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Dr Sandra Nederbragt

Dr Sandra Nederbragt

Stable Isotope Mass Spectrometer Specialist

School of Earth and Ocean Sciences

Email:
nederbragta@cardiff.ac.uk
Telephone:
+44 (0)29 2087 6665
Location:
1.56, Main Building, Park Place, Cardiff, CF10 3AT
  • Mid-Cretaceous Oceanic Anoxic Events
  • Holocene climate variability
  • Stable isotope systems
    • Stable Isotope Mass Spectrometer Specialist – School of Earth and Ocean Sciences, Cardiff Unviersity (2012-present)
    • Postdoctoral Researcher – Department of Earth Sciences, University College London (1997-2008)
    • Postdoctoral Researcher – Institute of Earth Sciences, VU University Amsterdam (1991-1997)
    • PhD - Institute of Earth Sciences, VU University Amsterdam (1990)
    • MSc Geology - VU University Amsterdam (1985)

Academic positions

  • Postdoctoral Researcher – Department of Earth Sciences, University College London (1997-2008)
  • Postdoctoral Researcher – Institute of Earth Sciences, VU University Amsterdam (1991-1997)

2019

2018

2016

2011

2010

2009

2008

2005

2004

2001

2000

Much of my research to date stems from my interest in the Cretaceous period as an example of a greenhouse world with climate conditions that are fundamentally different from the modern icehouse setting. Especially the mid-Cretaceous (120-90 Ma years ago) was a time of optimum warmth during which the global ocean was periodically anoxic. During these so-call Oceanic Anoxic Events organic-rich sediments were deposited at a scale that is inconceivable in the modern ocean. I have used micropalaeontology, stable isotope stratigraphy, and 2-box ocean modelling to try to understand the mechanisms that are responsible for these climate events and their impact on the global carbon cycle.

To better quantify the relation between organic matter production, sedimentation, and preservation I have looked at anoxic basins in the modern ocean. Due to lack of bioturbation at the sea floor the seasonal variation in sediment composition is preserved as varved sediments. By measuring the composition of such varves it is possible to reconstruct the accumulation rates of organic matter at annual resolution and relate it to other indicators for climate change, something that is rarely possible for ancient sediments. The main result was that sedimentation of organic matter is largely controlled by the presence of other sediment particles (ballast minerals). Calcareous microsfossils are the main ballast particles in the open ocean. However, riverine sediments are much more important as ballast mineral in near-coastal basins, implying that organic carbon burial in the oceans is sensitive to changes in river discharge either natural or man-made.

My interest for future research is to revisit the geologic past to explore what role ballast minerals played in ancient settings. During much of the past, like the mid-Cretaceous, lithogenic sedimentation rates were low, and calcareous microfossils must have been the main ballast mineral that was available. However, severe carbonate dissolution is common in anoxic sediments. This suggests that the production and preservation of both organic matter and carbonate are intrinsically linked.