Ewch i’r prif gynnwys
Alexandra Nederbragt

Dr Alexandra Nederbragt

Arbenigwr Sbectromedr Màs Isotop Sefydlog

Ysgol Gwyddorau'r Ddaear a'r Amgylchedd

Y Prif Adeilad, Ystafell 1.56, Plas y Parc, Caerdydd, CF10 3AT


Rwy'n rhedeg y cyfleuster isotop sefydlog, lle rydym yn mesur isotopau ysgafn (H, C, N, O) mewn ystod o ddeunyddiau. Mae'r cyfleuster yn darparu gwasanaeth i Ysgol Gwyddorau'r Ddaear a'r Amgylchedd yn ogystal ag ysgolion eraill ym Mhrifysgol Caerdydd ac ymchwilwyr o sefydliadau eraill.



















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.


  • M.Sc. Earth Sciences, VU University Amsterdam, the Netherlands (1985)
  • Ph.D. Micropalaeontology, VU University Amsterdam (1990)
  • Post-doctoral Researcher, VU University Amsterdam (1990-1997)
  • Post-doctoral Researcher, University College London, UK (1997-2008)
  • Stable Isotope Mass Spectrometer Specialist, Cardiff University, since 2012

Safleoedd academaidd blaenorol

  • Ymchwilydd Ôl-ddoethurol – Adran Gwyddorau Daear, Coleg Prifysgol Llundain (1997-2008)
  • Ymchwilydd Ôl-ddoethurol - Sefydliad Gwyddorau Daear, Prifysgol VU Amsterdam (1991-1997)