Late Pleistocene-Holocene sea level and climate changes in the Gulf of Saros: Evidence from seismostratigraphic record and sediment core data
Kürşad Kadir ErişCerennaz YakupoğluDemet Bi̇lteki̇nNurettin YakupoğluAsen SabuncuAlina PoloniaLuca Gasperini
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Last Glacial Maximum
Transgressive
Abstract Decreases in equilibrium-line altitudes (ELAs) varied geographically during the last glacial maximum (LGM), with a mid-range value of ~ 900 m commonly deduced from altitude ratio and accumulation–area ratio calculations. Sea level, however, was 120 m lower during the LGM, so the ELA lowering relative to sea level would only be 780 m for a 900-m absolute lowering. With a lapse rate of 0.006°C m −1 , this implies a 4.7°C lowering of global temperature. It has been argued that this correction for sea-level change is unnecessary, but the logic on which this is based requires adiabatic compression to apply over much longer time scales than is typically invoked. We find that the correction is necessary. In addition, geometric changes in the atmosphere during the LGM, pointed out by Osmaston (2006), could lead to 0.4°C decrease in the average temperature of the troposphere. Additionally, orographic effects could significantly change the snow distribution on mountain masses near sea level.
Last Glacial Maximum
Orographic lift
Lapse rate
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Abstract Analysis of the four cases of the sequence boundary (SB)‐transgressive surface (TS) relation in nature shows that applying transgressive surfaces as sequence boundaries has the following merits: it improves the methodology of stratigraphic subdivision; the position of transgressive surface in a sea level curve is relatively fixed; the transgressive surface is a transforming surface of the stratal structure; in platforms or ramps, the transgressive surface is the only choice for determining the sequence boundary; the transgressive surface is a readily recognized physical surface reflected by seismic records in seismostratigraphy. The paper reaches a conclusion that to delineate a SB in terms of the TS is theoretically and practically better than to delineate it between highstand and lowstand sediments as has been done traditionally.
Transgressive
Sequence (biology)
Transgressive segregation
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Last Glacial Maximum
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At its maximum extent during the last glacial cycle, Lake Franklin covered 1100 km2 of the Ruby Valley of northeastern Nevada, making it one of the largest pluvial lakes between Lakes Bonneville and Lahontan. Mapping of shorelines, surveying of topographic profiles, and radiocarbon dating of gastropod shells were employed to reconstruct the latest Pleistocene history of the lake. During the first half of the Last Glacial Maximum (LGM), Lake Franklin covered ∼42% of its maximum area. This extent increased to ∼60% during the second half of the LGM. Some radiocarbon ages suggest that the lake briefly rose to near its highstand between 20 and 18 ka, but the best constrained rise occurred ca. 17 ka, when the lake rapidly transgressed to its highstand elevation of 1850 m. This rise was synchronous with highstands of nearby pluvial lakes, implicating a regional shift in the balance between precipitation and potential evaporation. The lake dropped to 1843 m, before rising once more to 1850 m ca. 16.0 ka. After falling and stabilizing at 1843 m again ca. 15.4 ka, the lake rapidly regressed to <1818 m (a loss in area of >70%) by 14.8 ka. This regression was synchronous with the fall of Lake Bonneville from the Provo shoreline and the regression of Lake Lahontan from the Sehoo shoreline. Radiocarbon ages and stratigraphic evidence document a final transgression in the latest Pleistocene that reached 1820 m (34% of maximum area) ca. 13.0 ka, synchronous with the Recess Peak Glaciation in the Sierra Nevada, and overlapping with the start of the Younger Dryas and minor transgressions of Lakes Bonneville, Lahontan, and Owens. The correspondence of this Lake Franklin history with other climate archives from this region underscores the value of pluvial lake deposits as sources of paleoclimate information and indicates synchronous forcing of climate changes during the last glacial-interglacial transition.
