The 9th Mapping Ancient Africa seminar, and first of 2023, took place on Thursday 19 January. The seminar was delivered by Celine Vidal (University of Cambridge) and showcased recent work on the dating of volcanic deposits to constrain the age of hominin fossils in eastern Africa.
Vidal, C.M., Lane, C.S., Asrat, A., Barfod, D.N., Mark, D.F., Tomlinson, E.L., Tadesse, A.Z., Yirgu, G., Deino, A., Hutchison, W., Mounier, A. & Oppenheimer, C. (2022) Age of the oldest known Homo sapiens from eastern Africa. Nature601, 579-583. https://doi.org/10.1038/s41586-021-04275-8
Vidal, C.M., Fontijn, K., Lane, C.S., Asrat, A., Barfod, D., Tomlinson, E.L., Piermattei, A., Hutchison, W., Tadesse, A.Z., Yirgu, G., Deino, A., Moussallam, Y., Mohr, P., Williams, F., Mather, T.A., Pyle, D.M. & Oppenheimer, C. (2022) Geochronology and glass geochemistry of major Pleistocene eruptions in the Main Ethiopian Rift: Towards a regional tephrostratigraphy. Quaternary Science Reviews 290, 107601. https://dx.doi.org/10.1016/j.quascirev.2022.107601
I am pleased to announce the opening up of a new DPhil position at the University of Oxford Department of Earth Sciences that I will be involved with. The main supervisor for the project is Prof. Tamsin Mather and the position is part of her recently funded European Research Council project. The project is entitled “Sniffing out global volcanic fingerprints using mercury in Quaternary sedimentary records”.
For full details of the project click here and how to apply click here.
IBEDs Crystal McMichael hard at work sampling sediments in the Andes
Insights into recent field work in Ecuador by a team lead by Crystal McMichael can be found in a recent blog from our collaborators at the Instituto Geofisico, Escuela Politecnica Nacional, Quito (Ecuador).
Hayley Keen getting excited about sediments during fieldwork in Ecuador (2012). Photo: J. Malley
Keen, H.F. (2015) Past environmental change on the eastern Andean flank, Ecuador. PhD Thesis, Department of Environment, Earth & Ecosystems, The Open University.
Abstract The eastern Andean flank of Ecuador (EAF) contains some of the world’s most biodiverse ecosystems. Andean montane forests are threatened due to anthropogenic pressures and both current and projected climate change. This thesis examines the palaeoecological history of two stratigraphic sequences (Mera Tigre West [MTW] and Mera Tigre East [MTE]) obtained from the Ecuadorian modern lower montane forest. The sediments preserved were analysed using eight analytical techniques, allowing an insight into the ecosystem’s potential response to projected changes derived from their past responses. Palaeoecological studies on the EAF are rare, and those that do exist are debated relating to: i) the inference of robust ecological data from pollen records in floristically diverse locations, and ii) the past source area of sediments preserved in fluvially exposed sequences, potentially leading to contamination with older material.
A statistical sub-sampling tool was developed (debate i), capable of producing statistically robust count sizes for each pollen sample; MTW and MTE count sizes ranged from 196-982 showing the diversity within sequences. The depositional environment of MTE was analysed, investigating sediment provenance throughout (debate ii). Results found that large scale volcanic events were critical in the preservation of the sediments, whereas fluvial influence caused a regional sediment source area in the upper stratigraphy, impacting on the palynological interpretation of MTE. Pollen records demonstrated the presence of a diverse vegetation community with no modern analogue at MTE (abundant taxa (>15 %): Hedyosmum, Wettinia, Ilex) and upper montane forest at MTW (Alnus, Hedyosmum, Podocarpus). Fire was not the main driver for the vegetation reassortment at either site (MTW correlation coefficient: -0.37, MTE: 0.16). The two sites have demonstrated the EAF plays host to floristically dynamic ecosystems, susceptible to drivers of change (fire and landscape) and should be considered when predicting the montane forests’ future response to environmental change.
Trecking with sediment corer in the high Andes of Peru
When it comes to collecting sediments from lakes its all about having the right tools for the job. Working in remote areas of the tropics we tend to favour the Colinvaux-Vohnout corer; supplied by Vince Vohnout at Geo-core). The advantages of this system are:
its light-weight nature (can be backpacked or donkeyed into field sites), and
the cam system (which allows hammering to penetrate tough sediments).
Eric Martinez carrying an Avon Redstart back out from Laguna Khomer Kotcha (Williams et al., 2011a)
With the right platform (two banana boats and an A-frame) we have manged to retrive c. 20 m of sediment from 20 m of water (c. 40 m of drill rod extended); Lake Pacucha, Peru (Hillyer et al., 2009). More typically we use two Avon Redstart inflatables and a platform following the design of Colinvaux et al. (1999).
One of the key goals of the fieldtrip to Ecuador (August-September) was to sample organic and volcanic (tephra) layers from sedimentary exposures with the aim of obtaining new information about past envrionmental change in the region. Our Ecuadorian collaborator, Dr Patricia Mothes (Instituto Geofisico), had identified four of sites she thought might be useful too us: El Fatima Dique, Mera “2” Dique, El Rosol and Vinillos.
At the Fatima site, near Puyo, a thin organic bed was sampled sandwiched between volcanic ash deposits. Wood macrofossils from this deposit have been dated to the last glacial period.
For further descriptions of what we found and field photos read on…