Fault-generated mountain fronts in southeast Spain: geomorphologic assessment of tectonic and seismic activity

Lake sediments in 10 Ethiopian, Kenyan, and Tanzanian rift basins suggest that there were three humid periods at 2.7 to 2.5 million years ago (Ma), 1.9 to 1.7 Ma, and 1.1 to 0.9 Ma, superimposed on the longer-term aridification of East Africa. These humid periods correlate with increased aridity in northwest and northeast Africa and with substantial global climate transitions. These episodes could have had important impacts on the speciation and dispersal of mammals and hominins, because a number of key events, such as the origin of the genus Homo and the evolution of the species Homo erectus, took place in this region during that time.

https://science.sciencemag.org/content/sci/early/2005/08/18/science.1112964.full.pdf

Late Cenozoic Moisture History of East Africa

https://meetings.copernicus.org/www.cosis.net/abstracts/EGU2007/05299/EGU2007-J-05299.pdf

High- and low-latitude forcing of Plio-Pleistocene East African climate and human evolution.

Large paleolakes (∼33,000–60,000 km2) that once occupied the high-altitude Poopo, Coipasa, and Uyuni Basins in southern Bolivia (18–22°S) provide evidence of major changes in low-latitude moisture. In these now-dry or oligosaline basins, extensive natural exposure reveals evidence for two deep-lake and several minor-lake cycles over the past 120 k.y. Fifty-three new U-Th and 87 new 14C dates provide a chronologic framework for changes in lake level. Deposits from the "Ouki" deep-lake cycle are extensively exposed in the Poopo Basin, but no deep lakes are apparent in the record between 98 and 18.1 ka. The Ouki lake cycle was ∼80 m deep, and nineteen U-Th dates place this deep-lake cycle between 120 and 98 ka. Shallow lakes were present in the terminal Uyuni Basin between 95 and 80 ka (Salinas lake cycle), at ca. 46 (Inca Huasi lake cycle), and between 24 and 20.5 ka (Sajsi lake cycle). The Tauca deep-lake cycle occurred between 18.1 and 14.1 ka, resulting in the deepest (∼140 m) and largest lake in the basin over the past 120 ka. Multiple 14C and U-Th dates constrain the highest stand of Lake Tauca along a topographically conspicuous shoreline between 16.4 and 14.1 ka. A probable post-Tauca lake cycle (the Coipasa) produced a ≤55-m-deep lake that is tentatively dated between 13 and 11 ka.

We suggest that paleolakes on the Bolivian Altiplano expanded in response to increased moisture in the Amazon and enhanced transport of that moisture onto the Altiplano by strengthened trade winds or southward displacement of the Intertropical Convergence Zone (ITCZ). Pole-to-equator sea-surface temperature (SST) and atmospheric gradients may have influenced the position of the ITCZ, affecting moisture balance over the Altiplano and at other locations in the Amazon Basin. Links between the position of the ITCZ and the ca. 23 ka precessional solar cycle have been postulated. March insolation over the Altiplano is a relatively good fit to our lake record, but no single season or latitude of solar cycling has yet to emerge as the primary driver of climate over the entire Amazon Basin. Temperature may influence Altiplano lake levels indirectly, as potentially dry glacial periods in the Amazon Basin are linked to dry conditions on the Altiplano. Intensification of the trade winds associated with La Nina–like conditions currently brings increased precipitation on the Altiplano, and deep-lake development during the Tauca lake cycle coincided with apparently intense and persistent La Nina–like conditions in the central Pacific. This suggests that SST gradients in the Pacific are also a major influence on deep-lake development on the Altiplano.

Geochronology and stratigraphy of late Pleistocene lake cycles on the southern Bolivian Altiplano: Implications for causes of tropical climate change

14C and Th/U Dating of Pleistocene and Holocene Stromatolites from East African Paleolakes

Single dates obtained on mollusk shells by the U-series nuclides method are highly unreliable, primarily because of the mobility of uranium isotopes. However, in several cases, a statistical approach was demonstrated to yield coherent chronologies in both continental and marine environments. The authors report on 34 new Th and U isotope measurements on Strombus Bubonius and Glycymeris glycymeris fossils from raised marine terraces in the Almeria area, southeastern Spain. The results yield a coherent chronology that indicates the presence of the warm water S. bubonius fauna in the Mediterranean basin. Reconsideration of the Tyrrhenian stratigraphy based on the presence of S. bubonius is thus required.

Odette Carro

Papers

14C and Th/U Dating of Pleistocene and Holocene Stromatolites from East African Paleolakes

Th/U dating of Strombus bubonius-bearing marine terraces in southeastern Spain

Detection of Adulterated Maple Products by Stable Carbon Isotope Ratio