People at Fort Hoofddijk

Bas van den Berg
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B.C.J. van den Berg
Paleomagnetic Laboratory
Fort Hoofddijk
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Department of Earth Sciences
Utrecht University
Budapestlaan 17, 3584 CD Utrecht 
The Netherlands 

Phone +31 30 253 1670


Research of Bas van den Berg

Late Eocene sediments in the Xining basin, China: recorders of local or global changes ?
The early Cenozoic is one of the most interesting time periods for climate change research. During this Era, the Earth’s climate changed from a greenhouse world to an icehouse world. This dramatic change took place at the Eocene-Oligocene boundary. This boundary marks an abrupt cooling step, which caused a drop in eustatic sea-level and major faunal turnovers. 

This cooling event has been well documented in ocean cores, but rarely in continental sediments. The climate conditions preceding and leading to this transition are poorly understood and referred to as the ‘doubthouse’ period, a subject of much debate. 
The most important climate event in this doubthouse time period is the Middle Eocene Climatic Optimum (MECO). The MECO (44-42 Ma) is a hypothermal event of anomalous warm temperatures in a period of general cooling. This event is found in d18O records of the Ocean Drilling Program, but also on the northern hemisphere, e.g. in marine limestone sections in Central Italy.
One of the main reasons for naming it the doubthouse period is because there are few continental records  which cover this time period. The Xining Basin is one of the few, making it unique and valuable. 
The main difficulty is how to relate them to global paleoclimate records. The key is to precisely date features of environmental changes, and this is exactly the main aim of this project.
Bas with his back to the geology of the Xining basin(left) and sampling with Wentao (above).

In October 2009, the Tiefo section (NE of Xining) was studied, and dated using magnetostratigraphy. The section contains a 115 meter-thick and continuous sequence of red mud-gypsum alternations ranging in age 43-37.5 Ma. The sequence covers the Late Eocene doubthouse period, including the MECO interval. So far, the results are very promising, but it is essential to find a section parallel to the Tiefo section to test the recorded sedimentary features in terms of their spatial distribution.

So far, under supervision of Guillaume Dupont-Nivet, accompanied by Roderic Bosboom and Hemmo Abels, and helped by Huang Wentao, we carried out a successful fieldwork in the Xining basin. The Tazeko section is parallel to the Tiefo section, is studied and sampled, intended to be dated using magnetostratigraphy, and then correlated to the existing stratigraphic framework. This must give crucial constraints on whether the features found in both sections are either representing local anomalies or are a result of changes in global paleoclimate. 

Tazeko section

publications Publications of Bas van den Berg