Karst drainage of lake Chakanbacán and its relation to Icaiche Formation.

Sudden drainage of Lake Chakanbacán (also known as Om or Chakambacab) occurred naturally and without warning between 19 and 21 August, 2018. Lake Chakanbacán, located in southern Quintana Roo, 16.5 Km WNW of Nicolás Bravo, Quintana Roo is part of the western edge of the composite Morocoy-Nuevo Becak polje. Slumping associated with lake drainage has opened up fractures on the west bank of the lake, exposing gypsum of the Icaiche Formation. This occurrence establishes the western lake bank as the easternmost known outcrop of Icaiche gypsum in the area. Drainage of Lake Chakanbacán appears to be part of a karst process that proceeds by rapid dissolution and selective removal of layers of gypsum of the Icaiche Formation beneath the lake bed. Thus, the August 2018 lake drainage may demonstrate, in real-time, an ongoing weathering process responsible for a major regional geomorphic feature: the numerous internally drained karst depressions (poljes) up to >100km long in Campeche and southern Quintana Roo. It has been proposed that these poljes are collapse features resulting from removal in solution of gypsum of the Icaiche Formation. They occur both within and adjacent to a large area where the Icaiche Formation crops out, and, notably, over an estimated 10000 km2 or more within that formation where massive beds of gypsum are present on the surface or beneath a thin protective cap of rock resistant to chemical weathering. [ABSTRACT FROM AUTHOR]