Morphometric Analysis to Assess Sea Level History and Uplift Rate in the Pleistocene Marine Terraces of Chabahar

Abstract Marine terraces have long been used as baseline geodetic markers of relative past sea levels, reflecting the interaction between vertical crustal movements and sea level oscillations. The terraces age and elevation of shoreline angles can be used to determine uplift rate. Disparate uplift rates in pervious investigation in the study area are related to manual measurements based on the surface morphology without considering erosion and other natural factors were deformed the marine terraces morphology. The uplift rate strongly depends on the temporal and spatial accuracy of shoreline angle measurement. In this research, Chabahar Marine Terrace has been assessed by using geologic information, morphometric analysis, and radiocarbon dating along with using of digital elevation model and TerraceM program to estimate accurate uplift rate and to determined mechanism of uplift. High-resolution topographic data and TerraceM program significantly simplify the remote identification of shoreline angles, to rapidly assess and map them at regional and local scales and providing accurate estimation of past sea levels. Uplift rate was estimated by 15 topographic swath profile along a sequence using digital elevation map. Calibrated radiocarbon ages of 3 samples fall between 46944±3055 yr B.P. and 29304±557 yr B.P., revealing that strata uplifted about 29 ka years ago with a rate of between 2-5 mm/yr (average: 4 mm/yr). In general, uplift rates increase from west to east of the Chabahar Marine Terraces. However, some local increases or decreases in uplift rates were observed due to local tectonics. According to morphology of terraces, correlation of rock units, faults density and variations of thickness of litho-stratigraphic units, it is concluded that the coastal area of study can be divided into two separate zones I and II which can be separated by faults. The sequence of Chabahar Terrace coincides with the interstadial stage of Marine Isotope Stage 3 (MIS3). Chabahar wave-cut terrace has been built by uplift along with sea level rise at 29 ka years ago. Altogether, considering the stability of sea level changes in the region, factors such as tectonics, erosion and sedimentary basin have determined the current shape of Chabahar Terraces.