Sequence Stratigraphic Hierarchy of the Upper Devonian Foreknobs Formation, Central Appalachian Basin

Home , Catskill Formation, Foreknobs Formation, Greenland Gap Group, Lock Haven Formation, New River Formation

Palaeogeography, Palaeoclimatology, Palaeoecology 387 (2013) 104–125

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Palaeogeography, Palaeoclimatology, Palaeoecology

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Sequence stratigraphic hierarchy of the Upper Devonian Foreknobs Formation, central Appalachian Basin, USA: Evidence for transitional greenhouse to icehouse conditions☆

Wilson S. McClung a,⁎, Kenneth A. Eriksson b, Dennis O. Terry Jr. c, Clifford A. Cuffey a a Chevron USA Inc., 15 Smith Rd, Midland, TX 79705, United States b Department of Geosciences, Virginia Tech, Blacksburg, VA 24061, United States c Department of Earth and Environmental Science, Temple University, Philadelphia, PA 19122, United States article info abstract

Article history: The Foreknobs Formation (Upper Devonian; Upper Frasnian to basal Famennian) comprises the uppermost ma- Received 6 December 2012 rine strata of the progradational “Catskill clastic wedge” of the south-central Appalachian Mountains (Virginia- Received in revised form 7 July 2013 West Virginia; USA). The Foreknobs Formation consists of 14 lithofacies arranged in four facies associations Accepted 18 July 2013 which record the following depositional settings: 1) storm-dominated distal to proximal offshore to shoreface Available online 27 July 2013 (facies association A); 2) sharp-based conglomeratic shoreface (facies association B); 3) fluvial redbed (facies association C); and 4) incised-valley fill (IVF; facies association D). Vertical juxtaposition and stacking patterns Keywords: Late Devonian of lithofacies and facies associations permit recognition of a hierarchy of three scales of cyclicity. Up to 70 Catskill short-term 5th-order cycles, each averaging ~65 kyr, consist of coarsening-upward parasequences of storm- Foreknobs Formation dominated offshore marine facies in the distal setting which correspond to high frequency (unconformity Sequence stratigraphy bound) sequences (HFS) of fluvial redbed strata overlain by offshore marine strata in the proximal setting. Paleosol These facies relationships are a consequence of 10–15 m of sea-level fluctuations. Up to 12 intermediate-term fi Incised-valley ll 4th-order cycles, each averaging ~375 kyr, consist of stacked 5th-order cycles. The 4th-order cycles are bounded Icehouse by regressive surfaces of marine erosion (RSME) at the base of sharp-based conglomeratic shoreface sandstones in the distal setting that correspond with paleosols in the proximal setting. In some cases, the 5th-order cycles within each 4th-order cycle exhibit stacking patterns indicative of increasing or decreasing accommodation space. These facies relationships are a consequence of 25–35 m of sea-level fluctuations. Three complete and portions of two additional 3rd-order cycles, each averaging ~1.12 Myr, consist of stacked 4th-order cycles. The 3rd-order sea-level trends reflected in the Foreknobs Formation are nearly identical to published eustatic sea- level curves. Incised-valley fills are present at one of the 3rd-order cycle boundaries and are a consequence of a35–45 m sea-level fluctuation. The amplitudes of the inferred sea-level fluctuations are comparable to the expansion and contraction of ice volumes within the current Greenland and Antarctic ice sheets which suggests glacioeustasy was the primary control on sea-level fluctuations and cyclicity within the Foreknobs Formation. Such an interpretation is consistent with knowledge of Devonian climate, transitioning from Middle Devonian greenhouse to Late Devonian icehouse, as indicated by evidence of glaciation during parts of the Late Devonian in South America and the Appalachians. © 2013 Authors. Published by Elsevier B.V. All rights reserved.

1. Introduction Devonian, and Jurassic–Cretaceous (Frakes et al., 1992), which were characterized by high-frequency but low-amplitude (b10 m) sea-level Earth's climate has alternated between greenhouse and icehouse ﬂuctuations (Read, 1995; Lehrmann and Goldhammer, 1999; Séranne, conditions throughout its geologic history (e.g., Frakes et al., 1992). 1999). Greenhouse stratigraphic successions typically consist of Greenhouse conditions prevailed during the Early Ordovician, Early 4th-order sequences and 5th-order parasequences (orders of Vail et al., 1991) which exhibit systematic thickness changes and facies proportions. These are bounded by minimum accommodation ﬂooding ☆ This is an open-access article distributed under the terms of the Creative Commons surfaces and are stacked into 3rd-order sequences (Tucker et al., 1993; Attribution-NonCommercial-No Derivative Works License, which permits non-commercial Lehrmann and Goldhammer, 1999). use, distribution, and reproduction in any medium, provided the original author and source In contrast, notable icehouse eras prevailed during the Late are credited. ⁎ Corresponding author. Tel.: +1 432 352 3162. Neoproterozoic, Late Paleozoic (Carboniferous), and the Late Cenozoic E-mail address: [email protected] (W.S. McClung). (Frakes et al., 1992). Classic icehouse conditions are characterized by

0031-0182/$ – see front matter © 2013 Authors. Published by Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.palaeo.2013.07.020 W.S. McClung et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 387 (2013) 104–125 105 high-frequency (4th- and 5th-order) and high-amplitude (N100 m) sea-level fluctuations as a consequence of expansion and contraction of voluminous continental ice sheets. Icehouse stratigraphic successions are characterized by abundant subaerial exposure surfaces (sequence boundaries), relatively chaotic vertical thickness and facies distribu- tions, and abrupt shifts of fluvial deposits over marine facies (or vice- versa) (Heckel, 1983; Lehrmann and Goldhammer, 1999). High frequency (4th- and 5th-order) icehouse, unconformity-bounded sequences tend to be relatively thin compared to greenhouse sequences, and are stacked to form higher-order sequence sets or composite sequences. Global sea-level curves for the Devonian constructed by several workers suggest low-amplitude, greenhouse-type fluctuations during the Middle Devonian, followed by moderate to higher amplitude fluctuations during the Late Devonian, especially the Late Frasnian to Late Famennian (e.g., Johnson et al., 1985; Haq and Schutter, 2008). Portions oftheLateDevonianhaverecentlybeenidentified as icehouse episodes with evidence of glacial ice in both South America and the Appalachians (Caputo, 1985; Crowell, 1999; Brezinski et al., 2008, 2009, 2010). Current state of knowledge suggests that the extent and volume of Late Devonian Fig. 1. Stratigraphic nomenclature of the Catskill clastic wedge in WV and VA (stratigraph- ice was likely smaller than that in Carboniferous and Late Cenozoic ic units are not drawn to scale with regard to time). Stratigraphy is based on Dennison icehouse times (Stanley, 2009). Consequently, it would seem reasonable (1970), McGhee and Dennison (1976),andMcGhee (1977). that less severe icehouse episodes would produce high-frequency sea- level fluctuations of various intermediate amplitudes, depending upon ice volumes. Also, it would seem reasonable that during transitions 2. Previous work from greenhouse to icehouse, the overall pattern would be one of increasing amplitude of sea-level fluctuations, although not necessarily The upper marine strata of the “Catskill clastic wedge” in Maryland a smooth or gradual transition, again depending on the history of ice vol- and the Virginias, originally termed “Chemung Formation,” were umes. Moreover, the stratigraphic record of both transitional greenhouse renamed the Greenland Gap Group by Dennison (1970) (Fig. 1). He to icehouse, and small-scale icehouse conditions is not as well docu- subdivided it into a lower Scherr Formation and upper Foreknobs mented as either greenhouse or more severe icehouse times. Formation. Dennison (1970) and McGhee and Dennison (1976) further During the Acadian Orogeny within the Appalachian region of subdivided the Foreknobs Formation into five members along the North America, spanning approximately 30 Myr from Middle Devonian Allegheny Front outcrop belt: Mallow, Briery Gap, Blizzard, Pound, through Middle Mississippian, tectonic flexure and subsidence pro- and Red Lick (in ascending order; Fig. 1). The Mallow and Blizzard duced the Acadian foreland basin (Ettensohn, 1985; Kaufmann, 2006; Members are predominantly shaly, whereas the Briery Gap and Pound Ver Straeten, 2010). This foreland basin contains a thick Middle and Sandstone Members contain more sandstone than the other members. Upper Devonian stratigraphic record, the “Catskill clastic wedge,” in- Based on brachiopod and other macrofossil biostratigraphy, the cluding both marine and non-marine deposits (Barrell, 1913; Willard, majority of the Foreknobs Formation in the study area is Late Frasnian 1939; Cooper et al., 1942; Ayrton, 1963; Sutton, 1963; McCave, 1969; in age, with the uppermost portion earliest Famennian in age (Fig. 1) Oliver et al., 1971; Faill, 1985). Previous workers have recognized cyclicity in these strata, but have not made estimates of the amplitudes of sea-level fluctuation (Van Tassell, 1987, 1994; Filer, 2002) nor has this key interval been properly addressed in the context of sequence stratigraphy. Thus, the transitional marine to non-marine interval, the Foreknobs Formation, was re-examined and this paper will present a depositional model relevant not only to the Upper Devonian of the Appalachians but also to foreland-basin ramp settings in general. Fur- thermore, these data and interpretations are used as a test of currently available sea-level curves, and of hypothesized characteristics of transitional greenhouse to icehouse and small-scale icehouse conditions. The objectives of this study are to: 1) describe constituent lithofacies and facies associations, and interpret their depositional environments; 2) describe and utilize paleosols to identify major hiatuses in the rock record that can be equated with sequence boundaries; 3) identify multiple scales of cyclicity and stacking patterns, from which amplitudes and frequencies of sea-level fluctuations are inferred; 4) integrate these data into a comprehensive sequence stratigraphic framework including an explanation of sediment deposition and preservation due to changing accommodation on a foreland basin ramp setting; 5) reinterpret the origin of both “shelf sand bar (and conglomerate) complexes” and “prograding muddy shoreline” deposits; 6) explain the distribution of named members within the Foreknobs Formation, and its overall progradational nature; and 7) infer the causes of Fig. 2. Study area and location of measured sections: 1. Rt 50, Augusta, WV; 2.Rt55,Baker, sea-level fluctuations reflected in the stratigraphic record, focusing on WV; 3. Rt 33, Shenandoah Mtn., WV; 4. Rt 606, Brush Mtn, VA; 5.BrieryGapRd,WV;6.Rt glacioeustasy during times of transition from greenhouse into icehouse 50, Romney, WV; 7. Rt 42, Scherr, WV; 8. Rt 33, Elkins, WV; 9. Rt 250, Durbin, WV; 10.Rt conditions. 39, Marlinton, WV. See Appendix A for section location details. 106

Table 1 Lithofacies and facies associations. *Fluvial sedimentary structure types and architectural element interpretations after Miall (1992). ..MCuge l aaoegah,Pleciaooy aaoclg 8 21)104 (2013) 387 Palaeoecology Palaeoclimatology, Palaeogeography, / al. et McClung W.S.

