Bucket Structure in Carbonate Accumulations of the Maldive, Chagos and Laccadive Archipelagos

Authors

Wolfgang Schlager, VU University Amsterdam - The Netherlands
Samuel J. Purkis, Nova Southeastern UniversityFollow

Document Type

Article

Publication Date

11-1-2013

Publication Title

International Journal of Earth Sciences

Keywords

Shelf edge, Carbonate platform, Ring reef, Atoll, Nutrient uptake, Size-frequency analysis, Fractal

ISSN

1437-3254

Volume

102

Issue/No.

8

First Page

2225

Last Page

2238

Abstract

Peritidal platforms rimmed by reefs, and raised reefs rimming deep lagoons, are characteristic morphologies of the tropical carbonate factory; their geometry contrasts sharply with the seaward-sloping shelves of siliciclastic margins. The structure has been compared to a bucket—stiff reef rims holding a pile of loose sediment. Remote-sensing data from the Maldive, Chagos and Laccadive archipelagos of the Indian Ocean show that ring reefs with bucket structure are the dominant depositional pattern from patch reefs of tens of meters to archipelagos of hundreds of kilometers in diameter, that is, over more than 4 orders of magnitude in linear size. Over 2.5 orders of magnitude, the bucket structures qualify as statistical fractals, exhibiting self-similar patterns and size distributions following power laws. However, most regional or genetic subsets of the data follow lognormal distributions and small subsets of lagoon reefs exhibit exponential distributions. Seismic data and boreholes in the Maldives indicate that the bucket has been a dominant depositional motif since the Oligocene. Ecological and hydrodynamic studies on modern reefs suggest that the bucket structure is a form of biotic self-organization: the edge position in a reef is favored over the center position because bottom shear is higher and the diffusive boundary layer between reef and water thinner. Thus, the reef edge has easier access to nutrients and is less likely to be buried by sediment. The bucket structure reflects these conditions. Karst processes have accentuated the surface relief of the buckets, particularly in the late Quaternary.

Comments

©Springer-Verlag Berlin Heidelberg 2013

NSUWorks Citation

Wolfgang Schlager and Samuel J. Purkis. 2013. Bucket Structure in Carbonate Accumulations of the Maldive, Chagos and Laccadive Archipelagos .International Journal of Earth Sciences , (8) : 2225 -2238. https://nsuworks.nova.edu/occ_facarticles/272.

ResearcherID

B-8552-2013

DOI

10.1007/s00531-013-0913-5