Features of the Recent Rise of Various Segments of the Greater Caucasus

The author studied the history of the development of the recent uplift of the Greater Caucasus. There are two stages of its development: (I) the formation of relatively low‒altitude deformational uplifts and (II) the subsequent rapid rise, which led to the transformation of these uplifts into a current high-altitude structure. Stage (I) had different duration and intensity in different segments of the Greater Caucasus. Stage (II), which appeared in the entire Greater Caucasus except for its northwestern segment (the Northwestern Caucasus), began in the Pliocene and developed with acceleration. Stage (I) began in the Oligocene with the emergence of lowland in the central segment of the Greater Caucasus. The eastern part of the central segment (the Central Caucasus) reached middle-mountain altitudes by the end of the Sarmatian epoch (Tortonian), and erosion and transportation of fragments of the Paleozoic basement rocks began in the Maeotian (7.6–6.1 Ma). In the western part of the central segment of the Greater Caucasus (the Western Caucasus), basement erosion has also been recorded since the Maeotian, but the altitudes of the Western Caucasus remained on the low-mountain level until the middle of the Pliocene. As a result of the subsequent rise of stage (II), the Central Caucasus has reached the maximum height for the Greater Caucasus (up to 5200 m), while the Western Caucasus is ~1000 m lower. In the eastern segment of the Greater Caucasus (the Eastern Caucasus), the beginning of stage (I) is recorded in the Middle Miocene (~20 Ma), but the uplift of the Eastern Caucasus remained low-mountain until stage (II), during which, especially in the Quarternary, the Eastern Caucasus rose faster than the Central Caucasus, reaching the average height of the summit surface almost 4000 m. The first signs of exhumation of the Northwestern Caucasus are dated to 10–8 Ma. At the end of the Miocene, this segment underwent deformation, which led to uplift up to 1400 m high. Ongoing deformation combined with advanced erosion had kept the summit surface at heights of ~1000 m. There are no signs of uplift of the stage (II) type in the Northwestern Caucasus. The intensive uplift of the central segment of the Greater Caucasus is due to the thickening of its crust as a result of the under-thrusting of the continental crust of the edge of the Scythian Plate under the segment in the Late Paleozoic. In other segments of the Caucasus, the edge of the Scythian Plate was probably sub-oceanic, and its subduction did not affect the intensity of uplift. The consequences of the thickening of the crust of the Central Caucasus were: (i) its uplift in the Cimmerian epoch, which led to the erosion of the Lower-Middle Jurassic cover, (ii) the reduced thickness of subsequent marine sediments, (iii) the early occurrence and relatively high altitudes of the stage (I) uplift. The intensification of upward movements in stage (II) may be due to the penetration of a decompressed sub-lithospheric flow from the African superplume under the Central Caucasus. Later, this flow spread under the Western and Eastern Caucasus, causing their accelerated uplift.