Wednesday, 27 January 2016

From tiny seeds PhD student Leslie Bode

Me looking rather seed-crazed in the
Archaeobotany lab at Bar Ilan University 
Hi, my name is Leslie Bode, and I am exploring new applications of archaeobotanical isotopic research. I am currently a 3rd year PhD candidate at the University of Nottingham and am co-supervised between Archaeology (Dr Alexandra Livarda) and Geography (Dr Matthew Jones). I also receive a lot of extra isotope guidance from Dr Angela Lamb at the British Geological Survey.

Thanks to a NERC Isotope Geosciences Facility grant, I am using a combination of archaeobotanical and stable carbon isotope (δ13C) analysis of charred (carbonized) seed remains from Kharaneh IV (a ca. 20,000 year old archaeological site in the Azraq Basin in Eastern Jordan) to test whether the plants living during this period and, by extension, the hunter-gatherers using this ancient site experienced water stress. I’m especially interested in whether water stress increased leading up to the site’s abandonment almost 20,000 years ago: did a lack of water contribute to collapse?

One of the well organized boxes of
reference material at Bar Ilan University 
Identifying the ancient, charred seeds from Kharaneh IV to the species level is a real challenge due to the small number of seeds, how well preserved they are, and their small size (one seed would, literally, fit on the head of a pin). Adding to this, botanical reference collections are few and far between for this time period and region.  To help identify these mystery seeds, I have been traveling to reference collections around the UK, such as the ‘Hillman’ Near Eastern seed collection in the Department of Archaeology at the University College London, and the University of Sheffield’s Archeobotanical reference collection.  Along the way, I have been graciously helped by experts in this area (notably: Sue Colledge at UCL and Mark Nesbitt at Kew Gardens).  Despite these productive, knowledge building research visits, I was still left with a lot of unidentified material and needed to get closer to the source of these seeds.

So, in November 2015, I travelled to the archaeobotany labs at Bar Ilan University in Israel to have a look at their impressive collection of Levantine and Near Eastern seeds.   While visiting, I was fortunate to meet Prof. Ehud Weiss and Dr Yoel Melamed and the friendly and amazing team of archaeobotanists who work in their labs, who have excellent knowledge of the local and regional flora on top of an archaeobotanical perspective on the early time period I am interested in. I was blown away by the extent of the reference collection at Bar Ilan.  Every species and even various varieties I had hoped to see were there, waiting for me in well organised boxes of slides and capsules. I only managed a few days of browsing the reference collection, but plan to return during the final stages of identification for the material I am studying from Kharaneh IV.
Map of the location of Khareneh IV in Eastern Jordan

In the meantime, I’ve been back in the lab at BGS, working with Dr Angela Lamb to measure δ13C in my seeds and learning a lot about statistical analyses and some of the real challenges to using isotopic methods on such ancient seeds. The initial results have certainly given me lots to think about, but I won’t give any of them away here. Keep an eye out for the publication that will hopefully result from our findings.

Monday, 25 January 2016

Millions of years of lake sediment: looking at the links between climate change and human Jonathan Dean

Jonathan Dean is a Postdoctoral Research Assistant working at the Stable Isotope Facility at the British Geological Survey, and here he gives us an update on the research project he is involved with, investigating climate changes and human evolution.

I’ve just returned from Atlanta, where around 50 scientists from the US, Canada, UK, Europe and Africa came together to discuss progress on our project, the Hominin Sites and Paleolakes Drilling Project. In short, we are analysing the ancient sediments from five lakes in Ethiopia and Kenya, close to places where anthropologists have discovered the remains of ancient Homo sapiens (our species) or our ancestor species. Combined, the sediments from all the sites span the time from close to the present day to millions of years ago. By analysing the changes in the chemistry of the lake sediments, and how this changes back through time, we are trying to establish how climate change may have contributed to the biological evolution of humans and cultural changes such as migrations out of Africa.

Some of the scientists working on the five lakes
 As I discussed in a previous blog, the lake I’m working on – Chew Bahir – has sediments that probably span the last 500,000 years or so, and is close to the site where the oldest known Homo sapiens remains have been found. In the autumn, I started analysing these sediments, and so far have probably gone back from the present to about 100,000 years ago or so. I have found large changes in the ratio of one type of oxygen to another, which indicates that there have been big shifts from wetter times when the lake was fairly fresh, to drier times when the lake would have been salty. Our samples are stored in laboratories in Minneapolis and this week I received my latest samples from there, so it’s back to the lab in the Stable Isotope Facility to extend our record of changes between wet and dry further back into the past.

