Termination of carbonate slope progradation: An example from the Carnian of the Dolomites, Northern Italy
- Author(s)
- Lorenz Keim, Rainer Brandner, Leopold Krystyn, Wolfgang Mette
- Abstract
The demise of carbonate platforms during Carnian time is a widespread phenomenon of the Western Tethys, but the controlling factors are not well-understood. The Dolomites of the Southern Alps (Northern Italy) are well-known for their large-scale Ladinian and Carnian prograding carbonate platforms. Platform growth stopped during the Early Carnian and both platforms and basinal areas were subsequently covered by mixed carbonate-siliciclastic sediments (Raibl Group). We present a carbonate platform, whose slope progradation came to a halt prior to draping by the siliciclastic sediments. Judging from the height of the clinoforms a platform-to-basin relief of at least 100 m existed during the final stage of progradation. This paleoslope was colonized by coral patches draped by skeletal packstones to microbial bindstones, forming typically lens-shaped mounds on the steep slope. The formation of mounds on the platform flank was only possible, because the downslope transport of detritus from the platform and/or upper slope was stopped. The sedimentary evolution in the adjacent basin indicates a poorly oxygenated environment with abundant brackish water ostracods of low diversity. Based on the inherited platform-to-basin relief and the lithofacies of the basin fill a local sea-level drop in the order of 60-80 m is postulated. With rising sea level the accommodation space between former basin and platform became filled by shallow-marine, mixed carbonate-siliciclastic sediments. The abundance of epibenthic suspension feeders of the basin fill such as megalodonts suggests increased nutrient supply. The termination of slope progradation was a multiphased process triggered by a stagnation of the regional subsidence, a reduction of water circulation, followed by a sea level-drop, the influx of freshwater and the input of siliciclastics. Fluctuating salinity caused intermittently a biotically stressed environment. Π2001 Elsevier Science B.V. All rights reserved.
- Organisation(s)
- Department of Palaeontology
- External organisation(s)
- Leopold-Franzens-Universität Innsbruck
- Journal
- Sedimentary Geology
- Volume
- 143
- Pages
- 303-323
- No. of pages
- 21
- ISSN
- 0037-0738
- Publication date
- 2001
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 105118 Palaeontology
- Sustainable Development Goals
- SDG 14 - Life Below Water
- Portal url
- https://ucrisportal.univie.ac.at/en/publications/910e3102-37b7-4fde-beda-a5f4ad246156