Lithofacies Lithology Grain size, sorting, Basal surface Bedding, sedimentary structures*, and Thickness Patterns of occurrence Interpretation* and constituents biota

Facies association A

Bioturbated Mudrock; gray-green Clay-silt, moderately to well typically gradational with Bioturbation, no preserved sedimentary 10 cm - meters Occurs as coarsening-upward Slow rates of accumulation with burrowing and browsing Mudrock (A1) sorted underlying facies structures; in-situ brachiopds rare successions ranging in thickness organisms below fair-weather wave-base: distal to from 4 to 30m; lower and proximal offshore thicker portions dominantly Shale (A2) Shale; gray-green Clay-silt, moderately to well typically gradational with Fissile; no biota 10 cm - meters lithofacies A1 and A2 with Absence of organisms and/or rapid rate of accumulation sorted underlying facies upward-increasing interbeds of below fair-weather wave-base: proximal offshore A3; in some cases, successions abruptly capped by lithofacies HCS sandstone (A3) Sandstone; gray-green Sand, very fine- to fine- sharp-based, irregular, Laterally impersistent, massive, plane-laminated, Up to 40 cm A4, with a thin basal transitional Rapid deposition by waves/storms above storm wave-base grained, moderately to well truncates underlying strata or HCS, typically grade upward to shale or interval; mica and plant and below fairweather wave-base: proximal offshore sorted; micaceous mudrock, rare symmetrical-rippled (10-30 cm fragments increase upward wavelength) caps; rare flute-casts and ball and pillow structures; rare brachiopod / crinoid bioclastic lags, plant fragments

Amalgamated, Sandstone; gray-green Sand, very fine- to med- sharp-based , irregular, Amalgamated, plane-laminated to HCS to trough Up to 1.5 m Deposition by waves/storms well above storm wave-base grained, moderately to well truncates underlying strata cross-stratified; uncommon symmetrical-rippled to unidirectional currents above fairweather wave-base: Cross-baded sorted; micaceous caps; rare marine fossils, plant fragments proximal offshore to upper shoreface Sandstone (A4)

Facies association B

Sharp-based Sandstone, Sand, fine- to very coarse- sharp-based, locally Amalgamated, massive, plane-laminated / HCS / Thinner amalgamated Occurs as sandstone bodies Deposition by waves/fair weather processes within lower Conglomeratic conglomeratic; gray- grained, moderately to well irregular (<0.5m relief) trough / tabular cross-stratified, common beds (<1.5m) are typically ranging from 2 to 19m thick; to upper shoreface near and above fair-weather wave- Sandstone (B1) green sorted; conglomeratic with truncating underlying layers symmetrical-rippled (10-30 cm wavelength) plane laminated or HCS, consists of thick interval of base

scattered ellipsoidal quartz caps; rare flute and gutter casts at base; rare whereas thicker amalg lithofacies B1 capped by – 125 pebbles and flattened marine fossils, common plant fragments beds (>2.0m) are typically lithofacies B2 mudstone clasts up to 2.0 cross bedded cm across

Pebby bioturbated Sandstone; gray-green Sand, very fine- to medium- typically gradational with Thin bedded, biotubated, uncommon large Up to 0.4 m Transgressive sheet sandstone recording ravinement Sandstone (B2) grained, moderately underlying sandstone facies wavelength symmetrical ripples (~50 cm surface (TRS) sorted; with scattered wavelength); rare siderite nodules; scattered quartz pebbles and brachiopods, crinoid ossicles mudrock intraclasts

Facies association C

Heterolithic Interbedded red shale, Sand, very fine-grained, sharp-based, irregular, Typically laminated with centimeter- to 0.25 m to 16 m, average Occurs as 0.5 to 12m thick Overbank fines (OF): fluvial Redbeds (C1) siltstone, and sandstone moderately sorted truncates underlying strata decimeter-scale sharp-based fining-upward 1.8 m intervals; dominated by successions; rare mudcracks, asymmetrical lithofacies C1, with scattered ripples (Sr); locally capped by pedogenic lenses of lithofacies C2; alteration (see Table 2) (Fl, Fm, Fsc); rare lithofacies C2 may fine up into rootlets, burrows; rare fish scales (Hyneria sp.) lithofacies C1; commonly along laminae capped by thin lithofacies C3 Reddish-grey Sandstone; reddish-gray Sand, fine- to medium- sharp but flat where Plane-laminated (Sh) or cross-bedded (St, Se, 0.25 to 8.0 m, average 2.2 m Laminated sand sheet (LS); sandy bedform (SB); lateral grained, moderately sorted; overlain by plane-laminated Ss); locally channelized; locally abundant accretion (LA): fluvial coarse member Sandstone (C2) rare mudstone clasts and sandstone; Archaeopteris plant fragments quartz pebbles up to 2.5 cm irregular/truncating with up across particularly at bases to 1.0 meter relief where of beds overlain by cross-bedded sandstone

Bioturbated Sandstone; gray-green Sand, very fine- to medium- sharp-base over underlying Thin bedded, biotubated; rare siderite nodules; Up to 0.25 m Transgressive sheet sandstone recording ravinement grained, moderately redbed facies (C1 and C2) scattered brachiopods, crinoid ossicles surface (TRS) Sandstone (C3) sorted; with scattered mudrock intraclasts

Facies association D

Coarse Conglomerate and Sand, medium- to coarse- sharp, truncates underlying Numerous channel-shaped, concave-up scoured 10 m Occurs in two modes: single Gravel bars and bedforms (GB): braided stream, proximal Conglomerate (D1) conglomeratic grained, very poorly sorted; strata, relief unknown from surfaces (Gt); large-scale tabular (Gp) and trough units of lithofacies D1 overlain IVF ..MCuge l aaoegah,Pleciaooy aaoclg 8 21)104 (2013) 387 Palaeoecology Palaeoclimatology, Palaeogeography, / al. et McClung W.S. sandstone; gray with abundant ellipsoidal nature of outcrop cross-stratification; pebble imbrication (Gm); by lithofacies D5; or quartz, igneous, and large plant and wood fragments up to 25 x 5 cm multistoried occurrences of metamorphic disseminated throughout; also local lenticular lithofacies D2 overlain by pebbles/cobbles up to 10.0 (up to 6 cm thick) coaly pods lithofacies D3, D4 or Facies cm across association A; in some cases lithofacies D2 fines up into lithofacies D4

Channelized Sandstone, Sand, medium- to coarse- sharp, irregular, truncates Numerous internal channel-shaped concave-up 2 to 16 m, average 5.2 m Sandy bedform (SB); lateral accretion (LA): channel conglomeratic ; gray to grained, moderately sorted; underlying strata with up scoured surfaces (Se), some overlain by dark bedform of braided stream, distal IVF Conglomeratic gray-white with scattered ellipsoidal to 1 m of relief gray carbonaceous mudrock; medium-scale Sandstone (D2) quartz pebbles and trough (St) and tabular (Sp) cross-stratification; mudrock clasts up to 2.5 cm abundant plant fragments up to 10 x 2 cm across

Skolithos- Sandstone, Sand, medium- to coarse- gradational with underlying Skolithos Ichnofacies preserved; channelized <0.2 m Marine drowning of distal IVF channel bedform conglomeratic; gray to grained, moderately sorted; D2 lithofacies Burrowed gray-white conglomeratic Sandstone (D3) Interbedded black Shale/mudrock, dark Sandstone very fine- to fine- mudrock/shale gradational Mudrock/shale typically bioturbated (Fsc, C), Mudrock/shale 1 to 6 m, Overbank fines (OF) / estuarine fines gray/black; interbedded grained, moderately sorted; to sharp with underlying with cut (<1 m relief) and fill features (Fl), average 2.0 m; sandsone < Shale and with sandstone lenses, shale/mudrock conglomeratic sandstone of abundant plant fragments up to 10 x 2 cm; 0.5 m Sandstone (D4) gray-white carbonaceous facies D2; sandstones sharp- sandstones thin bedded to massive, lenticular based and discontinuous, asymmetrical-ripple cross- laminated (Ss, Fl), rare plant fragments

PEBBLY BIOTURBATED Sandstone; gray-green Sand, very fine- to medium- typically gradational with Thin bedded, biotubated, uncommon large Up to 0.4 m Transgressive sheet sandstone recording ravinement grained, moderately underlying facies wavelength wave ripples (~50 cm wavelength), surface (TRS) SANDSTONE (D5) sorted; with scattered rare siderite nodules; scattered brachiopods, quartz pebbles and crinoid ossicles mudrock intraclasts – 125 107 108 W.S. McClung et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 387 (2013) 104–125

