The NSS Bulletin - ISSN 1090-6924
Volume 56 Number 1: 32-37 - June 1994

A publication of the National Speleological Society

Two New Types of Gypsum Speleothems from New Mexico: Gypsum Trays and Gypsum Dust
José María Calaforra and Paola Forti

Abstract

In this paper two new types of speleothems are described, and their genesis is discussed on the basic of the available climatic and hydrodynamic data. The speleothems are located in the Permian-age gypsum karst area of New Mexico, in several caves close to Carlsbad and Roswell (Rocking Chair Cave and Parks Ranch Cave). Inside of these caves gypsum speleothems are widespread and more developed than in the other gypsum karst areas of the world. In two cases the gypsum speleothems were identified which now or have never been described before in the literature. Gypsum trays are a type of stalactite with sub-horizontal development and a maximum axis of elongation outwards from the wall (Rocking Chair Cave). They are the product of evaporation and air flow direction and velocity, which factors control deposition and the expansion level of the speleothem. Gypsum dust is a powdery deposit (crystal size arrange between 15-30µ) located on the walls and ceiling of the first 300-500 m of Parks Ranch Cave, close to the entrance. Scanning electron microscope observations show that the dust is composed of small aggregate grains of gypsum crystals partially cemented by very small calcite grains (3-5% CaCO3 total dust composition). Its genesis is related to seasonal variations of deposition (dry conditions) and dissolution (flood conditions).

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