New Mexico Geological Society Annual Spring Meeting — Abstracts

The section of Paradise Formation exposed in the Peloncillo Mountains marks the northern and western most exposure of Paradise in New Mexico. The Paradise Formation is 60 m in the Central Peloncillo Mountains and is composed of a series of yellowish-brown weathering, slope-forming, mixed carbonates and siliciclastics. Stratigraphically the Paradise lies conformably above the Escabrosa Group, and disconformably below the Pennsylvanian Horquilla limestone. Although the Paradise in the Peloncillos has undergone at least one relatively mild metamorphic event, many of the original depositional textures in the carbonates remain intact allowing for some interpretation of depositional environments.

In the Peloncillo Mountains the Paradise Formation can be divided into several informal members. A lower siliciclastic-dominated member, a middle carbonate-dominated and an upper fine-grained siliciclastic-dominated member. The lower siliciclastic member consists of a single lithofacies composed of fme-grained, rounded to subrounded, quartz arenites. The middle carbonate member is composed of either a grain rich or a grain poor lithofacies. The grain-rich lithofacies contains abundant ooids, pelmatozoan fragments and rare brachiopods. The grain-poor lithofacies is composed entirely of medium-grained, equigranular sparry calcite. Very fine-grained to silt sized quarts is found in trace amounts throughout the carbonates. Overlying the carbonate member is a series of interbedded carbonates and shales. The carbonates are similar to those in the middle member. For the most part any textures in the shales were obliterated during metamorphism.

The lower member is interpreted as representing deposition in a shallow, offshore, siliciclasticdominated system as sea level gradually fell during the Late Mississippian. On a Q-F-R diagram these sandstones plot exclusively on the Q pole indicating that these are recycled sands derived from a cratonic source. The middle carbonate member marks a return to a more stable, clear-water carbonate conditions. The
abundance ooids and abraded grains suggest a location well within the zone of constant agitation in a, warm sea. The upper member marks a return to a clastic dominated system where a significant influx of silt and clay size material acted to reduce carbonate production during the final stages of Paradise deposition. While the sources of the terrigeneous material in the Paradise Formation are not well established, the changes in the rate of sediment delivery to the basin are consistent with increased tectonism related to the onset of the Ouachita Orogeny.