Hyperspectral analysis of core samples from Chew Bahir, Ethiopia, as climate proxy -implications on surface composition of the ExoMars rover landing site

Abstract

This work shows that hyperspectral reflection data analysis can be a suitable method for paleoclimatic reconstruction similar to chemical proxies. The link between the hominin development and climatic variations of the past is topic of the “Hominin Sites and Paleolake Drilling Project”. In this study two drilling cores were taken in the Chew Bahir basin in the Ethiopian Rift in 2014. The presented thesis is based on core data and their spectral reflectance in the wavelength range from 0.3 μm to 17 μm. The samples mostly consist out of weathered phyllosilicates with variable potassium content. An increase of potassium is a consequence of an increase of physical weathering and erosion from sparsely vegetated rift shoulders during arid phases. Therefore, potassium is a valid climate proxy. High potassium content indicates arid climatic phases. An analysis of the depths of specific signature absorption bands of magnesium- hydroxyl at 2.3 μm displays a correlation with the potassium marker. Instead, the absorption bands of aluminum-hydroxyl at 2.2 μm show an anti-correlation with potassium, that presents humid conditions. Therefore, the absorption bands are an evident climate proxy for dry and wet cycles in this region. The interpretation of hyperspectral data leads to similar results as the interpretation of the chemical proxies in previous studies in Chew Bahir. In the presented thesis, hyperspectral data are a valid tool complementary to chemical proxies for the reconstruction of paleoenvironmental conditions in East Africa. These results are implicated on the landing site of ExoMars2022 in the Noachian Mars. In this region on Mars, the Oxia Planum, the development of phyllosilicates also occurs under aqueous activity, such as in Chew Bahir. The implications show a correlation of minerals in layered stratigraphy. The phyllosilicates underwent a substitution of cations under the influence of the current climate phase. These parallels support the hypothesis of a changing climate in early Mars’ history. The alteration processes are similar to Chew Bahir. But the temporal sequence and formation processes remain divergent. The cores from Chew Bahir report sediments from 600ka. The sediments of the Noachian Mars display a time range from 4.7- 3.4 Ga