Abstract:
Algal stromatolites that contributed to the formation of bioherms of the Shawnee Group (Virgilian Stage, Upper Pennsylvanian) have historically been attributed to the Chlorophyta (green algae) and Cyanobacteria ("blue-green algae"). Archaeolithoplyllum, a genus of the Rhodophyta (red algae) had previously been identified in the Toronto Limestone, a regressive limestone of the Shawnee, but in no other member of the group. Therefore, field and laboratory work was conducted to: (1) confirm the published report of the presence of red algae in the Toronto Limestone; (2) search for red algae in other regressive limestones of the Shawnee Group; and (3) make preliminary interpretations of the bioherm environment based on the stromatolitic morphology of the algae.
Archaeolithoplyllum was identified in the Toronto, Ervine Creek, and Hartford limestones, but not in the Beil and Plattsmouth limestones. The Toronto, Plattsmouth, and Hartford limestones display only spheroidal stromatolites; the Beil Limestone contains only laterally linked hemispheroidal stromatolites; and the Ervine Creek Limestone has only vertically stacked hemispheroidal stromatolites.
Results of this study: (1) confirmed the presence of red algae in spheroidal stromatolites in the Toronto Limestone; (2) documented for the first time the presence of red algae in spheroidal stromatolites in the Hartford Limestone; and (3) discovered vertically stacked hemispheroidal stromatolites of red algae in the Ervine Creek Limestone. Because all previous reports in the literature of red algal stromatolites are of spheroidal structures, this is the first documentation of red algae forming vertically stacked hemispheroidal stromatolites.
