Sequence Boundaries and Chronostratigraphic Gaps in the Llandovery of Ohio and Kentucky: the Record of Early Silurian

Home , Bisher Formation, Brassfield Formation, Dayton Formation, Estill Shale, Osgood Formation

Research Paper

GEOSPHERE Sequence boundaries and chronostratigraphic gaps in the Llandovery of Ohio and Kentucky: The record of early Silurian

GEOSPHERE; v. 12, no. 6 paleoceanographic events in east-central North America

doi:10.1130/GES01343.1 Nicholas B. Sullivan1, Patrick I. McLaughlin2, Carlton E. Brett3, Bradley D. Cramer4, Mark A. Kleffner5, James R. Thomka6, and Poul Emsbo7 1Chemostrat Inc., 3760 Westchase Drive, Houston, Texas 77042, USA 14 figures; 1 table 2Indiana Geological Survey, 611 N. Walnut Grove Street, Bloomington, Indiana 47405, USA 3Department of Geology, University of Cincinnati, 7148 Edwards One, Cincinnati, Ohio 45221, USA 4Department of Earth and Environmental Sciences, University of Iowa, 115 Trowbridge Hall, Iowa City, Iowa 52242, USA CORRESPONDENCE: nicksullivan@chemostrat 5Division of Earth History, School of Earth Sciences, Ohio State University at Lima, 4240 Campus Drive, Lima, Ohio 45804, USA .com; nsullivan742@gmail.com 6Department of Geosciences, Crouse Hall 114, University of Akron, Akron, Ohio 44325, USA 7U.S. Geological Survey, Federal Center, West 6th Avenue and Kipling Street, Lakewood, Colorado 80225, USA CITATION: Sullivan, N.B., McLaughlin, P.I., Brett, C.E., Cramer, B.D., Kleffner, M.A., Thomka, J.R., and Emsbo, P., 2016, Sequence boundaries and chrono ABSTRACT work has been hindered by a scarcity of index fossils, pervasive dolomitiza stratigraphic gaps in the Llandovery of Ohio and Ken tion, and the lack of a uniformly applied nomenclature (see reviews of Berry tucky: The record of early Silurian paleoceanographic events in east-central North America: Geosphere, New and published data are integrated herein to resolve the age and strati and Boucot, 1970; McLaughlin et al., 2008b; Brett et al., 2012). v. 12, no. 6, p. 1813–1832, doi:10.1130 /GES01343.1. graphic relationships for problematic strata of the Aeronian and Telychian This study integrates carbon isotope chemostratigraphy, facies analysis, (Llandovery; Silurian) in Ohio and Kentucky (USA). At least two major depo and sequence stratigraphy to resolve the depositional history of Llandovery Received 14 April 2016 sitional sequences were traced along the eastern flank of the Cincinnati Arch; units exposed in Ohio and Kentucky at the transition between the Appalachian Revision received 10 August 2016 these are separated by a regionally angular unconformity with complex topog foreland basin and Cincinnati Arch (Fig. 1). This new synthesis lays the ground Accepted 12 September 2016 Published online 25 October 2016 raphy. Underlying units are progressively truncated to the northwest while work for highly refined chronostratigraphic interpretations, a revised sequence overlying strata change facies, condense, and onlap in the same direction. stratigraphic framework, and a more complete understanding of the Silurian The basal unit of the upper sequence is the Waco Member of the Alger paleoenvironments and far-field tectonic activity in Laurentia. Shale Formation in Kentucky and southern Ohio and the Dayton Formation 13 in western Ohio. A persistent, positive carbonate carbon isotope (δ Ccarb) ex GEOLOGIC SETTING cursion associated with the mid-Telychian Valgu Event is recognized in the upper subunit of the Waco Member; the absence of a comparable signal in the Early Silurian Tectonics and Paleogeography Dayton Formation corroborates interpretations that it is significantly younger. The correlations proposed here can be used to understand the nuanced The study area is situated near the western margin of the Appalachian depositional history and chronostratigraphic completeness of the lower Basin, which was located at ~lat 20°S–30°S during the early Silurian (Cocks Silurian in eastern North America. This framework can be used to characterize and Scotese, 1991). Starting in the Late Ordovician, accretion of island arcs sea-level history and local conditions that prevailed during global paleoenvi onto the eastern margin of Laurentia produced several episodes of moun ronmental events. tain building called the Taconian orogeny (Ettensohn and Brett, 2002). This produced structural loading and subsidence in the Appalachian Basin, which INTRODUCTION was rapidly filled with clastics flushed off the newly formed Taconic high lands (Beaumont et al., 1988; Ettensohn and Brett, 1998; Ettensohn, 2008). This The Aeronian and Telychian Stages of the Silurian record the transition event also created a structural arch on the western margin of the basin, pro from the Late Ordovician mass extinction and early Silurian recovery (Raup duced by flexure of the crust in response to the strain of accretion, and facili and Sepkoski, 1982; Sheehan, 2001; Krug and Patzkowsky, 2007) to the ecologi tated by deep-seated basement faults (Quinlan and Beaumont, 1984; Root and cal upheaval of the early Sheinwoodian Ireviken Event (Jeppsson et al., 1995; Onasch, 1999). Munnecke et al., 2003; Lehnert et al., 2010). The richly fossiliferous successions Toward the middle of the Rhuddanian, orogenic activity had begun to ta of eastern North America provide an important venue for study of this transi per, but renewed tectonism and uplift (the Salinic orogeny) is recorded by the tion (Zaffos and Holland, 2012), being represented by extensive exposures that thick packages of strata spanning the Llandovery to Ludlow Series (Goodman For permission to copy, contact Copyright have a long history of investigation (Hall, 1852; Orton, 1870; Foerste, 1906). and Brett, 1994; Ettensohn and Brett, 1998; Brett et al., 1998; van Staal et al., Permissions, GSA, or [email protected]. However, the temporal and stratigraphic resolution of this depositional frame 2009; Ettensohn et al., 2013).

Miami Columbus Madison 70 Franklin Silurian absent Silurian bedrock at the surface PLT CN JB CS Preble Dayton CV Silurian bedrock in the subsurface Greene Fig. 12 PNT Pickaway

Fayette 75 MN 71 Clinton MMNE MMSE Michigan MMSW NRF Basin Cincinnati Highland CCD SS Brown ESQ Adams BC Illinois Appalachian Basin 71 WU Basin Fig. 9 75

Bath 64 Lexington OVM

DCW IN Madison 0 mi 50 mi WWJY DCE Estill Fig. 11 0 km 50 km

Figure 1. Map showing the precise locations of studied outcrops and cores. Base maps were modified from GoogleEarth composite, Barry and Boucot (1970), Noger (1988), and 13 Slucher (2006). Black dots represent outcrops studied here; white dots represent cores. A label in bold indicates a succession for which new carbonate carbon isotope (δ Ccarb) 13 data were produced; a label in bold and italics indicates a succession with δ Ccarb data published in prior studies. Red lines denote the path of correlation cross sections in subsequent figures. These correlations are shown perpendicular to depositional strike. Abbreviations are shown in Table 1.

