CAVE FORMATION IN A COLLAPSE PALEOSOL BRECCIA IN THE DOLOMITIZED SEROE DOMI FORMATION, ARUBA

A reconnaissance trip aimed at documenting the occurrence of karst features within the Seroe Domi Formation on Aruba was conducted in December of 2012. Aruba, located in the Lesser Antilles, is classified as a composite island according to the Carbonate Island Karst Model. Payoff Cave, located within a dolomitized section of the Seroe Domi Formation on Aruba, contains remnant features of a paleosol collapse breccia. The collapse breccia implies at least one previous generation of cave development present in this location. The morphology and speleogenic mechanism of the original void is unknown; however, the current cave is classified, based on morphology, as a flank margin cave. Flank margin caves develop in the mixing zone at the flank of an enclosing landmass and the distal margin of a discharging freshwater lens.

After the first-generation cave was formed, sea level fell, and it was filled with the paleosol collapse breccia. The breccia is composed of clasts and soil material that entered the cave through collapse. Following subsequent sea level rise, the cave was once again located at the distal lens position. This second-generation void was created as the dissolutional zone of the lens easily dissolved the more soluble paleosol breccia, giving the cave its current morphology. The higher solubility, coupled with the likely higher permeability of the paleosol breccia, focused dissolution within the collapse fill. The paleosol breccia is now found as bedrock pillars and wall rock within the cave.

The diagenetic events documented in this cave suggest multiple stages of dissolution coupled with diagenetic alteration of limestone to dolomite. It is possible that dolomitization is related to the first-generation karstification event. Detailed petrography and geochemical analysis will determine the exact timing of diagenetic events that created this unique cave.