New Mexico Geological Society Annual Spring Meeting — Abstracts

This research documents a moderately well preserved, previously undescribed fossil leaf assemblage from the Crevasse Canyon Formation near Carthage, New Mexico. The Crevasse Canyon Formation has been correlated with two other localities, near Riley and near Truth or Consequences, for which the depositional environments have been established. The new flora is being analyzed in the context of the depositional environments described by Wallin (Truth or Consequences) and Johansen (Riley). Near Truth or Consequences the Crevasse Canyon Formation was deposited in a mixed sandy lagoonal setting and in mixed and suspended load streams of moderate sinuosity on an upper coastal or deltaic plain. The thick-bedded sands were interpreted as channel fill deposits, and moderately sorted sandstones as crevasse splay deposits. Near Riley the Crevasse Canyon is largely the consequence of crevasse splay deposits that comprise a wedge of coastal plain and littoral sediments which prograded northeastward into the western interior seaway. The important fossil-bearing strata in the Crevasse Canyon Formation at Carthage compare most favorably with the fluvially deposited rocks at Truth or Consequences and Riley. Both Wallin and Johansen note fossil plant material, but none as well preserved as the leaf material at Carthage, where one known bed of well-preserved leaf material occurs with more widely distributed fossilized tree trunks and vertebrate bone fragments. Taking the leaves in context with the associated rocks, we can better constrain the local depositional environment of the Crevasse Canyon Formation, and learn more about late Cretaceous climate in central New Mexico. So far, three of the taxa collected have been identified, including Quercus viburnifolia, Ficus sp., and cf. Plantanus sp.