The study area is within a transitional zone between deep-water, mud- Chronostratigraphy dominated depositional environments of the central Appalachian Basin and the shallower, carbonate-dominated systems in the northwest (Fig. 2; Hunter, Conodonts are widely used for biostratigraphy in the calcareous lower 1970; Brett et al., 1990, 1998). The bathymetric high occupied by this bank Silurian rock units found in eastern North America (e.g., Rexroad et al., 1965; (the proto–Cincinnati Arch) approximates the axis of the modern Cincinnati- Rexroad, 1967; Rexroad and Nicoll, 1972; Cooper, 1975; Kleffner, 1987, 1994). Findlay-Algonquin arch system (Root and Onasch, 1999). However, most of this work was conducted prior to recent advances in the field

13 A δ Ccarb ‰ (VPDB) Ma –2.0 0.0 2.0 4.0 6.0

Kockelella ortus ortus 431.0

Kockelella walliseri Michigan Basin Ireviken 432.0 Ozarkodina sagitta rhenana woodian enlock bonate Kockelella ranuliformis Car

Shale W estrial Shein Pterospathodus procerus Terr 433.0 tz Sand Quar Upper Pseudooneotodus bicornis Lower Pseudooneotodus bicornis

Basin Axis Illinois 434.0 Basin Pterospathodus amorphognathoides amorphognathoides 0 100 200 mi 435.0 0 100 200 300 km Pterospathodus amorphognathoides lithuanicus

Pterospathodus amorphognathoides lennarti

436.0 Pterospathodus amorphognathoides Silurian Outcrop Subsurface Silurian angulatus ry elychian Pterospathodus eopennatus ssp. n. 2 Figure 2. Distribution of Silurian strata in the east-central United States; major structural and T depositional provinces are labeled (modified from Berry and Boucot, 1970; Beaumont et al., 437.0 1987). The area that forms the central focus of this study is outlined on this map. Prevailing facies Pterospathodus eopennatus ssp. n. 1 Valgu belts are overlain on the outcrop pattern (modified from Hunter, 1970; McLaughlin et al., 2012).

438.0 Distomodus staurognathoides of conodont biostratigraphy, most notably the development of highly refined

conodont biozonations (Fig. 3; Jeppsson, 1997; Jeppsson et al., 2006; Männik, Llandove 2007a, 2007b). Earlier reports of Llandovery conodonts from the eastern flank 439.0 Late Aeronian of the Cincinnati Arch employed a comparatively low resolution zonation that was inconsistently applied (see discussion by Kleffner, in McLaughlin et al., 2008b). Although these previous studies did much to constrain the age and Pranognathus tenuis correlations of Llandovery strata, new initiatives have demonstrated promise ronian 440.0 Early Aeronian

for a much greater refinement in conodont-based correlations (Loydell et al., Ae 2007; Kleffner et al., 2012; Cramer et al., 2011). Aspelundia expansa

These improvements coincide with the rise of carbonate carbon isotope 441.0 13 (d Ccarb) chemostratigraphy as a tool for correlation of Silurian rocks (Saltzman, 2002; Cramer et al., 2010, 2011). Discrete and time-specific intervals character Conodont Biozones 13 ized by high d Ccarb values (i.e., positive excursions) have recently been char acterized in the well-constrained sections of the Baltic region, Anticosti Island, Figure 3. Silurian chronostratigraphic standard used for regional and global correlations of lower Silurian stratigraphic units in this study. Conodont biozonations are modified from Jeppsson and the U.K. (e.g., Munnecke et al., 2003; Kaljo and Martma, 2006; Munnecke 13 (1997), Männik (2007a), and Melchin et al. (2012). Composite carbonate carbon isotope (δ Ccarb) and Männik, 2009; Hughes et al., 2014). Such signals are known to be resistant curve is modified from Cramer et al. (2011), Melchin et al. (2012), and McLaughlin et al. (2012). to late diagenetic alteration (Saltzman et al., 2000) and recognizable in a wide VPDB—Vienna Peedee belemnite.

variety of facies and depositional settings (McLaughlin et al., 2012). A wealth STRATIGRAPHIC FRAMEWORK 13 of new d Ccarb data has recently been summarized and integrated with bio 13 stratigraphic zonations to create a composite d Ccarb curve tied to the Silurian Mixed Carbonate-Shale Facies of Kentucky and Southern Ohio time scale, which provides a powerful tool for regional and global correlation (Fig. 3; Cramer et al., 2011). In east-central Kentucky and south-central Ohio, the names and definitions 13 Recognition of d Ccarb excursions in Silurian strata of eastern North Amer of Silurian stratigraphic units at group and formational rank have undergone ica has greatly facilitated correlation, even when biostratigraphic data are many revisions that are inconsistently applied (Fig. 4; Foerste, 1935; Rexroad limited (Saltzman, 2001; Cramer and Saltzman, 2005; Cramer et al., 2006; Mc et al., 1965; Simmons, 1967; McDowell, 1983; Ettensohn et al., 2013). However, 13 Laughlin et al., 2012). At least one global d Ccarb excursion has been recognized these stratigraphic divisions are invariably built around a succession of litho in Llandovery strata of the Appalachian Basin; this is closely associated with logically distinct subunits, the terminology of which has remained stable since the Valgu Event, a phase of biotic and climatic turnover recorded in the Ptero- the report by Foerste (1906) on the Silurian stratigraphy of the Cincinnati Arch. spathodus eopennatus conodont Superzone (Männik, 2005, 2007a; Munnecke In ascending stratigraphic order, this succession comprises the Brassfield, and Männik, 2009; McLaughlin et al., 2012). The Valgu excursion therefore pro Plum Creek, Oldham, Lulbegrud, Waco, and Estill units (Fig. 4; Foerste, 1906; vides a useful chronostratigraphic anchor for Llandovery strata in the western Brett and Ray, 2005; Ettensohn et al., 2013). Appalachian Basin. The upper beds of the Brassfield, sometimes informally referred to as the Rose Run iron ore or upper massive member, are genetically distinct from the underlying strata (Fig. 5; Foerste, 1906; Gordon and Ettensohn, 1984). The Sequence Stratigraphy subunit is recognizable by dark red, ferruginous dolograinstone bearing cog wheel-shaped crinoid columnals, commonly referred to as “beads” (Fig. 6; In Brett et al. (1990, 1998) a sequence stratigraphic framework was estab Foerste, 1906; Rexroad et al., 1965; McDowell, 1983), but more accurately iden lished for the Silurian of the Appalachian Basin that comprises six third-order tified as the morphogenus Floricolumnus (col.) sp. (Donovan and Clark, 1992). sequences (in ascending order, S-I to S-VI), roughly equivalent to group-level These show evidence of reworking out of the underlying shaly member of the stratigraphic units. Although the primary basis for this framework was the clas Brassfield (Thomka et al., 2013). sic Niagaran Series of western and central New York, it was subsequently ex The overlying Plum Creek Shale Member (of the Drowning Creek For tended into east-central Kentucky and south-central Ohio (Brett and Ray, 2005; mation) is a relatively thin (1–2 m) interval of blue-gray mudstone with silty Cramer, 2009). interbeds; this in turn is overlain by 3–4 m of bedded ferruginous dolostone Comparatively thick successions of siltstone, shale, and marl have been in and shale called the Oldham Member (of the Drowning Creek Formation), terpreted as highstand and falling stage deposits in these sections (Brett et al., which is characterized by abundant brachiopods, particularly the distinct large 1990; McLaughlin et al., 2008b). Transgressive intervals are often associated pentamerid Ehlersella norwoodi (Foerste, 1906; Rexroad et al., 1965). In the with authigenic minerals (e.g., glauconite, hematite, phosphate, or pyrite), southern part of the study area, the Oldham and Waco are separated by the abundant conodonts, hardgrounds and/or firmgrounds, and reworked clasts Lulbegrud Shale Member (of the Alger Shale Formation), a 3–5-m-thick, unfos (see Brett et al., 1998; McLaughlin et al., 2008a). The link between these un siliferous blue-gray shale (Foerste, 1906). usual facies and transgression has been attributed by some to condensation In the vicinity of central Kentucky, the Waco consists of a 1-m-thick basal (i.e., Brett et al., 1990; McLaughlin et al., 2008a); however, factors relating to carbonate horizon overlain by 3–4 m of green-gray shales interbedded with seawater chemistry and redox conditions likely play an important role as well fossiliferous dolostones and siltstones; however this is sometimes truncated (McLaughlin et al., 2012). by the sub-Devonian Wallbridge Unconformity (Fig. 7; Foerste, 1906, 1935; Mc The rocks studied here have been assigned to sequences S-I, S-II, and Dowell, 1983; Sullivan et al., 2012). The contact with the overlying Estill Shale S-IV; sequence S-III was presumed absent in Ohio and Kentucky due to a Member of the Alger Shale Formation is a cryptic shale-shale boundary, recog regional angular unconformity beneath S-IV in New York that progressively nizable by abundant, granular glauconite overlain by one or more bands of truncates underlying beds to the west (Fig. 4; Brett et al., 1990, 1998; Brett and bright red mudstone (Rexroad et al., 1965; McDowell, 1983). Ray, 2005). New chronostratigraphic data suggest that stratigraphic units pre At localities in southern Ohio, the Waco manifests as stacked dolomitic viously recognized as the basal transgressive systems tract of S-IV are of differ carbonates that were historically labeled “Dayton” (Fig. 4; Rexroad et al., ent ages in Ohio (Cramer, 2009; McLaughlin et al., 2008b, 2012; Kleffner et al., 1965; McDowell, 1983). Here it can be subdivided in to a lower light colored, 2012), Kentucky (Sullivan et al., 2014a), and New York (Loydell et al., 2007; fossiliferous subunit, informally termed white Waco, and an upper ferrugi Sullivan et al., 2014b). Ongoing work (Sullivan et al., 2012; Ettensohn et al., nous, heavily bioturbated subunit, termed the orange Waco (Fig. 8; Sullivan 2013) attempts to reconcile these new results with the sequence stratigraphic et al., 2014a). In southern Ohio, the Estill unit is a thick succession of green, interpretations in Brett et al. (1990). red, and maroon shales with zones of abundant glauconite and occasional

