Late Quaternary variations in the silicon flux from the River Nile to the Mediterranean: silicon-isotope evidence from lacustrine diatoms

2012 ◽  
Vol 279-280 ◽  
pp. 93
Author(s):  
Helen E. Cockerton
1987 ◽  
Vol 2 (6) ◽  
pp. 543-559 ◽  
Author(s):  
Rainer Zahn ◽  
Michael Sarnthein ◽  
Helmut Erlenkeuser

1991 ◽  
Vol 35 (1) ◽  
pp. 103-115 ◽  
Author(s):  
John Lewin ◽  
Mark G. Macklin ◽  
Jamie C. Woodward

AbstractDetailed morpho- and lithostratigraphic investigations, allied with radiometric dating, in the Voidomatis basin, Epirus, northwest Greece, have identified four Quaternary terraced alluvial fills that range from middle Pleistocene to historic in age. Major-periods of alluviation during the late Quaternary were associated with valley glaciation (ca. 26,000–20,000 yr B.P.) and subsequent deglaciation (ca. 20,000–15,000 yr B.P.) in the Pindus Mountains during Late Würmian times, and more recently linked to overgrazing sometime before the 11th century AD. The late Quaternary alluvial stratigraphy of the Voidomatis River is more complex than the “Older Fill” and “Younger Fill” model outlined previously, and it is suggested that these terms should no longer form the basis for defining alluvial stratigraphic units in the Mediterranean Basin.


Science ◽  
2012 ◽  
Vol 335 (6075) ◽  
pp. 1477-1480 ◽  
Author(s):  
C. Fitoussi ◽  
B. Bourdon

2020 ◽  
Author(s):  
Shuang Zhang ◽  
Christina Manning ◽  
Christopher Satow ◽  
Simon J Armitage ◽  
Simon Blockley

<p>The Eastern Mediterranean is an important region for understanding the late Quaternary, as there is evidence for a complex pattern of climatic and environmental change, influenced by orbital forcing and complex feedback mechanisms (Rohling et al., 2013). It is also a key region for examining the dispersal of humans out of Africa. Consequently, it is important to develop robust chronologies for palaeoclimatic, environmental and archaeological records in the region, to allow synchronisation, comparison and hypothesis testing. Tephrochronology is a vital tool for correlating such records, but the fine detail of the Eastern Mediterranean tephra depositional history is not yet well defined. Part of the problem relates to a lack of cryptotephra (non-visible ash) studies on long stratigraphic records. It is well known from the Atlantic and Central Mediterranean that cryptotephra studies can significantly improve tephra inventories, and constrain the relationship between key tephra markers and important environmental transitions. Another key problem for the region is that for distal tephra there is a relatively limited geochemical database from different volcanic centres, especially in terms of trace element compositions. One important method for addressing this problem is to develop detailed tephrostratigraphic records and tephra geochemical inventories from long sediment sequences (e.g. Bourne et al., 2010; Satow et al., 2015).</p><p>Here we present the first marine crypto-tephrostratigraphy from the Levantine Sea, covering approximately the last ~200,000 years, from a long marine core (MD81-LC31). The new data for the core include tephra shard concentrations, major and trace element geochemistry, correlations to the eruptive record of the Aegean and Anatolian volcanic centres, and new radiometric age information. Our new data is compared to existing chronological information from LC-31, including sedimentological, geochemical, paleomagnetic and radiocarbon evidence. Our data helps to refine the chronology for this important record and will underpin ongoing studies into the detail of palaeoceanographic and environmental change in the region.</p><p> </p><p>Bourne, A.J., Lowe, J.J., Trincardi, F. et al. 2010. Distal tephra record for the last ca 105,000 years from core PRAD 1-2 in the central Adriatic Sea: implications for marine tephrostratigraphy. Quaternary Science Reviews, 29(23-24), 3079-3094.</p><p>Rohling, E.J., Grant, K.M., Roberts, A.P. et al. 2013. Paleoclimate variability in the Mediterranean and Red Sea regions during the last 500,000 years: implications for hominin migrations. Current Anthropology, 54(S8), S183-S201.</p><p>Satow, C., Tomlinson, E.L., Grant, K.M. et al. 2015. A new contribution to the Late Quaternary tephrostratigraphy of the Mediterranean: Aegean Sea core LC21. Quaternary Science Reviews, 117, 96-112.</p>