(McGhee, 1977; Dennison, 1985; Clausen and McGhee, 1988; Rossbach, Color, 2009). Paleosols were classified using USDA Soil Taxonomy 1992, 2001; Brame, 2001). The precise biostratigraphic position of the (Soil Survey Staff, 1998). Frasnian–Famennian boundary is uncertain due to lack of diagnostic Based on the vertical juxtaposition of facies associations, stacking conodonts within the Foreknobs Formation, and has been placed various- patterns of cycle thickness, and distribution of bounding surfaces, ly from the middle of the Pound Member to within the Red Lick Member, including paleosols, three scales of cyclicity are identified. The cyclic- depending on location and which fossils are used. The upper contact ity naturally presents a hierarchy which can be readily interpreted in with the Hampshire Formation is located above the Frasnian–Famennian terms of sequence stratigraphy. The vertical juxtaposition of facies boundary (Fig. 1), a time of major world-wide sea-level fall (Johnson associations and depositional environment interpretations, com- et al., 1985; Haq and Schutter, 2008). bined with the number of cycles, allows for an estimation of both Filer (1994) convincingly correlated the Foreknobs Formation with amplitude and temporal duration of sea-level fluctuations. More- widespread black shale–gray shale cycles within the Upper Devonian over, these interpretations permit an evaluation of various hypothe- of the Appalachian Basin, thus permitting reliable correlation with the sized causes of sea-level fluctuations, including eustasy, tectonics, New York state section (Rickard, 1975; Filer, 1994, 2002; Ver Straeten, and autocyclic processes. 2010). The Mallow Member of the Foreknobs Formation correlates to the upper part of the Rhinestreet Shale, whereas the uppermost portion 4. Lithofacies, facies associations, and depositional environments of the Foreknobs Formation (upper Red Lick Member) correlates to the Dunkirk Shale (Rickard, 1975; Filer, 1994). In New York state, the In the study area, the Foreknobs Formation consists of 14 lithofacies; Frasnian–Famennian boundary is located just below the base of refer to Table 1 for detailed descriptions. Based on co-occurrences, these the Dunkirk Shale, based on precise conodont biostratigraphy (Over, lithofacies can be grouped into four facies associations (Table 1). 2002). Thus, the Frasnian–Famennian boundary most likely occurs in the lower Red Lick Member (Fig. 1), which is consistent with the range 4.1. Facies association A of positions previously reported, corroborating the chronostratigraphic position of the Foreknobs Formation. This association comprises four lithofacies: 1) bioturbated mudrock Originally, the “Catskill clastic wedge” was considered to be a (A1); 2) shale (A2); 3) hummocky cross-stratified (HCS) sandstone prograding delta complex (e.g., Willard, 1939). Later, Walker (1971) (A3); and 4) amalgamated, cross-bedded sandstone (A4) (Table 1; and Walker and Harms (1971) re-interpreted the marine–nonmarine Fig. 3). Bioturbated mudrock, shale, and HCS sandstone lithofacies are transition of the Foreknobs Formation equivalent in Pennsylvania as a interpreted to have been deposited in an offshore setting below fair- succession of prograding muddy shoreline “motifs” because of the lack weather wave-base. Bioturbated mudrock and shale were deposited of classic deltaic facies, such as coarsening-upward successions capped during times of quiescence, with burrowing and browsing organisms with prominent distributary mouth-bar and distributary channel sand- and slow rates of sedimentation, versus lack of organisms or more stones. Dennison and Dewitt (1972), Smith and Rose (1985), Cotter rapid sedimentation, respectively. The HCS sandstone lithofacies repre- and Driese (1998),andSlingerland et al. (2009) reached the same sents storm event beds deposited above storm wave-base but below interpretation. Randall (1984), in a study of the Foreknobs Formation fair-weather wave-base. In contrast, the capping (where present) amal- in west-central and southwest Virginia, described local red-colored gamated, cross-bedded sandstone lithofacies formed near and above fining-upward successions abruptly overlying offshore marine strata, fair-weather wave-base within a shoreface depositional setting where which resemble muddy-shoreline “motifs”. sedimentation was influenced by storms, waves, and unidirectional cur- Other studies recognized that storm and wave-dominated “shelf” rents. The coarsening-upward stacking of these lithofacies is interpreted facies are widespread in the Foreknobs-equivalents of New York and to represent progradation which is corroborated by the upward increas- Pennsylvania (Sutton et al., 1970; Bowen et al., 1974; Craft and Bridge, ing abundance of mica and plant debris within the HCS sandstone 1987; Slingerland and Loule, 1988; Cotter and Driese, 1998; Schieber, and amalgamated, cross-bedded sandstone lithofacies. Moreover, the 1999; Castle, 2000). In West Virginia and Virginia, McClung (1983) abrupt upward “transition” to the amalgamated, cross-bedded sand- and Randall (1984) documented stacked, upward-coarsening succes- stone lithofacies is interpreted to represent accelerated progradation sions dominated by hummocky cross-stratification (HCS) and attribut- and facies shift. ed individual HCS beds to storm events. Offshore marine facies in the Foreknobs Formation are similar to Despite the predominantly fine-grained nature of the Foreknobs ancient deposits described by Kreisa (1981), Duke et al. (1991) and Formation, quartz pebble concentrations are ubiquitous both in proxi- Myrow and Southard (1991) and comparable to modern shelf deposits mal and distal strata, and throughout the formation (Dennison, 1970; described by Fisk et al. (1954), Allen (1964), Hayes (1967) and (Saito, Slingerland and Loule, 1988). These authors did not propose a mecha- 1989). Similar offshore marine facies have been described in strata nism to adequately explain this depositional pattern, thus posing an of comparable age in Pennsylvania by Cotter and Driese (1998) and interesting problem. Castle (2000). The amalgamated, cross-bedded sandstone lithofacies is very similar to shoreface deposits described by Clifton et al. (1971), 3. Methods Hunter et al. (1979),andClifton (2006).

Ten Foreknobs Formation sections were measured and described in 4.2. Facies association B this investigation (Fig. 2). These measured sections are positioned in outcrop belts which are oriented approximately parallel to depositional Two lithofacies comprise this facies association: 1) sharp-based con- strike, recording the full spectrum of proximal (eastward) to middle glomeratic sandstone (B1); and 2) pebbly bioturbated sandstone (B2) to distal (westward) facies relationships. Locations of the measured (Table 1; Fig. 4). The sharp-based conglomeratic sandstone lithofacies sections are given in Appendix A and details of the sections are avail- is interpreted to have been deposited within a shoreface depositional able in McClung (1983). Lithofacies were identified, described, and setting near and above fair-weather wave-base. Beds displaying plane- grouped into facies associations based on their characteristics and laminations and HCS were deposited in lower shoreface settings under co-occurrence. Environments of deposition of the facies associations the influence of storms, whereas cross-stratified beds developed under are interpreted on the basis of lithologies, sedimentary structures, the influence of unidirectional currents in an upper shoreface setting. contact relationships, and fossils. In addition, paleosols were identi- The relatively thin cap of pebbly bioturbated sandstone lithofacies is fied and their macromorphologic and micromorphologic features interpreted as a transgressive sheet sandstone, indicative of base-level were described (following Brewer, 1964; Fitzpatrick, 1993; Munsell rise, ravinement, and drowning (TRS: transgressive ravinement surface; W.S. McClung et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 387 (2013) 104–125 109

Fig. 3. (A) Facies model for idealized facies association A. (B) Outcrop photograph of facies association A coarsening-upward parasequences (Rt. 50, Augusta, WV: 16–41 m, see Fig. 9); lithofacies A1–A2–A3: offshore; lithofacies A4: shoreface; C-U: coarsening-upward; FS: ﬂooding surface. (C) Rose diagrams of ﬂute-cast paleocurrent and wave-ripple-oscillation directions from HCS sandstone lithofacies (A3) and amalgamated cross-bedded sandstone lithofacies (A4).

terminology from Catuneanu et al., 2011). Similar sharp-based sand- Similar facies are described within the Catskill Formation of stone bodies are described and interpreted as shoreface sandstone Pennsylvania and New York, and have been interpreted as deposits of bodies within the Lock Haven Formation (northern equivalent of the an alluvial plain setting, including both fluvial channel and overbank Foreknobs Formation) of north-central Pennsylvania (Castle, 2000). deposits (Allen and Friend, 1968; Tunbridge, 1981). Associations of sim- In addition, Walker and Plint (1992) and Bergman and Walker ilar lithofacies are well documented from modern alluvial settings (e.g., (1987, 1995) described similar sharp-based sandstone bodies from Miall, 1977, 1992; Bridge, 2006). the Upper Cretaceous Cardium Formation of western Canada and Shannon Sandstone of Wyoming which they interpret as shoreface 4.4. Facies association D sandstone bodies. This facies association is comprised of five lithofacies: 1) coarse con- 4.3. Facies association C glomerate (D1); 2) channelized pebbly sandstone (D2); 3) Skolithos- burrowed sandstone (D3); 4) interbedded black shale and sandstone This facies association consists of three lithofacies: 1) heterolithic (D4); and 5) pebbly bioturbated sandstone (D5) (Table 1; Fig. 6). The redbeds (C1); 2) reddish-gray sandstone (C2); and 3) bioturbated sand- coarse conglomerate lithofacies (D1) is interpreted to have been depos- stone (C3) (Table 1; Fig. 5). Facies association C is interpreted to have ited in a braided stream setting, including gravel bars and bedforms (GB been deposited in a fluvial system. Specifically, the reddish-gray sand- element, Miall, 1992). The channelized pebbly sandstone lithofacies stone lithofacies (C2) represent fluvial channel deposits (Table 1;LS, (D2) is interpreted to have been deposited in a braided stream setting, SB, and LA elements of Miall, 1992), an interpretation which is support- including sandy bedform (SB) and lateral accretion (LA) elements of ed by sharp irregular bases, sedimentary structures, and red mudstone Miall (1992). The interbedded black shale and sandstone lithofacies clasts. The heterolithic redbed lithofacies (C1) represents overbank de- (D4) was deposited in overbank to estuarine margin marshes (OF ele- posits flanking channels (OF element of Miall, 1992). The abundance of ment of Miall, 1992; Zaitlin et al., 1994). This is corroborated by the pres- asymmetric ripple cross-lamination corroborates the interpretation of ence of current-ripple cross-lamination indicating unidirectional current unidirectional flow within a fluvial depositional environment. In addi- flow and the abundance of plant debris. The Skolithos-burrowed sand- tion, the presence of rare dessication cracks indicates periodic wetting stone lithofacies (D3) represents rapid marine drowning of the underly- and drying which is typical of overbank environments. The relatively ing channelized pebbly sandstone lithofacies (D2). The relatively thin thin and capping bioturbated sandstone is interpreted as a transgressive and capping pebbly bioturbated sandstone lithofacies (D5) is interpreted sheet sandstone, indicative of base-level rise, and drowning; its basal as a transgressive sheet sandstone, indicative of base-level rise, and surface is a transgressive ravinement surface (TRS). drowning; its basal surface is a transgressive ravinement surface (TRS). 110 W.S. McClung et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 387 (2013) 104–125