Foerste, Foerste, Foerste, Rexroad Simmons, McDowell, Gordon & Hull Brett and McLaughlin Brett Sullivan 1897 1906 1935 et al., 1967 1983 Ettensohn, et al., Ray, et al., et al., et al., 1965 1984 2004 2005 2008b 2012 2014a Schematic Pro le Ribolt Estill Estill Estill Estill Estill Estill

Estill HST Dayton east S-IV Equivalent (Upper)

Alger A

Alger shale -c co co co co co co co Alger Shale Alger Shale d TST d entral Kentuck y Wa Wa Wa Wa Wa Wa Wa basal

late lbegrud lbegrud lbegrud lbegrud lbegrud lbegrud lbegrud HST Lu Lu Lu Lu Lu Lu Lu Crab Orchar Crab Orchar CRAB ORCHARD CRAB ORCHARD CRAB ORCHARD CRAB ORCHARD B m Noland S-II TST ields Oldham Oldham Oldha Oldham Oldham Oldham Oldham ower) Plum Plum (L Plum Plum Plum eHST Plum Indian F Creek Plum Creek Creek Creek Creek Creek Creek iron ore ferruginous bed “bead bed” upper massive A TST upper massive d d u. shaly u. shaly Figure 4. A comparison of different litho

ON thin bed HST

Drowning Creek stratigraphic terminology from various ref Brass eld B Drowning Creek asseld Lower S-I TST erences for Llandovery stratigraphic units CLINT Br Brass eld Brass el Brass eld Massive Brass eld Brass el in east-central Kentucky, south-central Richmond Richmond Richmond Drakes Drakes Drakes Ohio, and western Ohio. Each area is ac companied by a schematic weathering south Ohio and nor Ribolt Estill profile, drawn only loosely to scale. Gray r shading indicates intervals and areas not Estill HST Estill Dayton Estill Estill Alge Alger Estill S-IV Equivalent discussed by a given study. Text in italics Alger A orange indicates member rank stratigraphic units; / Dayton Dayton Dayton co TST Dayton/Waco white capital letters indicate group rank strati Wa

elds late HST Lulbegrud Lulbegrud . ayton

Fi graphic units (when specified). Note that . Oldham

D Oldham CRAB ORCHARD CRAB ORCHARD CRAB ORCHARD Noland B TST Oldham Oldham some of the studies included (i.e., Sim Plum undi

S-II Creek undi Indian Plum Creek mons, 1967; Slucher, 2006) were large-

Creek eHST Plum Creek Drowning Plum Creek iron ore ferruginous zone bead bed A upper massive upper massive TST th- scale mapping projects not necessary Upper Upper Drowning HST focused on resolving highly refined strati CRAB ORCHARD shaly shaly central Kentuck N d Creek graphic units. In addition, for Brett and Ray d Thin- Thin- bedded bedded Brass eld Drowning Creek B (2005) only their sequence stratigraphic r CLIN TO

asseld S-I terminology was summarized; that study Brass el we Brass eld TST Brass eld Br Brass el

Lo also employed lithostratigraphic terminol Massive ogy, not shown here, which follows that of Belfast Belfast Belfast Belfast A LST? Belfast Gordon and Ettensohn (1984) and Foerste (1906, 1935). Richmond Richmond Richmond Drakes Drakes Drakes yw

Niagara Niagara Shales / Osgood Osgood Osgood Osgood Osgood Osgood shales

Dayton Dayton Dayton Dayton Dayton Dayton Dayton

Beavertown Beavertown Beavertown est

Clinton -c

red d red d red or entral Ohio Clinton Brass eld mbr. Brass eld Montgomery or Brass eld Brass eld Bed Brass eld white Brass el white Brass el Brass eld mbr. B Belfast Belfast Belfast A

Centerville Centerville Drakes Drakes

Owingsville Manor (OVM) Martin Marietta Quarry (MMNE)

e Plum Creek Drowning Creek e Upper Massiv Upper Massiv

Estill E

co Wae”co Wa Upper Shaly 4 ft “orang

1 m Brassfield

0 m1 ft

Upper Massive 0 m 0 ft 0 m 0 ft

Figure 5. Lithologic characteristics of the informal upper massive (or Rose Run) member of the Brassfield Formation as displayed at an outcrop near Owingsville Manor, Bath County, Kentucky (left) and the northeast wall of the Martin Marietta quarry, Highland County, Ohio (right).

