Sedimentary components, investigation of facies and depositional environments of Bandar-Anzali area

In this research, the facies and marine, coastal and continental depositional environments have been investigated in southern part of the south Caspian Basin (middle part of the Gilan province; Bandar-e Anzali area). In this study, seventy-one surface sediment samples were taken unsystematically from three hundred and twelve recorded points in the shallow areas of the Caspian seabed and surrounding land. Four sediments types, slightly gravelly sandy Mud, slightly gravelly muddy Sand, slightly gravelly Sand and gravelly Sand constitute the largest percentage of all components.Based on X-ray diffraction studies, the sediments are composed of calcite, quartz, feldspar, mica and smectite. The components are classified into two categories: clastic (quartz, feldspar, mica, rock-fragment and clay minerals) and organic-biogenic (plant debris, marine and non-marine organisms (ostracoda, bivalves and Gastropoda)).In general, sedimentation has been done in three areas: land (continental), transition (shore) and marine. The land part composed of the fluvial system (active channel, point bar, flood plain and crevasse splay), coastal plain, wetland, paleo-lagoon, marsh and washover deposits. The transitional and marine parts composed of the shore barrier and the shoreface, respectively. The shore barrier sequence consists of foreshore, backshore and shore dune ridges. Non-marine bioclasts (such as non-marine bivalves Monodancacaspia and Dreissea polymorpha and non-marine gastropods such as Lymnaeidae sp.) in wetland/lagoon, marsh environments and washover deposits and marine bioclasts (such as bivalves Cerastoderma glaucum) has been observed in the washover deposits, shore (shore barrier sequence) and shoreface environments.The sea-level fluctuations (the general trend of the relative sea-level fall along with the short-term fluctuating cycles of sea-level rise and fall), cause the shifting of the facies and shoreline towards the sea (progradation/regression) from the past to the present.