Tectonostratigraphic Evolution of the North Anatolian Palaeorift (NAPR): Hettangian-Aptian Passive Continental Margin of the Northern Neo-Tethys, Turkey

Authors: ALİ KOÇYİĞİT, DEMİR ALTINER

Abstract: The Jurassic-Early Cretaceous stratigraphical, sedimentological and structural evolutionary history of the northern branch of Neo-Tethys is recorded and preserved within an average 6-km-thick basin fill. The basin fill is well-exposed as discontinuous inliers of varying size and thickness within, and to the north of, the Late Cretaceous-Early Tertiary İzmir-Ankara-Erzincan Suture throughout northern Turkey. This basin fill unconformably overlies a substratum comprising the deformed rock assemblages of the Triassic Karakaya palaeorift and its Hercynian basement. Detailed studies based on geological mapping at a 1/25,000 scale and stratigraphic sections measured at 14 type localities show that this infill includes stratigraphical and sedimentological key units, which comprise a 0.1-3.8-km-thick basal association (proto- and syn-rift infill), a 0.1-1.5-km-thick platform association, a 1.6-km-thick basinal association (transitional to post-rift stage infill), and syn-depositional megabreccias and slumps. This basin fill is shaped by a series of structural units which result from four distinct phases of extensional faulting. These structural units comprise interior grabens, subplatforms, platforms, palaeohighs, rift-related unconformities (proto-, syn- and post-rift unconformities) and rift-related faults. The latter include older growth faults, inner and outer master fault systems, and a marginal fault complex. This thick Jurassic-Lower Cretaceous basin fill has been interpreted to be the product of a palaeorift, designated here as the north Anatolian palaeorift (NAPR). The young substratum and the key stratigraphical and structural elements support the interpretation that the NAPR comprised the south-facing passive continental margin of north Neo-Tethys in northern Turkey. It had the character of a supradetachment basin and can be explained by the evolution of a three-stage graben model during the Hettangian-Aptian time interval.

Keywords: tectonostratigraphy, palaeorift, three-stage graben model, supradetachment basin, Hettangian-Aptian, northern Neo-Tethys, Northern Turkey

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