brown, dolomitic calcareous siltstone beds (Rexroad et al., 1965; McLaughlin Kleffner (1987). One of the co-authors on this study (Kleffner) identified zonal et al., 2008b, 2012). conodonts of the Pt. eopennatus Superzone in the Waco at Eagle Stone Quarry Many meters of strata, comprising the Plum Creek, Oldham, and Lulber in Brown County, Ohio (Figs. 2 and 9; McLaughlin et al., 2008b). This is con 13 grud units, separate the ferruginous upper massive member of the Brassfield sistent with elevated d Ccarb values (+2‰ to +3‰) recorded in the upper Waco, Formation and the Waco Member of the Alger Shale Formation in central interpreted as a local manifestation of the lower Telychian Valgu excursion Kentucky, but these units are progressively truncated to the northwest by a (McLaughlin et al., 2012). Although the lower Estill has not been placed within sub-Waco unconformity (Fig. 9). At its northern terminal extent, the Waco may the updated biozonation of Männik (2007a), the middle and upper parts of the directly overlie the Brassfield (Figs. 5 and 8). unit have been assigned to the Pt. am. amorphognathoides Zone based on Age control for these strata is limited. Conodont samples from the Brass the occurrence of Oz. polinclinata and Pt. am. amorphognathoides (Kleffner, field have yielded specimens of Distomodus kentuckyensis and Ozarkodina reported in McLaughlin et al., 2008b). hassi, suggesting a Rhuddanian or possibly earliest Aeronian age for this unit (Cooper, 1975; Kleffner, in McLaughlin et al., 2008b). The presence of the Carbonate-Dominated Facies of Western Ohio brachiopod Ehlersella in the Oldham also points to a middle Aeronian age (Rexroad et al., 1965; McLaughlin et al., 2008b). In western Ohio, the sub-Waco unconformity caps a complex association of Although conodonts are sparse in the Waco, McDowell (1983) assigned lower Silurian dolograinstone and shale containing abundant corals, echino it to the Pterospathodus celloni Zone. The lower Estill was also assigned to derms, and cephalopods (Fig. 10). This is commonly called the Brassfield For the Pt. celloni Zone by McDowell (1983). The rest of the unit was assigned mation, but its precise relationships to strata of that name in central Kentucky to the Pt. amorphognathoides Zone, a diagnosis that was later corroborated in are uncertain (McLaughlin et al., 2008b). It is informally subdivided into a lower

Unconformably overlying the red Brassfield is the Dayton Formation, which consists of light gray dolomitic carbonates that often display a styo litic, nodular texture. Unlike the Waco, it is sparsely fossiliferous, though rare pentamerid brachiopods are found (Fig. 10). Mineralized hardgrounds with abundant pyrite and phosphate occur at several horizons (Fig. 10; McLaughlin et al., 2008b). The overlying Osgood Formation is a succession of blue-gray mudstones interbedded with dolomitic marls that has been correlated with the upper Estill Shale (McLaughlin et al., 2008b, 2012; Brett et al., 2012). The 1 cm Dayton thins progressively to the west. In the vicinity of Preble and Miami Counties, Ohio, it is present only as a thin (10–20 cm) phosphatic carbonate horizon that overlies the red Brassfield (Kleffner, 1994; Kleffner et al., 2012). Pt. am. amorphognathoides and Oz. polinclinata have been recovered from the Dayton, suggesting a late Telychian age; Pt. am. amorphognathoides is also found in the lower Osgood, but the presence of Kockelella ranuliformis in higher strata suggest this stratigraphic unit straddles the Llandovery-Wenlock boundary (Kleffner, 1990; McLaughlin et al., 2008b; Kleffner et al., 2012). Ele 13 vated or rising-upward d Ccarb values in the Osgood are interpreted as features of the early Sheinwoodian Ireviken positive excursion (Munnecke et al., 2003; Cramer, 2009; McLaughlin et al., 2008b, 2012).

METHODS

We measured and sampled 20 outcrops along a proximal-to-distal tran sect of the Cincinnati Arch between Madison County, Kentucky, and Greene

1 cm County, Ohio (Fig. 3; Table 1). Material was collected at 10–30 cm intervals de pending on availability of carbonate. Powdered rock samples were generated 13 for d Ccarb analysis using a power drill with a tungsten carbide bit. Samples were generated from minimally altered samples, with the goal of isolating primary micrite. Vugs, stylolites, weathering varnishes, and other fea tures of clearly late diagenetic origin were avoided. Processed samples were sealed in plastic capsules and sent to the W. M. Keck Paleoenvironmental and Environmental Stable Isotope Laboratory (KPESIL) at the University of Kansas (Lawrence). Carbonate samples were mixed with phosphoric acid, and carbon dioxide produced by the reaction was analyzed by a ThermoFinnigan Gas Bench II in-line with a Finnigan MAT 253 isotope ratio mass spectrometer. The d13C and d18O values were analyzed with respect to internal standards and Figure 6. Close-up photographs of typical beads, the cog-wheel shaped carb carb remains of the crinoidal morphogenus Floricolumnus (col.) sp. These are are presented here in per mil (‰) notation, normalized to the Vienna Peedee a common component of the upper massive member of the Brassfield. belemnite standard.

white Brassfield, and an upper red Brassfield (Fig. 4; sensu McLaughlin et al., RESULTS 2008b). Recognition of the conodont Icriodina stenolophata and the brachio pod Ehlersella in the red Brassfield (Rexroad et al., 1965; C.B. Rexroad, per Physical Stratigraphy sonal commun., 1983) have led some to suggest equivalence with the Oldham of Kentucky (McLaughlin et al., 2008b). Although Rexroad et al. (1965) reported The Waco Member of the Alger Shale Formation and upper massive Floricolumnus (col.) sp. in the red Brassfield near the city of Dayton, this has member of the Brassfield vary little in their overall thicknesses and litho not been corroborated in subsequent field work, and other echinoderm faunal logic characteristics, which are recognizable at nearly every locality be data do not suggest a correlation (Ausich et al., 2015). tween Madison County, Kentucky, and Highland County, Ohio (Fig. 1).

Below: Hypichnial burrows (Teichichnus) above basal Waco carbonate bed.

Boyle (Devonian) 2 m

Figure 7. Lithology, facies, and stratigraphic relationships of the Waco Member of the Alger Shale 1 m Formation in the vicinity of its type area. A photograph of the outcrop at Drowning Creek West is shown at the top of the figure; major lithostratigraphic units are labeled. Diagnostic lithological basal features and common fossils of the Waco are shown. Waco

Lulbegrud Above: Favosites in the basal Waco carbonate beds.

0 5 cm Above: Carbonate horizon with pyritic surfaces at the base of the Waco Member.

Martin Marietta Quarry (MMSW) 2 m

05 cm Above: Polished slab at white/orange Waco orange Waco contact. Note piping of orange-green Estill sediment into underlying cavities.

1 m white Waco

shaly Brass eld Figure 8. Lithological characteristics and facies of the Waco Member in south-central Ohio near its northern most occurrence. The outcrop photos show the upper shaly member of the Brassfield, Waco, and lower Estill units d at the south wall of the Martin Marietta quarry. Typical sedimentary features ded Brass el and fossils of the Waco are shown. thin-bed

0 m

Hematitic rip-up clast of upper Coral fossils in the white Waco, Orange-stained burrows massive member of the Brass eld stained orange (ankerite?). in upper orange Waco. in basal white Waco.

