Along-strike variations in the composition of sandstones derived from the uplifting western Greater Caucasus: causes and implications for reservoir quality prediction in the Eastern Black Sea

Abstract

Oligo-Miocene outcrops along the southern margin of the western Greater Caucasus preserve a record of sediments shed from the range into the northern and central parts of the Eastern Black Sea. Sandstones in the Russian western Caucasus are significantly more quartz-rich than those located farther SE in western Georgia. The latter contain appreciably more mudstone and volcanic rock fragments. Oligo-Miocene turbidite systems derived from the Russian western Caucasus in the Tuapse Trough and central Eastern Black Sea may therefore form better-quality reservoirs at shallow to moderate depths than sediments derived from west Georgian volcaniclastic sources in the easternmost part of the basin. Palynomorph analysis indicates sediment derivation predominantly from Jurassic and Cretaceous strata in the Russian western Caucasus and from Eocene strata, and an increasing proportion of Cretaceous strata upsection, in western Georgia. An Eocene volcaniclastic source is proposed for the increased rock fragment component in west Georgian sandstones. Eocene volcaniclastic rocks are no longer exposed in the Greater Caucasus, but similar rocks form the inverted fill of the Adjara–Trialet Basin farther south in the Lesser Caucasus. The former presence of a northern strand of this basin in the west Georgian Caucasus is supported by earlier thermochronological work.Supplementary material:A sample data table, petrographic data table, petrographic key, QFL sandstone compositional plot and palynomorph reworking Stratabugs™ charts are available at www.geolsoc.org.uk/SUP18662.

Relict basin closure and crustal shortening budgets during continental collision: An example from Caucasus sediment provenance

“…White dots indicate previously reported detrital zircon analyses of Oligo‐Miocene [ Vincent et al ., ] and Jurassic (Bajocian) [ Allen et al ., ] sandstone. Gray dots show locations of other published provenance data discussed in text, including three samples at the Chanis River section (WG28b/3, WG28c/5, WG28c/1, and WG27/4) [ Vincent et al ., , , ]. Schematic cross sections indicate that basin was wide during latest Cretaceous to Paleocene time, but narrow both during Jurassic opening and late Miocene closure (ATA: Anatolide‐Tauride‐Armenian block; B‐P: Bitlis‐Pötürge; EAAC: East Anatolian Accretionary Complex).…”

“…Below (section 6.1), we infer that the Greater Caucasus Basin was likely on the order of ~350–400 km wide prior to Cenozoic closure. This differs from previous interpretations of a relatively narrow Paleogene transtensional basin [e.g., Vincent et al ., ], in which sediments were locally derived [e.g., Vincent et al ., , ]. The key difference between the relict‐ocean and transtensional basin models is in the latest Mesozoic to Paleogene paleogeography (Figure ).…”

“…We combine these results with the limited detrital zircon data available for the Caucasus region (Table S1), including all reported analyses of Mesozoic (1 sample) [ Allen et al ., ] and Oligo‐Miocene‐aged sandstones (5 samples) [ Vincent et al ., ] (Figures a and b), as well as modern sediment from large modern rivers draining into the Caucasus region from the Eurasian continent (Don, Dnieper, and Volga Rivers in Russia) [ Wang et al ., ] (Figure a). We report depositional ages for previously published Cenozoic samples using both the Paratethyan and international chronostratigraphic stages (e.g., Chokrakian; Langhian) as originally reported [ Vincent et al ., , ]. We exclude earlier detrital zircon studies of the modern Volga [ Allen et al ., ; Safonova et al ., ] and Don [ Safonova et al ., ], because they conform with the results of Wang et al .…”

“…(a) Simplified tectonic map of Greater and Lesser Caucasus, showing locations of main structures and new U‐Pb detrital zircon samples (diamonds: bedrock sandstone; stars: modern river sediment, with catchments delineated by black lines edged in white). Dots denote locations of previously reported detrital zircon (white fill) [ Allen et al ., ; Vincent et al ., ] and provenance analyses (gray fill) [ Vincent et al ., , , ] discussed in text; see Figure for additional sample numbers. Fault geometries are simplified on northern margin of central Greater Caucasus and shown as north directed thrusts; true geometries are south directed backthrusts above a triangle zone at the leading edge of a generally north directed thrust system [e.g., Sobornov , 1994].…”

Sediment provenance studies in hydrocarbon exploration and production: an introduction

“…The along-strike variation in sandstone composition derived from the uplift of the greater Western Caucasus, and supplied to the Black Sea, is documented in Vincent et al (2013). The authors predict that good quality, quartz-rich sandstone reservoirs, derived from the Russian Western Caucasus, are likely to be present in the Tuapse Trough and central Eastern Black Sea.…”