A Micromorphological and Mineralogical Study of Site Formation Processes at the Late Pleistocene Site of Obi-Rakhmat, Uzbekistan Carolina Mallol, 1, * Susan M. Mentzer, 2 and Patrick J. Wrinn 2 1 Universidad de La Laguna, Departamento de Prehistoria, Antropología e Historia Antigua, Campus de Guajara, La Laguna, Tenerife, Spain 2 University of Arizona, Department of Anthropology, 1009 E. South Campus Drive, Building #30A, Tucson, AZ 85721-0030 Site formation processes at the Late Pleistocene rockshelter deposit of Obi-Rakhmat were reconstructed through soil micromorphology and Fourier transform infrared spectroscopy (FTIR). The entire sequence has undergone limited diagenesis and is well preserved. The base of the stratified sequence represents a karstic setting with intermittent, low-energy deposi- tion of autochthonous gravitational debris and anthropogenic material in a wet, muddy envi- ronment. These sediments were post-depositionally affected by episodic waterlogging. The bulk of the sequence overlying the karstic layers comprises a continuous series of primary freshwater spring deposits containing reworked anthropogenic material that was buried penecontemporaneously with calcium carbonate deposition. The top of the sequence is weakly cryoturbated, indicating a periodically cold, wet environment. No alluvial elements that could suggest sediment inputs from the nearby river terraces were documented. A single exogenous layer was identified, representing an episode of colluviation from directly above the rock- shelter preceding a major roofspall event. The basal part of the sequence contains slightly reworked anthropogenic remnants of intense activities, including combustion. The anthro- pogenic elements present in the spring deposits show higher degrees of reworking, suggest- ing within-layer translocation. The development of spring activity at the site did not cause humans to abandon the rockshelter; they continued to carry out their activities throughout a changing local environment. © 2009 Wiley Periodicals, Inc. INTRODUCTION Obi-Rakhmat rockshelter is a Late Pleistocene archaeological site located in northeastern Uzbekistan, at the southwestern end of the Talassky Alatau range of the western Tien Shan Mountains, 100 km northeast of Tashkent (Figure 1). The site was discovered in 1962 and is currently investigated jointly by members of the Institute of Archaeology and Ethnography, the Siberian Branch of the Russian Academy of Science, and the Institute of Archaeology of the Uzbekistan Academy of Science (Derevianko, 2004). With its stratigraphic sequence currently dated to Geoarchaeology: An International Journal, Vol. 24, No. 5, 548–575 (2009) © 2009 Wiley Periodicals, Inc. Published online in Wiley Interscience (www.interscience.wiley.com). DOI:10.1002/gea.20280 *Corresponding author; E-mail: cmallol@ull.es.