GEOSPHERE | Volume 12 | Number 6 Sullivan et al. | Llandovery stratigraphy in Ohio and Kentucky Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/12/6/1813/1000625/1813.pdf 1821 by guest on 29 September 2021 on 29 September 2021 by guest Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/12/6/1813/1000625/1813.pdf Research Paper are shown at the right side of figure. The symbols and lithology fill keys used throughout this study are shown in the lower left. Arch. Dashed lines indicate a comparatively greater uncertainty in correlation. Red lines denote unconformities. New carbonate carbon isotope data from Drowning Creek West Figure 9. Lithostratigraphic correlation of the upper massive member of the Brassfield and Waco Member of the Alger Shale Formation along the eastern flank of the Cincinnati he Fe gl py ph 3 m 0 m 1 m 2 m (NRF) Rock Nor Ir Mudstone Sandy Siltstone Grainstone Calcareous Sandstone / Siltstone Sandstone C P Che rt Shale Siltstone Dolograinstone Dolopackstone / Dolowackestone Dolomicrit glauconite iron o cephalopods gastropods bivalves tabulate corals rugose corals trilobites branching br f ar graptolites F echinoderms py phosphate hematit ackestone / onstone onglomerat enestrate br th loricolumnus ticulate brachiopods rite y F xides ork e W e yozoans yozoans (col.) sp ackestone / M 0 m 1 m 2 m (ESQ Quar Eagle Stone . (beads) ) he gl gl ry

icrit e 3 m 4 m 0 m 1 m 2 m (W W est Union U) Fe gl Fe Fe e he he he orange white W

W ac ac o o 3 m 7 m 0 m 1 m 2 m 4 m 5 m 6 m 8 m 9 m (BC Brush Creek py py gl gl ) 11 m 10 m 3 m 4 m 7 m 8 m 0 m 1 m 2 m 5 m 6 m 9 m ( Mano O OVM) wingsville he he Py r he gl 10 m 11 m 12 m 13 m 3 m 7 m 0 m 1 m 2 m 4 m 5 m 6 m 8 m 9 m (DCE) Creek East Drowning py gl gl gl . T . . py py cher py asphaltic eichichnus sp py py py cher cher cher asphaltic py py vugs he he Hardgroun he . . . vugs . . . . he he py he . py . he . t he t t t (Rose Run) . . .v . . . . L ug s eptaena Massive Upper d . 15 m 16 m 17 m 18 m 10 m 11 m 12 m 13 m 14 m 0 m 1 m 2 m 3 m 4 m 5 m 6 m 7 m 8 m 9 m T he he he he he he he he he gl he gl eichichnus sp py cher gl (D CW Creek Drowning cher cher gl . , py , py , py he L –2 t ulbegrud t t (undi Creek Plum (Devonian) he he Oldham Uncon . basal ) sub Brass eld Bo Uncon Wa W -W erentiated) yle fo –1 llbridge est ac rmit W fo o δ rmit ac y 13 o

y C carb 01

GEOSPHERE | Volume 12 | Number 6 Sullivan et al. | Llandovery stratigraphy in Ohio and Kentucky 1822 Research Paper

6 m Dayton

05 cm Above: Contrast-enhanced sample with styliolitic, nodular fabric.

5 m

4 m Above: Internal mold of Pentamerid Figure 10. Lithologic characteristics brachiopod in the Dayton. and stratigraphic relationships of the red Brassfield and Dayton For mation in western Ohio. The out crop photo shows the Cemex North section, with major lithostrati graphic units labeled. The figure also shows the various sedimentary 3 m features and fossils common to the red Brassfield and Dayton.

Above: Mineralized, pyritic horizon at the base of the Dayton. 2 m d red Brass el

1 m

Above: The cephalopod bed of the 0 m red Brass eld at CEMEX.

TABLE 1. LOCALITY INFORMATION Locality name Abbreviation State County Latitude Longitude Brush Creek BC Ohio Adams 38.893603 –83.453239 Cedarville Township Core (OGS-3245) CV Ohio Greene 39.737806 –83.791824 Cemex Quarry North CN Ohio Greene 39.801410 –83.976375 Cemex Quarry South CS Ohio Greene 39.785428 –83.965206 Concord Township Core (OGS-2626) CCD Ohio Highland 39.089884 –83.615939 Drowning Creek East DCE Kentucky Estill 37.712889 –84.087069 Drowning Creek West DCW Kentucky Madison 37.726558 –84.115656 Eagle Stone Quarry ESQ Ohio Brown 38.999800 –83.684139 John Bryan State Park JB Ohio Greene 39.785045 –83.859494 Irvine North IN Kentucky Estill 37.726764 –83.986933 Martin Marietta Quarry Northeast MMNE Ohio Highland 39.267500 –83.744044 Martin Marietta Quarry Southwest MMSE Ohio Highland 39.264333 –83.742686 Martin Marietta Southwest MMSW Ohio Highland 39.260283 –83.751934 Melvin Township Core (OGS-3240) MN Ohio Clinton 39.475294 –83.729273 North Rocky Fork NRF Ohio Highland 39.183847 –83.591314 Owingsville Manor OVM Kentucky Bath 38.126320 –83.756416 Paint Township Core (OGS-3243) PNT Ohio Fayette 39.690370 –83.461783 Pleasant Township Core (OGS-3244) PLTOhio Franklin 39.885637 –83.229514 Sinking Springs Core (OGS-2882) SS Ohio Highland 39.062058 –83.397228 West Union WU Ohio Adams 38.821289 –83.511931 Winston Junkyard WJYKentucky Estill 37.709342 –84.078003

Both units overlie sharp lithologic contacts, and the intervening strata thin pro bonates (the orange Waco sensu Sullivan et al., 2014a) sharply overlies this gressively to the north (Fig. 9). At all localities in Estill and Madison Counties, (Fig. 7). At these northern localities, the Estill contains numerous bands of Kentucky, the base of the Waco is a thin (3 cm) bed containing mineralized green, red, and maroon mudstone, interbedded with orange calcareous silt surfaces (Fig. 7); above this, the calcareous basal Waco is a 40–50 cm inter stone beds (Figs. 9 and 12). val of light gray dolostone containing favositid corals, glauconite, and pyrite In Ohio, through northern Adams and Clinton Counties, the Waco Member (Fig. 7). This is overlain successively at all localities by ~10 cm of shale capped of the Alger Shale Formation and the ferruginous upper massive member of by a carbonate bed with abundant hypichnial burrows referable to Teichichnus the Brassfield appear to be mutually exclusive in individual outcrops. At locali sp. (Fig. 7). ties where the upper massive is present, the Waco is absent, save perhaps for At several sites, the Waco is unconformably overlain by the Devonian-age a 10 cm ferruginous bed of the orange Waco (Figs. 5 and 12). Conversely, at Boyle Formation (Fig. 7). However, the Irvine North locality in Estill County, Ken localities where the entire Waco is present, the upper massive member of the tucky, contains the typical Waco in its entirety (Fig. 11). Overlying the Teichichnus Brassfield is absent. At some of these sections, large ferruginous rip-up clasts Bed at this locality is a 5 m interval of green-gray shale, the lower half of which derived from this bed can be found in the lower white Waco (Fig. 8). North of contains richly fossiliferous orange dolostone interbeds. The upper shale is Clinton County, Ohio, the sub-Waco unconformity caps the red Brassfield (Fig. comparatively barren, with several light gray siltstone beds that are hummocky 12; McLaughlin et al., 2008b). cross-stratified and heavily bioturbated with numerous discrete Planolites and The transition between Waco-bearing and Dayton-bearing successions can Chondrites. The base of the Estill Shale is recognized at this locality by a band of be observed in a procession of cores and outcrops found through Highland, bright red mudstone and abundant granular glauconite pellets (Fig. 11). These Fayette, Franklin, and Greene Counties, Ohio (Fig. 12). Along this transect the features have been recognized widely in central Kentucky and are used to iden lower Estill becomes increasingly calcareous, a phenomenon that was also tify the Waco-Estill contact (cf. Rexroad et al., 1965; McDowell, 1983). documented in McLaughlin et al. (2012). This stratigraphic change is docu In Ohio, fossiliferous Waco shales could not be identified, but the lower mented by the Pleasant and Paint Township cores, where phosphatic calcar light colored, calcareous, coral-bearing horizon (white Waco sensu Sullivan eous strata, transitional between Estill and Dayton facies, overlie the Waco. et al., 2014a) persists in outcrops as far north as Highland County (Fig. 1). A North and west of here the Dayton Formation (sensu Brett et al., 2012) directly succession of unfossiliferous, dark orange, heavily burrowed dolomitic car overlies the red Brassfield (Fig. 12).

