Climatic forcing and tectonic control on environments in evolving lake basins of Africa and North America

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Orbital cycles, which affect the amount of solar energy on the surface of the Earth, and tectonic activity together controlled paleoenvironments during periods of climate change and evolution. Lake basins are particularly sensitive to changing inputs of precipitation and sediment as influenced by these controls, and preserve the best evidence to interpret changing environments and their impact on paleoecosystems. My research uses detailed studies of sediments and animal behaviour (i.e., trace fossils) to recognize cycles and changing environments in the rock record, used to reconstruct changing landscapes through time. Integrated with other lines of evidence (e.g., minerals, elemental composition, diatom assemblages), we can interpret how conditions in environments change within and between each of the cycles. My research program focuses on three long-term projects: 1) Pliocene lakes of the central Kenya Rift Valley; 2) Pliocene lakes of Afar, Ethiopia; and 3) Cretaceous lakes of Alberta. These projects focus on important periods for evolutionary change, namely the Pliocene-Pleistocene in East Africa, where early humans evolved (~5-1.5 million years ago) during the onset of “icehouse” conditions in the northern hemisphere, and the Cretaceous “greenhouse” of North America, where dinosaur fossils are especially abundant (~80-75 million years ago). Initial results indicate that, in the Baringo Basin of central Kenya where Austrolopithecus and Homo fossils are known after ~3.8 million years ago (Project 1), wide swings in lake level occurred due to orbital cycles and resulted in extremely different environments with periodicity of ~23,000 years (precession) modulated by ~100- and 400-thousand-year eccentricity. These short-term cycles are not the only controls; rifting events and hydrothermal input to the lake basin also influenced the lake system, as did longer term global change in climate, which led to the ice age in the northern hemisphere. Short-term climate cycles are also observed further north in Africa in the Afar region of Ethiopia, where “Lucy” lived during the late Pliocene (~3.5 million years ago; Project 2), but the sedimentary record of these cycles is also complicated by volcanism and faulting events. Once we are able to distinguish the more local geological controls, we can compare between central Kenya and northeast Ethiopia to better interpret the influence of global climate change and changing environments home to early humans. The approach taken for the Plio-Pleistocene will also be applied to a recently recognized lake basin with cyclical deposits in the Cretaceous of Alberta (Project 3) to provide an entirely new look at the potential for climate control on dinosaur evolution. By focusing on tectonically active lake basins during times of climate change and distinct turnover events in animal fossil assemblages, my research impacts our understanding of how Earth and atmospheric processes have repeatedly impacted life on Earth.