International Journal of Coal Geology 154–155 (2016) 136–154 Contents lists available at ScienceDirect International Journal of Coal Geology journal homepage: www.elsevier.com/locate/ijcoalgeo Sequence stratigraphy of fluvially-dominated strata of the Mid-Late Pennsylvanian Conemaugh Formation, Central Appalachian Basin Ronald L. Martino Department of Geology, Marshall University, Huntington, WV 25755, United States article info abstract Article history: Sequence stratigraphic analysis of nonmarine, fluvially-dominated strata is particularly challenging compared to Received 14 August 2015 paralic and marine sequences due to rapid facies changes and limited lateral continuity of key beds. The Received in revised form 29 December 2015 Conemaugh Formation of central West Virginia is a prime example of this type of stratigraphic interval. This Accepted 30 December 2015 study describes the stratigraphy and sedimentary facies from 68 outcrops in the lower 100 m of the Mid-Late Available online 31 December 2015 Pennsylvanian, nonmarine Conemaugh Formation in this area. Facies identified include 1) fluvial–upper estua- Keywords: rine channel sandstones, 2) crevasse splay channel and sheet sandstones, 3) lacustrine shale, mudstone, and Paleosols claystone, 4) lacustrine/palustrine limestone, 5) paludal coal and carbonaceous shale, and 6) hackly mudstone Sequence stratigraphy and claystone paleosols. Conemaugh Fm. Mature, polygenetic, high-chroma calcic vertisols and calcisols are the regionally developed interfluvial sequence Nonmarine cyclothems boundaries (IFSBs) of seven fourth-order sequences (major cyclothems) between the Upper Freeport and Har- lem coal horizons. Initial paleosol development occurred under well-drained conditions and strongly seasonal, semiarid–arid climate approaching and during glacial maxima at a time of minimal accommodation space on the interfluves. Subsequent rising water table associated with rising base level occurred as interglacial sea level rose and the climate became less seasonal and more humid. This initially led to deposition of thin, carbonaceous mud and peat followed by lacustrine and palustrine limestones. The presence of spirorbid microconchids indi- cates that the lakes were at least intermittently connected to the sea, which reached to within 50–80 km of all outcrops in the study during five transgressions. The tops of these limestones represent maximum flooding sur- faces. They are overlain by coarsening–upward lake-fill sequences formed during high accommodation on the in- terfluves during the HST. A nonmarine sequence stratigraphic model and a polygenetic paleosol model are proposed for the Conemaugh in central West Virginia. This study underscores the importance of recognizing re- gionally developed IFSB paleosols and microconchid limestones in correlation and sequence stratigraphic analysis. © 2015 Elsevier B.V. All rights reserved. 1. Introduction perception that deposition was dominated by autocyclic processes such as delta switching and river avulsion that precluded the develop- The study of Pennsylvanian cyclothems in North America has had a ment of widespread marker beds (e.g. Donaldson, 1979). long history dating back to the early 1900s (e.g. Weller, 1930; Sequence stratigraphic studies of fluvial successions are hindered by Wanless and Weller, 1932; Wanless and Shepard, 1936). Cylcothems rapid lateral facies changes and inability to distinguish time-significant have more recently been viewed within the context of sequence stratig- surfaces. The recognition of widespread mature paleosols as interfluvial raphy (sensu Vail et al., 1977; e.g. Miall, 2010). The bulk of sequence sequence boundaries between incised valley fills (IVFs) has led to signif- stratigraphic studies to date have addressed stratigraphic intervals icant progress in this area (Wright and Marriott, 1993; Shanley and with marine components. Marine–coastal cyclothems have been de- McCabe, 1994; Gibling and Bird, 1994; McCarthy et al., 1999; McCarthy, scribed from the lower Conemaugh Glenshaw Formation of the north- 2002). The purpose of this study is to develop a high-resolution ern and central Appalachian Basin (e.g. Stout, 1947; Sturgeon and stratigraphic framework by correlating paleosol-bounded terres- Hoare, 1968; Busch and Rollins, 1984; Busch and West, 1987; Martino, trial cyclothems in central West Virginia with their downdip, 2004). Henry et al. (1979) and Windolph (1987) were unable to distin- marine-influenced equivalents. Sedimentary facies architecture will guish or correlate Conemaugh cyclothems in central West Virginia. be analyzed and compared with nonmarine sequence stratigraphic Their efforts were hindered by 1) the absence of marine shales/lime- models. The sequence stratigraphic significance of “nonmarine” (brack- stones and the paucity of laterally persistent coal beds, and 2) the ish-freshwater) limestones will be evaluated. http://dx.doi.org/10.1016/j.coal.2015.12.016 0166-5162/© 2015 Elsevier B.V. All rights reserved. R.L. Martino / International Journal of Coal Geology 154–155 (2016) 136–154 137 Fig. 1. Map showing outcrop locations used in this study. The regional paleoslope was toward the northwest. The transgressive maximum line is based on projected maximum extent of Brush Creek and Ames marine units (modified from Busch and West, 1987). Conemaugh outcrops southeast of this line (i.e. updip) are comprised of nonmarine cyclothems whereas those northwest of it (i.e. downdip) contain marine-cored cyclothems (Martino, 2004). 