The relative significance of depth and substrate in lower paleozoic community distributions

Abstract

Consideration is given to the factors which control the changing composition of stratigraphic arrays of Lower Paleozoic communities dominated by brachiopods and other filter feeders. Most environmental factors can be represented by depth and substrate while the major time-dependent factors are evolution, biogeographic changes related to tectonism and climate, and ecologic succession. Because evolutionary, biogeographic and depth-related events occur much less frequently, and by several orders of magnitude, than events involving changes in substrate, it is possible to isolate substrate as an independent factor and evaluate its significance in controlling community composition. But first stratigraphic arrays of communities must be shown to be non-random and not due to ecologic succession. This method was applied to a Silurian section in north New Brunswick with results that indicate that substrate plays a subsidiary role as an independent factor and that depth is probably the most significant control on the distribution of Lower Paleozoic brachiopod communities.