LOWER-MIDDLE DEVONIAN (PRAGIAN-LOWER GIVETIAN) CONODONT BIOSTRATIGRAPHY, MIDDLE DEVONIAN SEA LEVEL RECORD 18 AND ESTIMATED CONODONT APATITE δO SEA SURFACE TEMPERATURE CHANGES IN THE SOUTHERN ILLINOIS BASIN, USA James E. (aka Jed) Day1, Sofie Gouwy2 and Kenneth G. MacLeod3 1Geography
& Geology, Illinois State University, Campus Box 4400, Normal, IL 61790-4400,
[email protected], 2Department of Paleontology, Royal Belgian Institute of Natural Sciences, Vautierstraat 29, B-1000, Brussels, B-1000, Belgium, 3Department of Geological Sciences, University of Missouri-Columbia, Columbia, MO 65211
ABSTRACT Investigation of the Devonian stratigraphy, conodont biostratigraphy and conodont apatite δ18O geochemistry of the Clear Creek, Grand Tower and St. Laurent formations was conducted in southern Illinois to develop refined biostratigraphic correlations, constrain the timing of 3rd order sea level changes and estimate stable oxygen isotopic paleotemperature changes of Devonian sea surface waters along the southern continental margin of Laurussia. Conodonts from the White County Core indicate a Pragian age for the upper Clear Creek Formation in the subsurface of White County. At Grand Tower (Jackson Co.), conodonts document an upper Emsian age (serotinus Zone) of the lower Dutch Creek Member of the Grand Tower Fm. and place the Emsian-Eifelian Stage boundary 7 m above the base of the Dutch Creek. The remainder of the Dutch Creek is lower Eifelian age (costatus Zone). Drowning of sandy platform deposits of the Dutch Creek by deeper subtidal muddy carbonates of the “upper Member” of the Grand Tower Fm. records the first Eifelian sea level rise within the australis Zone (first occurrence of P. pseudofoliatus). Conodonts from deposits within a second marine flooding interval in the upper part of the “upper Member” identify a late Eifelian marine flooding event within the kockelianus zone. A third Middle Devonian flooding surface occurs at the contact of the Grand Tower and St. Laurent fms. and falls within the ensensis Zone. The lowest I. obliquimarginatus in the lower St. Laurent suggests a basal hemiansatus Zone (Givetian age), followed by the first occurrence of P. timorensis (timorensis Zone).
Upper Mb – Grand Tower Fm.
Dutch Creek Mb Grand Tower Fm. Upper Mb – Grand Tower Fm.
Analysis of Icriodid P1 elements gives δ18O values ranging from 17.4 and 21.2 ‰V-SMOW through the middle Grand TowerSt. Laurent formations suggesting considerable changes in subtropical temperatures and/or changes in local seawater δ 18O values in the southern Illinois Basin during the Eifelian and Early Givetian. Within the mid-upper Grand Tower Formation, δ18O values decrease by 4‰ then increase by 2.5‰. In the overlying St. Laurent Formation, values decrease by 1‰. If solely due to temperature, these values suggest warming of up to 16°C during the middle Eifelian followed by a 11°C cooling in the Late Eifelian and 4°C warming in the Early Givetian.
Saint Laurent Fm.
Dutch Creek Mb Grand Tower Fm. Dutch Creek Mb Grand Tower Fm.
Upper Mb – Grand Tower Fm.
Clear Creek Chert/Fm.
A
Joe Devera of the ISGS for scale
Dutch Creek Mb – Grand Tower Fm.
FIGURE 2A.—Lithostratigraphy and previous correlations of the Lower to Middle Devonian (Lochkovian-Middle Givetian) marine sedimentary rocks in the southern Illinois Basin as proposed in earlier investigations including : Orr 1964, Collinson (1967), Collison & Atherton (1975), Faunfelter & Devera (1989), and Norby (1990). Photographs are of outcrops of the Clear Creek, the Dutch Creek and Upper members of the Grand Tower Formation, and Saint Laurent Formation north of the town of Grand Tower in Jackson County, Illinois (see Fig. 1B).
A FIGURE 8.—Plots of genus specific δO18 values of skeletal apatite of species of Icriodus, Latericriodus and Polygnathus from the Devils Bake Oven outcrop sections (Fig. 1), and estimated Sea Surface Temperature (SST) values using the equation of Kolodny et al. (1983), assuming an ice-free world and a Devonian sea-water composition equal to the present one. Calibrated to the current international conodont zonation based on revised-refined correlations. Positions of Middle Devonian marine flooding events as in Fig. 3.