Irvine North 7 m (IN)

gl Estill 6 m gl

gl Wa

llbridge Unconf

5 m Unfossiliferous Waco shale Boyle

4 m (Devonian)

ormit

3 m Drowning Creek

18 m West (DCW) Drowning Creek 13 m Fossiliferous East (DCE) 2 m Waco shale chert 17 m

chert

12 m chert

1 m gl. chert

16 m Teichichnus sp. Teichichnus sp. gl basal Waco Teichichnus sp.

11 m

0 m py. sub-Waco unconformity py py

–8 –7 –6 –5 –4 –3 –2 –1 0 15 m py δ13C VPDB (‰)

10 m –2 –1 0 1 δ13C VPDB (‰) Lulbegrud 14 m

13 Figure 11. New carbonate carbon isotope (δ Ccarb) data and field observations from the Silurian Waco Member of the Alger Shale Formation near its type area in Madison –2 –1 01 and Estill Counties, Kentucky. VPDB—Vienna Peedee belemnite. δ13C VPDB (‰)

13 δ Ccarb Chemostratigraphy were fairly low, with a mean of –0.4‰. The highest values were recorded in the lower Brassfield, the upper Oldham, and the Waco. The upper massive Brass 13 New d Ccarb data are plotted against stratigraphic height in Figures 9, 11, field yields much lower values between 0.0‰ and –1.0‰. The lower carbonate 13 and 12 (supplemented with data from Cramer, 2009; McLaughlin et al., 2012). bed of the Waco yields d Ccarb values that are between 0.5‰ and 1.0‰ (Fig. 9). The most extensive section sampled below the Waco is at Drowning Creek At Irvine North in Estill County, Kentucky, values are ~1.0‰–2.0‰ lower, West in Madison County, Kentucky (Fig. 9). Here, the carbon isotope values and the range of values is much higher (values range from –8.2‰ to –0.5‰,

NW SE Cedarville Sinking Springs OGS-3245 Martin Marietta OGS-2882 (MMSW) (SS) (CV) Osgood Concord 7 m OGS-2626 ph (CCD) 130’ Paint gl OGS-3243 150’ gl (PNT) gl. Melvin OGS-3240 260’ (MV) gl. Pleasant 6 m OGS-3244 gl. (PLT) Estill 110’

Gummy clay Fe

gl gl. 510’ burrows 5 m 290’ gl ph gl

4 m py gl gl Estill 140’ Dayton 160’ gl

gl gl

gl 270’ 3 m 120’ ph gl gl gl ph gl gl. gl. orange gl 520’ he gl, he 2 m Upper Massive orange Teichichnus sp. gl, he Waco 300’ gl.

Waco colonial he corals; he favositid gl white

0 123 white gl Waco hematitic rip 13 δ C VPDB (‰) 1 m up clasts he he ph. Data from Cramer, 2009 Waco shell hash articulated ph, he, gl Log from McLaughlin et al., 2008b crinoids ph, he Oldham rip up ph clasts 170’ 0 123 py. 01 2 Plum Creek 13 13 –1 0 12 δ C VPDB (‰) δ C VPDB (‰) 130’ 13 δ C VPDB (‰) he 0 m 280’ –3 –2 –1 012 δ13C VPDB (‰) red Brass eld he, ph py

he, gl

530’ 01 2 3 gl Brass eld δ13C VPDB (‰) he Data and log from Figure 12. Correlation between Waco-bearing sections of southern Ohio and Dayton-bearing sections of western Ohio. McLaughlin et al., 2012 13 The carbonate carbon isotope (δ Ccarb) data points marked by squares were initially presented in Cramer (2009); the

01 2 3 stratigraphic column for the Cedarville core is modified from Figure 5 in McLaughlin et al. (2012), as are the figure and δ13C VPDB (‰) carbon isotope data for the Sinking Springs core.

with a mean of –3.8‰). Nevertheless, the data show distinct trends and a low cides with the transition from orange fossiliferous dolomitic beds to biotur degree of scatter (Fig. 11). A negative shift in carbon isotope values coincides bated gray siltstones (Fig. 10). Farther north in Ohio, the localities in Highland 13 with a shale horizon between the lower coral-bearing zone and the Teichich- County recorded d Ccarb values that are, on average, much higher than the nus bed. A similar pattern occurs at the upper contact of the basal Waco car Irvine North section. bonate bed at all localities. A positive shift in values can be traced through The upper massive Brassfield was sampled at the Martin Marietta quarry the lower 1.5 m of fossiliferous Waco shales at Irvine North; values drop off and Concord Township core in Adams County, Ohio, as well as in the Melvin again in the subsequent 1.5 m; the level at which they begin to decline coin Township core in Clinton County, Ohio (Fig. 12). It consistently yields values

