Relief and Deposits of Assumption Island, Seychelles, Indian Ocean


  • Aleksey Korotky
  • Nadejda Rajigaev
  • Nicolay Kovalukh


Atoll, calcarenite eolian relief, karst topography, marine terrace, marine transgression, sea-level change


The geomorphology of Assumption Island is distinguished by elevated marine terraces .formed when the island was an atoll. Two high marine terraces (III: 10-14 m elevation; II: 4-8 m elevation) composed,of reefal limestones, correspond to two or possibly three peaks of transgression of the world ocean during the Riss-Wurm (Isotopic Stage 5), that are confirmed by 230Th/234U dates of 127± 2.7 ka. 125 ± 1.8 ka, 110 ± 4.0 ka, 96 ± 3.0 ka and 82 ± 2.7 ka. Low Marine Terrace I at 2-3 m elevation, was formed during two phases of Holocene transgression. Calcarenites from the base of the lower terrace were deposited during the first phase, while an upper unit was emplaced during the second. Accumulation of a large volume of Holocene sand in eastern Assumption Island occurred as detrital material was blown from the exposed shelf during the end of the Late Wurm-Early Holocene.