RESULTS AND CONCLUSIONS Biostratigraphy & Sea Level Event History (figs. 3, 4 & 9) •Outcropping Clear Creek, Grand Tower, St. Laurent formations are of Emsian (serotinus Zone) to Lower Givetian age (timorensis Zone). •Emsian-Eifelian Stage (Lower-Middle Devonian) Boundary (base of partitus Zone) is in middle of Dutch Creek Mb. of the Grand Tower Fm. in the outcrop
B
•The Marine flooding event that initiated Grand Tower (Dutch Creek Mb.) deposition is within the Emsian serotinus Zone.
FIGURE 1A.— Middle Devonian (Eifelian-Early Givetian) paleogeography of Euramerica showing location of study sites in southern part of the subtropical epeiric Illinois basin area (after Blakey). The southern Illinois Basin was positioned within an embayment north of the Ouachita continental margin of southwestern Euramerica with the Rheic Ocean to the south. 1B.—Locations of surface outcrop and subsurface core sections of Early to Middle Devonian (Pragian-Middle Givetian) subtidal inner and middle shelf carbonate and sandy carbonate platform deposits in the Grand Tower area in Union County, and the Illinois State Geological Survey White County Core in White County, Illinois.
•The Upper Member of type Grand Tower is entirely Eifelian in age (costatus to ensensis zones). FIGURE 3.—Early-Middle Devonian lithostratigraphy and revised conodont biostratigraphy of the Clear Creek, Grand
FIGURE 4.—Conodont sequence in 197 samples documented by S. Gouwy & J. Day through
Tower and Saint Laurent formations based on study of 112 samples by S. Gouwy & J. Day taken every 50 cm through the Devils Bake Oven and 12 samples in the Devils Backbone sections in the Grand Tower area in Jackson County, Illinois (Fig. 1B). Positions of marine flooding surfaces of sea level rises of Euramerican Devonian Transgressive-Regressive Cycles IC to If of Johnson et al. (1985) are shown by green arrows. The Bake Oven section was sampled by Day and ISU students in 2005 & 2006, and the Devil’s Backbone section by Gouwy, Devera, and Day in 2011.
the Early-Middle Devonian Clear Creek, Grand Tower and Saint Laurent formations in the Illinois State geological Survey’s White County Core (Fig. 1B). Charles Collinson of the ISGS and assistants processed alternate one foot (30 cm) intervals through the entire 6 inch diameter ISGS White County core for conodonts in the1960s. Depth of formation contacts after Collinson & Schwalb (1955).
•The Marine flooding event that initiated Upper Member (Grand Tower Fm.) deposition is within the Eifelian costatus Zone, with a second flooding event within the kockelianus Zone •The Eifelian-Givetian Stage Boundary (base hemiansatus Zone; Walliser et al., 1995) is within the lower St. Laurent Fm. in the surface and subsurface sections. • The marine flooding event at the Grand-Tower-St. Laurent contact is within the ensensis Zone (Late Eifelian). •The upper “Clear Creek” Formation Collinson and Schwalb (1955) in the White County Core is Pragian (Lower Devonian) in age. •The “Grand Tower “ Formaton” of Collinson and Schwalb (1955) in the White Core spans the entire Emsian & most of the Eifelian Stage.
δ18O Stratigraphy & Estimated SSTs (Figs. 7 & 8) •Analyses of conodont apatite of Latericriodus, Icriodus & Polygnathus provide a δ18O record spanning the late Emsian to Early Givetian. •δ18 O values show a distinct shift to lower numbers in the lower part of the australis-kockelianus-ensensis zones interval and a distinct increase in its upper part after fluctuations in its middle part. •A decrease of nearly 1 ‰ marks the uppermost part of the Eifelian and is followed by an increase and decrease in the lower part of the Givetian.
FIGURE 7.—Plots and comparison of FIGURE 5.—Everything you ever wanted to know about conodonts, including: known stratigraphic range, craniate chordate affinities, skeletal chemistry, utility as high-resolution biostratigraphic tools; and geochemical paleoceanographic and paleoclimatic proxies. Color Alteration Index (CAI) refers to the degree of color changes to elements of the feeding apparatus undergo in response progressively higher temperature conditions related to burial and hydrothermal affects (Epstein, 1977, Harris & Eptsein, 1977). CAI values of all conodonts analyzed for this investigation were 2.