Fig. 4. (A) Facies model for idealized facies association B. (B) Outcrop photograph of facies association B speciﬁcally, sharp-based conglomeratic sandstone lithofacies (B1) overlying a regressive surface of marine erosion (RSME) truncating facies association A (Rt. 33, Shenandoah Mountain, WV: 70–80 m, see Fig. 9). (C) Rose diagram of ﬂute-cast paleocurrent direction from sharp-based conglomeratic sandstone lithofacies (B1).

The close association of these lithofacies and their inferred deposi- paleosols were identified within the Foreknobs Formation (Table 2; tional environments indicates facies association D is the result of depo- Fig. 7). These soil types represent differences in soil orders (as per sition within incised-valleys. Reconnaissance field work nearby the two USDA Taxonomy; Soil Survey Staff, 1998)aswellasgradationsinthede- outcrops where facies association D crops out failed to find any evidence gree of pedogenic features within individual soil orders (Fig. 7). These of significant conglomerate. This, plus their overall rarity, suggests they four levels represent differing degrees of ancient soil formation (on a are not laterally extensive, nor sheet-like deposits, consistent with our scale of 1 to 4 with 4 = greatest), as well as pedologic features critical interpretation. The basal surface of facies association D is sharp, and to paleoenvironmental and paleoclimatic interpretations (Figs.7,8). overlies the mudrock and shale lithofacies of facies association A. Mud- stone intraclasts within the channelized pebbly sandstone lithofacies 6. Sequence stratigraphy indicates erosional truncation of underlying facies association A. Abun- dant coalified plant debris associated with the coarse conglomerate A sequence stratigraphic framework is proposed to explain the cyclic lithofacies (D1) indicates that water-logged material was vigorously and overall progradational nature of the Foreknobs Formation (termi- transported downcurrent, rapidly deposited, and covered before further nology after Catuneanu et al., 2011). This framework is based on four organic deterioration could take place (cf., Miall, 1977). Finally, the criteria: 1) vertical juxtaposition and repetitive patterns of cyclicity of presence of fining-upward successions from channelized pebbly sand- the four facies associations; 2) cycle stacking patterns; 3) recogni- stone (D2) to the interbedded black shale and sandstone lithofacies tion of a hierarchy of three scales of cyclicity; and 4) types of major (D4) is similar to composite conglomeratic channel-bars transitioning bounding surfaces. The lithofacies and facies associations, and their to overbank or estuarine deposits. vertical juxtaposition, are different at different positions across the study area. Also, the thickness scales of proximal versus distal facies 5. Paleosols associations overlap significantly because of presumed differences in accommodation space and sedimentation rates in the different depo- A total of 20 paleosol profiles were measured and described from the sitional settings. Augusta, Baker, and Shenandoah Mountain sections (Fig. 2). We have The study area occupies a portion of the ramp developed in the fore- chosen to not classify these profiles as individual pedotypes at this land basin west of the Acadian Mountain Belt (Ettensohn, 1985). From time (sensu Retallack, 1994) since our pedologic interpretations are east to west, the study area is divisible into three facies belts, based on only based on macroscopic observations and limited petrographic anal- occurrence of lithofacies and facies associations. These facies belts are ysis. Instead, a relative ranking of the degree and type of soil formation approximately parallel to the inferred paleoshoreline. The proximal fa- is provided pending acquisition of geochemical and clay mineralogy cies belt (furthest east) is characterized by alternating fluvial redbeds data, as well as additional petrographic data. Four main types of (facies association C) and offshore marine strata (facies association A), W.S. McClung et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 387 (2013) 104–125 111

Fig. 5. (A) Facies model for idealized facies association C. (B) Outcrop photograph of facies association C interbedded with facies association A showing parts of two high-frequency sequences (HFS) separated by a subaerial unconformity (SU); also note transgressive surface of ravinement (TRS) (note 50 cm long pick-hammer in lower right) (Rt 33, Shenandoah Mtn, WV: 710–727 m, see Fig. 9). (C) Outcrop photograph of facies association C overlying and truncating facies association A with subaerial unconformity (SU) (CR 33/4, Briery Gap, WV: 640–644 m, see Fig. 12). and includes the inferred paleoshoreline. The middle facies belt is char- widely throughout the world on continental shelves (Walker and acterized by offshore marine strata (facies association A) with Plint, 1992). numerous occurrences of sharp-based conglomeratic (shoreface) sandstones (facies association B). The distal facies belt (furthest west) is 6.1. Short-term (5th-order) cycles almost entirely offshore marine strata (facies association A). Due to the overall progradational nature of the Foreknobs Formation, the posi- Within some portions of the western sections as well as the lower tions of these facies belts shift westward over time. portions of eastern sections of the Foreknobs Formation (middle facies The Foreknobs Formation approximately spans the middle part of belt), the short-term cyclicity consists of repeated successions of Conodont Zone 11 through the middle part of the triangularis Zone of coarsening- and shallowing-upward marine strata (facies association the Montagne Noire standard, based on correlation with the upper A; either A1–A3, or A1–A4 where fully developed) (Figs. 3, 9;forexam- Rhinestreet through lower Dunkirk interval (Over, 1997). By compari- ple, Shenandoah Mountain 0–70 m, 480–530 m; Baker 0–85 m). In son of these conodont zones with detailed Devonian chronostratigraphy contrast, within the upper portions of eastern sections of the Foreknobs established by Kaufmann (2006), the Foreknobs Formation is inferred to Formation (proximal facies belt), the short-term cyclicity is represented have been deposited during a time span of approximately 4.5 Myr, thus predominantly by offshore marine strata (facies association A) overlain permitting reliable estimates of the temporal duration of the cyclicity. by fluvial redbeds (facies association C; specifically lithofacies C1 and The cycles recognized herein match the temporal durations of three of C2) with sharp and locally truncated contacts (Figs. 5, 9; for example, the orders of Vail et al. (1991): 5th-order cycles span 10's of thousands Augusta 117–173 m, 210–249 m). Fluvial redbeds (facies association of years, 4th-order cycles span 100's of thousands of years, and 3rd-order C) are next overlain by offshore marine strata (facies association A; cycles span a few millions of years (typically b3Myr)(Vail et al., 1991; shaly lower portion to be specific), locally with the bioturbated sand- Plint et al., 1992; Miall, 2010). stone lithofacies (C3) defining the boundary between the two facies We infer the amplitude of relative sea-level fluctuations which pro- associations. Pedogenic development is locally present capping fluvial duced the cyclicity from the vertical juxtaposition of lithofacies and redbeds. Based on the data presented herein, we estimate there are facies associations, and their inferred depositional environments rela- approximately 70 short-term cycles within the Foreknobs Formation. tive to fair-weather (FWWB) and storm wave-base (SWB). To quantify Each short-term cycle represents approximately 65 kyr, and are thus estimates of sea-level rise and fall, our facies associations were com- 5th-order. The short-term cycles are interpreted to be the product of pared with observed FWWB and SWB in the modern Arabian/Persian high-frequency relative sea-level fluctuations. Gulf, which is a foreland basin somewhat analogous to that of the The extent of relative sea-level fall associated with short-term cyclic- Appalachian Acadian foreland basin. In the Arabian Gulf, FWWB is ap- ity is estimated based on the amalgamated cross-bedded sandstone proximately 5–15 m deep, whereas storm wave-base is approximately lithofacies (A4) directly overlying shaly offshore marine strata of facies 40–50 m deep (Purser and Seibold, 1973). Similar depths are reported association A (bioturbated mudrock, shale, and HCS sandstone). This 112 W.S. McClung et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 387 (2013) 104–125

