Click the star to add/remove an item to/from your individual schedule.
You need to be logged in to avail of this functionality,
and to see the links to virtual rooms.
Log in
- Convenor:
-
John Gowlett
(University of Liverpool)
Send message to Convenor
- Stream:
- Climate Change
- Sessions:
- Wednesday 16 September, -, -
Time zone: Europe/London
Short Abstract:
The Baringo Basin in Kenya is well known for its record of human evolution and of geological and environmental change through the last several million years. We focus on new explorations at Kilombe Mountain at the southern end of the basin, comparing its long term record with others in the region.
Long Abstract:
The Baringo Basin in the central Rift Valley of Kenya is well known for its record of human evolution and of geological and environmental change through the last several million years. The session focuses on the long Pleistocene records under investigation in various parts of the basin. New explorations around and especially in the caldera of Kilombe Mountain, an extinct volcano, are revealing its near continuous record through the Pleistocene. In the first part of the Pleistocene, there was a caldera lake at high level. Volcanic ashes deposited in and around it preserve exceptional traces of animal and early hominin activity, including Oldowan sites. The 100 metre geological sequence is the subject of continuing geological, geochemical and palaeonvironmental research. The southern flanks of the mountain preserve later sequences. These can be compared with the record in other parts of the Baringo basin, where for example the Chesowanja sequence provide other important evidence of hominin evolution including late appearances of Australopithecus boisei and an early Acheulean record. The Kapthurin Formation is especially important for its record through the period of modern human origins, also now represented at Kilombe. Other environmental research examines changes in vegetation within the Holocene. The session explores the overall contribution which this sector of the Rift Valley is making to studies of early human adaptations in environmental contexts susceptible to multi-disciplinary investigations. It shows the rare ability of this basin to preserve a high grade record from almost every period through the last two million years.
Accepted papers:
Session 1 Wednesday 16 September, 2020, -John Gowlett (University of Liverpool) Sally Hoare (University of Liverpool) Caroline Komboh (University Of Liverpool) Ian Stanistreet (The University of Liverpool) Rosa Maria Albert (University of Barcelona) Stephen Mathai Rucina (National Museums of kenya)
Paper short abstract:
The Baringo Basin extends for around 120 km north-south in the Eastern or Gregory Rift Valley in Kenya. Pleistocene research has taken place since the 1970s. We discuss in particular the very long Pleistocene sequences of the extinct Kilombe volcano and its geology, palaeoecology and archaeology
Paper long abstract:
The Baringo Basin extends for around 120 km north-south in the Eastern or Gregory Rift Valley in Kenya. It is bounded to east and west by the Laekipia escarpment and the Tugen Hills. The area was extensively mapped by the East African Geological Research Unit (EAGRU) during the 1970s under the direction of Bishop and King. Since then successor projects have taken place at localities in different parts of the basin, locating important faunal localities, some with hominin remains, and with discoveries of artefact localities ranging from Oldowan to the Later Stone Age technologies, and pastoral Neolithic. Chesowanja to the east of Lake Baringo preserves one of the longest records of this kind. The Kapthurin Formation to the west of the lake, investigated by Hill, McBrearty and colleagues, provides a particularly strong record of the last 500kyr, with indications of advanced late Acheulean, and very early Middle Stone Age. Recently Blegen and colleagues have shown that MSA sites with obsidian artefacts in this area go back at least 200,000 years, and assemblages include components of obsidian transported long distances from the Lake Naivasha region. The extinct early Pleistocene Kilombe volcano stands at the south end of the basin. A major Acheulean site on its southern flanks is long known , but recent work has expanded the record, and revealed details of a long early Pleistocene sequence in the caldera of the volcano, providing evidence of a caldera lake, fauna and traces of hominin occupation which we discuss in these papers.
Sally Hoare (University of Liverpool)
Paper short abstract:
This paper examines palaeolimatic change at Kilombe mountain, using geochemical analysis of bulk sediment samples from lacustrine units in the caldera fill, and its influence on hominin occupation.
Paper long abstract:
Quaternary lacustrine sequences from East Africa are important archives of orbitally forced paleoclimatic changes, which effects limit lake-level and palaeovegetation, and are considered to control hominin occupation of and evolution within East Africa. Here we investigate in detail a well preserved and fairly continuous lake sedimentary sequence from Kilombe Volcano, whose caldera-fill also preserves traces of hominin activity from several localities, involving Oldowan and Acheulean technologies. Changes in chemical weathering intensity are examined using a variety of proxy indices including major and trace element ratios (Chemical Index of Alteration, WIP); Fe-oxide mineralogy (S-ratio, χFD%); and Total Organic Carbon. Combined, the magnetic and geochemical properties of the clays document from incipient through to intense changes in catchment weathering, recording palaeoclimatic change during the Quaternary.
