Paleontology of Cretaceous Coon Creek Editors Dana Ehret, Lynn Harrell & Sandy Ebersole BULLETIN ALABAMA MUSEUM of NATURAL HISTORY
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Bulletin 33 May 1, 2016 Paleontology of Cretaceous Coon Creek Editors Dana Ehret, Lynn Harrell & Sandy Ebersole BULLETIN ALABAMA MUSEUM OF NATURAL HISTORY The scientific publication of the Alabama Museum of Natural History. Dr. Dana J. Ehret, Editor. BULLETIN ALABAMA MUSEUM OF NATURAL HISTORY is published by the Al a bama Museum of Natural History, a unit of The University of Alabama. The BULLETIN succeeds its predecessor, the MUSEUM PAPERS, which was ter mi nat ed in 1961 upon the transfer of the Museum to the University from its parent orga ni za- tion, the Geological Survey of Alabama. The BULLETIN is devoted primarily to scholarship and research concerning the natural history of Alabama and the Southeast. It appears twice yearly in consec u tive ly numbered issues. 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Digital versions of the Bulletin are available online through Ebscohost. When citing this publication, authors are requested to use the following ab bre vi- a tion: Bull. Alabama Mus. Nat. Hist. ISSN: 0196-1039 Copyright 2015 by The Alabama Museum of Natural History Bulletin 33 May 1, 2016 Bulletin 32 June 1, 2015 Paleontolgy of the Cretaceous Coon Creek Editors Dana Ehret, Lynn Harrell & Sandy Ebersole THE UNIVERSITY OF ALABAMA TUSCALOOSA, ALABAMA MAY 1, 2016 The Late Cretaceous Coon Creek Formation type section; an introduction to the lithofacies and time-equivalent units Sandy Ebersole Geological Survey of Alabama Tuscaloosa, AL, U.S.A. [email protected] INTRODUCTION AND SETTING in 2005 by this author from the Coon Creek type section at The Coon Creek and Ripley Formations are fossiliferous creek level to 10 feet (~3 m) above creek level contained Q. Late Cretaceous shallow marine clastic units that extend trifidum (pers. comm. C. Smith), and Wade (1926) noted N. along the eastern side of the Mississippi Embayment (Figs. 1 hyatti present at the type section, placing the Coon Creek and 2) and Eastern Gulf Coastal Plain in North America. In in the uppermost Campanian. Additional samples taken Tennessee, the Coon Creek has formation status with an in the Ripley Formation in Mississippi ranged from latest upper and lower facies. In Mississippi, however, the Coon Campanian to early Maastrichtian based on nannofossil Creek facies is a part of the time-equivalent Ripley Formation. assemblages (Ebersole, 2010). The continuation of The Ripley lithology also more closely resembles that of the research on cephalopods (such as Larson’s article, volume Coon Creek upper facies in Tennessee. 2) and fossil pollen (such as Baghai-Riding’s article, Following the Coon Creek Formation type locality’s first volume 2) will continue to help correlate units within the comprehensive taxonomic review by Bruce Wade (1926), the region. Coon Creek Formation type section (Figs. 1 and 2) located in McNairy County, Tennessee, and its equivalent facies in the region have for decades been of great interest to paleontologists, LITHOLOGY OF THE COON CREEK FACIES geologists, and stratigraphers in the southeastern U.S. and Gulf Coastal Plain (see Brister and Young, this volume). This The upper facies of the Coon Creek and much of bulletin highlights some of the paleontological interests, the Ripley consists of dark gray (sometimes brownish or collection history, and research at the type section and other greenish), micaceous, glauconite-bearing, silty to clayey Coon Creek and Ripley outcrops. sand, with local siderite concretions. While fossiliferous in some locations (see the article by Harrell, Gibson, and Langston, volume 2), this upper facies is generally poorer AGE AND BIOSTRATIGRAPHIC in preservation when compared with the Coon Creek lower CORRELATIONS lithofacies. The lower facies of the Coon Creek (present at the type section) is gray (sometimes bluish or greenish, The definition of the Maastrichtian Stage base includes and brownish when more weathered), micaceous, clayey the auxiliary taxa ranges of the last occurrence (LO) of sand. The Coon Creek and Ripley are overlain by the the ammonite Nostoceras hyatti (Odin and Lamaurelle, McNairy Sand and underlain by the Demopolis Chalk 2001a) and the LO of the calcareous nannofossil Quadrum (Russell and Parks, 1975). trifidum (Odin and Lamaurelle, 2001b). Samples collected The type section itself is approximately 40-feet-thick Bull. Alabama Mus. Nat. Hist. 33:1–4 May 1, 2016 2 BULLETIN 33 May 1, 2016 FIGURE 1. The Coon Creek type section