Fig. 6. (A) Facies model for proximal and distal IVF. (B) Outcrop photograph of proximal IVF near top of Foreknobs Formation; coarse conglomerate lithofacies (D1) (Rt 33, Shenandoah Mountain, WV, 776–786 m, see Fig. 9). (C) Outcrop photograph of distal IVF; channelized conglomeratic sandstone lithofacies (D2) overlain by interbedded black shale and sandstone lithofacies (D4) in turn overlain by channelized conglomeratic sandstone lithofacies (D2); note cut and fill features (arrows) within interbedded black shale and sandstone lithofacies (D4) (1.5 m Jacob staff in lower left-center; Rt 33, Elkins, WV: 340–360 m, see Fig. 15). juxtaposes rocks deposited above fair-weather wave-base (b5 m to up- within extremely fine-grained sediment. Shallowing-upward succes- wards of 15 m deep) and rocks deposited below but near fair-weather sions of this type can be formed either by rapid progradation during wave-base (shallower range of 15–50 m), respectively. Approximately constant base-level, or by forcing due to base-level fall as described by 10–15 m of sea level fall is estimated to account for this facies juxtapo- Posamentier et al. (1992). The observation that up-paleoslope to the sition (Fig. 10). Cotter and Driese (1998) inferred that muddy shoreline east, the parasequences are truncated by a SU which are, in turn, over- “motifs” in equivalent strata in Pennsylvania, also characterized by the lain by fluvial redbeds (facies association C) strongly suggests that juxtaposition of fluvial redbeds (facies association C) over marine strata forced regression is the most likely explanation. (facies association A), are a result of similar sea-level amplitude. Subsequent relative sea-level rise resulted in deposition of another During sea-level highstands, a coarsening-upward and aggradational/ coarsening-upward succession comprised of offshore marine strata progradational succession of offshore marine strata (facies association (facies association A; specifically A1–A3), in the middle facies belt A; specifically A1–A3: bioturbated mudrock, shale, and HCS sandstone (Fig. 11A: Time 3). In the proximal facies belt, fluvial redbeds lithofacies) was deposited across most of the study area (Fig. 11A: (heterolithic redbeds or reddish-gray sandstone lithofacies) aggraded Time 1). A subsequent, abrupt relative sea-level fall induced a forced re- on the alluvial plain to the east and up-paleoslope of the inferred shore- gression that exposed and eroded the upper part of facies association A line (Fig. 11A: Time 3). The laminated nature of most of the heterolithic in the proximal facies belt and produced a subaerial unconformity (SU) redbeds lithofacies is indicative of relatively short exposure duration, landward of the new shoreline (Fig. 11A: Time 2). Seaward of the new and is consistent with our interpretation that these short-term cycles shoreline, in the middle facies belt, this rapid forced regression was represent high-frequency, 5th-order cycles. Paleosols are only local- responsible for the rather abrupt and thin transition from the shale- ly developed. Continued sea-level rise ultimately drowned the allu- dominated part of facies association A (A1–A3) to the amalgamated, vial plain locally producing a thin veneer of bioturbated sandstone cross-bedded sandstone lithofacies (A4) (Fig. 11A: Time 2). Although lithofacies (C3) on top of a transgressive ravinement surface (TRS) it is possible that truncation, and hence development of a regressive (Fig. 11A: Time 4). This was succeeded by renewed deposition of off- surface of marine erosion (RSME; Walker and Plint, 1992; Catuneanu shore marine strata (facies association A) across the proximal facies et al., 2011) occurred locally, conclusive evidence for such has not belt during the next sea-level highstand (Fig. 11A: Time 4). Finally, been observed. Seaward, but still in the middle facies belt, this horizon the next rapid relative sea-level fall again produced a SU in the prox- becomes a correlative conformity (CC) at the top of a coarsening- imal facies belt, and its CC in the distal facies belt as described above upward succession of offshore marine strata (facies association A; (Fig. 11A: Time 5). specifically A1–A3) (Fig. 11A: Time 2). Still further seaward and in In the middle facies belt, these short-term cycles resemble deeper water of the distal facies belt, these cycles are unrecognizable parasequences (Fig. 9; for example, Shenandoah Mountain 0–70 m, in outcrop through standard field methods due to very subtle changes 480–530 m; Baker 0–85 m). Up-paleoslope in the proximal facies Table 2 Paleosol data. *Soil classification after soil Survey Staff (1998).

Orig. strata Profile thickness Color Horizonation Relict bedding Peds Roots Other Soil order*; interpretation; time of development ..MCuge l aaoegah,Pleciaooy aaoclg 8 21)104 (2013) 387 Palaeoecology Palaeoclimatology, Palaeogeography, / al. et McClung W.S.

Level 1 - weakly developed

cm - 10's cm 0.2 - 0.5 m 10R 3/2 to Weakly developed soil Prominent Medium angular blocky to Infrequent - drab- scale fining- 10R 4/2 Hyneria sp.fish Entisol (Udifluvent); Immature soils forming structure and microfabric; blocky within mudstone, haloed when present, scales and some upward fluvial (Dusky Red gradual lower contact over on proximal floodplain settings under a humid medium platy lower in 5GY 7/1 to 2.5YR 7/4 successions to Weak Red) invertebrate burrows climate; 10's to 100's yrs 2-3 cm with lowermost profile (Light Greenish Gray 2mm in diameter sandstone and sharp, wavy to Pale Yellow) and 5 cm in length (2-5 cm) upper contact with overlying sandstone

Level 2 - weakly to moderately developed

cm - 10's cm 0.2 - 0.5 m 10R 3/2 to Limited to differences in Minor, but increases with Medium to coarse angular Frequent - drab- scale fining- 10R 4/2 Entisol to Inceptisol (Udifluvent to parent sediment and as a depth blocky to blocky within haloed, 5GY 7/1 to Hapludept); Immature to incipient soil upward fluvial (Dusky Red concentration of roots at mudstones, platy lower in 2.5YR 7/4 (Light successions to Weak Red) formation on proximal to medial floodplain top; sharp upper contact profile Greenish Gray to Pale settings under a humid climate; 10's to 1,000's yrs with overlying sandstone Yellow)

Level 3 - moderately developed

cm - 10's cm 0.3 - 0.8 m 10R 3/2 to Well developed; gradual Preserved in varying Medium wedge shaped Few to common - drab- Vertisol (Uderts); Expansive soils forming scale fining- 10R 4/2 lower contact with degrees, mainly in basal peds with slickensides in haloed, 5GY 7/1 to upward fluvial (Dusky Red under a climate with pronounced seasonality; sandstone and sharp upper portion of profile mudstone becoming 2.5YR 7/4 (Light 10's to 1,000's yrs successions to Weak Red) contacts with individual medium platy with depth; Greenish Gray to Pale sandstone beds curvilinear fractures Yellow) – 125

Level 4 - strongly developed

cm - 10's cm 0.5 - 0.8 m 10R 3/2 to Prominent; sharp lower and Minor at depth, to none Very fine to medium Abundant - drab- scale fining- Soil microfabrics in Vertisol (Uderts); Expansive soils forming 10R 4/2 upper contacts between wedge shaped peds with haloed, 5GY 7/1 to mudstones include upward fluvial (Dusky Red individual profiles under a climate with pronounced seasonality; slickensided surfaces; 2.5YR 7/4 (Light successions clinobimasepic, 10's to 1,000's yrs to Weak Red) curvilinear fractures, Greenish Gray to Pale vosepic, and some fractures near Yellow) omnisepic profile tops are infilled with silt and sand 113 114 W.S. McClung et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 387 (2013) 104–125

Fig. 7. Diagram of example paleosol profiles representing varying levels of pedogenic alteration (on a scale of 1 to 4 with 4 = greatest pedogenic alteration); A: uppermost soil horizon, zone of loss or mix of mineral matter and organics; B: zone of accumulation via translocation from overlying horizons; Bss: slickensided B horizon; Bw: Cambic horizon, incipient formation of a B horizon; C: parent material; 2C: parent material of different grain size. See Fig. 9 for the stratigraphic position of individual profiles. belt, these cycles are unconformity-bounded, and therefore are techni- association A) which alternate with multiple 5th-order cycles domi- cally sequences (Fig. 9; for example, Augusta 117–173 m, 210–249 m). nated by fluvial redbeds (facies association C) (Figs.9,12; for exam- We refer to them as high-frequency sequences (HFS) because of their ple, Augusta 85–117 m versus 117–140 m; Baker 466–509 m versus relative thinness and inferred short duration of deposition. These 509–535 m). The 5th-order cycles either thicken upward (predomi- HFSs, consisting of alternating gray-green marine strata and red fluvial nantly offshore marine strata of facies association A) or thin upward strata (Figs. 5, 9), have previously been described as muddy shoreline (including fluvial redbeds of facies association C), demonstrating in- “motifs” where they occur in similar-aged strata in Pennsylvania creasing accommodation followed by decreasing accommodation. (Walker, 1971; Walker and Harms, 1971; Cotter and Driese, 1998). Within this part of the Foreknobs Formation, pedogenic develop- These workers attributed their deposition to prograding muddy ment is present at all of the intermediate-term cycle boundaries. shorelines. As we have demonstrated, however, the fluvial redbeds McCarthy and Plint (1998) describe similar pedogenic alteration unconformably overlie the offshore marine strata, thus making it unlikely from comparable strata in the Upper Cretaceous of western Canada. that they are genetically related as part of a single progradational succes- The short-term parasequences and HFSs are stacked into approxi- sion. Moreover, the ubiquitous presence of sandy and conglomeratic mately 12 intermediate-term cycles (Fig. 12). Each intermediate-term shoreface deposits (amalgamated, cross-bedded sandstone lithofacies cycle is inferred to represent approximately 375 kyr, and are thus 4th- A4 and sharp-based conglomeratic sandstone lithofacies B1, respectively) order. Our temporal interpretations of 4th- and 5th-order cyclicity are precludes the existence of a muddy shoreline. consistent with conclusions of previous authors regarding Late Devoni- an cycle durations within the Appalachians (Van Tassell, 1994; Cotter 6.2. Intermediate-term (4th-order) cycles and Driese, 1998; Castle, 2000; Filer, 2002). The amplitude of relative sea-level fall associated with the Within some portions of the western sections, as well as the lower intermediate-term cycles is estimated based on the sharp-based portions of the eastern sections of the Foreknobs Formation (middle fa- conglomeratic sandstone lithofacies (B1) sharply overlying truncated cies belt), the intermediate-term cyclicity is represented predominantly offshore marine strata of facies association A (bioturbated mudrock by facies association B (specifically, sharp-based conglomeratic sand- and shale lithofacies). This juxtaposes rocks deposited near and above stone lithofacies B1) sharply overlying truncated parasequence sets fair-weather wave-base within a shoreface depositional setting (b5to comprised of coarsening-upward marine strata of facies association A 15 m) and rocks deposited perhaps closer to storm wave-base (deeper (Figs.4,9,12; for example, Shenandoah Mountain 74, 173, 247, 280 m; range of 20–50 m), respectively. Approximately 25–35 m of sea-level Baker 85, 124 m; Briery Gap 305, 335, 460, 560, 626 m). The sharp- fall is estimated to account for this facies juxtaposition (Fig. 10). based conglomeratic sandstone lithofacies (B1) is typically overlain by During 4th-order sea-level highstands, up to 7 stacked 5th-order the thin pebbly bioturbated sandstone lithofacies (B2) succeeded by off- “parasequences” or HFSs were deposited in the middle and proximal shore marine strata (facies association A) (Figs.4,12). facies belts, respectively (Fig. 11B: Time 1). Subsequently, a higher- In the upper portion of eastern sections of the Foreknobs Formation amplitude relative sea-level fall produced lowstand conditions, and (proximal facies belt), the intermediate-term cyclicity is recognized by resulted in a forced regression which exposed the proximal facies multiple 5th-order cycles dominated by offshore marine strata (facies belt landward of the new shoreline (Fig. 11B: Time 2). This exposure W.S. McClung et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 387 (2013) 104–125 115

