Late Quaternary Paleoshorelines and Sedimentary Sequences in Chabahar Bay (Southeast of Iran)

Abstract

Chabahar Bay is located along the coast of Sistan province in SE Iran. This area is part of the coastal Makran zone (one of the geological zones of Iran), which had undergone sea-level changes along the Late Quaternary. Due to these processes, multiple sedimentary sequences and several paleoshorelines were created. In this investigation, by using the Geological Information System method, 21 paleoshorelines were recognized. In the borehole at the north of Chabahar Bay, we found 14 layers, which were related to Late Quaternary sedimentary sequences and correlated to glacial and interglacial periods. All layers of borehole were analyzed for grain size, sedimentary structures, and fossil content. Four radiocarbon measurements were done on the lowest and uppermost marine layers of borehole and on C7 and C21 of paleoshorelines. The lowest layer of borehole has 17,600 14C YBP date, related to Cataglacial or Flanderian Transgression, which outcropped at 15 m height and 5,300 m distance to the present shoreline. Sedimentary sequences showed four transgressions and retrogressions occurred from cataglacial to the present. On the other hand, from 4690 ± 40 YBP, 20 paleoshorelines have been created, for which the duration of each may have been about 230 years.