Contrasting variations in the structure and stable carbon isotopic composition of botryococcenes through the last glacial–interglacial transition in Lake Masoko (southern Tanzania)

AbstractAn oxygen isotope temperature record over a large part of the past 30,000 yr has been obtained for the southern Cape Province of South Africa by combining data on the isotopic composition of a stalagmite from a deep cave with that of a confined groundwater aquifer in the same region. Results show that temperatures during the last glacial maximum were on average about 6°C lower than those today, with peaks up to 7°C lower. A detailed analysis of the past 5000 yr suggests multiple fluctuations, with generally lower temperatures (1–2°C) around 4500 and 3000 yr B.P. The carbon isotopic composition of the stalagmite indicates significant vegetation changes between the late Pleistocene and today, and also during the second half of the Holocene.

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Environmental influences on the stable carbon isotopic composition of Devonian and Early Carboniferous land plants

Palaeogeography Palaeoclimatology Palaeoecology ◽

10.1016/j.palaeo.2019.02.025 ◽

2019 ◽

Vol 531 ◽

pp. 109100 ◽

Cited By ~ 6

Author(s):

Zhenzhu Wan ◽

Thomas J. Algeo ◽

Patricia G. Gensel ◽

Stephen E. Scheckler ◽

William E. Stein ◽

...

Keyword(s):

Isotopic Composition ◽

Environmental Influences ◽

Carbon Isotopic Composition ◽

Early Carboniferous ◽

Land Plants ◽

Stable Carbon ◽

Carbon Isotopic

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Radiocarbon in Porewater of Continental Shelf Sediments (Southeast Mediterranean)

Radiocarbon ◽

10.1017/s0033822200035682 ◽

2004 ◽

Vol 46 (2) ◽

pp. 633-642 ◽

Cited By ~ 2

Author(s):

O Sivan ◽

B Lazar ◽

E Boaretto ◽

Y Yechieli ◽

B Herut

Keyword(s):

Sediment Cores ◽

Carbon Isotopic Composition ◽

Mediterranean Coast ◽

Shelf Water ◽

Stable Carbon ◽

Last Glacial Period ◽

Carbon Isotopic ◽

Shelf Sediments ◽

Water Depths ◽

The Last Glacial

In this study, we aim to characterize the main processes controlling 14CDIC concentrations in porewater at the shallow shelf (water depth less than 120 m) off the Mediterranean coast of Israel. At these water depths, we expected to find evidence for seawater penetration toward the coast, since this area was flooded by seawater only some 18,000 yr ago (the end of the Last Glacial period).Measurements of the chemical composition (14CDIC) and stable carbon isotopic composition (δ13CDIC) were performed in several sediment cores (40–250 cm long) at water depths between 6 and 115 m. At water depths of 60 m, represented by a 2.5-m-long sediment core, the porewater 14CDIC levels (85–87 pMC) were lower than the corresponding sediment values in each layer (92–95 pMC), mainly due to the oxidation of relatively old organic matter (about 70 pMC) with no evidence to advection. In contrast, sediment cores from water depths shallower than 50 m showed only slight anaerobic oxidation and high 14CDIC values of approximately 100 pMC, indicating possible downward advection. These geochemical observations support the perception that the penetration of seawater into the coastal aquifer occurs at the shallow water zone (<50 m), while further verification by deeper cores is required.

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