MARSH FORAMINIFERAL PATTERNS, PACIFIC COAST OF NORTH AMERICA

Resumen

Foraminiferal populations were analyzed from Pacific marshes between Alaska and northern Mexico. The following geographic assemblages are distinguished: a Californian assemblage in northern Mexico and southern California, an Oregonian assemblagefrom Oregon to Vancouver, British Columbia, and a sub-Artic assemblage in Alaska and British Columbia north of Vancouver. Distinctive faunas within a marsh characterize the tide flat, marsh channel, low marsh and high marsh environments. The largest living populations are in the high marsh. Relative rates of sediment deposition, based on population ratios, are high. Relative deposition rates are higher in the northern than in the southern marshes; this is related to heavy runoff in the northern areas and no runoff in the southern marshes examined.

There are more species in the southern marsh faunas than in the northern ones. Nearshore, opean-ocean species are introduced into the southern faunas with undiluted nearshore water which inhabits the southern lagoons. In the northern areas high runoff restricts invasion of open-ocean water and species. Northern marsh fauna are almost 100% of arenaceous species which generally characterize low salinity areas of high runoff. Southern faunas have an appreciable content of calcareous specimens, a result of open-ocean influence.