scholarly journals Characteristics of late Miocene Lithofacies - Paleogeography in the Southeast Region of Hanoi Depression

2021 ◽  
Vol 37 (1) ◽  
Author(s):  
Nguyen Thi Phuong Thao ◽  
Tran Nghi ◽  
Dinh Xuan Thanh
Keyword(s):  
Sea Level ◽  
Late Miocene ◽  
Large Scale ◽  
River Mouth ◽  
Sea Level Change ◽  
Alluvial Fan ◽  
Depositional Sequence ◽  
Southeast Region ◽  
Level Change ◽  
Sedimentary Evolution

The characteristics of late Miocene lithofacies in the southeast region of  Hanoi depression have been revealed on the basis of sedimentary evolution in relation to sea level change and tectonic movement. During late Miocene, global sea level change has created one depositional sequence and three sedimentary systems tract. The lowstand systems tract (LST) is characterized by 5 rhythms of  alluvial lithofacies. These rhythms are represented by rough, humoc seismic wave  fields. This environment is not favorable condition for coal formation. The transgressive systems tract (TST) is characterized by 6 transitional lithofacies rhythms. Each lithofacies rhythm consists of 4 facies: the tidal flats sand facies of the bay, the  mud facies of the river mouth lagoon, the coastal marshy mud facies creating coal and the bay greenish-gray clay facies. The pacing process involves changes in the local sea level caused by tectonic lift. Each tectonic subsidence phase takes place at a very slow velocity, so it is compensated for fine-grained sediment creating marshy mud facies to develop mangroves on a large scale. It is a prerequisite to create thick coal seams distributed near the end of each rhythm. A part of highstand systems tract (HST) are eroded due to the improved folding process, creating an angular unconformity boundary with Pliocene-Quaternary sediments. However, after reconstracting of deformated section, it was clear that this systems tract  had only one  rhythm including 2 facies: prodelta mud facies and alluvial fan sandstone facies. Keywords: Lithofacies-paleogeography, sedimentary systems tract, sedimentary rhythm

scholarly journals On the geophysical processes impacting palaeo-sea-level observations

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Yusuke Yokoyama ◽  
Anthony Purcell
Keyword(s):  
Sea Level ◽  
Large Scale ◽  
Global Climate ◽  
Sea Level Change ◽  
Sea Level Changes ◽  
Factors Affecting ◽  
Ice Volume ◽  
Level Change ◽  
Recent Developments ◽  
Geophysical Processes

AbstractPast sea-level change represents the large-scale state of global climate, reflecting the waxing and waning of global ice sheets and the corresponding effect on ocean volume. Recent developments in sampling and analytical methods enable us to more precisely reconstruct past sea-level changes using geological indicators dated by radiometric methods. However, ice-volume changes alone cannot wholly account for these observations of local, relative sea-level change because of various geophysical factors including glacio-hydro-isostatic adjustments (GIA). The mechanisms behind GIA cannot be ignored when reconstructing global ice volume, yet they remain poorly understood within the general sea-level community. In this paper, various geophysical factors affecting sea-level observations are discussed and the details and impacts of these processes on estimates of past ice volumes are introduced.

scholarly journals Seismic stratigraphy of the broad, low-gradient continental shelf of the Palaeo-Agulhas Plain, South Africa

2019 ◽  
Author(s):  
Hayley C Cawthra ◽  
Peter Frenzel ◽  
Annette Hahn ◽  
John Compton ◽  
Lukas Gander ◽  
...  
Keyword(s):  
Continental Shelf ◽  
Sea Level ◽  
Tectonic Setting ◽  
Sea Level Change ◽  
Equal Proportion ◽  
Depositional Sequence ◽  
Level Change ◽  
Depositional Processes ◽  
Shelf Sediment ◽  
Stratigraphic Model

