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Architectural complexity of a carbonate transgressive systems tract induced by basement physiography
Three‐dimensional exposure of the Plio‐Pleistocene Calcarenite di Gravina Formation around Matera Horst, Italy, permits analysis of the architecture and internal complexities of carbonate sedimentary bodies around a palaeoisland. Spatial organization of the different lithosomes, along with their skeletal composition, sedimentary structures and bedding patterns, helps decipher the key factors that controlled platform architecture and distribution of heterogeneities: basement physiography, type and loci of carbonate production, bottom currents and changes in accommodation. Relative sea‐level changes resulted from high‐frequency glacioeustatic cycles that punctuated an overall tectonically induced transgression. Topographic relief, fragmentation of the limestone basement and wave energy controlled lithoclastic supply. Basement physiography and relative sea‐level changes determined the area available for carbonate‐producing biotas, and thus the amount and type of skeletal sediments. On the moderately dipping south‐western margin, waves and associated currents re‐distributed the lithoclasts derived from coastal abrasion. Bioclasts mostly derived from epiphytic seaweed production in the shoreface. Infralittoral prisms resulted from downdip transport (progradation) and longshore transport, which controlled along strike continuity of the prisms. Where basement continuity was interrupted at the margin of the palaeoisland, a lithoclastic fan was deposited from dumping sediments carried by shore‐parallel currents. Fan‐shaped skeletal bodies coalesced to form an apron on the steeper northern side of the palaeoisland, when a structural platform was flooded and epiphytic carbonates were shed. Red algae contribution depended on the available oligophotic area which, in turn, was controlled by high‐frequency sea‐level cycles, basement physiography and apron aggradation. The internal architecture of this apron resembles a low stand wedge but it accumulated during transgression. Deeper‐water, contour‐parallel currents formed a lithosome at the foot of the structural relief. Interpreted as drift deposits, it is composed of shallow‐water benthonic skeletal components, planktonic foraminifera and some limeclasts. 相似文献
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ATLE NYGÅRD HANS PETTER SEJRUP HAFLIDI HAFLIDASON MARCELLO CECCHI DAG OTTESEN 《Boreas: An International Journal of Quaternary Research》2004,33(1):1-17
Analysis of 2D and 3D seismic records from the continental shelf off western Norway, in combination with chronological constraints from 14 C dates, has led to a model for the glacial development in these shelf areas between c. 15 and 13 14 C ka BP. On the shallow Måløy Plateau adjacent to the Norwegian Channel, iceberg scours are preserved below a prominent moraine ridge, which by correlation to the Norwegian Channel indicate ice retreat at c. 15 14 C ka BP. Subsequently, the ice advanced across the scoured surface and deposited a till sheet before stabilizing to deposit a prominent moraine, termed the Bremanger Moraine. Based on location on the shelf, seismic stratigraphy, morphology and C dates the Bremanger Moraine is correlated with a significant moraine on the continental shelf off Trøndelag. We suggest that these features are products of a regional glacial event, the Bremanger Event, dated to <15–13.3 14 C ka BP. The Bremanger Event is probably a result of the deteriorating climatic conditions in the NE Atlantic during Heinrich event 1. 相似文献
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Anthropogenic climate forcing will cause the global mean sea level to rise over the 21st century.However,regional sea level is expected to vary across ocean basins,superimposed by the influence of natural internal climate variability.Here,we address the detection of dynamic sea level(DSL)changes by combining the perspectives of a single and a multimodel ensemble approach(the 50-member CanESM5 and a 27-model ensemble,respectively,all retrieved from the CMIP6 archive),under three CMIP6 projected scenarios:SSP1-2.6,SSP3-7.0 and SSP5-8.5.The ensemble analysis takes into account four key metrics:signal(S),noise(N),S/N ratio,and time of emergence(ToE).The results from both sets of ensembles agree in the fact that regions with higher S/N(associated with smaller uncertainties)also reflect earlier ToEs.The DSL signal is projected to emerge in the Southern Ocean,Southeast Pacific,Northwest Atlantic,and the Arctic.Results common for both sets of ensemble simulations show that while S progressively increases with increased projected emissions,N,in turn,does not vary substantially among the SSPs,suggesting that uncertainty arising from internal climate variability has little dependence on changes in the magnitude of external forcing.Projected changes are greater and quite similar for the scenarios SSP3-7.0 and SSP5-8.5 and considerably smaller for the SSP1-2.6,highlighting the importance of public policies towards lower emission scenarios and of keeping emissions below a certain threshold. 相似文献
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