Markus Fischer: Between Deserts and Lakes in southern Ethiopia – Modelling Environmental Dynamics for the African Humid Period

by Markus Fischer,
Eberhard Karls University Tübingen, Section Geosciences, AG Mikropalaeoontology

The Ethiopian rift in eastern Africa is known for its diverse landscape, ranging from arid and semi-arid savannahs to high and lush mountainous regions, where anatomically modern humans were present since at least 195 ka BP. Lacustrine sediments and paleo-shorelines near-by modern shallow lakes in the rift indicate that lakes have fluctuated dramatically in the past between deep fresh water lakes, to shallow highly alkaline lakes, down to completely desiccated lakes and thus moisture availability was not constant over time. In order to understand the impact and feedback of different paleoenvironmental changes due to a changing climate (e.g. vegetation, lake sizes) in southern Ethiopia, we here present a comprehensive study that focuses on the time between 15,000 and 5,000 years, a well-known time called the last African Humid Period (AHP). This time period was not only climatically completely different to today, also a big cultural shift occurred during this time. Here we present an interdisciplinary approach that links environmental modelling with lacustrine sediment analysis. This includes a comprehensive hydro-balance modelling approach of multiple rift lakes from the southern Ethiopian Rift (Abaya, Chamo, Chew Bahir) providing insights into paleo-precipitation conditions and lake dynamics.  This model is supported by the use of Sr-Isotopes measured on microfossils from drill core sediments to reconstruct water connectivity between the investigated lakes and to backtrack annual precipitation amounts. The model outcome is then used to model paleo-vegetation dynamics using remote sensing based boosted regression trees under different assumptions of paleo-seasonality changes. This model is supported by phytolith analysis from the drill core sediments. The results suggest that an increase in precipitation of 20-30% throughout the whole Southern Ethiopian Rift was necessary to fill quickly the deepest of the investigated lakes, Lake Chew Bahir, to its overflow level, but also small changes in the water budget allowed the lake to disappear within decades. This study highlights a) the sensitivity of the rift lakes to even moderate climate changes, b) that slight seasonal precipitation changes can have a huge impact, and c) that hydrological connection plays an important role.

 

 

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Event Information:

Date, Time:21/10/2019, 16:00 h – 17:30 h

Location: Hörsaal Geologie (310/EG/030), Zülpicher Str. 49a, Cologne

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Christine Lane: Volcanic Chronologies and Tephra Connections in East Africa

by Christine S Lane,
from Department of Geography, University of Cambridge

Reconstructing past spatial and temporal variability of palaeoclimate and palaeoenvironmental change across a continent as climatically diverse as Africa, relies upon comparison of data from widespread and diverse archives. However, generating accurate, precise and independent chronologies for the comparison of detailed and varied palaeo-proxy records is challenging. In Eastern Africa, explosive eruptions of rift volcanoes generate blankets of ash that can be preserved in sedimentary basins over hundreds to thousands of kilometres from their source. Distal tephra (including cryptotephra-) research offers opportunities for direct dating of sediment sequences (e.g. by 40Ar/39Ar methods) and for making precise stratigraphic correlations between archives at single moments in time. Currently however, the volcanic eruption record for the East African Rift is patchy and for tephrochronology to reach its full potential, detailed local to regional eruption stratigraphies are needed. 

Investigations into the presence of visible and non-visible (crypto-) tephra layers within lacustrine palaeoenvironmental records of the mid to late Pleistocene from across eastern Africa are revealing the potential for distal tephra research to (i) increase our knowledge of the history of Late Quaternary explosive volcanism in eastern Africa; (ii) provide age constraints for individual core chronologies, in particular beyond the limits of radiocarbon dating; and (iii) correlate palaeoclimate and archaeological archives within a regional tephrostratigraphic framework. 

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Event Information:

Date, Time:01/07/2019, 16:00 h – 17:30 h

Location: HS XVIIb Main Building UoC, Albertus-Magnus-Platz, Cologne

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William Gosling: Drivers of Ecosystem Dynamics in West Africa over the last c. 500.000 Years

Dear participants,
Please note: The meeting location has been changed to HS VI / main building / Albertus-Magnus-Platz and will beginn 5 p.m.”

by Prof. Dr. William Gosling
Department of Ecosystem & Landscape Dynamics, University of Amsterdam

Over the last half million years global climate systems have undergone significant reorganisation, largely due to changes in the Earths orbital configuration, which has resulted in significant modification of ecosystems. The reconfiguration of climate systems has resulted in changes in temperature and precipitation patterns across the globe. At high and mid-latitudes the impact of these climate changes on ecosystems is predominantly driven by the expansion and contraction of ice-sheets. However, at low latitudes the impact of global climate cycles on ecosystems is less well understood, in part due to a paucity of suitable study sites. Lake Bosumtwi (Ghana, 6oN) was formed around one million years ago when a meteorite hit the Earth. The sedimentary record that has since accumulated within Lake Bosumtwi provides a rare opportunity to explore past ecosystem dynamics in a lowland tropical setting. Here I present evidence obtained from the Lake Bosumtwi sediments, and link it with other datasets, to explore the role of fire, herbivores, CO2, temperature, precipitation, and seasonality in driving ecosystem dynamics (vegetation composition and diversity) around the crater over the last c. 500,000 years.

