Burrows of Callianassa major Say, geologic indicators of littoral and shallow neritic environments

Abstract

Burrows of the marine decapod, Callianassa major Say, are important structures in sand beaches along the coast from Florida to North Carolina. Abundant burrows, whose physical characteristics are described herein, can be seen in the low littoral zone and on offshore bars that are exposed at low tide. Detailed work in the area of Sapelo Island, Georgia, indicates that Callianassa major is confined to the high-energy littoral and shallow neritic environments. Sandstone of Pleistocene age at Racoon Bluff on Sapelo Island and at Sutherland Bluff on the Georgia mainland, 5 miles to the west, contains abundant structures that have been identified as burrows made by Callianassa major. These burrows establish that this Pleistocene sandstone was deposited in a littoral and shallow neritic environment. Structures, identified as Halymenites Sternberg or Ophiomorpha Lundgren and identical with Callianassa Leach burrows, in sandstones of Cretaceous age in the Rocky Mountain area presumably were formed by Callianassa or similar organisms. These fossils in the Upper Cretaceous rocks of Wyoming are confined to sandstone that has been deposited in shallow neritic and littoral environments. INTRODUCTION AND ACKNOWLEDGEMENTS The interpretation of depositional environments of ancient sediments is of prime importance in geologic investigations. Paleogeographic maps, which show the distribution of ancient seas and land areas, are based on the interpretation of ancient environments. In addition, the environment is the primary control in the development of facies. In studying paleogeography or facies, determining the position of the shoreline or the change from marine to nonmarine conditions is of paramount importance. The numerous studies of Recent sediments along the oceanic margin of the United States and elsewhere in the world are aimed at a better understanding of present environments of deposition. Through these studies the geologist hopes to improve his interpretations of ancient environments and thereby to reconstruct more accurately the geologic events recorded in ancient sediments. During the summer of 1961, while studying the Quaternary sediments of Sapelo Island and adjacent areas (Text-fig. 1), the writers observed burrow structures in Recent sands along the Atlantic coast which are characteristic of the low littoral and shallow neritic environments. The burrows, made by the decapod Callianassa major Say, have been described in detail in ecological studies by Lunz (1937), Pearse, et al. (1942), Pohl (1946), and others. The main question to be answered in evaluating the geologic importance of these structures is whether or not the burrows are preserved in the geologic record. Observations of similar structures in Pleistocene strata of the Georgia Coastal Plain convinced the writers that burrows made by the decapod Callianassa major Say have been preserved in the geologic record; are useful in interpreting littoral and shallow neritic deposits; and in determining the position of Pleistocene shorelines (Hoyt & Weimer, 1963; Hoyt, Weimer, & Henry, 1963). The purpose of this paper is to describe Callianassa major burrows in Recent deposits; to discuss the significance of Pleistocene occurrences; and to relate Cretaceous and Tertiary fossils of previously questioned origin to Callianassa major or to organisms with similar burrowing habits. This work was supported in part by the National Science Foundation under Grant NSFG16426. The use of facilities provided by the Sapelo Island Research Foundation is gratefully acknowledged. The report represents Contribution No. 58 from the Marine Institute, University of Georgia, Sapelo Island, Georgia. The writers express thanks to L. S. Land who determined the mineral composition of the cementing material in Recent Callianassa major burrows and to H. C. Kent for reviewing the manuscript. This paper was presented before the American Association for the Advancement of Science, Section E, December 27, 1961, in Denver, Colorado. THE ANIMAL, CALLIANASSA MAJOR SAY The species, Callianassa major, was named by Say (1818) for a decapod crustacean that he collected near Jacksonville, Florida, approximately 70 miles south of Sapelo Island, Georgia. Hay & Shore (1918) made brief mention of the animal in describing decapod crustaceans and emphasized the scarcity of C. major along the