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Gerald R Dickens - One of the best experts on this subject based on the ideXlab platform.
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timescale dependent sedimentary record during the past 130 kyr from a tropical mixed siliciclastic Carbonate Shelf edge and slope ashmore trough southern gulf of papua
Sedimentology, 2021Co-Authors: Gianni Mallarino, Gerald R Dickens, Jason M Francis, Stephan J Jorry, James Daniell, Andre W Droxler, Luc Beaufort, Samuel J Bentley, Bradley N Opdyke, Larry C PetersonAbstract:In tropical and sub-tropical mixed siliciclastic–Carbonate depositional systems, fluvial input and in situ neritic Carbonate interact over space and time. Despite being the subject of many studies, controls on partitioning of mixed sediments remains controversial. Mixed sedimentary records, from Ashmore Trough Shelf edge and slopes (southern Gulf of Papua), are coupled with global sea-level curves and anchored to Marine Isotope Stage stratigraphy to constrain models of sediment accumulation at two different timescales for the past 130 kyr: (i) 100 kyr scale for last glacial cycle; and (ii) millennial scale for last deglaciation. During the last glacial cycle, Carbonate production and accumulation were primarily controlled by sea-level fluctuations. Export of neritic Carbonate to the slopes was initiated during re-flooding of previously exposed reefs and continued during Marine Isotope Stage 5e and 1 interglacial sea-level highs. Siliciclastic fluxes to the slope were controlled by interplay of sea level, Shelf physiography and oceanic currents. Heterogeneous accumulation of siliciclastic mud on the slope, took place during Marine Isotope Stage 5d to Marine Isotope Stage 3 sea-level fall. Siliciclastics reached adjacent depocentres during Marine Isotope Stage 2. Coralgal reef and oolitic–skeletal sand resumed at the Shelf edge during the subsequent stepwise sea-level rise of the last deglaciation. Contemporaneous, abrupt siliciclastic input from increased precipitation and fluvial discharge illustrates that climate controlled deglacial sedimentation. Siliciclastic input persisted until ca 8.5 ka. Carbonate accumulation waned at the Shelf edge after ca 14 ka, whereas it increased on the slopes since ca 11.5 ka, when previously exposed reef and bank tops were re-flooded. When comparing the last sea-level cycle sedimentation patterns of the southern Gulf of Papua with other coeval mixed systems, sea level and Shelf physiography emerge as primary controls on deposition at the 100 kyr scale. At the millennial scale, siliciclastic input was also controlled by climate change during the unstable atmospheric and oceanic conditions of the last deglaciation.
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late quaternary shedding of shallow marine Carbonate along a tropical mixed siliciclastic Carbonate Shelf great barrier reef australia
Sedimentology, 2003Co-Authors: Gavin B Dunbar, Gerald R DickensAbstract:The north-east Australian margin is the largest modern example of a tropical mixed siliciclastic/Carbonate depositional system, with an outer Shelf hosting the Great Barrier Reef (GBR) and an inner Shelf dominated by fluvially sourced siliciclastic sediment wedges. The long-term interplay between these sediment components and sea level is recorded in the Queensland Trough, a 1-2 km deep N-S elongate basin situated between the GBR platform and the Queensland Plateau. In this paper, 154 samples from 45 surface grabs and six well-dated piston cores were analysed for total Carbonate content, Carbonate mineralogy and Sr concentration to establish spatial and temporal patterns of Carbonate accumulation in the Queensland Trough over the last 300 kyr. Surface Carbonate contents are lowest on the inner-Shelf (<5%) and in the trough axis (<60%) because of siliciclastic dilution. Carbonate on the Shelf is mostly Sr-rich aragonite and high-Mg calcite (HMC), whereas that in the basin is mostly low-Mg calcite. Once normalized to remove the effects of siliciclastic dilution, surface Sr-rich aragonite and HMC abundances decrease linearly to background levels 100 km seaward of the Shelf edge. Core samples show that, over time, normalized aragonite and Sr abundances are greatest during periods of Shelf flooding and lowest when sea level drops below the Shelf edge. This is consistent with changes in the production of coral and calcareous algae, and the shedding of their debris from the Shelf. Interestingly, normalized HMC concentrations on the slope peak during periods of major transgression, perhaps because of maximum off-Shelf transport from inter-reef areas or intermediate water dissolution. After accounting for siliciclastic dilution, there are strong similarities in both spatial and temporal patterns of Carbonate minerals between slopes and basins of the north-east Australian margin and those of pure Carbonate margins such as the Bahamas. A limited set of basic processes, including the formation and breakdown of Carbonate on the Shelf, the transport of Carbonate off the Shelf and eustatic sea level, probably controls Carbonate accumulation in slope and basin settings of tropical environments, irrespective of proximal siliciclastic sediment sources.
