Lake Titicaca - Geology

Geology

The Tinajani Basin, in which Lake Titicaca lies, is an intermontane basin. This basin is pull apart basin created by strike-slip movement along regional faults starting in the late Oligocene and ending latest Miocene. The initial development of the Tinajani Basin is indicated by volcanic rocks, which accumulated between 27 and 19 million years ago within this basin. They lie upon an angular unconformity cuts across pre-basin strata. Lacustrine sediments of the Lower Tinajani Formation, which are exposed within the Tinajani Basin, demonstrate the presence of a pre-Quaternary, ancestral Lake Titicaca within it between 18 and 14 million years ago. Little is known about the prehistory of Lake Titicaca between 14 million years ago and 370,000 BP because the lake sediments dating to this period lie buried beneath the bottom of Lake Titicaca and have not yet been sampled by continuous coring.

The Lake Titicaca drilling project recovered a 136-m-long drill core of sediments from the bottom of Lake Titicaca at a depth of 235 m and at a location just east of Isla del Sol. This core contains a continuous record of lake sedimentation and paleoenvironmental conditions for Lake Titicaca back to about 370,000 BP. For this period of time, Lake Titicaca was typically fresher and had higher lake levels during periods of expanded regional glaciation that corresponded to global glacial periods. During periods of reduced regional glaciation that corresponded to global interglacial periods, Lake Titicaca had typically low lake levels.

Lacustrine sediments and associated terraces provide evidence for the past existence of five major prehistoric lakes that occupied the Tinajani Basin during the Pliocene and Pleistocene. Within the northern Altiplano (Tinajani Basin), these prehistoric lakes were Lake Mataro at an elevation of 3,950 m, Lake Cabana at an elevation of 3,900 m, Lake Ballivián at an elevation of 3,860 m, Lake (North) Minchin at an elevation of 3,825 m, and Lake (North) Tauca at an elevation 3,815 m. The age of Lake Mataro is uncertain and may be as old as Late Pliocene. Lake Cabana possibly dates to the Middle Pleistocene. Lake Ballivián existed between 120,000 and 98,000 BP. Two high lake stands, between 72,000 - 68,000 BP and 44,000 - 34,000 BP, have been discerned for Lake Minchin within the Altiplano. The high lake levels of Lake Tauca have been dated as having occurred between 18,100 and 14,100 BP.