floodplain, eolian, lake, and solifluction sediments cemented by permafrost. In the 1990s and 2000s, a Russian-German multidisciplinary team, which included the Alfred Wegener Institute for Polar and Marine Research and Permafrost Institute, Russian Academy of Sciences, studied the cryolithology, geochronology, ground ice geochemistry, paleobotany, paleontology, sedimentology, and stratigraphy of these sediments. The age of these sediments were studied in great detail using radiocarbon dating of bones, ivory, and plant remains; optically stimulated luminescence dating of bone-bearing sediments; and uranium-thorium dating of associated peat. The oldest sediments exposed in the southern sea cliffs of Bolshoy Lyakhovsky Island consist of a layer of rocky, yellowish to greenish colored sediment. This layer is a thick Paleogene weathering crust (paleosol) that has developed within Permian sandstone. This paleosol has been largely modified by periglacial processes and development of ice wedges periodically during the Pleistocene. These deeply weathered sediments are unfossiliferous and characterized by the presence of weathering products like kaolinite and montmorillonite. Saalian sediments uncomfortably overlie this paleosol. The oldest known Pleistocene sediments exposed in the southern sea cliffs of Bolshoy Lyakhovsky Island consist of Saalian sediments, which accumulated between 200,000 and 120,000 years ago. The lower part of these sediments consist of ice-rich, silty and silty-sandy sediments that accumulated as a Saalian ice complex between 200,000 and 170,000 years ago. They contain pebbles, peat inclusions, and peat horizons. The presence of ice belts, reticulated ice interlayers, and wide, round-shouldered ice wedges indicate that permafrost formed in these sediments as they accumulated. The lower part of this unit contains the pollen of sparse grass-sedge vegetation, which reflects a stadial environment. The upper part of this ice-rich unit contains pollen associated with dense grass-dominated tundra, which is indicative of interstadial environments. The upper part of the Saalian sediments, which lie uncomfortably on the eroded surface of the lower Saalian ice complex deposits, consists of well-sorted fine-grained sand that contains pollen characteristic of sparse grass-sedge dominated interstadial vegetation and less ground ice. These loess-like sediments accumulated within floodplains and lakes. As they accumulated between 170,000 and 120,000 years ago, ice wedge polygons formed in these sediments as the result of extremely cold and dry conditions. Elsewhere along the coast of Bolshoy Lyakhovsky Island, the sea cliffs expose pre-Eemian floodplain and lake sediments at their base. Eemian lake sediments fill depressions, i.e. ice wedge casts and thermokarst lakes, which developed by the surficial thawing during Eemian interglacial