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Records of Lake Magadi in Kenya suggest environmental variability caused by changes in Earth’s orbit.

Deocampo et al. Are collecting samples from Lake Magadi Drill Core at the National Lake Core Facility. Photo provider Hominin Sites and Paleolakes Drilling Project. Credits: Photo Credits Hominin Sites and Paleolakes Drilling Project.

Lake Rift Valley in East Africa is home to diverse ecosystems, ranging from freshwater to highly alkaline systems. These Rift Valley lakes are also depository and provide high-resolution environmental records that can be aimed at better understanding the environmental and climatic conditions of human evolution over the last million years in East Africa. Bring.


A new study published yesterday Geology Examine the geochemical records of drill core deposits collected from Lake Magadi — saltwater, alkaline lake Located in the southern part of Kenya Lift. It provides nearly a million years of paleoenvironmental records from the rare Rift Valley Lake system.

Georgia State University lead author Dan Deocampo and a group of international co-authors drilled Lake Magadi as part of the Hominin Sites and Paleolakes Drilling Project (HSPDP), which collected deep sediment cores from the lake basins of the Great Rift Valley of East Africa. bottom.

“We are trying to understand how the Earth’s surface environment has changed over the last few million years and how it affected early Hominini habitats.” Deo Campo said. “We used many different proxies of the ancient environment to see how the environment changed, how the habitat changed, and thus how the dangers and resources of the early Hominini changed over time. I understand how it changed to. “

Geochemical analysis of Lake Magadi samples has shown some of the highest concentrations of elements such as molybdenum, arsenic, and vanadium reported so far in lake sediments. Over-accumulation of these elements has never been observed in other East African lakes and generally requires normal conditions. The normal state is Lake water Is both anaerobic and sulphide, usually caused during episodes of a negative water balance such as drought.

Records of Lake Magadi in Kenya suggest environmental variability caused by changes in Earth's orbit.

An overview of Lake Magadi from the west bank. Photo provider Hominin Sites and Paleolakes Drilling Project. Credits: Hominin Sites and Paleolakes Drilling Project

“The amount of molybdenum accumulated in the sulfide-rich sediments of the lake does not tell us the structure of the habitat inhabited by the Hominini, but the variation between their normal and freshwater conditions. It will tell you. Changes in the environment. “

Deocampo and co-authors discovered that Euxinia became common about 700,000 years ago and has since tended to occur at intervals where the Earth’s orbit becomes more elliptical. This happens every 100,000 years. As the Earth’s orbit becomes more elliptical, the Earth can move farther from the Sun, resulting in greater seasonal climate change. Euxinian episodes are an important indicator of the severe drought that occurred in the region during the widespread ice age.

These high-amplitude environmental changes that facilitated a shift between normal and well-mixed lake conditions would have had a significant impact on water availability and vegetation over the evolutionary timescale. ..

Records of Lake Magadi in Kenya suggest environmental variability caused by changes in Earth's orbit.

Excavate the core collection at the Lake Magadi site. Photo provider Hominin Sites and Paleolakes Drilling Project. Credits: Photo Credits Hominin Sites and Paleolakes Drilling Project.

The environmental variability suggested by the geochemical records of Lake Magadi is associated with the turnover of mammalian species and the first emergence of Middle Stone Age technology in southern Kenya Rift 500,000 to 320,000 years ago. I am.

“This is a kind of paleoanthropologist who is thinking about changes in the amplitude of environmental changes and how they relate to changes in gene pools and habitat structures, first and last appearances. It’s a moving point, “says Deocampo.


Read the rocks: geologists find clues to the ancient climate patterns of the charts


For more information:
DM Deocampo et al, Pleistocene Euxinia Orbit Control on Lake Magadi, Kenya, Geology (2021). DOI: 10.1130 / G49140.1

Quote: Changes in Earth’s orbit obtained from https://phys.org/news/2021-09-lake-magadi-kenya-environmental- on September 21, 2021, according to records of Lake Magadi, Kenya (2021) The variability of the environment caused by (September 21, 2014) has been suggested. variability.html

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Records of Lake Magadi in Kenya suggest environmental variability caused by changes in Earth’s orbit.

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