Tectonic, Climatic, and Sedimentary Processes Recorded by Pleistocene Fold Growth Strata, The South Caspian Basin, Azerbaijan

Abstract

The Pleistocene – Present-day sedimentary succession of the South Caspian Basin was deposited syntectonically alongside growing anticlines in an under-filled, rapidly subsiding basin. The combination of ample sediment supply from surrounding mountain belts, fast sedimentation rates (variously estimated at between 0.4 and 1.7 m/kyr) and high accommodation space has resulted in an exceptionally thick succession (up to 3000 m) which documents structural growth and regional tectonics at a high temporal resolution. The succession additionally records the palaeo-water level history of the Caspian Sea —an internally drained lake— which has fluctuated at much higher magnitudes and frequencies throughout the study interval than along comparable marine settings. The Pleistocene – Present-day Caspian stratigraphy therefore represents an ideal geological dataset with which to study depositional processes along syntectonic fold ‘growth strata’ and to investigate the relative impacts of tectonics and climate change on syntectonic sedimentation. This thesis presents three studies which describe South Caspian Basin fold growth strata at a variety of scales using offshore seismic data from the north-eastern portion basin and field data from western Azerbaijan. The studies examine; [1] the vertical spacing and regionally lateral synchronicity of angular unconformities within late Pliocene – Present-day growth strata; [2] Pleistocene basin margin syntectonic sedimentology, and: [3] the process of large scale slope failure from submarine landslide deposits along folds located in the basin interior. The results of these studies add to the scientific understanding of the regional geology and of tectono- sedimentary processes in general. However the main finding —recurrent in all three studies— is the presence of repetitive sedimentary patterns and correlations. These are suggested to represent orbital Milankovic cycles of 40,000 years (obliquity) and 100,000 years (eccentricity). Orbitally driven climate change appears to have been a major control on South Caspian fold growth strata architecture and sedimentary processes within anticline mini- basins. Fold growth effects are also observed but these are relatively subdued as tectonic uplift was outpaced by high sedimentation rates