Messinian carbonate and alluvial fan sedimentation in Alonnisos Island, Greece: sedimentary response to basement controls, inversion tectonics and climatic fluctuations
✍ Scribed by G. Poulimenos; P. Karkanas
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 979 KB
- Volume
- 33
- Category
- Article
- ISSN
- 0072-1050
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✦ Synopsis
A marginal marine carbonate environment, giving away to an alluvial one, was established during Messinian time on Alonnisos Island, the footwall upland of the Southern Marginal Fault of the Sporades Basin (SMFS). Analysis of the evolving depositional systems, with emphasis on their sedimentation processes, faulting patterns and palaeopedological factors, has permitted an interpretation of the simultaneous controls of tectonism and climate.
The carbonate sediments were deposited in a shallow marine environment formed along a faulted continental margin under warm and semi-arid climatic conditions. Faulting consisted of NE-trending dextral reverse faults and NW-trending strike slip faults, produced by WNW-directed compression. The basement structural elements aected the spatial distribution of the oshore and shoreface facies, whereas ®fth-order cycles of sea-level change were responsible for the development of metre-scale, shallowing-up cycles.
The compressional structures were subsequently reactivated by NNE extension. This tectonic inversion, together with a global sea-level fall, triggered alluvial fan sedimentation. Fan sedimentation was disrupted by long periods of nondeposition and soil formation under warm climatic conditions. Three distinct units are recognized in the fan: a lower unit consisting of clast-poor debris ¯ows, attributed to semi-arid±humid periods; an intermediate unit of clast-rich sheet¯oods and channel ¯ows, deposited during arid periods; and an upper unit consisting of matrix-rich sheet¯oods related to a return to semi-arid±humid conditions. We interpret that the water-¯ow processes responsible for deposition were most prevalent on fans of arid and semi-arid climates, whereas debris-¯ow processes were more typical of climates with higher rainfall.
As the extension proceeded during the Plio-Quaternary time, the main tectonic activity of the Sporades Basin was taken up by the SMFS causing signi®cant footwall uplift. Due to this process, Alonnisos Island was elevated above the Pliocene highstand and became an area starved of Quaternary sedimentation.