MAL6b

East Asia is a key area for probing into the interplay between Quaternary climate change and human adaptations to diverse terrestrial ecosystems. Integrated chronology based mainly on high-resolution magnetostratigraphy in conjunction with detailed biostratigraphy and high-precision isotopic dating of early humans and Paleolithic stone tools in mainland East Asia, western and southeastern Asia has provided insights into our understanding of climatic influence on human evolution in a variety of environments in the eastern Old World. For example, there is a prominent geographic expansion for early humans from low southern latitudes (e.g., tropical SE Asia and subtropical Yuanmou Basin and Bose Basin), through middle latitudes, to high northern latitudes (e.g., the Nihewan Basin). Especially, increased toolmaking skills and technological innovations are evident in temperate Nihewan Basin at the onset of the Mid-Pleistocene Climate Transition. The improved ability to adjust to diverse environments for early humans in East Asia has contributed to better understanding how climate change has shaped early human evolution.

How to cite: Zhu, R.: Early humans in East Asia: Insights into climatic influence on human evolution, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16330, https://doi.org/10.5194/egusphere-egu21-16330, 2021.

Rock magnetics can be used to identify orbitally-forced global climate cycles in sedimentary rock sequences. The identification of Milankovitch cycles with nominal periods of 20, 40, 100 and 400 ka can be used to construct a high-resolution chronostratigraphy for a rock sequence that can have a variety of important geologic applications. Several examples will be presented. The rock magnetic cyclostratigraphy of Eocene marine, deltaic mudstones and marls of the Arguis Formation illustrates how rock magnetics can be used to determine the deformation rates of a salt tectonics growth fold in the Pyrenees. The duration of the Ediacaran Shuram carbon-isotope excursion was determined to be 8-9 Ma from rock magnetic cyclostratigraphy studies of marine rocks from Death Valley, California (Rainstorm member of the Johnnie Formation), southern Australia (Wonoka Formation), and in central and southern China (Doushantuo Formation).  Further cyclostratigraphic study of the Rainstorm member in the Desert Range, Nevada, allowed the construction of a high-resolution magnetostratigraphy by combining and calibrating magnetostratigraphic results from Death Valley and Nevada to reveal a high reversal rate of 12.7 reversals/Ma in the Ediacaran. More detailed study of the Doushantuo Formation at Huangliaba, China indicated that even though its ferromagnetic minerals were predominately secondary pyrrhotite, magnetic susceptibility measurements could still detect a depositional, orbitally-forced cyclostratigraphy carried by paramagnetic minerals. Finally, the Carboniferous Mauch Chunk Formation red beds from Pottsville, Pennsylvania yielded a magnetic susceptibility cyclostratigraphy in terrestrial, fluvial sediments despite their discontinuous sedimentation. This study showed that both portable susceptibility meter measurements and lab-based measurement of rock samples could discern the same period cycles. Detailed low and high temperature magnetic susceptibility measurements indicate that the ferromagnetic mineral hematite, rather than paramagnetic clays, is the predominant carrier of the orbitally-forced global climate signal. All these studies show the power of rock magnetics for constructing a high-resolution chronostratigraphy for sedimentary rock sequences.

How to cite: Kodama, K.: High-Resolution Chronostratigraphy for Sedimentary Rocks using Rock Magnetics, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-522, https://doi.org/10.5194/egusphere-egu21-522, 2021.