The Posht-e-Badam block is situated in the central part of the Central-East Iranian Microcontinent (CEIM), as part of the larger Alpine‒Himalayan orogenic system. Eocene volcanic rocks of the Posht-e-Badam block present very good exposures in the Saghand (Khoshumi Mountain), Allahabad and Chapedony areas (Yazd province, Central Iran). These Eocene volcanic rocks are basic to acidic in composition (SiO2 = 48.9 to 63.4 wt
The spatial distribution of sediment source areas and paleodrainage evolution of the Ciscaucasian Foredeep’s Neogene‒Quaternary deposits have remained contentious. Here, we resolve this debate through systematic analysis of the Upper Miocene Lysogorskaya Formation’s alluvial facies, which constrain provenance terranes via integrated paleocurrent direction (PCD) compositional data and stratigraphic position. Comprehensive representative paleocurrent datasets (n = 70) were acquired from the formation’s spectacular exposures in two deeply incised river valleys of two biggest Terek’s tributaries: The Baksan River section near village Islamey and the Cherek River section near village Aushiger (Kabardino-Balkarian Republic). These continuous, vertically-oriented outcrops display the complete stratigraphic architecture, featuring five main conglomerate units separated by minor erosional remnants of floodplain deposits. Systematic evaluation of six distinct sedimentary structure types within the formation demonstrates a predominant northeastward paleocurrent direction during alluvial deposition. This directional trend unequivocally identifies the sediment source area as the southwestern, axial zone of the Central Caucasus, directly opposing the paleoflow. The conglomerates’ composition, featuring crystalline rock fragments intermingled with sedimentary lithologies and granitoid clasts, provides definitive evidence for syn-depositional exposure of the Central Caucasus crystalline core through orogenic uplift during this period. The observed unconformities, with their north‒east-directed dips, record tectonic uplift along the south‒west margin of the depositional basin during the Miocene‒Quaternary. That uplifted zone simultaneously acted as a sediment source for the basin, as indicated by angular discordances between the Lysogorskaya Formation and the underlying/overlying sedimentary units. These findings collectively with polymictic contain and pebble-boulder dimension of alluvium establish the crystalline highlands of Central Caucasus in the south‒west as the principal sediment provenance while documenting active tectonic uplift in the Late Miocene foredeep setting.
Our analysis of the paleontological data allowed us to assess the chronology and characteristics of the formation of the Caucasian land mass and the emergence of its mountainous relief. It has been established that the origin of the Caucasian land mass occurred in the Oligocene. The studied fossil records of Caucasian land mass biota showed that it is reliably recorded in sediments beginning from the Late Oligocene. Data from the Late Middle and Early Late Miocene (13–8 Ma) bears evidence of dissected relief and the existence of altitudinal zonation. In the Late Pliocene and Early Pleistocene (3.6–1.5 Ma), the Caucasian land mass acquired the characteristics of its modern relief.
The article examines the Late Miocene deposits of the Western Ciscaucasia, represented by the Gaverdov (Belaya River) and Armavir (Kuban River) formations. Based on field and laboratory studies conducted by the authors in 2024–2025 and earlier studies, which Provided new stratigraphic, lithological, and paleontological data, as well as U–Pb dating of detrital zircon, their stratigraphic features and provenances are compared. These results allowed us (i) to refine the chronology of the geological development of the Greater Caucasus folded structure; (ii) to identify evidence of exposure of its crystalline core in the Late Miocene; (iii) to investigate the influence of neotectonic uplifts on the formation of continental sedimentary strata and the dynamics of core exposure. Our data refine and complement the thermochronology and lithostratigraphy of the study region.