ranging from –1.0‰ to 0.5‰, significantly lower than those found in overlying The fossiliferous lower interval of the shaly upper Waco in Kentucky likely 13 strata of the white Waco. In contrast, the red Brassfield yields high values, correlates to the orange Waco of south Ohio. A positive arc of d Ccarb values ranging from 1.0‰ to 2.0‰ (Fig. 12). coincident with the lower fossiliferous Waco shale (Fig. 11) could be an expres 13 The orange Waco generally yields the highest d Ccarb values observed in sion of the excursion that is well documented within the orange Waco (Fig. 13 a given section; these were typically 0.5‰–1.0‰ greater than the values re 12; McLaughlin et al., 2012). This zone of elevated d Ccarb represents the Valgu corded in the underlying white Waco (Fig. 11). The Estill, Osgood, and Dayton excursion (Fig. 13; McLaughlin et al., 2008b, 2012). Flat-lying values are char 13 yield d Ccarb values that are lower than those recorded in the orange Waco, acteristic of the lower Estill where data range from <0.2‰ of the mean (Fig. 12); 13 yet higher than those recorded in the white Waco. Generally, d Ccarb curves this is always lower than peak values recorded in the underlying orange Waco. through Estill, Dayton, and lower Osgood are relatively flat, with a few excep The same sequence of patterns (flat-lying values over a positive excursion) is 13 tions. At the Irvine North locality, d Ccarb values generated from bands of red found above the Waco in the Pleasant Township core of south-central Ohio, shale were negatively offset from surrounding values (Fig. 11). This is also the where argillaceous, phosphatic carbonates overlying the Waco show charac case in the Melvin core, where there is a ~3.0‰ negative excursion coincid teristics that are transitional between the Dayton and Estill units (Fig. 12). 13 ing with a band of red shale in the lower Waco. The Dayton Formation yields At least two distinct dolomitic beds with different d Ccarb signatures can be lower values that may steadily rise upward into overlying shales of the Osgood identified in the Paint Township core from Ohio: a lower (~1 m) bed with mod (Fig. 11). erate values (2.0‰) assigned to the Waco, and an upper (~2 m) light colored 13 interval with low d Ccarb values (1.3‰) at its base that rise steadily upward to DISCUSSION 2.4‰, which represents the Dayton. These are separated by an ~5-cm-thick glauconitic bed, similar to that found in basal Estill strata. This rising trend of 13 Correlation d Ccarb values is therefore interpreted as the rising limb preceding the Ireviken excursion (Munnecke et al., 2003; Cramer, 2009; McLaughlin et al., 2012). This The progressive truncation of units between the Waco Member of the same pattern has been documented in the Cedarville core, which bears strata Alger Shale Formation and upper massive member of the Brassfield is docu unambiguously assigned to the Dayton Formation (Cramer, 2009). mented as far north as the Martin Marietta quarry and Melvin core, where the sub-Waco unconformity may cap the Brassfield (Fig. 9). The precise re Sequence Stratigraphic Framework lationships between the ferruginous upper massive and the red Brassfield are difficult to determine. Although Rexroad (Rexroad et al., 1965; C.B. Rex Three regionally consistent unconformity-bound packages of strata can be road, personal commun., 1983) reported diagnostic faunal elements of the identified in the Aeronian–Telychian interval of the Cincinnati Arch (Fig. 14). upper massive (Floricolumnus [col.] sp.) and the Oldham (Ehlersella and These were recognized previously, but categorized as two third-order strati Icriodina stenolophata) in the red Brassfield, none of these observations graphic sequences in Brett and Ray (2005), and have been slightly modified could be independently corroborated in our own field studies. The crinoids in light of the new data presented here. The lower sequence is bound by the may be an unrelated large discoidal columnal, which is found at Cemex base of the upper massive member of the Brassfield and at its upper con quarry in Greene County, Ohio (Thomka, this study). Furthermore, the red tact by the sub-Waco unconformity. This was recognized as S-II in Brett et al. 13 Brassfield and upper massive ironstone yield differentd Ccarb signatures (1990; also see Brett and Ray, 2005). Given the lateral persistence of the unit, (Fig. 12). Slightly elevated values in both the Oldham and red Brassfield are its assemblage of abraded and reworked fossils, rip-up clasts, and the high consistent with arguments for their lateral equivalence (Fig. 13; McLaughlin concentration of authigenic minerals, we suggest that it is a time-averaged et al., 2008b). basal transgressive deposit (Fig. 14). An ensuing episode of a highstand is re 13 The similarity of d Ccarb isotope profiles generated for the Waco at most lo corded by the Plum Creek Shale, which reflects increased siliciclastic input as calities confirms its isochroneity. A confident correlation can be made between sedimentation rates began to outpace the rate of sea-level rise. The overlying the basal Waco carbonate bed in Kentucky and the lower white Waco of south Oldham, dominated by ferruginous, dolomitic packstones, is interpreted as a ern Ohio through conventional physical stratigraphic procedures. Although re fourth-order transgressive episode overlain by its highstand counterpart, the sults from Kentucky have different ranges of absolute values than sections in Lulbegrud Shale Member. Units of this sequence are progressively truncated Ohio, this may be due to local phenomena, such as the influence of isotopically to the northwest by the sub-Waco unconformity (Fig. 14). light terrestrial or meteoric carbon (Hudson, 1977; Cowan et al., 2005; Algeo The distribution of the upper massive member of the Brassfield, the Waco et al., 1992). The section at Irvine North in particular (Fig. 11) is characterized Member of the Alger Shale Formation, and the Dayton Formation can be used by exceptionally low values. However, systematic positive and negative shifts, to understand the topography of the sub-Waco unconformity surface. Concen with relatively few outliers, may indicate that the primary structure of the curve trations of authigenic minerals (e.g., carbonate, glauconite, and pyrite) in the remains intact. basal beds of the Waco, coupled with the abundance of colonial frame-building

n Graptolite Conodont 200 km Ma Composite δ13C Curve SW IN WC KY W OH SC OH EC KY woodia Zonation Zonation carb NW SE enloc k 433.0 W Pterospathodus procerus Shein Cyrtograptus murchisoni IREVIKEN Upper Pseudooneotodus bicornis Cyrtograptus centrifugus Lower Pseudooneotodus bicornis Cyrtograptus insectus

434.0

Pterospathodus Cyrtograptus lapworthi amorphognathoides amorphognathoides Estill

435.0 Osgood

Pterospathodus amorphognathoides lithuanicus Dayton Oktavites spiralis Pterospathodus amorphognathoides lennarti

436.0 Pterospathodus amorphognathoides Monoclimacis crenulata angulatus

elychian Monoclimacis greistoniensis T Pterospathodus Streptograptus crispus 437.0 eopennatus ssp. n. 2 VALGU Pterospathodus orange eopennatus ssp. n. 1 Spirograptus turriculatus Lee Creek white Waco basal 438.0 ry

Distomodus Spirograptus guerichi staurognathoides sub-Waco Unconformity Lulbegrud

Stimulograptus sedgwickii 439.0 Lituigraptus convolutus Oldham Llandove Monograptus argenteus Pristiograptus leptotheca red Brasseld Plum Creek Pranognathus tenuis golden Brasseld Demirastrites pectinatus ronian 440.0 sub-upper massive Brass eld Unconformity Ae Demirastrites triangulatus Upper Massive

Aspelundia expansa Upper Thin-Bedded and Shaly Brasseld

441.0 Monograptus revolutus Coronograptus cyphus white Brasseld Lower Massive Brasseld 442.0 Cyrtograptus vesiculosus

Distomodus kentuckyensis sub-Brass eld Unconformity Parakidograptus Rhuddanian 443.0 acuminatus Belfast “B” Akidograptus ascensus

Figure 13. Chronostratigraphic chart summarizing the interpreted age relationships of Llandovery units exposed on the Cincinnati Arch (modified from Brett et al., 2014, Fig. 2 therein). IN—Indiana; KY—Kentucky; OH—Ohio.

organisms, may indicate sediment starvation during transgression, which was Township core) or it may have onlapped against minor topographic highs covered by highstand shales of the upper Waco (Brett et al., 1998; McLaughlin and mounds (northeast side of Martin Marietta quarry and Melvin Township et al., 2008b). The clastic mudstone and argillaceous carbonates of the Estill core). This is also consistent with observations from eastern Indiana, where may represent a subsequent third-order highstand, likely enhanced by the in localized, lower Telychian, glauconitic dolostones referred to as the Lee Creek flux of sediment with the beginning of the Salinic disturbance (Goodman and Member of the Brassfield Formation represent outliers of Waco deposition Brett, 1994). The transgressive systems tract for this highstand would not be (Fig. 13; Kleffner et al., 2012; Brett et al., 2012). the Waco, but rather the highly glauconitic shales of the basal Estill. The Waco is assigned to the Pt. eopennatus Zone and is thus older than any The Waco was deposited over an irregular topography along the proto– strata assigned to sequence S-IV in the type region of New York State (Brett Cincinnati Arch. In some areas, deposition was restricted to local topographic et al., 1990, 1998; Loydell et al., 2007; McLaughlin et al., 2012; Sullivan et al., lows (such as southwest wall of the Martin Marietta quarry and the Paint 2014b). Therefore, the regionally angular sub-Waco unconformity more likely

Ohio Kentucky Greene Fay. Franklin Clinton Highland Brown Adams Bath Richmond Estill WJY MMNE CCD DCW Third Fourth Fifth CN CS JB CV PNT PLT MVN MMSE MMSW NRF ESQ WU BC OVM DCE IN SS Order Order Order OS DT RB

0 10 20 30 mi Estill 0310 20 0 40 km S-IV

5 m 15 ft Transgressive 4 Intervals 10 3 Highstand Intervals 2 co 5 S-III? 1 Late Highstand to Falling Wa Stage Intervals 0 0 Locality Abbreviations BC - Brush Creek CCD - Concord Core NRF - North Rocky Fork ulbegrud