The continental shelf of the Palaeo-Agulhas Plain (PAP) is scattered with Pleistocene deposits with subdued topography. Their exaggerated lateral extension is the expression of a flat underlying substrate and availability of accommodation space, depositional processes and response to glacio-eustatic sea-level change have influenced deposition and distribution of these units. We present new results for the upper ~30 m (up to ~200 ka) of the stratigraphic record in this area and show that this shelf offers the opportunity to examine the response of a stable tectonic setting to the effects of sea-level change. This paper presents the results of extensive sub-bottom profiling surveys and chronostratigraphic investigations from marine sediment vibracores. Radiocarbon and Optically stimulated Luminescence dates are integrated into a seismic stratigraphic model composed of twenty Quaternary units, where two depositional sequences are bounded by shelf-wide unconformities. The upper sequence was cored where Pleistocene deposits were observed to be close to the seafloor and are draped in a thin veneer of marine shelf sediment and allow us to describe the environments of deposition of the PAP. The most pervasive stratigraphic pattern in these shelf deposits is made up of the depositional sequence remnant of the Falling Stage Systems Tract (FSST) forced regression from Marine Isotope Stage 5e–2. The other dominant stratigraphic group is the Transgressive Systems Tract (TST) associated with the Postglacial Marine Transgression. Surprisingly, the TST makes up an almost equal proportion of deposits in both sequences in the sedimentological record as the FSST, despite the shorter temporal span of the TST. The sub-bottom profiles were acquired on regional surveys extending from the Breede River in the west to Plettenberg Bay in the east, and to a maximum depth of 110 m below Mean Sea Level, with the exception of one ~200 m deep shelf-edge profile.

The southern North Sea as a natural palaeo-laboratory to reconstruct the coastal response to Last Interglacial sea-level rise

2020 ◽  
Author(s):  
Natasha Barlow ◽  
Victor Cartelle ◽  
Oliver Pollard ◽  
Lauren Gregoire ◽  
Natalya Gomez ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
North Sea ◽  
Large Scale ◽  
Recent Observation ◽  
Sea Level Change ◽  
Last Interglacial ◽  
Large Area ◽  
Level Change ◽  
Southern North Sea

<p>Current models that project sea-level rise beyond 2100 have large uncertainties because recent observation encompass a too limited range of climate variability to provide robust tests against which to simulate future changes. It is crucial to turn to the geological record where there are large-scale changes in climate, but the current interglacial provides limited evidence for how the Earth-system responds to increased temperatures, and therefore it is necessary to study previous climatically-warm periods. Global temperatures during the Last Interglacial were ~1<sup>o</sup>C warmer than pre-industrial values and 3-5<sup>o</sup>C warmer at polar latitudes, during which time global mean sea level was likely 6-9 m above present. Though the drivers of warming during the Last Interglacial are different to those of today, it is the amplified warming at polar latitudes, the primary locations of the terrestrial ice masses likely to contribute to long term sea-level rise, which makes the Last Interglacial an ideal palaeo-laboratory to understand coastal response to sea-level rise.  However, our understanding of Last Interglacial sea level change is primarily limited to tropical and sub-tropical latitudes and it is important to understand the response of temperate estuarine settings to rising sea level.</p><p>The ERC-funded RISeR project (Rates of Interglacial Sea-level Change, and Responses) focuses on specifically targeting palaeo shorelines buried within the southern North Sea, preserved beyond the limit of the Last Glacial Maximum ice sheets. Buried Last Interglacial sequences in this area provide a valuable record of marine transgression and are being unveiled in new geophysical and geotechnical datasets acquired to support the offshore renewable energy development. This offshore sedimentary archives offer significant advantages over the geomorphologically restricted onshore records allowing us to trace the transgression over a much large area, and should capture the earliest flooding of the Last Interglacial North Sea basin, when the far-field data suggests ice sheet melt was at it maximum. By integrating the already available datasets with newly acquired samples as part of the project, we aim to develop new palaeoenvironmental reconstructions of the Last Interglacial sea-level change from northwest Europe, providing the first chronological constraints on timing, and therefore rates. This has the potential to allow us to ‘fingerprint’ the source of melt (Greenland and/or Antarctica) during the interglacial sea-level highstand.</p>

SEA LEVEL CHANGES IN THE NEOGENE OF SOUTHERN VICTORIA

1978 ◽  
Vol 18 (1) ◽  
pp. 64 ◽  
Author(s):  
C. W. Mallett
Keyword(s):  
Grain Size ◽  
Sea Level ◽  
Marine Sediments ◽  
Late Miocene ◽  
Sea Level Change ◽  
Early Miocene ◽  
Sea Level Changes ◽  
Sea Levels ◽  
Level Change ◽  
Gippsland Basin

