CONTRIBUTIONS FROM THE MUSEUM OF PALEONTOLOGY THE UNIVERSITY OF MICHIGAN VOL. 24, No. 11, p. 119-123 (1 text-fig.) OCTOBER4, 1973 PALEOECOLOGICAL INTERPRETATION OF THE ROGERS CITY LIMESTONE (MIDDLE DEVONIAN, NORTHEASTERN MICHIGAN) BY ROBERT M. LINSLEY Colgate University, Hamilton, New York 13346 MUSEUM OF PALEONTOLOGY THE UNIVERSITY OF MICHIGAN ANN ARBOR CONTRIBUTIONS FROM THE MUSEUM OF PALEONTOLOGY Director: ROBERTV. KESLING The series of contributions from the Museum of Paleontology is a medium for the publication of papers based chiefly upon the collection in the Museum. When the number of pages issued is sufficient to make a volume, a title page and a table of contents will be sent to libraries on the mailing list, and to individuals upon request. A list of the separate papers may also be obtained. Correspondence should be directed to the Museum of Paleontology, The University of Michigan, Ann Arbor, Michigan 48104. VOLS.2-23. Parts of volumes may be obtained if available. Price lists available upon inquiry. VOLUME24 1. A new species of Porocrinus from the Middle Ordovician Kimmswick Limestone of Missouri, by Robert V. Kesling. Pages 1-7, with 2 plates and 8 text-figures. 2. Strataster devonicus, a new brittle-star with unusual preservation from the Middle Devonian Silica Formation of Ohio, by Robert V. Kesling. Pages 9-15, with 2 plates and 3 text-figs. 3. Coccoliths and related calcareous nannofossils from the Upper Cretaceous Fencepost Limestone of northwestern Kansas, by John M. Huh and Charles I. Smith. Pages 17-22, with 2 plates. 4. Ordovician vertebrates from Ontario, by Kathleen Anne Lehtola. Pages 23-30, with 2 plates and 1 text-figure. 5. New Botryocrinus and Glossocrinus from the Middle Devonian Bell Shale of Michigan, by Robert V. Kesling. Pages 31-46, with 8 plates and 2 text-figures. 6. Evolution of Middle Devonian species of Euglyphella as indicated by cladistic analysis, by Sabeekah Abdul-Razzaq. Pages 47-64, with 12 text-figures. 7. Euglyphella bellensis, a new Middle Devonian ostracod from Michigan, by Robert V. Kesling. Pages 65-67, with 1 plate. 8. The stereomic microstructure of the blastoid endoskeleton, by Donald B. Macurda, Jr. Pages 69-83. with 8 ~lates. 9. A new species of ~letiheriufrom the Middle Silurian Fiborn Limestone of Michigan, by Robert V. Kesling, Terry L. Chase, Cynthia H. Devore, and Robert D. Lattanzi. Pages 85-99, with 8 plates and 1 text-figure. 10. Silicified cones and vegetative remains of Pinus from the Eocene of British Columbia, by Charles N. Miller, Jr. Pages 101-118, with 5 plates. PALEOECOLOGICAL INTERPRETATION OF THE ROGERS CITY LIMESTONE (MIDDLE DEVONIAN, NORTHEASTERN MICHIGAN) ROBERT M. LINSLEY Colgate University, Hamilton, New York 13346 INTRODUCTION near Rogers City providing almost six miles of THE ROGERSCITY LIMESTONEwas named by continuks exposu;e in thewalls of the quarry. My interest in the Rogers City was initially Ehlers & Radabaugh (1938) when they recog- nized that the upper part of what had been stimulated by G. M. Ehlers and R. V. Kesling known as the Dundee Limestone of Presque of The University of Michigan Museum of Isle County, Michigan, had a lithology and Paleontology. I had the very good fortune to fauna distinct from that of the lower part of accompany both of these gentlemen into the the "Dundee Limestone" (the "true" Dundee) . field in the northern Michigan area during the It was recognized that the Rogers City fauna late 1950's, and for the last six years I have was similar to that found in the Winnipegosis been working on various aspects of the mag- Formation of Manitoba, Canada, and differed nificent gastropod fauna found in these beds. strikingly from the faunas in the underlying The Rogers City Limestone was originally Dundee Limestone and the overlying formations described (Ehlers & Radabaugh, 1938) as con- of the Traverse Group. sisting of four units which were faunally and The Rogers City Limestone outcrops in lithologically distinctive. More recently it was the northeastern part of the Michigan Basin. redescribed (Ehlers & Kesling, 1970) as having Because of extensive glacial cover the number six distinctive units. As this latest description of exposures are relatively few, but because of is more complete and consistent with the paleo- the chemical purity of the limestone two large ecological interpretations I give below, I shall quarries have been opened in the formation and, add my own observations to it. as a result, the formation is well exposed and LITHOLOGY AND GENERAL PALEONTOLOGY understood in these two localities. OF THE ROGERS CITY LIMESTONE The total outcrop belt extends roughly 30 miles from Middle Island near Rockport The paleontology of the Rogers City Lime- Quarry to a point about two miles west of stone has not been given the attention it de- Rogers City where it disappears beneath the serves. It had never been treated in its en- glacial drift. The two major outcrops of the tirety until the