First reliable chronology for the Early Khvalynian Caspian Sea transgression in the Lower Volga River valley

Kurbanov, R.; Murray, A.; Thompson, W.; Svistunov, M.; Taratunina, N.; Yanina, T.

Авторы: Kurbanov R., Murray A., Thompson W., Svistunov M., Taratunina N., Yanina T.
Журнал: Boreas
Том: 50
Номер: 1
Год издания: 2021
Издательство: Taylor & Francis
Местоположение издательства: United Kingdom
Первая страница: 134
Последняя страница: 146
DOI: 10.1111/bor.12478
Аннотация: During the Late Quaternary, dramatic changes in relative sea-level (of ~170 m) are known to have occurred in the Caspian Sea. However, all previous attempts at resolving the uncertainty associated with the timing of these transgressive/regressive events, primarily using 14C, have produced inconclusive or controversial results. Here we present the first reliable chronology for the largest known transgression (Early Khvalynian). This was derived using optically stimulated luminescence (OSL) analysis of sand-sized quartz, with support from infra-red stimulated luminescence (IRSL) from K-rich feldspar grains, all extracted from 16 sediment samples collected along the Lower Volga River. These samples were taken from loessic sediments, marine clays (known as Chocolate Clays) and overlying modern soils exposed at three sections (Srednyaya Akhtuba, Raygorod, Leninsk) ~200 km upstream of the present-day estuary. The differential bleaching rates of the quartz OSL and feldspar IRSL signals were used to evaluate the degree of resetting of quartz (and feldspar) signals; it was possible to conclude that all signals, and particularly quartz OSL, were sufficiently reset at deposition to allow accurate age estimation. Our results show unambiguously that the Early Khvalynian marine Chocolate Clays present at all three sections were deposited post-LGM, between ~17 ka and ~13.1 ka ago. These age estimates are further constrained by those from the overlying Kastanozem soils (9.6 to 0.7 ka) and underlying loess-soil series (32-19 ka), confirming a young (17-13 ka) age of the transgressive stage of the Early Khvalynian. This is the first reliable instrumental age estimate for the largest known Late Quaternary Caspian Sea transgression. Relative sea-level during this period must have been well above the sampling altitude of 11.7 m (Srednyaya Akhtuba), 11.3 m (Raygorod) and 4.7 m (Leninsk) to explain the absence of significant alluvial sand and to allow the deposition of the fine Chocolate Clays marker horizon.
Добавил в систему: Янина Тамара Алексеевна

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First reliable chronology for the Early Khvalynian Caspian Sea transgression in the Lower Volga River valleyстатья

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