Fig. 8. Outcrop photographs and photomicrographs of paleosol features with original up directions (U). See Fig. 9 for the stratigraphic position of individual profiles. (A) Relict bedding (R) and incipient soil formation. Note blocky structure, cm and inch scale (Rt. 33, Shenandoah Mtn, WV, 823 m). (B) Photomicrograph of fining-upward relict bedding (Rt. 55, Baker, WV, 465 m). (C) Drab-haloed root traces (D), cm scale (Rt. 50, Augusta, WV, 225 m). (D) Invertebrate burrow (B), cm scale (Rt, 55, Baker, WV, 634 m). (E) Curvilinear fractures (CF), some defined with black lines (Rt.50, Augusta, WV, 86 m). (F) Slickensided fracture plane (SS) and silt-filled wedge structures (W), cm scale (Rt. 50, Augusta, WV, 238 m). (G) Clinobimasepic soil fabric (Rt. 50, Augusta, WV, 238 m). (H) Omnisepic fabric (Rt. 50, Augusta, WV, 238 m). Photomicrographs taken under cross-polarized light. produced a SU during which time there was presumably erosion of westward into a CC in the distal facies belt, although these are not some of the underlying parasequence or HFS. Due to the inferred readily identifiable, or distinguishable in outcrop, from their 5th- greater magnitude of relative sea-level fall, and the longer duration order counterparts (Fig. 11B: Time 2). Similar abrupt facies shifts of exposure, the strata at the SU (whether offshore marine strata of have been attributed to forced regression caused by sudden sea-level facies association A or fluvial redbed strata of facies association C) were fall (Posamentier et al., 1992). pedogenically altered. Down-paleoslope to the west in the middle facies The sharp-based conglomeratic sandstone lithofacies (B2) are in- belt, scouring of the sea-floor during relative sea-level fall is inferred to triguing because they are conglomeratic, but in a more distal setting. have produced a RSME (Plint, 1988; Catuneanu et al., 2011). This was This is in contrast to the non-conglomeratic amalgamated cross-bedded overlain by the sharp-based conglomeratic sandstone lithofacies (B1), sandstone lithofacies (A4) of the 5th-order parasequences. Due to the inferred to be a lowstand systems tract (LST), which was deposited con- higher magnitude 4th-order relative sea-level fall, fluvial gradients on currently with paleosol development up-paleoslope (Fig. 11B: Time 2). the alluvial plain are inferred to have increased significantly more This RSME and up-paleoslope paleosol (and SU) are interpreted to define than during the 5th-order fall. This base-level fall is inferred to have en- the lower boundary of a 4th-order sequence. The RSME underlying abled the transport of pebbles within higher-gradient fluvial channels the sharp-based conglomeratic sandstone bodies is inferred to pass down-paleoslope to the marine environment. Pedogenesis occurred in 116 W.S. McClung et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 387 (2013) 104–125

Fig. 9. Measured sections illustrating the 5th-order cycles within the Foreknobs Formation. Tick marks show the position of the 5th-order cycle boundaries; short tick marks are parasequence boundaries; long tick marks are high-frequency sequence (HFS) boundaries.

interfluve environments between the fluvial channels (McCarthy and higher relative sea-level resulted in deposition of multiple, stacked, Plint, 1998). thinning-upward 5th-order parasequences or HFSs, as described previ- Subsequent relative sea-level rise drowned the sharp-based con- ously (Fig. 11B: Time 4). These strata comprise the highstand systems glomeratic sandstone lithofacies and pedogenically-altered interfluves tract (HST) of the 4th-order sequence. Finally, the next major relative of the alluvial plain. A thin layer of pebbly bioturbated sandstone sea-level fall and lowstand conditions again produced subaerial exposure lithofacies (B2), which formed from reworking underlying sediment (SU) and pedogenesis, with a corresponding RSME down-paleoslope in during transgression, typically overlies the sharp-based conglomeratic the marine environment, and with deposition of another sharp-based sandstone bodies as well as the up-paleoslope paleosols (Fig. 11B: conglomeratic sandstone body (Fig. 11B: Time 5). These unconformity Time 3). However, fluvial redbeds (facies association C) are locally pre- surfaces form the upper boundary of a single 4th-order sequence. served overlying paleosols, and are interpreted to be a product of fluvial Depending on position relative to the facies belts and the shoreline, aggradation related to sea-level rise analogous to the fluvial aggradation slightly different patterns of lithofacies developed within the TST of during development of the 5th-order HFSs. The surface between each 4th-order cycle (Fig. 13). Nearest to the shoreline in the most prox- the sharp-based conglomeratic sandstone lithofacies (B1) and the peb- imal region, where accommodation space was limited, the ramp was bly bioturbated sandstone lithofacies (B2) represents a transgressive subaerially exposed during the 5th-order sea level falls. Thus, HFSs ravinement surface (TRS). It is plausible that more mature paleosols consisting of alternating offshore marine strata (facies association A) were developed on the alluvial plain but were eroded and removed dur- and fluvial redbeds (facies association C) were deposited (Fig. 9;forex- ing ravinement (cf., Van Wagoner et al., 1990; Embry, 2009). Continued ample, Augusta 140–162 m, 210–222 m). Further out to sea, water was relative sea-level rise resulted in deposition of a few thickening upward deep enough such that the 5th-order sea-level falls were not sufficient 5th-order cycles, typically dominated by offshore marine strata of to expose the ramp. Thus, thicker parasequences entirely consisting of facies association A (Fig. 11B: Time 4). The TRS, pebbly bioturbated offshore marine strata (facies association A) were deposited in the west- sandstone, and these thickening upward parasequences or HFSs, repre- ern part of the proximal facies belt and the middle facies belt (Fig. 9;for sent the TST of the 4th-order sequence. An ensuing extended period of example, Augusta 58–74 m, 85–110 m). Still further out to sea, in much W.S. McClung et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 387 (2013) 104–125 117

