We are looking for a researcher with a geosciences background to explore the physical properties of the sediments recovered from Lake Bosumtwi (Ghana). The Lake Bosumtwi sediments we recovered by the International Continental Scientific Drilling Program in 2004 and have been found to span the last c. 1.07 million years (Koerbel et al., 2005). This project will examine the borehole data and relate this ongoing palaeoenvironmental studies at the site (Miller & Gosling, 2014; Miller et al., 2016).
Yesterday (day 3) was excursion day of the AFQUA conference (photos to follow). Day 4 of the meeting was back in the National Museum Nairobi and kicked off with a session on “African archaeological landscapes”. The opening talk reviewed the career of Karl Butzer who coined the term ‘geoarchaeology’ back in the 1970’s when writing about his work integrating geological, archaeological and anthropological information (C.A. Cordova). Two talks then followed highlighting work on Lake Makagadikgadi from the perspective of archaeology and landscapes (D.S.G Thomas) and geochemical fingerprinting of stone tools to determine their source (D.J. Nash).
To take us up to lunch Boris Vanniere and Daniele Colombaroli gave a ‘double header’ plenary talk highlighting the exciting advances in the development of the Global Charcoal Database and how understanding past fire histories in Africa is key to interpreting environmental change. The after lunch session continued the palaeo-fire theme with records from Lake Botswana (C.E. Cordova), Lake Bosumtwi (W.D. Gosling – me), and Madagascar presented (A. Razafimanantsoa); as well as work on the usefulness of the morphometric’s of charcoal in determining the plant of origin (L.Bremond).
In the final session of the day we were back to “Southern Africa” as a theme. Under which banner we were “boggled” by sea-surface and sub-surface temperature reconstructions (M.A. Berke), shown how to extract climate records from Hyrax middens (B.M. Chase) and given insights into the past flora of the Cape Floristic region from fossil pollen records spanning 130,000 years (L.J. Quick).
OPEN ACCESS ONLINE:
Miller, C.S., Gosling, W.D., Kemp, D.B., Coe, A.L. & Gilmour, I. (2016) Drivers of ecosystem and climate change in tropical West Africa over the past ∼540 000 years. Journal of Quaternary Science online. DOI: 10.1002/jqs.2893
Shanahan, T.M., Hughen, K.A., McKay, N.P., Overpeck, J.T., Scholz, C.A., Gosling, W.D., Miller, C.S., Peck, J.A., King, J.W. & Heil, C.W. (2016) CO2 and fire influence tropical ecosystem stability in response to climate change. Scientific Reports 6, 29587. DOI: 10.1038/srep29587
Miller, C.S. (2014) 520,000 years of environmental change in West Africa. PhD Thesis, Department of Environment, Earth & Ecosystems, The Open University.
Global temperatures are predicted to rise by 2–2.5°C by 2065, profoundly affecting the Earth’s environment. The response of ecosystems to past climate fluctuations can inform on how systems will respond in the future. This thesis focuses on Quaternary environmental changes in West Africa, a region important because of its high ecological value and role in the global carbon cycle.
In 2004, the International Continental Drilling Program recovered c. 291m of sediments spanning the last c. 1 Myr from Lake Bosumtwi (Ghana). Pollen, charcoal and nitrogen isotopes (d15N) were analysed from the most recent c. 150m (c. 520 kyr). The latitudinal position and long duration of this core makes it unique for understanding West African monsoon dynamics and vegetation change.
To aid characterisation of the Bosumtwi pollen succession, an atlas of present-day pollen was constructed for 364 pollen and spore taxa.
The pollen record from Bosumtwi reveals dynamic vegetation change over the last c. 520 kyr, characterized by eleven biome shifts between savannah and forest. Savannah vegetation is dominated by Poaceae (>55%) associated with Cyperaceae, Chenopodiaceae-Amaranthaceae and Caryophyllaceae. Forest vegetation is palynologically diverse, but broadly characterised by Moraceae, Celtis, Uapaca, Macaranga and Trema. Low d15N values correspond to forest expansion and these are driven by high lake levels. The timescale indicates that the six periods of forest expansion correspond to global interglacial periods. The record indicates that the wettest climate occurred during the Holocene, and the driest during Marine Isotope Stage 7.
The vegetation and d15N records show a strong response to glacial-interglacial variability between c. 520–320 kyr and 130–0 kyr. Between c. 320–130 kyr there is a weaker response to glacial-interglacial cycles probably related to high eccentricity during the peak of the 400-kyr component of eccentricity, with high eccentricity resulting in greater seasonality and ultimately drier conditions.
With the redesign and refocusing of the blog underway, I’m delighted to announce the launch of our very own “Ecology of the past”YouTube channel. Initially this will host videos produced as part of the Lake Bosumtwi pollen chemistry project, which includes a strong emphasis on impact and outreach activities. The videos are being targeted to a secondary school/sixth form audience, and will demonstrate both how we are doing the research and who we are as academics, highlighting the different roles and career pathways within the team. As time goes on this channel will be a platform for videos from other members of the research group, again showing who we are, what we do and how we do it.
For now, here are the first two videos: a diary of the field trip to Ghana that Adele and I went on last Autumn, and an accompanying piece showing how you too can make your own pollen trap. Enjoy!
The latter half of 2013 seems to have been incredibly busy and I have not managed to get my monthly update posts completed since October. Rather than a rapid series of backdates here is a quick summary of what I think the main activities through this period have been!
Thesis defence: Congratulations to both Lottie and Natalie for sucessfully defending their PhD theses! Exeptional effort and hard work from both of you. Well done.
Grant: We have been awarded further 14C dates from NERC radiocarbon facility to improve the chronology on Laguna Khomer Kotcha Upper so that the timing of temperature osscilations revealed by new chironomid analysis (by Frazer Bird) can be related to the last global degalciation (c. 18,000 years ago) and the Younger Dryas cooling event (c. 12,800 – 11,500 years ago). This research builds on that of former PCRG PhD student and current research collaborator Joe Williams (Williams et al., 2011; Williams et al., 2012).
Fieldwork: Trips to Ghana (Adele and Phil) and Ecuador (Nick, Encarni and Will) have been super successful; AND all the samples have made it back! See posts elsewhere on the blog for details of field work fun.
I am sure other stuff has happened… more in the New Year… and maybe some more pictures when I can get back on my newly “optimized” (killed) office computer 🙂