Pluvial
Last Glacial Maximum
Marine transgression
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During the Pleistocene, a period covering the last two million years, sea level is known to have risen above and fallen below the present sea level. The evidence for such fluctuations comes from marine and estuarine sediments, including beaches, far above present sea level and from freshwater sediments, beaches and valley systems now submerged. In southeast England there are Lower Pleistocene marine deposits at 183 m O.D . at Netley Heath in Surrey and upper Pleistocene freshwater sediments at - 35 m O.D . in the Channel. Thus we have in this area evidence of an amplitude of sea-level fluctuation relative to the present sea level of some 218 m. While such limits of relative sea-level fluctuation are not so difficult to identify, very considerable difficulties arise in determining the relation of sea-level change to the passage of time, and in the analysis of sea-level change - whether it be a real lowering of sea level relative to land, or an uplift of land relative to sea level. Let us briefly consider each of these two fields of difficulty. To date a particular stand of sea level, we have to know the relation of a particular deposit, say beach or shallow marine sediment to sea level at the time, and we have to know the correlation of this deposit to a part of the sequence of geological events which make up the Pleistocene. Both of these aspects may be problematical. It may not be certain what depth of water a deposit was formed in, and the age and correlation of the deposit may be doubtful.
Sea-Level Change
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Abstract Long-standing interpretations of the Last Glacial Maximum (LGM; 21,000 ± 2,000 years ago) in Australia suggest that the period was one of extreme cold and aridity, during which the Indo-Australian summer monsoon (IASM) system collapsed, and human populations declined and retreated to ecological refuges to survive. Here, we use transient iTRACE simulations, combined with palaeoclimate proxy records and archaeological data to re-interpret the late LGM and terminal Pleistocene (21,000–11,000 yrs) in Australia. The models suggest climates during the peak LGM were cooler than present (-4 to -6°C), but there is no evidence of IASM collapse or substantial precipitation decreases in northern Australia. Kernel Density Estimates (KDE) of archaeological ages show relatively stable and persistent human activity across most regions throughout the late LGM and terminal Pleistocene, consistent with genetic evidence. Spatial coverage of archaeological sites steadily increased across the terminal Pleistocene; however population collapse is not evident.
Last Glacial Maximum
Before Present
Proxy (statistics)
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在 Yanchang 的 Chang 8 成员以内的水库() 在西南的 Ordos 盆的形成被低渗透描绘。为这些水库的探索和发展造一个高分辨率的顺序 stratigraphic 框架是重要的。基于井日志，地震数据，核心和露头的综合调查， Chang 8 成员作为第三顺序被解释transgressive回归( T-R )也就是，分别地，顺序，它由六4th顺序 T-R 组成定序 K1 ， K2 ， K3 ， K4 ， K5 和 K6 从对基础最高。各个 4th 顺序顺序包括 transgressive 一条回归的系统道覆盖的系统道。从 K1 到 K4 的 transgressive 系统道，它被描绘由向陆地，外形的移动和全面 retrogradational 定序在第三顺序期间多于沉积供应由于住所增加叠模式底级的上升。支流隧道主要在酒吧主要是的海湾，表沙，和小规模的嘴响应 4th 顺序在回归的系统道开发了的 transgressive 系统道，和 interdistributary 被扔底级的变化。从到 K6 的 K4 的回归的系统道，因为住所，它被外形和全面 progradational 顺序叠模式的 basinward 移动描绘在第三顺序在下降期间增加不到沉积供应库水平。支流隧道主要在 transgressive 系统道被积累，并且支流隧道和嘴酒吧由于 4th 顺序在回归的系统道被扔底级的变化。详细 stratigraphic 和 sedimentological 分析显示序列 K1， K2， K5 和 K6，以及 K3 和 K4 的盆边，响应低住所和更多的沉积供应由于他们的高水库质量为探索和发展仍然保持潜在。
Transgressive
Sequence (biology)
Sequence Stratigraphy
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Further understanding of past climate requires a robust estimate of global ice volume fluctuations that in turn rely on accurate global sea-level reconstructions. An advantage of Marine Isotope Stage 2 (MIS 2) is the availability of suitable material for radiocarbon dating to allow comparison of sea-level data with other paleoclimatic proxies. However, the number and accuracy of sea-level records during MIS 2 is currently lacking. Here we present the history of MIS 2 eustatic sea-level change as recorded in the Bonaparte Gulf, northwestern Australia by reconstructing relative sea level and then modeling glacial isostatic adjustment. The isostatically-corrected global sea-level history indicates that sea-level plateaued from 25.9 to 20.4 cal kyr BP (modeled median probability) prior reaching its minimum (19.7 to 19.1 cal kyr BP). Following the plateau, we detect a 10-m global sea-level fall over ~1,000 years and a short duration of the Last Glacial Maximum (global sea-level minimum; 19.7 to 19.1 cal kyr BP). These large changes in ice volume over such a short time indicates that the continental ice sheets never reached their isostatic equilibrium during the Last Glacial Maximum.
Post-glacial rebound
Last Glacial Maximum
Marine isotope stage
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