Bruno C Vendeville - One of the best experts on this subject based on the ideXlab platform.
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contrasting mixed siliciclastic Carbonate Shelf derived gravity driven systems in compressional intra slope basins southern hikurangi margin new zealand
Marine and Petroleum Geology, 2021Co-Authors: Barbara Claussmann, Julien Bailleul, F Chanier, Vincent Caron, Adam D Mcarthur, Geoffroy Mahieux, C Chaptal, Bruno C VendevilleAbstract:1. Abstract Along active margins, the combination of predominant tectonic activity and shallow-marine mixed siliciclastic-Carbonate source systems developing upon and around actively growing structures challenges traditional source-to-sink models. This study aims to investigate the implications of mixed siliciclastic-Carbonate Shelfal domains located in contrasting geotectonic settings (thrust forelimb and backlimb) for the development of the concomitant gravity-driven systems beyond the Shelf edges. Here, we document the vertical and lateral stratigraphic variabilities of the Shelf-derived turbidites and mass-transport deposits (MTDs) at outcrop-scale through the integrated interpretation of photogrammetry, field and taphonomic data from the emerged southern portion of the Hikurangi subduction margin. Results highlight the role and importance of varying structural setting of the sediment source, whereby the different morphologies of the source regions (continent-attached forelimb, continent-detached backlimb) control the development of highly varied Shelf-derived gravity-driven depositional systems that interact with the structures across the same confined intra-slope basin. The deposits are tens to a few hundred of meters in thickness and have a lateral extent of several kilometers. The depositional systems are characterized by durations of 1–2 Ma and were primarily controlled by the geometries and tectonic motion of the underlying structures at the Shelf edges. Shelf-derived mass-wasting systems occurred on both sides of the actively growing thrust structures and were sourced from both Shelfal domains that were attached or detached from the continental domain. When sourced from the backlimbs however, the subsequent MTDs exhibit more complex internal architectures, ultimately recording the dynamic changes in slope gradient, and can therefore be used as proxies for unraveling the tectonic activity of an individual structure. Our study provides new insights to better predict mixed siliciclastic-Carbonate depositional settings along active margins, sourced from thrust forelimb and backlimb. These results may be important for deep-marine exploration and tectonostratigraphic reconstruction of fold-and-thrust belts.
Grzegorz Racki - One of the best experts on this subject based on the ideXlab platform.
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isotopic chemostratigraphy across the early middle frasnian transition late devonian on the south polish Carbonate Shelf a reference for the global punctata event
Chemical Geology, 2012Co-Authors: Agnieszka Pisarzowska, Grzegorz RackiAbstract:Abstract The coupled high-resolution carbon isotope data from whole-rock limestone and organic matter samples of the transitans (Early Frasnian), punctata and the earliest hassi Zones (Middle Frasnian) from the South Polish Carbonate Shelf successions reveal the presence of a large, multi-part δ 13 C excursion, one of the largest known carbon cycle disturbance of Devonian period. This Early–Middle Frasnian (E–MF) δ 13 C perturbation consists of two positive excursions (a minor event I and a major event III) and two negative shifts (events II and IV). The major positive excursion, up to 5‰, begins near the E–MF boundary and the onset of Middlesex transgressive–anoxic event. The latter broader-scale positive δ 13 C perturbation correlates with the worldwide punctata Event documented across eastern and western Laurussia as well as northern Gondwana. The large magnitude of the punctata Isotopic Event, paired with negligible biotic effects, is similar to the Silurian biogeochemical perturbations but contrasts markedly with the younger Kellwasser Events. The distinctive protracted (about 1 Ma) E–MF δ 13 C variations may be only partly explained by escalated sea water exchange between epeiric seas and the anoxic open ocean during successive transgressive pulses. Very high δ 13 C plateau values of the punctata Event correspond to a positive 87 Sr/ 86 Sr shift, as well as elevated clastic input proxies and magnetic susceptibility, suggesting altogether that delivery of tectonically-promoted land-derived nutrients to marine basins was a key factor stimulating the biogeochemical perturbation. Extreme increases in primary productivity and enhanced organic matter burial in restricted deeper basinal settings would promote a gradual drawdown in surface-water as well as atmospheric p CO 2 , and consequently a climatic cooling by 5 °C, as indicated by the high-resolution δ 18 O phosphate record.