CN - Cemex Quarry North PNT - Paint Township Core L CS - Cemex Quarry South PLT - Pleasant Township Core CV - Cedarville Core SS - Sinking Springs Core DCW - Drowning Creek West WU - West Union S-II DCE - Drowning Creek East WJY - Winston Junkyard

ESQ - Eagle Stone Quarry Oldham JB - John Bryan Park Formation Abbreviations IN - Irvine North BR - Brass eld (undi erentiated) MVN - Melvin Core DT - Dayton PC MMNE - Martin Marietta northeast OS - Osgood

MMSE - Martin Marietta southeast PC - Plum Creek UM MMSW - Martin Marietta southwest RB - red Brass eld OVM - Owingsville Manor UM - upper massive member BR

Figure 14. Schematic cross section summarizing the stratigraphic relations among lower Silurian stratigraphic units examined in this study. The vertical scale is exaggerated to highlight trends. The position of each locality along the lateral transect is shown above the cross section, where counties are also labeled. A schematic sequence stratigraphic interpretation is to the right of the cross section.

represents that base of the slightly older S-III (Gillette, 1947; Brett et al., 1990). ACKNOWLEDGMENTS This is supported by the findings of Hunter (1960, 1970), who correlated the Detailed criticism from Alyssa Bancroft and Wojciech Kozłowski greatly strengthened the final Waco Member with the Wolcott Limestone, a pentamerid-rich limestone found report. We thank Arnold I. Miller and David L. Meyer, who provided helpful feedback on an earlier draft of this manuscript. Financial support for this study was provided in part by a grant from the in east-central New York. However, this was placed within the sequence S-II U.S. Geological Survey STATEMAP project, a Graduate Student Research Grant from the Geologi by Brett et al. (1990, 1998) as a distinct upper fourth-order sequence. Although cal Society of America, a Graduate Student Assistance Grant from the SEPM (Society for Sedimen very few biostratigraphic data are available from the Wolcott Limestone, cono tary Geology), and the Department of Geology at the University of Cincinnati (Caster Fund and Sed Fund). We also thank the Ohio Geological Survey for providing drill core for analysis and sampling. donts from the Wolcott Furnace Hematite, which caps the limestone, suggest The research presented here is a component of the master’s thesis of Sullivan, completed at the assignment to the Pt. eopennatus Zone (Sullivan et al., 2014b). University of Cincinnati. This paper is a contribution to the International Geoscience Programme Current data favor correlation of the Wolcott Limestone and Wolcott Fur (IGCP) 591, The Early to Middle Paleozoic Revolution. nace Hematite to the Waco Member of the Alger Shale Formation, and suggest REFERENCES CITED that they are basal transgressive units of sequence S-III (as argued by Sullivan Algeo, T.J., Wilkinson, B.H., and Lohmann, K.C., 1992, Meteoric-burial diagenesis of middle Penn et al., 2012; Ettensohn et al., 2013). However, this is also an imperfect solution. sylvanian limestones in the Orogrande Basin, New Mexico: Water/rock interactions and ba The extensive paleontological data compiled by Gillette (1947) suggest that sin geothermics: Journal of Sedimentary Petrology, v. 62, p. 652–670, doi:10 .1306 /D426797E -2B26-11D7-8648000102C1865D. the Wolcott Limestone shares more genetic and faunal affinities with underly Ausich, W.I., Peter, M.E., and Ettensohn, F.R., 2015, Echinoderms from the lower Silurian Brass ing strata than with overlying units. Furthermore, the Wolcott Limestone has a field Formation of east-central Kentucky: Journal of Paleontology, v. 89, p. 245–256. gradational lower contact with the underlying Sodus Shale, both of which are Beaumont, C., Quinlan, G., and Hamilton, J., 1987, The Alleghanian Orogeny and its relationship to the evolution of the eastern interior, North America, in Beaumont, C., and Tankard, A.J., progressively truncated to the west by a regionally angular unconformity at eds., Sedimentary Basins and Basin-Forming Mechanisms: Canadian Society of Petroleum the base of S-IV (Gillette, 1947; Brett et al., 1990, 1998). Geologists Memoir 12, p. 425–445. The base of the Dayton Formation is a younger surface that has merged Beaumont, C., Quinlan, G., and Hamilton, J., 1988, Orogeny and stratigraphy: Numerical models of the Paleozoic in eastern North America: Tectonics, v. 7, p. 389–416, doi:10.1029 with the sub-Waco unconformity. This contact is cryptic in the southeast, but it /TC007i003p00389. may be coextensive with the glauconite granule zone that has long been used Berry, W.B.N., and Boucot, A.J., eds., 1970, Correlation of the North American Silurian Rocks: to delineate the base of the Estill Shale Member in Kentucky (Fig. 10; Rexroad Geological Society of America Special Paper 102, 289 p., doi:10.1130/SPE102. Brett, C.E., and Ray, D.C., 2005, Sequence and event stratigraphy of the Silurian strata of the et al., 1965) and may correlate to the basal S-IV boundary in New York. Cincinnati Arch region: Correlations with New York-Ontario successions: Royal Society of The unconformity surfaces and facies traced throughout the study area Victoria Proceedings, v. 117, p. 175–198. highlight the complex interplay between sea-level change, paleoceanographic Brett, C.E., Goodman, W.M., and LoDuca, S.T., 1990, Sequences, cycles, and basin dynamics in events, and clastic deposition associated with the distant effects of Salinic the Silurian of the Appalachian Foreland Basin: Sedimentary Geology, v. 69, p. 191–244, doi: 10.1016/0037-0738(90)90051-T. orogeny. By establishing the interval of recorded time and the duration of Brett, C.E., Baarli, B.G., Chowns, T., Cotter, E., Driese, S.G., Goodman, W.M., and Johnson, M.E., stratigraphic gaps, the results presented here may provide a firmer founda 1998, Early Silurian condensed intervals, ironstones, and sequence stratigraphy in the Appa tion for understanding early Silurian bioevents and the aftermath of the Late lachian Foreland Basin, in Landing, E., and Johnson, M.E., eds., Silurian Cycles: Linkages of Dynamic Stratigraphy with Oceanic, Atmospheric, and Tectonic Changes: New York State Ordovician extinction in the Appalachian foreland basin and Cincinnati Arch. Museum Bulletin 491, p. 89–143. Brett, C.E., Cramer, B.D., McLaughlin, P.I., Kleffner, M.A., Showers, W.J., and Thomka, J.R., 2012, Revised Telychian-Sheinwoodian (Silurian) stratigraphy of the Laurentian mid-continent: CONCLUSIONS Building uniform nomenclature along the Cincinnati Arch: Bulletin of Geosciences, v. 87, p. 733–753, doi:10.3140/bull.geosci.1310. Sequence S-II is bound at its base by the ferruginous upper massive mem Brett, C.E., Thomka, J.R., Sullivan, N.B., and McLaughlin, P.I., 2014, Anatomy of a compound se 13 quence boundary: A karstic unconformity in the Cincinnati Arch region: GFF, v. 136, p. 42–47, ber of the Brassfield of east-central Kentucky and southern Ohio; d Ccarb values doi:10.1080/11035897.2014.882978. recorded in this unit are significantly different from those of the red Brassfield, Cocks, L.R.M., and Scotese, C.R., 1991, Global biogeography of the Silurian Period, in Bassett, which occurs in western Ohio, casting doubt on a possible correlation of these M.G., et al., eds., The Murchison symposium: Proceedings of an International Symposium units. New isotope results from the Oldham may corroborate arguments for its on the Silurian System: Palaeontology Association Special Papers in Palaeontology 44, p. 109–112. equivalence with the red Brassfield. 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