Small exposures of Late Proterozoic schistose, quartzose sandstones and phyllitic, sericite-quartz schist (turbidites) also occur in the southeastern part of Bolshoy Lyakhovsky Island.

The bulk of this island consists of Late Jurassic to Early Cretaceous turbidites composed of interbedded fine-grained sandstones, thinly bedded siltstones, and argillites.

Overlying these sediments are Pliocene to Pleistocene colluvial, alluvial, and nearshore marine sands, silts, and clays that contain occasional gravel layers.

Contrary to the interpretations of Baron von Toll[6] and earlier geologists, glacial tills and related sediments are completely absent within Bolshoy Lyakhovsky Island.

[8] The southern sea cliffs of Bolshoy Lyakhovsky Island, which were first studied by Baron von Toll,[6] expose a complex sequence of fossiliferous Late and Middle Pleistocene floodplain, eolian, lake, and solifluction sediments cemented by permafrost.

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.

[9][10][11][12] Elsewhere along the coast of Bolshoy Lyakhovsky Island, the sea cliffs expose pre-Eemian floodplain and lake sediments at their base.

In some locations, the Eemian lake deposits are thicker and laterally continuous enough to form a complete blanket overlying older sediments.

[9][10][11] At many localities along the sea cliffs, typically over 10 meters of Early Weichselian lacustrine and loess-like floodplain deposits overlie the Eemian and pre-Eemian sediments.

They contain ice wedge polygon systems that formed during the Early Weichselian stadial, about 100,000 to 50,000 years ago, as the result of extremely cold and dry conditions.

[9][10][11] Within the southern sea cliffs of Bolshoy Lyakhovsky Island, Late Weichselian sediments of the Last Glacial Maximum have not been found.

New ice wedge polygon systems later formed in these sediments during the Late Holocene as result of pronounced climatic cooling, which only recently has reversed in the last couple of hundred years.

[10][11] Because of the formation of permafrost in these sediments and their depositional environments, prehistoric bone, shell, and plant material are well preserved and abundant.

[9][10][11][14] Baron Eduard von Toll[6] was among the first to report in detail about the abundance of Pleistocene fossils found within Bolshoy Lyakhovsky Island.

Under a peat composed of water mosses covering what he described as "perpetual ice", now known to be permafrost, Baron von Toll found fragments of willow and the bones of post-Neogene mammals.

He also reported having found in a frozen, sandy clay layer and lying on its side, a complete tree of Alnus fruticosa 15 to 20 ft (4.6 to 6.1 m) in length, including roots, with leaves and cones adhering.

Lacking modern radiocarbon dating techniques, Baron von Toll[6] assigned this tree and other fossils to single "mammoth period".