2. Methods described at 68 outcrops (Fig. 1, Table 1). Paleosols were identified in the field using soil structure, horizonization, and root traces (Retallack, 1988). A total of 2251 m of strata was measured through the lower 80–100 m of Elevations were determined with an American Paulin System Micro altime- the Conemaugh Formation and component sedimentary facies were ter, or from satellite imagery using Google Earth software. Lithostratigraphic Table 1 Outcrop location coordinates in latitude and longitude and UTM coordinates (WGS 1984 Zone 17N datum). Loc. Latitude Longitude Northing Easting Loc. Latitude Longitude Northing Easting BX2 38.68838 −80.68688 4282243 527231.8 K51 38.3855 −81.83572 4248919 427010.8 BX3 38.66811 −80.77741 4279971 519364 K52 38.38717 −81.7918 4249071 430848.4 BX5 38.68706 −80.68956 4282096 526999.5 K53 38.39175 −81.81247 4249594 429048.2 BX6 38.70611 −80.65954 4284219 529602.4 K54 38.45545 −81.49139 4256465 457125.7 BX7 38.69973 −80.66369 4283510 529244 K55 38.45793 −81.49527 4256741 456788 BX8 38.62732 −80.72181 4275458 524214.8 K56 38.45793 −81.49527 4256741 456788 BX9 38.62833 −80.71881 4275571 524475.4 K57 38.52115 −81.35114 4263699 469390.3 BX14 38.65836 −80.72679 4278901 523771.1 K58 38.52115 −81.35114 4263699 469390.3 BX15 38.65836 −80.72679 4278901 523771.1 K59 38.52939 −81.33951 4264609 470407.8 BX20 38.64676 −80.7194 4277616 524418.4 K60 38.42554 −81.52571 4253163 454112.2 BX22 38.61624 −80.84808 4274203 513225.5 K61 38.37817 −81.60347 4247948 447289.7 C1 38.24939 −82.28829 4234271 387273.9 K62 38.36272 −81.84536 4246399 426146 C2 38.26804 −82.25398 4236300 390303.4 K63 38.3676 −81.82152 4246922 428233.8 C3 38.26871 −82.20683 4236319 394429.8 K64 38.41507 −81.67188 4252083 441344.3 C4 38.27642 −82.23976 4237212 391559.9 K65 38.42002 −81.64309 4252615 443861.9 C5 38.25644 −82.28838 4235054 387276.5 L1 38.29213 −82.18998 4238898 395937.2 C6 38.26382 −82.29592 4235882 386628.4 L2 38.27939 −82.12436 4237413 401658.7 C7 38.32634 −82.21858 4242727 393486 L3 38.26064 −81.83011 4235060 427376.6 C8 38.32783 −82.20703 4242879 394497.2 L4 38.26696 −81.82177 4235754 428112.4 K36 38.39691 −81.59226 4250020 448282.5 L5 38.23305 −81.83867 4232005 426600.2 K37 38.4191 −81.55082 4252461 451915.5 L7 38.24726 −81.8335 4233578 427066.5 K38 38.44799 −81.51548 4255649 455018.8 L11 38.2826 −82.17377 4237823 397340.9 K39 38.44022 −81.51693 4254787 454887.2 L12 38.28259 −82.17381 4237821 397337.5 K40 38.30428 −81.7007 4239809 438734.7 R1 38.57037 −81.26346 4269134 477049.4 K41 38.36352 −81.72219 4246397 436907.8 R2 38.58355 −81.20568 4270585 482085.6 K42 38.33656 −81.70144 4243391 438697.4 R3 38.551 −81.29602 4266994 474206.1 K43 38.40991 −81.65176 4251498 443096.8 R4 38.54639 −81.30682 4266485 473263.3 K44 38.41429 −81.6242 4251967 445506.1 R5 38.58218 −81.21691 4270435 481107.2 K45 38.37554 −81.79396 4247781 430649.3 R6 38.5632 −81.13186 4268314 488512.1 K47 38.38151 −81.60131 4248317 447480.9 R7 38.56283 −81.14188 4268275 487639.4 K48 38.38522 −81.61397 4248736 446378.2 R8 38.57196 −81.2605 4269311 477307.3 K49 38.40384 −81.62 4250806 445864.9 R9 38.56941 −81.15995 4269008 486066.1 K50 38.40111 −81.66085 4250527 442295.9 R10 38.57085 −81.26767 4269189 476682.5 138 R.L. Martino / International Journal of Coal Geology 154–155 (2016) 136–154 correlations were based on similarities in well-developed paleosols taking Sandy Grove Sandstone (Windolph, 1987) and the Pittsburgh coal (West into account their thickness, type, and elevation, and were guided in part by Virginia Geological and Economic Survey Coal Bed Mapping Project; Krebs their relations to the elevation of structural contours on the top of the and Teets, 1914). Fig. 2. Stratigraphic framework showing (from left to right) North American subsystem, North American series, eastern European stages, central and western European series and stages, global eastern European stages, and lithostratigraphic units in West Virginia. Lithostratigraphic framework for Conemaugh is based on Fonner (1987),andMartino (2004) and relies on coal beds and marine units which are absent or limited in the study area. Twomile Limestone and Sandy Grove Sandstone are units that have been mapped in the Charleston area (Windolph, 1987). Ranges of selected palynomorphs are from Peppers (1996) and Eble et al.