CIRCULAR EARLY PERMIAN THROMBOLITES IN THE GOULDBUSK LIMESTONE MEMBER OF THE MORAN FORMATION, BURKETT, TEXAS

Circular mounds between 0.3 and 4 meters in diameter, found in the Gouldbusk Limestone Member of the Moran Formation, are Early Permian thrombolites with a unique form. All mounds are approximately 0.1 meters high, have raised rims with lower interiors and larger mounds have raised central peaks. Some are isolated and, in one instance, join an elongated raised platform, composed of coalesced circular mounds, by small raised isthmuses. On the hand sample scale, burrowing and boring by fusulinids (Schwagerina and Pseudoschwagerina) are visible, as are skeletal mesozoans in the mounds’ rim’s interior. Thin section analysis of the mounds show the classic clotted fabric of thrombolites. The thrombolite community under study covers 1,460 square meters, not including a portion that is currently submerged. Additional exposures of the same community are visible upstream of the one studied. The study area’s community consists of 56 individual and coalescing mounds distributed across an algal boundstone. Using satellite imagery and image analytical software, a distribution of the mounds’ size and spacing was created. Further searches for similar structures of the surrounding 5 km² using Google Earth proved fruitless and none have been reported from the Gouldbusk Limestone. A search of the literature has failed to produce any thrombolitic mounds with a structure like this anywhere, at any time, in the geologic record.