People at Fort Hoofddijk

Marcela Haldan
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M.M. Haldan, MSc
Paleomagnetic Laboratory
Fort Hoofddijk
Department of Earth Sciences
Utrecht University 
Budapestlaan 17, 3584 CD Utrecht 
The Netherlands 

E-mail  haldan@geo.uu.nl

Research
Publications



Research of Marcela Haldan

Records of secular variation in red beds during the Permo-Carboniferous Reversed Superchron and implications for the geodynamo 
Both theory and numerical models speculate that the state of the geodynamo during Superchrons (long periods without polarity reversals) is different from its state during (even longer) periods of mixed polarity. Robust observational data, however, are still conspicuously lacking. 

A recently acquired high-quality red bed record in the Dome de Barrot (right) showed non-reduced secular variation during the Permo-Carboniferous Reversed Superchron (PCRS, ~50 Myr). The secular variation is comparable to recent times, a result that contrasts with model predictions.

A recent analysis of paleointensities during the Cretaceous Normal Superchron (CNS, ~35 Myr), however, provided tentative support that secular variation, indeed, may have been reduced during this Superchron. This discrepancy may indicate that the geodynamo was fundamentally different during these two Superchrons.The observational data base, however, is still too small and its quality often inadequate, thus prohibiting firm conclusions

Right: Gorges de Daluis, Dôme de Barrot (France).

Dome de Barrot

This proposal aims to provide high-quality secular variation records during the PCRS, a period for which observations are most critical. We intend to analyse red bed sediments because they contain a high-quality magnetic signal. Our recent advance in understanding the natural remanent magnetisation (NRM) in red beds permits to distinguish the various modes of NRM acquisition in these rocks. 

The primary nature of the NRM will be assessed by an array of paleomagnetic and rock magnetic tests, including recently developed and promising new laboratory techniques. In addition, we aim to develop a suitable method to obtain for the first time - relative paleointensity records for hematite-bearing rocks. The required precise time constraints will be obtained through cyclostratigraphic (Milankovitch) chronology. 


Cyclical section of Permian redbeds on Lac du Salagou, Lodève (France)

Finally, we aim to compare our observations to both (new) results from the CNS, the Triassic (intermediate interval between two superchrons) and to predictions from theory and models. 


Cyclical section of Triassic red (brown ?) beds from the Argana Basin, Morocco

publications Publications of Marcela Haldan
2009
  • Haldan, M.M., Langereis, C.G., Biggin, A.J., Dekkers, M.J. and Evans, M.E. (2009). A comparison of detailed equatorial red bed records of secular variation during the Permo-Carboniferous Reversed Superchron, Geophys. J. Int, in press