RECENT FOLDING, GEOMORPHIC EVOLUTION, AND PALEOCLIMATE: APSHERON PENINSULA, AZERBAIJAN

The Apsheron Peninsula, Azerbaijan in the southern foreland of the Caucasus Mountains exposes the Pliocene clastic Productive Series and Pleistocene-Quaternary flanking carbonate-rich units in a number of long, narrow oil-saturated anticlines. We are beginning to study the tectonics, geomorphology, and exhumation history of the Apsheron Peninsula and Yasamal and Kirmaky anticlines using GIS, apatite U-Th-He and fission-track thermochronology, and ¹⁰Be and ²⁶Cl surface exposure dating. With GIS (digital elevation models, Google Earth, aerial photos, and digital geologic maps), we investigated the morphology, gradients, and relative timing of streams flanking and crossing these two anticlines and how they vary along, across, and between the two structures. Drainage density varies systematically along and across the Yasamal anticline. The higher drainage density of streams on the eastern flank of the anticline may be associated with steeper surface slopes and/or steeper bedrock dips along this flank. The systematic decrease in drainage density toward the southern fold nose probably indicates that the anticline recently propagated to the south during an older (T1) wet climate. The flanking “dry” Yasamal valley post-dates earlier (fold-related) streams which are left as “hanging valleys” on west side of Yasamal valley and east side of the Yasamal anticline. Yasamal valley has a non-standard rectangular cross-sectional shape, trends N-S, parallel to today’s prevailing winter and summer winds, and slopes southward toward the Caspian Sea. Yasamal valley appears to be wind sculpted, and likely formed during a dry period, T2, that followed T1. Kirmaky Valley appears to be a similar T2 N-S, wind-sculpted, rectangular valley. Kirmaky anticline has no T1 fold-affected streams, suggesting that it may be younger than Yasamal anticline. Results from a suite of ~30 U-Th-He, apatite fission-track samples, and several ²⁶Cl and ¹⁰Be samples will be forthcoming; these, and links to calibrated paleoclimate records, will help us establish the absolute timing of the exhumation (unburial) of the rocks in the two Apsheron anticlines and that of the wet/dry climate cycles that helped sculpt the landscapes of the Apsheron peninsula.