Late Cretaceous to Early Eocene Sedimentation in the Sinop–Boyabat Basin, North‐Central Turkey: A Deep‐Water Turbiditic System Evolving into Littoral Carbonate Platform

Abstract

The Sinop-Boyabat Basin is a southeast-trending elongate basin in the Central Pontides, northern Anatolia, filled with a succession of Lower Cretaceous to middle Eocene deposits, nearly 7 km thick. The basin evolved from a backarc rift related to the Western Black Sea crustal extension into a retroarc foreland basin of the Central Pontides, and was eventually inverted by tectonic compression in the late Eocene. The present sedimentological study, supplemented with petrographical, micropalaeontological and ichnological data, is focused on the Upper Cretaceous to lowest Eocene part of the basin-fill succession, which is ~2 km thick, comprises the Gürsökü, Akveren and Atba1ı formations and corresponds to the basin's transformation from a failed rift into an orogenic foreland. The succession's facies associations reveal a deep-marine turbiditic system that underwent prolonged aggradation and evolved into a wave-dominated littoral carbonate platform, to be drowned again due to a eustatic sea-level rise and rapid tectonic subsidence in late Paleocene time.The upper Campanian to lower Maastrichtian Gürsökü Formation consists of alternating siliciclastic sandstones, calcareous mudstones and subordinate marlstones. The deposits represent a basin-floor turbiditic system directed towards the east, supplied with epiclastic volcanic detritus and increasingly more abundant bioclastic sediment from the basin's southwestern margin. The bioclastic admixture indicates development of a reefal platform at the basin margin. The northeastern margin was submerged and insignificant as a sediment source. The sheet-like turbidites indicate non-channelized currents of low to high density, and the succession represents transition from the medial to distal part of the system. At least one isolated palaeochannel occurs in the lowermost, thicker bedded part of the succession. The system was supplied with sediment from a storm-dominated littoral ramp perched on the basin margin and was subject to gradual retreat (back-stepping) by onlapping the margin.The upper Maastrichtian-Paleocene Akveren Formation consists of sheet-like calcarenitic turbidites interbedded with marlstones and calcareous mudstones. Its uppermost part is dominated by tempestites, with wave-worked shoreface calcarenites and a reefal limestone unit at the top. Eastward sediment dispersal persisted, and the basin-floor turbiditic system was supplied with sediment from a distally steepened ramp with bypass chutes. As the turbiditic system aggraded, the ramp became homoclinal and the ignition of turbidity currents declined, giving way to

Cross-sectional anatomy and geodynamic evolution of the Central Pontide orogenic belt (northern Turkey)

“…A second period of subsidence, during the Late Cretaceous-Paleocene, corresponds to the formation of the Bartın basin and the Sinop-Boyabat basin (now the Sinop Range; e.g., Leren 2003), extending from Cide to Samsun between the Early Cretaceous basins (Fig. 1).…”

Facies Anatomy of a Sand‐Rich Channelized Turbiditic System: The Eocene Kusuri Formation in the Sinop Basin, North‐Central Turkey

“…3) has a combined stratigraphic thickness of ~7000 m and provides an important record of the region's tectonic development and palaeogeographical history. The ensuing review of the basin's dynamic stratigraphy compiles the results of previous studies (Ketin & Gümüb, 1963;Aydın et al, 1986Aydın et al, , 1995bTüysüz, 1990Tüysüz, , 1993Görür et al, 1993;Görür & Tüysüz, 1997) and the present research (see also Leren, 2003;Janbu, 2004;Uchman et al, 2004;Leren et al, this volume, pp. 401-456).…”

“…3). This turbiditic succession is ≤ 1200 m thick and consists of siliciclastic (mainly epiclastic volcanic) sediment increasingly richer in calcareous bioclastic admixture, supplied mainly from the west/southwest and spread eastwards along the basin axis (Leren, 2003;Leren et al, this volume, pp. 401-456).…”

Sedimentary record of mid-Miocene seismotectonic activity in the Sinop Peninsula, north-central Turkey

“…The retroarc foreland basin evolved from a failed Late Cretaceous rift (Leren et al, 2007). The marginal trough, paralleling the folded and thrustdeformed foreland, is presently exposed only in the Sinop Peninsula ( Figure 1B).…”

“…The present study from a middle Miocene shallowmarine siliciclastic succession in the Sinop Peninsula, north-central Turkey ( Figure 1B), is the first documentation of a syndepositional seismic fault activity that can be attributed to the early onset phase of neotectonics in Leren et al, 2007); note the neotectonic pattern of strike-slip deformation along the East Anatolian (EAF) and North Anatolian (NAF) fault zones driving the westward "tectonic escape" of the Anatolian craton. B) Geological map of the Sinop Peninsula, showing the tectonically-inverted foreland basin of Central Pontides to the south and the associated marginal trough to the North (modified from Gedik and Korkmaz, 1984).…”