Lateral and Temporal Facies Variations in a Quaternary Travertine Deposit, Belen, New Mexico

This study examines the spatial relationships within travertine deposits, including variations in facies, constituents, and porosity, in two Quaternary travertine quarries near Belen, New Mexico. It integrates a combination of field examination and laboratory analyses, which allows for the interpretation of multiple scales of features. The travertine was deposited as tongues on the hanging wall of a fault on the western edge of the Rio Grande Rift. The quarries are composed of primary travertine and interbedded conglomerate layers that have been cross-cut by multiple generations of fractures, resulting in abundant veins filled with carbonate precipitates. A wide variety of constituents, including both biotically and abiotically induced features, are present within the field area. The travertine within the quarries transitions, both laterally and temporally, between terrace mound and sloping mound morphologies. The terrace mound morphology exhibits distinct pools and rimstone dams. The pools have vertically stacked horizontal layers that are composed of bacterial shrubs, pisoids, rafts, and foam rock. Rimstone dams are composed of thin, vertical layers of ray-crystal crusts that separate the pools. The location of the terrace pools and rimstone dams was fairly stationary, but through time the height of the rimstone dam decreased and the morphology of the deposit transitioned into a sloping mound. The sloping mound is composed of layers that dip between 5 and 20 degrees. The layers range from smooth slopes that are composed of feather dendrites to microterraced slopes with rapidly fluctuating pools and rimstone dams. The length of the microterrace pools depends heavily on the slope of the layer, but regardless of length, they are composed of crystal fans, rafts, and pisoids. Both primary and secondary processes form the porosity within the quarry. The shape and connectivity of the pores is heavily dependent upon the constituents and degree of cementation. The permeability is anisotropic due to the layered natured of the travertine deposit, but the presence of abundant vertical fractures increases the vertical permeability. The knowledge gained from this study can be used in conjunction with other studies to provide a model that will be beneficial in areas where data are difficult to obtain, such as in the subsurface.