Miospore lateral distribution in upper Famennian alluvial lagoonal to tidal facies from eastern United States and Belgium

Abstract

Miospore assemblages from continental rocks of mid late Famennian age of the Hampshire Formation of Virginia and West Virginia, U.S.A., are compared with those from the nearly coeval marine facies of the Ourthe Valley, Belgium. Eighteen spore taxa from the type Famennian 2c section in Belgium are also found in the continental beds of Virginia and West Virginia. Nearshore sediments carry more uniform and richer miospore assemblages than any one continental facies. Offshore currents or barriers, however, can alter the mixture of miospores coming from various land source areas by different drainages. Onshore autochthonous and allochthonous beds generally show correspondence between the recovered megafossils and the miospore assemblages. But the miospore assemblages enable us to distinguish between deposits resulting from short-term flooding episodes, those of autochthonous upland backswamps and deltaic marshes. We can thus distinguish upstream from downstream environments in our continental samples. Near-shore sediments in Belgium show a dominance of upstream over downstream derived miospores that suggests frequent strong floods in their fluvial systems.