FIGURE 6.—Procedures and methods used by S. Gouwy in K. MacLeod’s stable isotope lab at the University of Missouri for isolation and δ18O analysis of conodont apatite. Genus- and species –specific analyses were done on specimens from the same samples, where sample yields permitted, for comparison and assessment of difference in δ18O between genera because of vital effects.
δ18O
values of skeletal apatite of species of Icriodus, Latericriodus and Polygnathus from the Devils Bake Oven outcrop and ISGS White County core sections. Oxygen isotope data is plotted to scale in meters above the base of the surface section, and depth positions in the core section, calibrated to the current international conodont zonation. Positions of Middle Devonian marine flooding events as in Fig. 3.
•Assuming an ice-free world and a Devonian sea-water composition equal to the present one, paleotemperature reconstruction would give estimated SST° between 16° and 35° C (Kolodny et al., 1983). •The δ18O data would then indicate an important T° increase in the lower part of the australis-kockelianusensensis zones followed by a stepped decrease . The EG boundary interval is marked by a fluctuation to slightly higher T°C.
FIGURE 9.—Previous (Collinson et al. 1968) and revised – refined biostratigraphic correlations proposed for the Early Middle Devonian strata of the southern Illinois Basin.
REFERENCES CITED COLLINSON, C., 1968, The north-central region, United States, in Oswald, D.H., ed., International Symposium on the Devonian System, Calgary, Alberta, 1967: Calgary, Alberta Society of Petroleum Geologists Memoir, 1, 933-971. COLLINSON, C., and ATHERTON, E., 1975, Devonian System, in Willman, H.B., et al., eds., Handbook of Illinois Stratigraphy: Illinois State Geological Survey, Bulletin 95, 104-123. COLLINSON, C. and SCHWLAB, DEVERA, J. A., and G. H. FRAUNFELTER, 1989. Middle Devonian paleogeography and tectonic relationships east of the Ozark Dome, southeastern Missouri, southwestern Illinois and parts of southwestern Indiana and western Kentucky. In McMillan, N. J., Embry, A. F., & Glass, D. J. (eds.). Devonian of the World, Canadian Society of Petroleum Geologists Memoir 14, 3: 179-196. JOHNSON, J.G., KLAPPER, G. & ELRICK, M., 1996. Devonian transgressive-regressive cycles and biostratigraphy, northern Antelope Range, Nevada: Establishment of reference horizons for global cycles. Palaios 11, 3–14. JOHNSON, J.G., KLAPPER, G. & SANDBERG, C.A., 1985. Devonian eustatic fluctuations in Euramerica. Geological Society of America Bulletin, 96, 567-587. KOLODNY, Y., B. LUZ, and O. NAVON. 1983. Oxygen isotope variations in phosphate of biogenic apatites; I, Fish bone apatite; rechecking the rules of the game. Earth and Planetary Science Letters, 64(3), 398. NORBY, R.D., 1990. Biostratigraphic Zones in the Illinois Basin. American Association of Petroleum Geologists Memoir 51, 179-194. ORR, R.W. , 1964. Conodonts from the Devonian Lingle and Alto formations of southern Illinois. Illinois State Geological Survey Circular . WALLISER, O.H., BULTYNCK, P., WEDDIGE, K., BECKER, R.T. & HOUSE, M., 1995. Definition of the Eifelian-Givetian Stage Boundary. Episodes, 18 (3), 107-115.
ACKNOWLEDGEMENTS •National Science Foundation (NSF) – MacLeod’s
funding of Post-Doctoral
Research Appointment for S. Gouwy 2010-2011.
• Illinois State Geological Survey (ISGS) - Ancillary Mapping Program Funding (2005-2006) to Day supporting Investigation of Clear Creek, Grand Tower & St. Laurent Fms.
• United States Geological Survey (USGS) - Support of Day’s investigation of Devonian conodont apatite geochemistry, and S. Gouwy during Fall 2011 & Spring of 2012
• ISGS Scientists – J. Devera, R. Norby, D. Mikulic, Z. Lesemi • ISU Students – T. Arospide, K. Biondo, A. East, J. Clark, J. Breeden