The distribution and lithology of marine sediments in southern Victoria are related to climatic events and the associated sea level changes. The most extensive transgression on the northern (onshore) margin of the southern Victorian Tertiary basins occurred late in the Early Miocene, with widespread deposition of calcareous muds and localised calcarenites with Lepidocvclina. Shallowing at approximately 14 m.y. affected all southern Victoria, initiating lithological changes in the Otway and Port Phillip Basins, and coinciding with erosion in the Gippsland Basin. Throughout the Late Miocene the grain size of sediments tended to increase and cross-bedded calcarenites became more common, consistent with shallowing deposition and sea withdrawal. By approximately 6 m.y., near the end of the Late Miocene, the sea had completely withdrawn from the onshore areas of southern Victoria.Pliocene and Pleistocene outcrops are scattered and thin, and marine beds are exclusively of nearshore and shallow deposition. For much of this period sea level was lower than at present. High levels in the Pliocene are indicated at approximately 5 m.y. and 3.5 m.y. High sea levels, associated with the rapid alternation of glacial and interglacial periods which typify the Pleistocene Epoch, were initiated late in the Pliocene, close to 2 m.y.Changes to the planktonic foraminiferal faunas parallel the sedimentological responses to sea level change. These suggest that palaeoclimatic events were the main controlling factor in Neogene sea level changes in southern Victoria, and allow differentiation of the eustatic and tectonic controls on sedimentation.

scholarly journals Seismic stratigraphy of the broad, low-gradient continental shelf of the Palaeo-Agulhas Plain, South Africa

2019 ◽  
Author(s):  
Hayley C Cawthra ◽  
Peter Frenzel ◽  
Annette Hahn ◽  
John Compton ◽  
Lukas Gander ◽  
...  
Keyword(s):  
Continental Shelf ◽  
Sea Level ◽  
Tectonic Setting ◽  
Sea Level Change ◽  
Equal Proportion ◽  
Depositional Sequence ◽  
Level Change ◽  
Depositional Processes ◽  
Shelf Sediment ◽  
Stratigraphic Model

The continental shelf of the Palaeo-Agulhas Plain (PAP) is scattered with Pleistocene deposits with subdued topography. Their exaggerated lateral extension is the expression of a flat underlying substrate and availability of accommodation space, depositional processes and response to glacio-eustatic sea-level change have influenced deposition and distribution of these units. We present new results for the upper ~30 m (up to ~200 ka) of the stratigraphic record in this area and show that this shelf offers the opportunity to examine the response of a stable tectonic setting to the effects of sea-level change. This paper presents the results of extensive sub-bottom profiling surveys and chronostratigraphic investigations from marine sediment vibracores. Radiocarbon and Optically stimulated Luminescence dates are integrated into a seismic stratigraphic model composed of twenty Quaternary units, where two depositional sequences are bounded by shelf-wide unconformities. The upper sequence was cored where Pleistocene deposits were observed to be close to the seafloor and are draped in a thin veneer of marine shelf sediment and allow us to describe the environments of deposition of the PAP. The most pervasive stratigraphic pattern in these shelf deposits is made up of the depositional sequence remnant of the Falling Stage Systems Tract (FSST) forced regression from Marine Isotope Stage 5e–2. The other dominant stratigraphic group is the Transgressive Systems Tract (TST) associated with the Postglacial Marine Transgression. Surprisingly, the TST makes up an almost equal proportion of deposits in both sequences in the sedimentological record as the FSST, despite the shorter temporal span of the TST. The sub-bottom profiles were acquired on regional surveys extending from the Breede River in the west to Plettenberg Bay in the east, and to a maximum depth of 110 m below Mean Sea Level, with the exception of one ~200 m deep shelf-edge profile.

The case for sea-level change as a dominant causal factor in mass extinction of marine invertebrates

1989 ◽  
Vol 325 (1228) ◽  
pp. 437-455 ◽  
Keyword(s):  
Sea Level ◽  
Large Scale ◽  
Ecological Model ◽  
Marine Invertebrates ◽  
Sea Level Change ◽  
Mass Extinctions ◽  
High Turnover ◽  
Level Change ◽  
Species Area ◽  
The 1960S

A correlation between global marine regressions and mass extinctions has been recognized since the last century and received explicit formulation, in a model involving habitat-area restriction, by Newell in the 1960s. Since that time attempts to apply the species-area relation to the subject have proved somewhat controversial and promoters of other extinction models have called the generality of the regression-extinction relation into question. Here, a strong relation is shown to exist between times of global or regional sea-level change inferred from stratigraphic analysis, and times of high turnover of Phanerozoic marine invertebrates, involving both extinction and radiation; this is valid on a small and large scale. In many cases the most significant factor promoting extinction was apparently not regression but spreads of anoxic bottom water associated with the subsequent transgression. The sea-level-extinction relation cannot be properly understood without an adequate ecological model, and an attempt is made to formulate one in outline.

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