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Event Information:

Date, Time:14/01/2019, 17:00 h – 18:00 h

Location: HS VI Main Building UoC, Albertus-Magnus-Platz, Cologne

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Alexander Gerner: Strata- Geophilosophische Notizen zu Sergio Costa

by Dr. Alexander Gerner
Center for Philosphy of Sciences of the University of Lisbon
(presentation will be held in English)

Within his talk the German philosopher and theater director Alexander Gerner takes up abstract geology as a complementary perspective: strata as a concept derived from geology and made operational in the human realms’ arts and knowledge development. He will present an atlas of friendship between philosophy, science, art and human technology by means of an observational program presented in the painting series “Strata” and other working images of the artist Sérgio Costa. The presentation will present experimental maps, illustrating an enhanced thinking of the concept „Strata: How are we able to experience long-time change?

 

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Event Information:

Date, Time:03/12/2018, 16:00 h – 17:00 h

Location: HS XVIIb Main Building UoC, Albertus-Magnus-Platz, Cologne

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Daniela Holst: Subsistence & resource management in the early Holocene

The profound environmental changes at the beginning of the early Holocene worldwide are accompanied by innovations in human land-use, leading to a sedentary lifestyle and domestication in some parts of the world. The talk focuses on subsistence and land-use strategies in the contemporaneous European Mesolithic. Well-preserved archives allow for high-resolution reconstructions and quantitative assessments of the processing and stockpiling of high return harvests of energy rich foods. The hazelnut-roasting camps of Duvensee in Northern Germany form a prime example of Mesolithic subsistence strategies. Their potential implications on land-use and mobility are discussed in context with new evidences. A future research project on ground stone tools will contribute to the complement of our patchy image of the Mesolithic.

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Event Information:

Date, Time:19/11/2018, 16:00 h – 17:30 h

Location: HS XVIIb Main Building UoC, Albertus-Magnus-Platz, Cologne

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Martin Theuerkauf: From guesswork to maps – recent progress in quantitative vegetation reconstruction

The talk will give an overview of the main current approaches and illustrate their strength and weaknesses in a number of examples. It will then introduce the new ROPES approach. This method does not require pollen productivity as a parameter, and so may overcome major limitations of the present methods. It is suited to extend quantitative vegetation reconstruction into new regions and pre-Holocene periods, and allows analysis of long pollen records that cover several glacial/interglacial cycles. 

By Dr. Martin Theuerkauf from the

Institute of Botany and Landscape Ecology, University of Greifswald

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Vegetation reconstruction from pollen data, although dealing with counts and percentage values, has long been a mere semi-quantitative field. Pollen percentages do not directly represent past vegetation composition, because plants species produce pollen in very different amounts and with different dispersal patterns. This bias in pollen data is well known since the inception of the field 100 years ago, but correction for a long time relied on ad-hoc informed guesswork.

Today, a suite of methods is available that enable true quantitative interpretation of pollen data. The methods cover different spatial scales: REVEALS for example aims to translate pollen deposition from large lakes into regional vegetation composition. LOVE and Marco Polo reconstruct stand-scale vegetation composition using pollen data from very small sites. The extended downscaling approach and the multiple scenario approach explore vegetation patterns in landscapes using multiple pollen records.

So far these methods are still rarely applied, however, for a number of reasons. Most importantly, the underlying parameters pollen productivity and pollen dispersal require elaborate calibration and are hence so far available for some regions only.

Event Information:

Date, Time:05/11/2018, 16:00 h – 17:30 h

Location: HS XVIIb Main Building UoC, Albertus-Magnus-Platz, Cologne

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Paleolithic research in Armenia – eclectic point of view and future directions

Paleolithic research in Armenia by Dr. Ariel Malinsky-Buller, Senior Researcher at the Monrepos Archaeological Research Centre and Museum for Human Behavioural Evolution.

Armenia is situated in the Southern Caucasus at the geographical intersection of Africa and Eurasia. The geography of the Armenia posed major challenges and opportunities for Palaeolithic hunter gatherer populations, with its mosaic of distinct ecological niches, large temperature gradients, and strong seasonal fluctuations across elevation gradients. This, in turn, make Armenia an ideal natural laboratory for testing models of climatic impact on hominin settlement patterns and population dynamics. The lecture will present two on-going projects in two eco-geographic regions within Armenia. The first is Kalavan 2, a Middle Palaeolithic open-air site located at 1630 masl on the northern slopes of the Areguni Mountains north of Lake Sevan. The second area is close to Ararat village at around 700 masl. Preliminary results and future directions of research will be presented in the lecture. 