publication by Ehlers & Kesling ( 1970). The magnificent plates that accompany Rogers City Limestone are in the Calcite Quarry their article (pls. 9-12) give an idea of the rich- of Michigan Limestone Operations of the U.S. ness and diversity of the fauna of the Rogers Steel Corporation at Calcite, SSE of Rogers City Limestone. Beyond this paper the only City ("the world's largest limestone quarry") group that has received any concerted attention and the Quarry of Presque Isle Corporation is the Bivalvia, which has been discussed by (formerly Lake-of-the-Woods Quarry) in east- LaRocque (1949a, 1949b). More recently ern Presque Isle County, Michigan. In addi- Kesling (1971 ) published on a most unusual tion there are smaller surface outcrops on starfish from the lower units of the formation. Middle Island, the beach north of Rockport The two basal stratigraphic units of the Quarry, a good series of beach exposures on Rogers City Limestone are termed the the north and east sides of False Presque Isle, Emanuella zone (Ehlers & Kesling, 1970). The lowest unit (unit 1) is an extremely fine poorer exposures on Presque Isle south of the grained dolomitic limestone about six feet thick. lighthouse, the Adams Point Quarry, and two The bedding is thin, and upon weathering the small road cuts west of Rogers City. rock breaks up into slabs that are two to three As a result our entire knowledge of the inches thick. The rock is essentially a buff- surficial Rogers City Limestone is based on colored stone that is mottled with dark about eight localities. Fortunately, two of these brownish-gray splotches. An examination of localities are indeed extensive, with the quarry thin sections and peels shows that this mottling 120 ROBERT M. LINSLEY is caused only by a variation in color and there Other fossils from unit one include the is no evidence of textural change over the color trilobite Dechenella (D.) valentini and crinoid boundaries. In most of the rock of unit one columnals. Although the unit has been ex- there is no evidence of depositional structures tensively collected, it still yields surprises; such as graded bedding, banding, flute casting, recently a rare starfish, Michiganaster inex- orientation of grains, tracks, and trails, nor pectatus Kesling, was found (Kesling, 197 1) . any evidence of burrowing. Only at one spot, Unit two of the Rogers City Limestone is on the southwest side of the Calcite Quarry of only two feet thick and is generally considered the Michigan Limestone Operations of the U.S. transitional between units one and three. It is Steel Corporation, SSE of Rogers City, Mich- still a dolomitic limestone, though with less igan, have I found a bed preserving rather magnesium than unit one. Like unit one, this thick mud cracks, to break this monotony. unit is irregularly mottled by dark-gray The one obvious variant in the unit is splotches on the light, buff-colored rock. It is created by the presence of discontinuous hori- thicker bedded than unit one and fossils are zontal bands of fossils; these shell hashes repre- less abundant. No bands of shells have been sent the only occurrence of fossils in unit one. found in this unit. The bands tend to be very thin, usually only Ehlers & Kesling (1970) characterize units one shell-width in thickness but occasionally a three to six of the Rogers City Limestone as band of shells may be up to an inch thick. The the O~nphalocirrus zone. Within this larger bands are extremely well sorted as to size and zone they separate unit three as the Atrypa shape of hard parts; consequently some bands zonule and unit four as the Gypidula zonule. may be made up almost exclusively of one spe- Unit three, the Atrypa zonule, is brownish cies of organism. The frequent presence of to buff-gray, even-bedded, porous limestone the brachiopod Emanuella aff. E. meristoides about five and one-half feet thick. The matrix (Meek) in these bands prompted Ehlers & of this unit is composed of silt-size particles of Kesling ( 1970) to propose the name Emanuella lime containing bioclastic debris composed zone. largely of fragmented brachiopod shells and These bands of shells contain a wide di- crinoidal debris. Occasionally small clumps of versity of fossils, including the brachiopods micrite can be seen in the bioclastics. The Carinatina dysmorphostrota (Crickmay) and a brachiopod Atrypa arctica Warren dominates productid in addition to Emanuella. The pelecy- the fauna of this rock, but a few specimens of pods include four described by LaRocque Gypidula can be found. Buechelia, Gyronema, ( 1949b) : A ctinopterella calliotis, A. peninsu- "Omphalocirrus," and other gastropods also laris, Leptodesma furcistriata, and Limoptera occur sparsely. (Myalinodonta?) migrans. The smaller gastro- Unit four, the Gypidula zonule, is a dark, pods are particularly well represented by one fine-grained, thick-bedded limestone with a loxonematid, two murchisonids, three belle- brownish-gray color.