Caroline Komboh (University Of Liverpool)
Paper short abstract:
This paper provides a record of the general topographical changes in relation to clay mineralogy and its paleo geographical implication for a succession that covers stratigraphy along the upper staircase, a stretch of approximately 280 meters.
Paper long abstract:
This study is dedicated in contributing to establishing the condition of past environments of Kilombe Caldera in Kenya. The Caldera is an extinct volcano with a crater that is partly infilled with lake sediments. In order to apply argillaceous (clay-rich) sediments analyses as tracers to the past environmental conditions of quaternary environments at Kilombe, sediment samples and survey data collected from the study were analyzed using: X-ray diffraction(XRD) that has proven to provide information of the source rock and any chemical changes that resulted from effects of different weathering process; Scanning Electron Microscopy (SEM) used to distinguish between the different depositional environments; Coulter Counter to help determine particle size distribution and establish the important changes in the sedimentary environment; and Loss on Ignition (LOI), to provide an index of biological productivity. General results from the analysis of the Kilombe caldera 2018 cores clearly record changes in mineralogy along the upper staircase which runs from the Acheulean assemblages down to the Oldowan assemblages at a distance of about 280 meters.
James Cole (University of Brighton) John Gowlett (University of Liverpool) Andy Herries (La Trobe University) Darren Mark (University of Glasgow) Stephen Mathai Rucina (National Museums of kenya)
Paper short abstract:
Chesowanja (Lake Baringo, Kenya) has along Pleistocene record including Oldowan and Acheulean artefact layers. We report on recent field investigations yielding new Acheulean bifaces and new dating of the Chesowanja basalt previoulsy reported as 0.7 Ka and 1.4 Ma in the 1970s.
Paper long abstract:
Chesowanja lies on the east side of Lake Baringo, Kenya. Its Pleistocene sites lie on a fault step to the east of Lake Baringo. The long Pleistocene record is laid out almost horizontally, running from earliest localities in the west to latest in the east, across a distance of about 1 km. Chesowanja was studied in the 1970s within the EAST African Geological Research Unit programme (EAGRU), and its archaeology was investigated at that time and subsequently. The oldest formation is the Chemoigut, consisting of clays and silts associated with mammal fauna, remains of Australopithecus boisei, and archaeological remains which were attributed to the Developed Oldowan. The Chemoigut Formation was originally capped by a flow of basalt, which has largely eroded away. The basalt makes up the lower part of the Chesowanja Formation, which is associated with Acheulean artefacts and some fossil fauna. Later archaeology, including pastoral Neolithic, is represented further east in and around a former course of the Mukutan river. We report on a reassessment of the Chemoigut and Chesowanja Formation industries following further investigation which has yielded new Acheulean bifaces. The age of the Chesowanja basalt has been in doubt since seemingly conflicting dates of 0.7 Ka and 1.4 Ma were published in the 1970s. We report new Ar-Ar dating evidence which contributes to dating the whole sequence.
Andrew Cohen (University of Arizona) Stephen Mathai Rucina (National Museums of kenya)
Paper short abstract:
Fossil pollen and 40Ar/39Ar dates from a core drilled from West Turkana in Kenya record vegetation changes from 1.87Ma to 1.38Ma. The vegetation data reveal salinity/alkalinity, conditions and, interactions of climate change, hominin and herbivores during desiccation period.
Paper long abstract:
1Stephen M. Rucina, 2Andy S.Cohen,
1Palynology & Palaeobotany Section, Earth Sciences Department, National Museums of Kenya, P.O Box 40658 00100 Nairobi Kenya
2 Department of Geosciences, University of Arizona, Tucson, AZ 85721 USA
Fossil pollen and 40Ar/39Ar dates from a core drilled from West Turkana in Kenya, record vegetation changes from 1.87Ma to 1.38 Ma. The data reveal savanna vegetation composition driven by interaction of climate change, hominin and herbivore activities. The abundance of Poaceae until 1.67 Ma indicates a drier climate. Amarathanceae, Asteraceae and Typha recorded in the same period reflect of salinity or alkaline soils in a desiccation period recorded between 1.87 to 1.52Ma. The abundance of Cyperaceae in the same period suggests similar conditions recorded by the Poaceae, Asteraceae and Amaranthaceae when the lake was getting shallow forming a swamp and getting more alkaline as it became drier. A major observation from 1.67 to 1.62Ma is the disappearance of Poaceae suggesting a mega drought. Such major change supported establishment of Amaranthaceae, Asteraceae, Cyperaceae and Typha resistant to increased alkalinity as drought intensified. The afromontane pollen taxa recorded probably was washed in from regional dry montane forests especially Ethiopian highlands. From 1.62 to 1.52Ma Asteraceae, Amaranthaceae, Cyperaceae, Poaceae and other taxa recorded in the landscape were sporadically present in the ecosystem. Such changes suggest variability in climate between 1.87 to1.52Ma, emphasizing that West Turkana region was occupied by heterogeneous vegetation mosaic of savanna grassland.
