title: Environmental Insights from Argillaceous Sediments of the Kilombe Caldera Upper Staircase, Kenya: Implications for Early Pleistocene Hominin Habitats.
Creators: name: Hering, Caroline
Publisher: name: University of Liverpool Repository
Year: 2024

description: The study of past human-environment interactions and their evolution over time is a prevalent
subject in archaeological research, especially when preserved in suitable environmental conditions
that act as archives. Kilombe mountain is an extinct volcano with a caldera partially filled with lake
sediments. Latest discoveries in and around the caldera are revealing an almost continuous record
through the Pleistocene, including documentation of a caldera lake at high level altitude at about
2550 meters above sea level, during the early Pleistocene. Volcanic ashes from nearby volcanoes,
and lahars or mudflows, have preserved findings of archaeological occurrences representing
Oldowan and Acheulean industries as well as indications of animal and early hominin activity,
providing unusual opportunities for multidisciplinary research.
In this study, argillaceous (clay-rich) sediment samples carefully collected through coring from the
Upper Staircase of the Kilombe caldera, have been studied mineralogically. Results from clay
mineralogy research have been used to interpret changes in the environment over time in the past,
but the application of clay minerals to understand a given environment is understudied compared to
other proxies such as geochemistry and palynology. There have been few previous mentions of clay
minerals from this geographic region and none with particular intensive focus on the various clay
minerals occurring in this area and what interpretations can be derived. An extensive collection of
results from Loss on ignition, Grain size analysis and X-ray diffraction quantification has been
compiled with the aim of contributing knowledge towards reconstructing past environmental
conditions of Kilombe Caldera. The whole rock and the clay fractions of the sediments' X-ray
diffraction study data are provided, together with potential interpretations for the qualitative and
quantitative findings.
The results of these investigations have revealed that Loss on ignition along the Upper Staircase has
low to medium organic productivity and presence of structural water loss. The grain size of the clayrich sediments along the Upper Staircase turns out to be relatively heterogeneous with very poor,
poorly to medium sorted. The mineralogy is composed of illite, smectite and interlayered kaolinsmectite for the clay minerals and quartz, K-feldspar, haematite, and plagioclase for the non-clay
minerals. The trend of the upper staircase sequence from the Oldowan locality up through the
Middle locality and up to the Acheulean locality indicates an increase in relative humidity, wet
conditions, and increased weathering toward the Acheulean levels due to higher kaolin-smectite
quantities as opposed to the Oldowan levels with higher illite quantities, which are indicative of
relatively dry conditions with an increased rate of sedimentation. Thus, the research illustrates local
environmental changes in the period of human evolution from around 1.8 to 1.6 million years ago
especially.