In the model, interior WAIS elevations are controlled by the interaction of accumulation rates and ice dynamics related to ice sheet/ocean interactions at the grounding line. WAIS Highstands occur early in interglacial periods during intervals of warmer temperatures and high accumulation rates, prior to the arrival of a wave of thinning. We hypothesize that the correspondence of rising regional WAIS elevation with debris pulses relates to increased ice (debris) flux and ablation in the local blue ice areas resulting from the warmer temperatures. The occurrence of clasts with exposure ages up to 200 ka on the WAIS surface indicates elevation changes near the Ohio Range were limited in extent during stage 5e. The geologic observations, combined with model results, place constraints on WAIS geometry during stage 5e and limit the WAIS contribution to the higher sea levels observed during the last interglacial to ~ 3 m.