A bit of sight-seeing in Atlanta
Martin Luther King's House
Other scientists in the UK, Germany and Ethiopia will be using other methods to help in the climate reconstruction, such as looking at changes in what species of diatoms (algae formed of silica) are present and using x-rays to look at what types of sediment were washed into the lake. In combination, our different methods will hopefully allow us to accurately reconstruct the past climate changes in this part of Africa. In particular, we’re interested in what the climate of the area was like when Homo sapiens evolved, around 200,000 years ago, and later on when some started to migrate out of Africa. We want to establish whether climate changes occurred around these times, and so to understand if these could account for the timing of our evolution and migrations.

Tuesday, 12 January 2016

A new PhD researching the effects of variation in the orbit of the Earth around the Savannah Worne

Hello, my name is Savannah and I have just started my PhD within the Centre for Environmental Geochemistry, between the University of Nottingham School of Geography and the BGS.  I recently graduated from the university with a BSc Geography, completing my dissertation research using the sediments to investigate environmental change over the last hundred years in Maloe More, Lake Baikal, Siberia. From my studies, I became very interested in palaeoenvironmental change and was keen to pursue a career in research, leading me to apply for this PhD.

The topic of my PhD is to investigate the role of Bering Sea oceanographic controls on the shift in Milankovitch orbital cycle dominance, during the Mid-Pleistocene Transition (MPT), which occurred between 1.2 and 0.7 million years ago. The Milankovitch orbital cycles occur due to gravitational interactions which cause variations in the Earth’s orbit of the Sun, and hence produce changes in the amount of solar energy the Earth receives and impacting on the climate. There are three dominant cycles called precession, obliquity and eccentricity, which cause changes on timescales of 26,000, 41,000 and 100,000 years, respectively (see here for further details). During the MPT there was a shift in the dominance of these cycles, switching from the formerly prevailing obliquity orbital cycle, to the lower frequency eccentricity cycle. However there was no significant change in the external orbital forcing; this implies that there must have been an internal forcing within the Earth’s climate system, which caused this system response instead.

To investigate this, I will be looking at sediments collected during an Integrated Ocean Drilling Program (IODP) cruise, taken from the continental shelf in the Bering Sea. I aim to use the microfossil assemblages of siliceous algae called diatoms, which sink to the ocean floor forming a preserved fossil record in the sediment, which can then inform us about the type of environment at the time of deposition. I will also be undertaking geochemical analysis to measure the chemical structure of a preserved micro-organism called foraminifera, as well as assessing the composition of the sediment itself (e.g. carbon and nitrogen content), to aid my diatom analysis in better understanding the changing environment through the MPT. One final proxy I plan to utilise is the ice-rafted debris (IRD) record; IRD is sediment derived from the land or seabed which is transported in a matrix of ice (e.g. sea-ice or icebergs), which then floats away from the adjacent land mass or ice sheet, melts, and is subsequently deposited in the sediment at the ocean floor. As my sediment core has been taken from near the historic coastline and the maximum winter sea ice extent, this record should prove useful to assess the magnitude of sea ice formation and hence infer climatic conditions such as temperature and wind strength.  Through these proxies, I hope to uncover the history of Bering Sea sea-ice, sea surface temperature, productivity and salinity through the middle Pleistocene, as well as assessing potential teleconnections with North Atlantic Ice Sheet growth and instability, through this period.

Currently, I am spending my time becoming familiar with the previous body of work completed in the Bering Sea and more broadly through this time period, to better understand how my PhD research will fit into this. I have also started to undertake my first batch of laboratory work, processing samples to pick out benthic (sea-floor dwelling) foraminifera which will later be used for isotopic analysis, to create a robust age model for my sediment core, U1343.

My supervisors for this project are Dr Sev Kender, Dr George Swann, Professor Sarah Metcalfe (all  (University of Nottingham), Dr James Riding (BGS) and Dr Zuzia Stroynowski (IPMA).