Fig. 10. Inferred amplitudes of sea-level fluctuations for 5th-order, 4th-order, and 3rd-order (IVF maximum) cycles; fair-weather wave-base (FWWB) and storm wave-base (SWB) of 10 m and 45 m deep, respectively, from Purser and Seibold (1973); letters with numbers refer to lithofacies. of the distal facies belt, there is very little evidence of the 5th-order indicates that the sharp-based conglomeratic sandstones were deposited sea-level falls thus making recognition of 5th-order cycles difficult or in shallower water than the underlying shaly dominated part of offshore impossible to detect, and producing CCs within intervals of offshore marine strata (facies association A; specifically A1–A3), suggesting marine strata (facies association A) (Fig. 12; for example, Briery Gap regression rather than transgression. Second, because the underlying 0–300 m). strata are predominantly shaly, and lack pebbles, it is unlikely that Similarly, slightly different patterns of lithofacies developed within winnowing of such sediment would produce conglomeratic sandstone. the HST of each 4th-order cycle, depending on position relative to the facies belts and the shoreline (Fig. 13). Nearest to the shoreline in the 6.3. Long-term (3rd-order) cycles and incised-valley fills most proximal region, 5th-order cycles are dominated by, or comprised entirely of, fluvial redbeds (facies association C) (Fig. 9;forexample, The intermediate-term cycles are stacked into three complete, and Baker 508–535 m, 558–580 m). Somewhat further down paleoslope, portions of two additional long-term cycles. Each long-term cycle is in- but still within the proximal facies belt, 5th-order cycles consist of alter- ferred to represent approximately 1.12 Myr, and are thus 3rd-order. nating offshore marine strata (facies association A) and fluvial redbeds This is consistent with temporal durations of 3rd-order cycles recog- (facies association C) (Fig. 9; for example, Augusta 110–140 m, 157– nized by Haq and Schutter (2008). The 3rd-order cycles are best recog- 172 m). Some paleosol development took place yielding immature nized in the proximal and middle facies belts, exemplified by the soils. Further down paleoslope in the middle facies belt, the 5th-order Shenanadoah Mountain and Briery Gap sections (Fig. 14). cycles are comprised entirely of coarsening-upward marine strata The highstand portion (HST) of most of the 3rd-order cycles is recog- (facies association A) (Fig. 9;forexample,Augusta0–50 m; Shenandoah nizable by a series of thinning-upward 4th-order cycles, each composed Mountain 0–73 m). Further out to sea in the distal facies belt, 5th-order of offshore marine strata (facies association A) and bounded by sharp- cycles are difficult or impossible to detect as CCs within intervals of off- based conglomeratic (shoreface) sandstone lithofacies B1 (Figs. 9, 12, shore marine strata (facies association A) (Fig. 12; for example, Briery 14; for example, Shenandoah Mountain 0–300 m; Baker 0–125 m). In Gap 0–300 m). other cases, primarily in the upper part of the Foreknobs Formation, Dennison (1970) stated that all five members of the Foreknobs 3rd-order highstands are comprised of westward-extending tongues Formation vary in thickness from one outcrop to the next (Fig. 1). More- of multiple-stacked cycles partially or totally composed of fluvial over, he also explained that the Briery Gap and Pound Sandstone mem- redbeds (facies association C). In some cases, these fluvial redbeds bers change facies abruptly perpendicular to depositional strike, and are associated with sharp-based conglomeratic sandstone bodies or that these members are not confidently identifiable east or west of the paleosols (Fig. 14; for example, Briery Gap 560–650 m; Shenandoah Allegheny Front (Fig. 2). We concur with these observations. Our se- Mountain 400–475 m). Both types of successions indicate decreas- quence stratigraphic framework provides the key to understanding ing accommodation space in different positions on the ramp. The the variability and lack of lateral continuity of Dennison's members per- transgressive portion (TST) of most 3rd-order cycles is less distinctive, pendicular to depositional strike. We interpret both the Briery Gap and typically represented by intervals of offshore marine strata (facies asso- Pound Sandstone Members to be lowstand system tracts (LST) deposit- ciation A) without sharp-based conglomeratic sandstone bodies, or ed just seaward of the shoreline during 4th-order relative sea-level falls. eastward-extending tongues of offshore marine strata (facies associa- As the LST correlates up-paleoslope to the east with paleosols, and tion A) (Fig. 14; for example, Shenandoah Mountain 480–530 m; Briery down-paleoslope to the west with a CC within offshore marine strata Gap 480–560 m). Most of the 3rd-order boundaries are inferred to (facies association A), neither member is present in their typical form be associated with sea-level amplitude fluctuations comparable with east or west of the Allegheny Front type outcrop belt. those of the 4th-order cycles because the same facies are vertically Dennison (1970) hypothesized that the Briery Gap and Pound juxtaposed. Sandstone Members (Fig. 1) represent barrier deposits formed from Two occurrences of incised-valley fills are located at one of the transgressive winnowing of underlying sediments. We disagree with 3rd-order cycle boundaries in the uppermost part of the Foreknobs For- this interpretation for two reasons. First, the sedimentologic evidence mation (Figs. 14, 15; for example, Shenandoah Mountain 776–786 m; 118 W.S. McClung et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 387 (2013) 104–125

Fig. 11. Development of 5th-order and 4th-order cycles. (A) Development of 5th-order cycles; 5th-order cycles are nested within the 4th-order cycles. (B) Development of 4th-order cycles; up to seven 5th-order cycles comprise a single 4th-order cycle, but only 2 are shown for simplicity; SL: sea-level; A1–A4: lithofacies of facies association A (offshore to shoreface); B1– B2: lithofacies of facies association B (sharp-based conglomeratic shoreface); C1–C3: lithofacies of facies association C (ﬂuvial redbeds); SU: subaerial unconformity; RSME: regressive surface of marine erosion; SB: sequence boundary; CC: correlative conformity; TRS: transgressive ravinement surface; HFS: 5th-order high frequency sequence. W.S. McClung et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 387 (2013) 104–125 119

Fig. 12. Measured sections illustrating the twelve 4th-order cycles recognized within the Foreknobs Formation. Fifth-order cycles within the enlarged Augusta section are demarcated with tick marks as in Fig. 9;seeFig. 9 for legend.

Elkins 335–400 m). The incised-valley fill (facies association D; specifi- lithofacies D2 overlain by interbedded black shale and sandstone cally coarse conglomerate lithofacies D1 or channelized pebbly sand- lithofacies D4). This is consistent with the interpretation that the IVFs stone lithofacies D2) overlies the truncated and shaly lower portions are a consequence of lower-order cyclicity, containing higher-order cy- of offshore marine strata (facies association A; specifically bioturbated cles within, as well as possibly representing compound IVFs (cf., Zaitlin mudrock and shale lithofacies), with a sharp basal contact (Fig. 6). et al., 1994; Maynard et al., 2006). The conglomeratic IVF lithofacies are, Sea-levelfallexposedsignificant portions of the ramp, and caused inci- in turn, overlain by offshore marine strata of facies association A. These sion into the alluvial plain as well as the sea-floor. This contact directly successions are very similar to the deposits recorded by the rapid Holo- juxtaposes strata deposited below fair-weather wave-base (and possi- cene drowning of the Gironde estuary located in southwestern France bly just above storm wave-base) at 20–50 m water depth, and coarse, (Allen and Posamentier, 1993). conglomeratic braided stream deposits overlying a SU and deposited The overall progradational nature of the Foreknobs Formation is par- above sea-level. This observation suggests the possibility that relative ticularly well illustrated by both vertical and lateral facies relationships sea-level may have fallen in the range of 35–45 m (Fig. 10). Cotter and within the 3rd-order cycles (Figs. 14, 15). Within each successive HST, Driese (1998) discussed IVFs within the red fluvial Catskill Formation progressively more proximal facies dominate. The lowest HST is domi- in Pennsylvania, and argued for a somewhat smaller relative sea-level nated by sharp-based conglomeratic sandstones (B1). HFSs consisting change (10–30 m), although their interpreted IVF deposits were non- of alternating offshore marine strata (facies association A) and fluvial conglomeratic and interpreted specifically as estuarine deposits. redbeds (facies association C) dominate the middle and upper HST. During the initial stages of relative sea-level rise, the incised-valleys Stacked fluvial redbeds of the Hampshire Formation dominate the up- were back-filled with conglomeratic braided-alluvial sediment of facies permost HST (Figs. 14, 15). Within successive HSTs, ever-more proximal association D (coarse conglomerate and channelized pebbly sandstone facies extend progressively further seaward (westward). Finally, the lithofacies), producing the locally observed IVFs at Shenandoah Moun- base of fluvial redbed intervals (facies association C) is diachronous tain and Elkins. Moreover, the IVF at Elkins is multi-storied, and consists and climbs ever-higher in the Foreknobs Formation as a series of step- of several stacked, fining-upward cycles (channelized pebbly sandstone wise shifts toward the west (Fig. 15). 120 W.S. McClung et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 387 (2013) 104–125

Fig. 13. Idealized internal architecture of a 4th-order sequence, showing both facies changes perpendicular to deposition strike across facies belts and the vertical stacking patterns of 5th-order cycles within; LST: lowstand systems tract; SU: subaerial unconformity; RSME: regressive surface of marine erosion; cc: correlative conformity; TST: transgressive systems tract; HST: highstand systems tract.

