PALAEOGEOGRAPHIC EVULATION OF SİVAS TERTIARY BASIN'(W-SW SİVAS)

Abstract

Sedimentological studies has been made at the west and the south west of Sivas (Figure 1) and investigated palaegeographic evolution fades and environmental features of deposite rocks. A A1 A2 A 3 fades have been recognized at the middle Eosen aged Sahantepe member. A A1 fades has deposited at the continental shelf; A2 A3 facies at swamp and coastal sabkha. B B1 B2 B3 fades have been recognized at the Oligocene aged Küçüktuzhisar Formation. B facies in lagoon, B1 facies has deposited-in barrier island. B2 B3 facies have deposited at continental sabkha and playa lake enviroment. At the Akören formation C C1 C2 C3 C4 C5 C6 C7 facies have been recognized..C C1 C2 facies at the meandering river and subenviroments. C3 C4 facies at the playa lake. C5 C6 facies meandering river and C7 facies has deposited at alluvial fan enviroments. Continental shelf deposits cinsists of claystone, siltstone and sandstone, has very well (Ta-Tb), (Ta-Tc) and (Ta) structures These have been deposited by turbidite flows is shallow sea improved. At in the coastal sabkha enviroment have been deposited gypsum series and they are together with elastics. Meandering river deposits consist of channel fill, point bar and flood plain subfacies finning upward cycles. Playa lake and continental sabkha deposits consist of terrestrial elastics with interlayer gypsum and anhidrite; alluvial fan deposits consist of conglomerates and poorly sorted, pebbly sandstone with muddy matriks and show normal and reserve grading. In the studied area the marine regime has been the dominating agent up to of Eocene- then the marine influence has restrained but continental rejime, as a result of this swamp and coastal sabkha enviroments have improved During Oligocene period has become more effective. During this period continental sabkha, playa lake, meandering river and alluvial fan enviroments have been made. At the Sahantepe member palaeocurrent direction is towards from the NE to NW: at the Küçüktuzhisar Formation palaeocurrent directions are towards from the N to S and NW to SE and at the Akören formation palaeocurrent directions are towards from S to N, SW to NE. In Eocene period the formations (Bozbel Formation - Sahantepe Member) was supported by the ofhiolites and metamorhic units, situated in the NE of the region and Oligocene period these for mations (Küçüktuzhisar and Akören Formations) were supported by the ophiolites and metamorphic units and deep asidic and basic rock as well as volcanits situated in the SW and NW of the region. On the basis of these observations, in can clearly be in dicated that the Sivas basin reflects a intraplate basin characteristics following the continent-continent collision.