Nick Blegen (University of Cambridge)
Paper short abstract:
The paper studies presence and continuity of several important hominin behaviors across the Acheulean / MSA technological boundary and throughout the period of modern human evolution in East Africa, with particular reference to the Kapthurin Formation.
Paper long abstract:
The Middle Pleistocene (780–130 ka) of equatorial East Africa is an important time and place for modern human evolution. This period records the continuing existence of Early Stone Age Acheulean technologies as well as the development of new types of tools (i.e. hafted points) and techniques for producing them, often collectively referred to as Middle Stone Age (MSA) technologies. Equally significant as the events of modern human evolution in East Africa is our ability to accurately date and reconstruct these events in the region. Volcanic ashes (tephras) in East Africa provide the ability to precisely date archaeological sites, and volcanic glass (obsidian) artifacts from the region are used to determine distances hominins transported raw materials. Recent correlation and dating of tephras found at Kapthurin Formation archaeological sites show Levallois recurrent and blade methods of core preparation were present along with Acheulean tools by 465–396 ka, over 100,000 years older than previously demonstrated in the region. Recent geochemical sourcing of obsidian artifacts shows long-distance raw material transport (>150 km) was a feature of human behavior by ~200 ka, over 150,000 years older than previously demonstrated. New obsidian-sourcing data further show that by 465-396 ka hominins making Acheulean tools transported obsidian raw materials, from multiple sources, distances of 55–120 km. Thus, in East Africa, both diverse prepared core technologies and long-distance raw material transport appear in the Middle Pleistocene in association with Acheulean tools and persist into the Late Pleistocene (130–10 ka) where these behaviors are found alongside MSA tools. This indicates continuity of several important hominin behaviors across the Acheulean / MSA technological boundary and throughout the period of modern human evolution in East Africa. These behaviors are not tethered to defined typological categories such as Early or Middle Stone Age, nor to a single particular hominin species. Further, by pre-dating technological features of the MSA and biological features of Homo sapiens anatomy by ~100,000 years in East Africa, diverse lithic technologies and long-distance raw material transport were likely important selective pressures on the evolution and dispersals of modern humans.
Lucy Timbrell (University of Liverpool) Andrea Manica (University of Cambridge) Kimberly Plomp (Simon Fraser University) Matt Grove (University of Liverpool) Matthew Fitzjohn (University of Liverpool)
Paper short abstract:
Environmental change in the Eastern African Rift has long been assumed to play a key role in hominin evolution. We use distribution modelling of past climates to analyze the trajectory of habitability around Kilombe in the Baringo basin.
Paper long abstract:
Environmental change in the Eastern African Rift System (EARS) has long been assumed to play a key role in hominin evolution, speciation, extinction, and migration. Climatic conditions in Pleistocene Africa are known to have varied asynchronously across the landscape, affecting the distribution of suitable habitats and contributing to the fragmentation and coalescence of hominin populations. Our paper explores how climatically mediated habitat suitability in the EARS may have varied through time using distribution modelling based on new high-resolution climate simulations from the Global Model Climate Emulator. We analyze the trajectory of habitability at Kilombe, Moricho, and surrounding areas, with a focus on temperature and precipitation conditions during late Acheulean and MSA occupations.
Laura Basell (University of Leicester)
Paper short abstract:
The Baringo basin has played a critical role in understanding human evolution and long term palaeoenvrionmental change in eastern Africa. This paper considers the Baringo Basin in its regional archaeological and palaeoenvironmental contexts.
Paper long abstract:
The Baringo basin has played a critical role in our understanding of human evolution and long term palaeoenvrionmental change in eastern Africa. Its sites have been important in establishing and maintaining the significance of the region in key debates concerned with the emergence and spread of Homo sapiens. This paper considers the Baringo Basin in its broader regional archaeological and palaeoenvironmental contexts. It also considers what implications recent discoveries (which have shifted the timing and location for the emergence of the first Homo sapiens) have for interpreting hominin MSA behavioural variability in eastern Africa.