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facies and geochemistry across the early middle frasnian transition late devonian on south china Carbonate Shelf comparison with the polish reference succession
Palaeogeography Palaeoclimatology Palaeoecology, 2008Co-Authors: Chengyuan Wang, Grzegorz Racki, Maria RackaAbstract:Abstract Dongcun and Longmen are two important reference sections for the study of the Frasnian Carbonate platform of Guangxi (southern South China). At the Dongcun section, conodonts recovered in the present study provide a robust biostratigraphic framework for the Lower–Middle Frasnian interval. The studied interval (uppermost Givetian to Middle Frasnian basal Palmatolepis hassi Zone) is characterized by repeated shallower and deeper water deposits, but the cyclic depositional trend was mainly deepening upward. Carbon isotopic investigation of bulk samples recognizes a major, four-step perturbation across the Lower–Middle Frasnian boundary, which is also evident in the Holy Cross Mountains (Poland). The pattern is reinforced by correlative organic carbon isotopic secular trends from the reference Polish sections: a prominent long-lasting increase in δ13Ccarb up to 4.5‰ (event III) is evident in the Palmatolepis punctata Zone, but is preceded and followed by rapid negative shifts (events II and IV, respectively) to ca. 0‰; a weak incipient positive excursion (event I) is recognized in Carbonate carbon only in the upper part of the Palmatolepis transitans Zone. In Chinese sections, different background isotopic values indicate decoupled, isotopically dissimilar, hydrothermally affected and mostly oxygenated water masses over the Carbonate Shelf, as shown by trace and rare earth elements. The shallower water, upslope, diagenetically unaltered Dongcun succession reveals lighter carbon isotopic ratios, on the order of 2‰, while the less densely sampled and less certainly dated, mostly muddy-siliceous Longmen downslope succession shows δ13Ccarb levels similar to those recorded worldwide. The onset of the bipartite event III is marked by 13C enrichment of 4.3‰ at Dongcun. Event IV, a light carbon excursion, is especially well recorded in the shallow-water facies by a 2.5‰ negative shift. The event I excursion in the transitans Zone is obscured, as in some Polish successions, but is probably recorded in organic carbon trends. Slight differences in timing and magnitude of the δ13Ccarb oscillations may originate from geochemical decoupling between the open ocean and the tectonically active, morphologically differentiated epeiric basins. Nevertheless, a global extent for this major punctata Event is clear from the similar biogeochemical signals recorded on the distantly separated south Laurussian and South China shelves.
Barbara Claussmann - One of the best experts on this subject based on the ideXlab platform.
