Abstract: Paleoecologic Potential of Microboring Organisms

Ronald D. Perkins

Microboring organisms comprised of blue-green algae, green algae, red algae, fungi, and microsponges are believed to have high paleoecologic potential with respect to paleobathymetry and paleoclimatology. Endolithic organisms, generally less than 100 µm in size, actively penetrate carbonate substrates and their remains or resultant microborings constitute a decipherable part of the sedimentary record. Holocene marine sediments collected at depths ranging from the intertidal to more than 1,000 m and from climatic settings ranging from polar to tropical have been analyzed for their contained microborings. Several components of the endolithic assemblages from polar, temperate, subtropic and tropic latitudes appear to be provincial in their distribution; others tend to be cosmopolitan and distributed more with regard to the effective penetration of light; i.e., the compensation depth.

Although there is considerable overlap within the depth distribution of individual endoliths, the upper part of the photic zone is characterized by a dominance of blue-green and green algae that gives way with depth to red algae and finally to heterotrophic fungi. Microsponges appear to be distributed most widely at depths generally greater than 18 m and are found from the tropics to polar waters, where they tend to dominate the endolithic assemblage.

The ubiquitous distribution of microborings within marine sediments, their small size, and their climatic and depth responsiveness reflected in assemblage differences, all suggest a potentially useful tool for environmental reconstruction. Preliminary examination of ancient sediments ranging in age from Pleistocene to early Paleozoic has revealed that excellent preservation of endolithic organisms is possible and that their paleoecologic potential as environmental indicators is high.

AAPG Search and Discovery Article #90972©1976 AAPG-SEPM Annual Convention and Exhibition, New Orleans, LA