Tropical Floras of the Late Pennsylvanian-early Permian Transition: Carrizo Arroyo in Context

The flora of Carrizo Arroyo is typical of a seasonally moisture-limited environment. Dominant elements were conifers, callipterids and the pteridosperm Sphenopteridium, all plants usually associated with indicators of seasonal moisture regimes. More generally, the Virgilian-Wolfcampian transition was a time of change from dominance of the tropical landscape by floras rich in tree ferns, pteridosperms, and lycopsids, to one dominated by conifers, peltasperms, and cycadophytes. The two types of floras do appear to have overlapped, but possibly in a manner reflective of local landscape heterogeneity. At Carrizo Arroyo for example, the wetland elements are rare and fragmentary, indicating local transport, most likely from wet microhabitats proximate to the site of deposition. Local environmental heterogeneity appears to have been part of larger scale heterogeneity in the region, probably reflective of climatic and edaphic differences in this tectonically active 105