1997 ◽  
Vol 47 (2) ◽  
pp. 206-217 ◽  
Author(s):  
Glen G. Fredlund ◽  
Larry L. Tieszen

Analyses of phytoliths and carbon isotopes document change in late Quaternary grasslands in the Red Valley of the southern Black Hills. Late Pleistocene grassland composition was equivalent to the C3grass parklands of modern central Alberta. The rise of mixed grassland occurred rapidly between 11,000 and 9000 yr B.P. Early Holocene mixed grasslands included both short and tall C4grasses. A mid-Holocene erosional unconformity (ca. 8000 to 4500 yr B.P.) precludes phytolith or isotope analysis, but suggests lack of vegetation and landscape denudation caused by a drier climatic. Basin-wide stability and soil development followed the erosional episode (ca. 4500 to 3600 yr B.P.). Mesic-adapted C4panicoid grasses increased during this period of soil development. Low-magnitude fluctuation in the C4-dominated mixed grassland occurred throughout the late Holocene (3600 yr B.P. to present). Rise in δ13C values during the last 1000 yr without corresponding change in phytoliths may indicate a decrease in woodlands caused by increased fire frequency.


2008 ◽  
Vol 70 (3) ◽  
pp. 358-367 ◽  
Author(s):  
Amos Frumkin ◽  
Miryam Bar-Matthews ◽  
Anton Vaks

AbstractThis paper explores the environmental conditions that faced the people of ancient Jawa during the Holocene, as well as previous prehistoric periods of the mid-late Pleistocene. Calcite speleothems in a lava tube are dated using the U-Th method, to marine oxygen isotope stage 7 from ∼ 250 to 240 ka and from ∼ 230 to ∼ 220 ka; and the stage 5/4 transition between ∼ 80 and 70 ka. The available evidence indicates general aridity of the Black Desert during most of the mid-late Quaternary, punctuated by short wetter periods, when the Mediterranean cyclonic systems intensified and penetrated the north Arabian Desert. These Mediterranean systems had a longer and more intense effect on the desert fringe closer to the Mediterranean and only rarely penetrated the Black Desert of Jawa. The results do not exclude some increase of rainfall which did not change water availability dramatically during the warm Holocene. The ancient Jawa city appears to have depended on technological ability to build elaborate runoff-collection systems, which became the prime condition for success.


2017 ◽  
Author(s):  
Ángela García-Gallardo ◽  
Patrick Grunert ◽  
Werner E. Piller

Abstract. Mediterranean-Atlantic exchange through the Strait of Gibraltar plays a significant role in the global ocean-climate dynamics in two ways. On one side, the injection of the saline and warm Mediterranean Outflow Water (MOW) contributes to North Atlantic deep-water formation. In return, the Atlantic inflow is considered a sink of less saline water for the North Atlantic Ocean. However, while the history of MOW is the focus of numerous studies, the latter has received little attention so far. The present study provides an assessment of the Mediterranean–Atlantic exchange with focus on the Atlantic inflow strength and its response to regional and global climate from 3.33 to 2.60 Myrs. This time interval comprises the mid-Pliocene warm period (MPWP, 3.29–2.97 Myr) and the onset of the Northern Hemisphere Glaciation (NHG). For this purpose, gradients in surface δ18O records of the planktonic foraminifer Globigerinoides ruber between the Integrated Ocean Drilling Program (IODP) Hole U1389E (Gulf of Cadiz) and ODP Site 978 (Alboran Sea) have been evaluated. Interglacial stages and warm glacials of the MPWP revealed steep and reversed (relative to the present) W-E δ18O gradients suggesting a weakening of Mediterranean–Atlantic exchange likely caused by high levels of relative humidity in the Mediterranean region. In contrast, periods of stronger inflow are indicated by flat δ18O gradients due to more intense arid conditions during the severe glacial Marine Isotope Stage (MIS) M2 and the initiation of the NHG (MIS G22, G14, G6–104). Intensified Mediterranean–Atlantic exchange in cold periods is linked to the occurrence of ice-rafted debris (IRD) at low latitudes and weakening of the Atlantic Meridional Overturning Circulation (AMOC). Our results thus suggest the development of a negative feedback between AMOC and exchange rates at the Strait of Gibraltar in the latest Pliocene as it has been proposed for the late Quaternary.


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