Abstract
In this paper data are presented on the composition of sediments deposited at the toe of slope during progradation or retreat of Triassic carbonate platforms in the Dolomites (Italy). For this purpose a succession was studied from the toe of slope of a Triassic (Carnian) carbonate platform (Picco di Vallendro/Dürrenstein, Dolomites, Italy). The microfacies analysis of selected calciturbidites sequences revealed a reduced input of oncolites and ooids during progradation and an increase in clasts. The main input, however, was derived from the reefs on the platform. Retrogradation of the platform showed an increase of filaments and radiolarians (open ocean biota) as well as carbonate mud and a reduced input of grains that originated within the reefs on the platform. Both during progradation and retrogradation parts of the platform were flooded and could produce excess sediment that could be exported to the surrounding basins. However, the absence of platform interior biota documents that progradation occurred from sediments of the reefal belt, probably during relative sea-level lowstands. Carbonate composition varies systematically with toe-of-slope progradation/retrogradation and, thus, argues for carbonate production as the main driver of the geometries observed at the toe of slope.
| Original language | English |
|---|---|
| Pages (from-to) | 436-448 |
| Number of pages | 13 |
| Journal | International Journal of Earth Sciences |
| Volume | 87 |
| Issue number | 3 |
| Publication status | Published - 1 Dec 1998 |
Funding
Acknowledgements J. Everaars is thanked for her help with the fieldwork and some of the statistics. For preparing numerous thin sections I thank the Rock Preparation Department of the Vrije Universi-teit, Amsterdam. The hospitality of A. Kamelger (University of Innsbruck) is greatly appreciated. I also thank the Landesrat of the province of Südtirol/Alto Adige for their permission to work in the National Park of the Dürrenstein/Picco di Vallandro. The paper greatly benefited from critical reviews by A.-J. Everts, W. Schlager and O. Weidlich. Fieldwork and a Postdoc at the Vrije Universiteit, Amsterdam, were funded by the Industrial Associates in Sedimentology Programme of the Sedimentology Department of the Vrije Universiteit (W. Schlager). The author also acknowledges reviewers G. Eberli (RSMAS, Miami), A. Vecsei (Universität Freiburg) and A. Strasser (Université de Fribourg) for their thoughtful suggestions for improvement of the manuscript.
Keywords
- Carbonate platform
- Progradation
- Retrogradation
- Sediment composition
- Southern alps
- Toe of slope
- Triassic
