New Mexico Geological Society Annual Spring Meeting — Abstracts

The Lamy Amphibian Quarry in Santa Fe County, New Mexico is stratigraphically low in the Upper Triassic (Adamanian) Garita Creek Formation. First discovered and collected by Harvard University in 1938, then reopened by the National Museum of Natural History (Smithsonian) in 1947 and in the 1960’s, in 2008 the New Mexico Museum of Natural History opened the quarry a fourth time. The quarry mostly produces well-preserved, disarticulated bones of the large temnospondyl amphibian, Buettneria perfecta. Some phytosaur material and sparse dinosaur/dinosauromorph bones are present together with a microfauna of amphibian and fish bones, scales, and teeth. The quarry bonebed is 3 m above the top of the Santa Rosa Formation in a 4-m-thick mudstone interval overlain by a 1.5 m-thick multistoried channel sandstone complex. The uppermost Santa Rosa conglomerate contains large bone fragments of phytosaur, metoposaur and aetosaur and underlies 2 m of red mudstone/siltstone at the base of the Garita Creek Formation. This unit is overlain by 2 m of red and green, massive, mottled mudstone with small, sparse, carbonate concretions and abundant Paleophycus burrows that contains the bonebed. The bones are coated with a thin (~ 1mm) carbonate layer and show moderately well-developed SW-NE orientation (most flow is to the NE), indicating the bones are allochthonous to the bonebed, having been transported there and current aligned to some extent. A 10- to 20-cm-thick bed of yellowish-brown mudstone with carbonate concretions up to 8 cm in diameter overlies the bonebed and is overlain by a channel sandstone that has numerous large plant stems and a few possible bone fragments. The bonebed-bearing mudstone complex shows lateral continuity for hundreds of meters and represents distal floodplain and floodplain pond facies. Within these facies, intercalated siltstone and fine-grained sandstone stringers represent individual sheetflood deposits. The uppermost yellowish-brown mudstone with concretions is a paleosol. The overlying crossbedded channel sandstone complex has erosively cut into the mudstone beds. Its multistoried character implies fluctuations in the flow regime.