Paleobiogeographic patterns in the Middle and Late Devonian emphasizing Laurentia

The relative importance of tectonism and sea-level change in driving Middle to Late Devonian biogeographic patterns in marine invertebrates is investigated using phylogenetic biogeography. Taxa considered include two clades of brachiopods, one bivalve clade, and a suborder of phyllocarid crustaceans. These organisms colonized different depositional environments and played different roles in the Devonian ecosystem which allows biogeographic patterns to be considered in a cross-faunal analysis. Vicariance patterns are well resolved and may reflect biogeographic relationships developed in the Early to early Middle Devonian due to the uplift of intracratonic arches. Uplift of tectonic arches is inferred to occur during times of tectonic quiescence during the second and third (and possibly also the first) tectophase (after Ettensohn, F.R., 1985. The Catskill Delta complex and the Acadian Orogeny: a model. In: Woodrow, D. L., Sevon, W. D. (Eds.), The Catskill Delta. Geological Society of America, Boulder, CO, Special Paper 201, pp. 39-49.) of the Acadian orogeny. Geo-dispersal patterns are not as well resolved, but may indicate dispersal across tectonic arches during downwarping associated with increased compressional tectonism during Ettensohn's (1985) [Ettensohn, F.R., 1985. The Catskill Delta complex and the Acadian Orogeny: a model. In: Woodrow, D. L., Sevon, W. D. (Eds.), The Catskill Delta. Geological Society of America, Boulder, CO, Special Paper 201, pp. 39-49] tectophases II and III. Geo-dispersal across relatively low arches may also be coincident with transgressive events IIa and IIc of Johnson et al. (1985) [Johnson, J.G., Klapper, G., Sandberg, C.A., 1985. Devonian eustatic fluctuations in Euramerica. Geological Society of America Bulletin 96, 567-587]. The overall lack of congruence between the vicariance and geo-dispersal patterns suggests that singular, tectonic events exerted more profound influence on Devonian biogeography than cyclical changes in sea level. Furthermore, the offset in perceived timing between vicariance and geo-dispersal patterns may indicate a fundamental change in the style of biogeographic patterns during the Middle Devonian and may have played a major factor in regulating biodiversity dynamics during the Late Devonian biodiversity crisis.