ROLE OF ORGANIC MATTER IN FORMATION OF STROMATOLITES AND MICRITIC OOIDS FROM CHANNING LAKE BED BASIN; RITA BLANCA FORMATION; PANHANDLE, TEXAS

The Channing lake beds occur in the Texas Panhandle about 65 km northwest of Amarillo. The approximately 55 km2 paleo-lake basin includes a complex of lakebed facies of Pliocene and Pleistocene age (Rita Blanca Formation, Ogallala Group). Our study locality is about 10 km west of Channing, TX, and focuses on stromatolites distributed sporadically, and directly overlying a ~25-cm-thick, well-consolidated, micritic ooid bed. The exposure is along a tributary of Rita Blanca Creek, and extends up to ~ 3.5 m beneath the surface of the High Plains. The stromatolites are spherical to subspherical ranging from 10.5 cm to 30 cm in diameter. Surface textures range from 1-mm deep circular bumps to 16-mm deep finger-like columns. Scanned sections of these stromatolites show multiple phases of growth. Interior textures include thrombolitic fabric, as well as accumulations of ostracodes and micritic ooids. Equant calcite crystals surround organic-rich, micrite cores. SEM images reveal remnants of microbial filaments and irregular surface textures typical of organic matter. The ooids and the associated ostracodes suggest that the stromatolites formed in a shallow, alkaline lake. Understanding the role of organic matter in formation of the stromatolites may have significant implications for other fields including medicine and industry.