The last interglacial high sea level in the granitic Seychelles, Indian ocean

In the granitic Seychelles islands, widely scattered remnants of marine limestones of Late Pleistocene age are found over a range of elevations within about 9 m with respect to present sea level. These exposures can be subdivided into coralgal buildups and rubbly conglomerates. 230Th/ 234U dating from corals indicates that the limestones were deposited during the last interglacial stage (140-120 kyr B.P.). In order to understand the sea level history for this time range, various fabrics related to sequences of rock-forming processes (i.e. frame building, bioerosion, internal sedimentation, cementation, other depositional and diagenetic processes) have been identified and used as possible indicators of paleosea level datum at their time of formation. Detailed examination of the rock fabric sequences, in combination with radiometric dating, reveals that sea level overstepped its present position around 140 kyr ago and reached its maximum altitude 135 kyr ago before retreating. There were presumably two distinct events in sea level rise, separated by a gap of about 10 kyr. Comparison between elevations of high sea stands of a similar age on a regional scale supports the contention that the Seychelles area has been relatively instable since at least the Late Pleistocene. Either hydro-isostatic uplift of the Seychelles granitic bank or volcanic subsidence of nearby atolls are assumed to be responsible for such differences in paleosea level records.