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contrasting mixed siliciclastic Carbonate Shelf derived gravity driven systems in compressional intra slope basins southern hikurangi margin new zealand
Marine and Petroleum Geology, 2021Co-Authors: Barbara Claussmann, Julien Bailleul, F Chanier, Vincent Caron, Adam D Mcarthur, Geoffroy Mahieux, C Chaptal, Bruno C VendevilleAbstract:1. Abstract Along active margins, the combination of predominant tectonic activity and shallow-marine mixed siliciclastic-Carbonate source systems developing upon and around actively growing structures challenges traditional source-to-sink models. This study aims to investigate the implications of mixed siliciclastic-Carbonate Shelfal domains located in contrasting geotectonic settings (thrust forelimb and backlimb) for the development of the concomitant gravity-driven systems beyond the Shelf edges. Here, we document the vertical and lateral stratigraphic variabilities of the Shelf-derived turbidites and mass-transport deposits (MTDs) at outcrop-scale through the integrated interpretation of photogrammetry, field and taphonomic data from the emerged southern portion of the Hikurangi subduction margin. Results highlight the role and importance of varying structural setting of the sediment source, whereby the different morphologies of the source regions (continent-attached forelimb, continent-detached backlimb) control the development of highly varied Shelf-derived gravity-driven depositional systems that interact with the structures across the same confined intra-slope basin. The deposits are tens to a few hundred of meters in thickness and have a lateral extent of several kilometers. The depositional systems are characterized by durations of 1–2 Ma and were primarily controlled by the geometries and tectonic motion of the underlying structures at the Shelf edges. Shelf-derived mass-wasting systems occurred on both sides of the actively growing thrust structures and were sourced from both Shelfal domains that were attached or detached from the continental domain. When sourced from the backlimbs however, the subsequent MTDs exhibit more complex internal architectures, ultimately recording the dynamic changes in slope gradient, and can therefore be used as proxies for unraveling the tectonic activity of an individual structure. Our study provides new insights to better predict mixed siliciclastic-Carbonate depositional settings along active margins, sourced from thrust forelimb and backlimb. These results may be important for deep-marine exploration and tectonostratigraphic reconstruction of fold-and-thrust belts.
Maria Racka - One of the best experts on this subject based on the ideXlab platform.
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facies and geochemistry across the early middle frasnian transition late devonian on south china Carbonate Shelf comparison with the polish reference succession
Palaeogeography Palaeoclimatology Palaeoecology, 2008Co-Authors: Chengyuan Wang, Grzegorz Racki, Maria RackaAbstract:Abstract Dongcun and Longmen are two important reference sections for the study of the Frasnian Carbonate platform of Guangxi (southern South China). At the Dongcun section, conodonts recovered in the present study provide a robust biostratigraphic framework for the Lower–Middle Frasnian interval. The studied interval (uppermost Givetian to Middle Frasnian basal Palmatolepis hassi Zone) is characterized by repeated shallower and deeper water deposits, but the cyclic depositional trend was mainly deepening upward. Carbon isotopic investigation of bulk samples recognizes a major, four-step perturbation across the Lower–Middle Frasnian boundary, which is also evident in the Holy Cross Mountains (Poland). The pattern is reinforced by correlative organic carbon isotopic secular trends from the reference Polish sections: a prominent long-lasting increase in δ13Ccarb up to 4.5‰ (event III) is evident in the Palmatolepis punctata Zone, but is preceded and followed by rapid negative shifts (events II and IV, respectively) to ca. 0‰; a weak incipient positive excursion (event I) is recognized in Carbonate carbon only in the upper part of the Palmatolepis transitans Zone. In Chinese sections, different background isotopic values indicate decoupled, isotopically dissimilar, hydrothermally affected and mostly oxygenated water masses over the Carbonate Shelf, as shown by trace and rare earth elements. The shallower water, upslope, diagenetically unaltered Dongcun succession reveals lighter carbon isotopic ratios, on the order of 2‰, while the less densely sampled and less certainly dated, mostly muddy-siliceous Longmen downslope succession shows δ13Ccarb levels similar to those recorded worldwide. The onset of the bipartite event III is marked by 13C enrichment of 4.3‰ at Dongcun. Event IV, a light carbon excursion, is especially well recorded in the shallow-water facies by a 2.5‰ negative shift. The event I excursion in the transitans Zone is obscured, as in some Polish successions, but is probably recorded in organic carbon trends. Slight differences in timing and magnitude of the δ13Ccarb oscillations may originate from geochemical decoupling between the open ocean and the tectonically active, morphologically differentiated epeiric basins. Nevertheless, a global extent for this major punctata Event is clear from the similar biogeochemical signals recorded on the distantly separated south Laurussian and South China shelves.