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Event Information:

Date, Time:02/07/2018, 16:00 h – 17:00 h

Location: Kleiner Hörsaal der Geologie (310a), Zülpicher Straße 49, Cologne

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Heinrich Events: An Unintentional Discovery And Its Possible Consequences for the future

In the mid 80ties an environmental impact assessment in relation to deep-sea dumping of medium-to-high level radioactive waste was carried out in the eastern margins of the Mid Atlantic Ridge next to the Bay of Biscaye. In one of the box corers recovered for radionuclide analysis a volcanic rock was found that triggered interest because of an unexpected geochemical feature on its surface. Subsequent investigations on the bordering sediment layer revealed hints on a massive ice rafting event possibly released from rapidly collapsing circum-Atlantic ice shields. The search for more of these events in numerous sediment cores exhibited a total of 11 layers since the end of the Saalian/Illinoian glaciation (OIS 6/5 to 2/1). The six events identified in the period OIS 4 to 2 indicated oceanographic conditions in the Northeast Atlantic Ocean that were different to those that prevailed during most time of this glacial period. Later, several authors proposed mechanisms that could have triggered the collapses, e.g. the Binge-Purge model (MacAyeal, 1993) or, access of relatively warm water to the grounding lines in conjunction with isostatic movements (Bassis, 2017).

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One of the consequences of rapid ice shield collapses is sea level rise. Paleo data report rates of up to several meters per century over a period of several centuries. The process described by Bassis et al. resembles to what nowadays can be observed along the ice margins of Greenland and the Antarctic where (man-made) warmed ocean water attacks the grounding lines. If this initiates something like a Heinrich event this is of widespread consequence for coasts, from displacement of populations to marine pollution.

Research on past Heinrich events is important for understanding the future developments of the existing ice shields and climate change.

Event Information:

Date, Time:18/06/2018, 16:00 h – 17:00 h

Location: Kleiner Hörsaal der Geologie (310a), Zülpicher Straße 49, Cologne

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Interglacial Diversity in the Mediterranean Basin, Insights from Central Italy Continental Carbonates

The Apuan Alps (central Italy).

Past interglacial periods can be seen as a series of natural experiments characterized by different boundary conditions (e.g. seasonal and latitudinal distribution of insolation, atmospheric greenhouse gas concentrations, extent of continental ice sheets), with different consequent effects on the character of climate change. Past interglacial are keys to understand past but also future-climate, because they represent potential analogues of the present warm period (Holocene) and offer the unique possibility to investigate the background of climate variability in which human-induced modifications operate, and to clarify their role in the natural sequence of events.

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Dr. Eleonora Regattieri (University Cologne).

Continental carbonates (speleothem and lacustrine sediment) from the Mediterranean basin represent invaluable archives of past climate. Particularly, oxygen stable isotope composition of these deposits responds sensitively to variations in regional hydrology. This information can be complemented by the study of others properties (e.g. elemental and mineralogical composition), to obtain more detailed information on local environmental changes. In this talk, several case studies from central Italy lakes and caves are presented.  They cover the Last Interglacial (ca. 130-90 ka), and the interglacial corresponding to the marine Isotope Stage (MIS) 19 (ca. 790-760 ka), considered the best orbital analog of the Holocene over the last million of years. All the presented records have independent, radiometric chronologies thanks to uranium-thorium dating of speleothem and to Argon/argon dating of volcanic ash layers interbedded to the lacustrine sediment. Climate evolution, hydrological response and millennial-scale variability are evaluated, and the potential link with the extra-regional and global climate is discussed.

Event Information:

Date, Time:07/05/2018, 16:00 h – 17:00 h

Location: Kleiner Hörsaal der Geologie (310a), Zülpicher Straße 49, Cologne

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Comparing the expansions of Middle Stone Age and Middle Palaeolithic populations in East Africa and South Asia

Tea break during my excavations at Katoati in Rajasthan.

Fossil and genetic studies on the origins and expansions of modern humans reveal an increasingly complex mosaic, including regionally structured populations within Africa, and numerous expansions into Eurasia resulting in multiple episodes of interbreeding with other hominins.

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Until recently, East Africa preserved the oldest fossil evidence for Homo sapiens, but it remains a key region to explore the emergence of modern
humans as a crossroads for interactions of structured populations within Africa and providing access to routes beyond. In contrast, South Asia is the last major region of Eurasia to present fossil evidence for the arrival of Homo sapiens, despite a similarly pivotal role in putative routes of expansion across Asia. These two regions share a broadly similar size, a coastline on the Indian ocean and a comparable range of habitats, but distinct differences in the evolution of behaviour evident in the archaeological record. In the first part of my talk, I will examine behavioural diversity within the Middle Stone Age of East Africa, based upon a comprehensive synthesis of the archaeological literature and the application of a quantitative approach. This identifies aspects of continuity throughout the MSA, as well as pulses of behavioural diversification, both regarding packages of lithic technology and landscape colonisation. In the second part of my talk, I will focus more broadly on the culture history of South Asia to examine modern human dispersal. With respect to the most current evidence, it appears modern humans used Middle Palaeolithic toolkits to colonise South Asia during MIS 5. In conclusion, I will argue that examinations of human expansion and behavioural variability need to be rooted within a biogeographic framework.

Event Information:

Date, Time:23/04/2018, 16:00 h – 17:00 h

Location: Kleiner Hörsaal der Geologie (310a), Zülpicher Straße 49, Cologne

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