ABSTRACT

Hemispheroid algal stromatolites and related stromatolite structures are found in intimate association with hydrozoa in the lowest biofacies zone of reef cores in the James Reef Complex (Lower Cretaceous) at Fairway Field, Texas. The stromatolite growth forms most commonly encountered are discrete forms that often grow from the upper surfaces of hydrozoa, and irregular forms that fill the irregular spaces between hydrozoa. Forms less commonly encountered include those that drape the sides of vertically-oriented hydrozoa and laterally linked hemispheroids.

The James stromatolites grew in a subtidal environment since: (1) the hydrozoa-stromatolite zone reflects the deepest water conditions during reef core development; (2) the 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 found in association with in-place marine organisms in other organic reefs and banks of the geological section. Obviously algal stromatolites are not restricted to the intertidal environment only.