in McNairy County, Tennessee, with horizons and fossil material as discussed in the text. For a correlated stratigraphic chart with other formations in the region, see Brister and Young, this volume. (~12.2 m) from the base of the creek to the soil horizon The lower 23 feet (~7 m) is the most fossiliferous in terms of the forested hill top (Fig. 1). The color of the sediment of well-preserved bivalve and gastropod fauna, with specimens varies from medium bluish gray for fresh exposures in from the lower 10 feet (~3 m) in particular having the best the creek (and down section closer to the underlying shell preservation (Fig. 3), including some with preserved Demopolis Chalk), to medium dark gray and dark olive nacre. Cephalopods, scaphopods, and decapods are found gray above the creek, and progressing to more brown throughout the lower 30 feet (~9.1 m), with some horizons and yellow tones up to 25 feet (~7.6 m) from the base. containing a greater abundance of decapods that is traceable Above this, light brown and dark yellowish orange colors down the creek. Burrows are found in most of the section and dominate. Multiple samples from the lower 20 feet (~6.1 lignitic plant material is found in at least two horizons (5 feet m) of the type section were collected in 2005 by this (~1.5 m) and ~30 feet (~9.1 m)). The lower 10 feet (~3 m) and author and were sieved and found to be 65–75% fine- to below the stream base is calcareous, and samples collected in very- fine-grained quartz sand. X-ray diffraction analyses 2005 were rich in calcareous nannofossils. of Coon Creek lower facies samples in the McNairy County Concretions can be found at multiple horizons (9, 16, and area collected in 2003 showed a mineralogical makeup 36) and some contain decapod and ammonite material. At ~20 averaging 15–20% illite, 10–15% kaolinite, 60–65% feet (~6.1 m) is a chalybeate horizon, with iridescent ochre- to quartz, ~5% muscovite, and traces of glauconite, biotite, rusty-colored leachate. A reddish brown moldic, condensed and heavy minerals such as ilmenite (Keller, 2003). Illite, zone creates an overhang from ~25 to 30 feet (~7.6 to 9.1 m). a gray clay, is the main contributor to the color (Fig. 3) at This resistant, condensed, iron-cemented sandstone (Figs. 1 the type section, and may also contribute to preservation and 3) contains a wide variety of taxonomically diverse internal quality. and external molds and some body fossils. Above this zone, the Ebersole The Late Cretaceous Coon Creek Formation type section 3 FIGURE 2. The Coon Creek Formation type section (black star) in McNairy County, Tennessee, and its correlated upper Campanian to lower Maastrichtian outcropping lithostratigraphic units outlining the upper Mississippi Embayment. Modified from Ebersole, 2010. Formations on map are geospatial data from state geologic maps (Miller et al., 1966; Bicker, 1969; McDowell et al., 1981; Szabo et al., 1988; Haley et al., 1993; Middendorf et al., 2003; Kolata, 1981). sand is brownish in color, coarser, and has some cross bedding and sand-clay laminations. PRESERVATION AND DEPOSITIONAL ENVIRONMENT The lower Coon Creek facies is highly fossiliferous in many locations (Fig. 3, and image on the front of this volume) with high preservation quality and high molluscan diversity. This has been identified as a lagerstätte as noted by Dunagan and Gibson (1993) and Gibson and Dunagan (2003). High preservation quality of the lower facies may be due, in part, to the highly impermeable non-swelling (illite) and very FIGURE 3. An example of the Coon Creek fossiliferous low-swelling (kaolinite) clay component. The preservation matrix with Crassatellites, Pterotrigonia, and other quality and diversity may also be associated with the protected bivalves. Coon Creek type section in a bank of the environment of deposition. Elongate, cross-bedded lenses Coon Creek, McNairy County, Tennessee. Brown rocks of lower McNairy Sand are found within the Coon Creek in the photo are talus from the overhanging resistant Formation in some locations (Russell and Parks, 1975). These sandstone above the creek. relict barrier bars and islands are age-equivalent to the Coon Creek, and, in the late Campanian, would have provided wave nearshore environments (not behind barrier islands), as protection for the back-barrier setting of the Coon Creek described by Russell and Parks (1975) and Ebersole (2010). For depositional environment (Ebersole, 2010). Upper facies of illustrations of the paleogeography of this area, see Brister and the Coon Creek and the Ripley are interpreted as open marine Young (this volume).