- GeoRef, Copyright 2008, American Geological Institute. Reference includes data from Bibliography and Index of North American Geology, U. S. Geological Survey, Reston, VA, United States
Hemispheroid algal stromatolites and related stromatolite structures are found associated with hydrozoa in the lowest biofacies. The stromatolite growth forms are discrete forms, often growing from the upper surfaces of hydrozoa, irregular forms fill spaces between hydrozoa, and some drape sides of hydrozoa. The James stromatolites grew in a subtidal environment since: (1) the hydrozoa-stromatolite zone reflects the deepest water conditions during reef core development; (2) intimate and varied growth associations between hydrozoa and stromatolites can be explained only as having developed under subtidal marine conditions; and (3) hemispheroid stromatolites and related forms are associated with in-place marine organisms in other organic reefs and banks of the geologic section. Obviously the algal stromatolites are not restricted to the intertidal environment only.