7. Sequence stratigraphy and paleopedology 8.2. Fourth- and ﬁfth-order: glacioeustasy

Paleosols of the Foreknobs Formation formed in response to relative Based on the regularity and repetitive patterns of the 4th- and 5th- changes in sea-level. As a whole, paleosols from the Augusta section are order cyclicity described herein, we conclude that the dominant control the most mature, whereas those at Shenandoah Mountain are the least on sea-level fluctuations was eustasy superimposed on the subsiding mature (Figs. 9, 12) which suggests that the Augusta section is the most distal portion of the foreland basin foredeep. Interestingly, we recognize proximal. It is also plausible however, that more mature paleosols near the same number of 4th-order cycles as Filer (1994, 2002, 2003),and the shoreline may have been removed by erosion during transgressive suggest that the 12 cycles recognized herein basically correlate with ravinement and this has been discussed in more detail by Van those of Filer as shown in Fig. 15. The suggested correlation is based Wagoner et al. (1990) and Embry (2009). Within the Shenandoah on two tie-points. First, we correlate the major prograding 3rd-order Mountain section, the identified profiles may be inconclusive since a HST that culminates with the Briery Gap Sandstone Member in outcrop good percentage of the upper portion of the section is covered. Between (cycle 6 herein) with the upper part of cycle 7 in the subsurface; this the Baker and Augusta sections, differences in the level of pedogenic agrees with the interpretation presented by Filer (1994, 2002, 2003). modification are evident throughout both sections, with periods of Second, the major 3rd-order TST comprising the uppermost Foreknobs more intense soil formation bracketing multiple episodes of less intense Formation (cycle 12 herein) correlates with the lower Dunkirk Shale in soil formation (Figs. 9, 12). Periods of more intense soil formation are the subsurface; this is consistent with the IVFs representing the major likely the result of relatively large falls in sea-level associated with sea level fall at, or very close to, the Frasnian–Famennian boundary, 4th-order sequence boundaries and likely represent interfluves be- followed by major transgression. This tie-point differs somewhat from tween incised-valley fills. Groupings of multiple, less mature paleosols Filer's correlation to the named members; further work will be necessary may possibly represent the near convergence of 5th-order boundaries to resolve this. Our 4th-order cycles are more easily recognized in the collectively merging up-paleoslope to a 4th-order boundary. Future middle to proximal facies belts where lithofacies contrasts are most ob- studies will be required to shed light on this issue. The facies overlying vious. In contrast, Filer (1994, 2002, 2003) recognized the cycles in the individual paleosols are variable, and reflect both the magnitude of very distal parts of the ramp west of our study area, where well logs sea-level rise and the position along the parasequence for that particular are more sensitive to subtle changes in shales making recognition of soil profile. these cycles easier. In the shalier, western outcrops, the greater degree of covered sections further complicates confident identification of cycles, 8. Relative sea-level controls as opposed to continuous data from subsurface well logs. The ability to correlate the 4th-order cycles in outcrop and subsurface, both parallel 8.1. Third-order: eustasy and perpendicular to depositional strike for long distances across the Acadian foreland basin, strongly suggests that eustatic sea-level fluctua- A 3rd-order sea-level curve for the Foreknobs Formation, based on tions, as opposed to short term tectonics, was the dominant factor in pro- the inferred sea-level amplitudes from the vertical juxtaposition of ducing the cyclicity observed within the Foreknobs Formation. lithofacies within and at 3rd-order cycle boundaries, and well displayed Eustatic control, as opposed to tectonic control, has been suggested at several measured sections (e.g., Shenandoah Mountain and Briery by previous workers for the development of cyclicity within Upper Gap) is illustrated in Fig. 14. This curve is remarkably similar to and cor- Devonian strata of the central Acadian foreland basin. Van Tassell relates almost exactly with the Haq and Schutter (2008) eustatic 3rd- (1987, 1994), Cotter and Driese (1998) and Filer (1994, 2002, 2003) at- order sea-level curve, both in terms of numbers of cycles and the sea- tributed cyclicity in the Foreknobs Formation of northern West Virginia level amplitude of the cycles (Fig. 14). There is also close resemblance to Milankovitch cycles. Castle (2000) ascribed cyclicity in distal facies in to the Johnson et al. (1985) curve. Moreover, the IVFs are very close to, Pennsylvania to a combination of eustasy and tectonics, however, he did or just above, the Frasnian–Famennian boundary (Clausen and not discuss more proximal facies, making estimates of sea-level ampli- McGhee, 1988), and correspond with the highest-amplitude sea-level tude difficult. Filer (1994, 2002, 2003) did not tie the logs to outcrop, fluctuation noted on global sea-level curves (Fig. 14). We conclude that core, or cuttings, thus making recognition of lithofacies, depositional en- the Foreknobs Formation stratigraphy records the globally recognized vironmental interpretations, and estimates of sea-level fluctuation am- 3rd-order sea-level cyclicity. plitudes difficult. W.S. McClung et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 387 (2013) 104–125 121

Fig. 14. Measured sections illustrating the 3rd-order cycles within the Foreknobs Formation; Fischer plots calculated as cumulative sum of difference between individual 4th-order cycle thickness and mean 4th-order cycle thickness; Foreknobs Formation sea-level curve based on sea-level amplitudes associated with vertical facies juxtapositions and stacking pattern trends; see Fig. 9 for legend; geochronology is based on Kaufmann (2006), Bond and Wignall (2008),andVan Tassell (1994); global sea-level curve is based on Haq and Schutter (2008); glacial events are based on Caputo (1985), Crowell (1999) and Brezinski et al. (2008, 2009, 2010).

Autocyclic controls on sequence development require static sea-level Devonian. These same workers have also suggested that the amplitude for relatively long periods of time to produce continuous and related fa- of sea-level fluctuations increased in a step-wise manner from the cies successions (Kosar et al., 1990; Maynard et al., 2006),butthisiscon- Frasnian into the Famennian stages of the Late Devonian as expected trary to the stratigraphic record of the Foreknobs Formation. Autocyclic if ice volume was increasing (Fig. 14). Various workers have identified processes would be too localized to explain the regional extent of the cy- glacialdepositsinSouthAmericabothduringLateFrasnian(Crowell, clicity (Filer, 1994),ortheamplitudeofsea-levelfluctuations, observed 1999) and Late Famennian (Caputo, 1985), and in the central Appala- within the Foreknobs Formation. Cotter and Driese (1998) reached a chians of North America during Late Famennian (Brezinski et al., 2008, similar conclusion for the Catskill Formation (=Hampshire Formation) 2009, 2010), indicating these time intervals were icehouse. in Pennsylvania. Amplitude of icehouse sea-level fluctuations is a consequence of the total volume of ice and is related to the areal size and number of ice 9. Glacioeustasy: transitional greenhouse to icehouse world sheets. For example, Late Cenozoic icehouse conditions were very severe and sea-level fluctuations were very large (100–140 m) due to very We suggest an interesting parallel between the greenhouse to ice- large volumes of ice contained within four dominant ice sheets during house transition of the Cenozoic to that of the Middle to Late Devonian. glacial maxima (Cuffey and Paterson, 2010). Moreover, the Late Cenozoic Moreover, the hierarchy of temporal scales of cyclicity and the inferred ice sheets did not appear simultaneously; instead there was a protracted amplitudes of sea-level fluctuations expressed within the Foreknobs transitional period with stepwise increase of ice volume. Greenhouse Formation can reasonably be interpreted as evidence for transitional conditions prevailed through the Cretaceous, Paleocene, and into the greenhouse to icehouse conditions during the Middle to Late Devonian. Eocene. The Antarctic ice sheet first developed at 35 Myr (latest Eocene Various workers have suggested relatively small amplitude 3rd-order or earliest Oligocene), followed by the initial inception of the Greenland sea-level fluctuations during the Middle to early Late Devonian (Early ice sheet at 6–7 Myr (latest Miocene), followed finally by the Laurentide Frasnian), consistent with greenhouse-magnitude meter-scale sea- and Fennoscandian ice sheets at 2.5 Myr (Pleistocene) (Cuffey and level amplitude (Fig. 14)(e.g.,Johnson et al., 1985; Haq and Schutter, Paterson, 2010). It is reasonable to conclude that as each ice sheet 2008). Currently, there is no evidence of glacial ice during the Middle formed, sea-level fluctuations would have increased between the glacial 122 W.S. McClung et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 387 (2013) 104–125

Fig. 15. Northwest to southeast cross-section parallel to depositional paleoslope based on interpretation of the sequence stratigraphic framework herein; note the Pound and Briery Gap Sandstone members within the Briery Gap section (Dennison, 1970); subsurface electric logs redrawn from Filer (1994). Fourth-order sequences (1–12) noted between the Har- rison Co., WV, and Barbour Co., WV, electric logs from Filer (1994). Fourth-order sequences (1–12) recognized between the Elkins, WV, and Briery Gap, WV, sections from this study. F/F (=Frasnian–Famennian boundary) noted on Filer's (1994) Noble, Co., electric log from conodont biostratigraphy by Over (1997, 2002). F/F noted on Briery Gap section (Pound Sandstone Member) from brachiopod biostratigraphy by McGhee (1977). and interglacial episodes. Thus, a step-wise increase in ice volume, tran- portions of the Late Devonian and then compared with the known sitional from greenhouse conditions of Middle and early Late Devonian distribution and aerial extent of glacial deposits from that time period. (early Frasnian) to icehouse conditions of the Latest Devonian (Late Future work would need to be done to test and corroborate this sugges- Famennian), is hypothesized. tion (association) by seeking further evidence not only of the presence We have demonstrated that Foreknobs Formation 5th- and 4th- of ice, but also aerial extent, number of ice sheets, and ice sheet volume, order cycles were produced by relative sea-level fluctuations in the all beyond the scope of this paper. range of 10–15 m and 25–35 m respectively; and that one of the 3rd- These conclusions are further supported by a comparison of the order sea level fluctuations was in the range of upwards of 35–45 m. Foreknobs Formation cyclicity with architectural differences between These are larger than greenhouse fluctuations, but not as large as classic sequences and parasequences deposited during greenhouse and ice- icehouse conditions as compared to the Pleistocene with multiple ice house times described earlier. Specifically, the abrupt shifts of fluvial sheets (100–140 m). Instead, the Foreknobs Formation sea-level fluctu- redbeds and incised-valley fill facies (facies associations C and D, respec- ations appear to be intermediate in amplitude, and hence indicative of tively) over offshore marine facies (facies association A) as well as more a transitional period between greenhouse and icehouse conditions, or dramatic flooding of offshore marine facies over fluvial redbed and one in which ice volumes are intermediate between greenhouse and incised-valley fill facies, both of which are typical of the Foreknobs For- severe icehouse conditions. For example, the modern Greenland and mation, are more akin to the stratigraphic record of icehouse conditions, Antarctic ice sheets, if melted, would raise sea level by 7 m and 57 m, such as cyclothems of the Pennsylvanian (Heckel, 1983; H. Posamentier, respectively (Cuffey and Paterson, 2010), and our hypothesized pers comm. 2011). Moreover, the presence of incised-valley fills is more sea-level amplitudes are within this range of one or two small- to typical of icehouse times, and is analogous to the numerous incised- medium-sized ice sheets. Moreover, our inferred sea-level amplitudes valley fills preserved in Mississippian and Pennsylvanian strata in the could be used to predict the volume of glacial ice present during United States (Greb and Chesnut, 1996; Miller and Eriksson, 2000; W.S. McClung et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 387 (2013) 104–125 123

Feldman et al., 2005; Matchen and Kammer, 2006; Greb et al., 2008; through time. We conclude this is a consequence of glacioeustasy during Korus et al., 2008; Grimm et al., 2013). a time of step-wise increase in number of ice sheets and volume of ice Classic deltaic indicators (e.g., coarsening-upward successions capped associated with the transition from greenhouse to icehouse conditions. by channel-incised distributary mouth-bars) are absent from the Foreknobs Formation of this study area. It is possible that these existed, Acknowledgments but were eroded either by fluvial processes during sea-level falls or marine processes during transgressions. This contrasts sharply with The root of this study was McClung's, 1983 VPI and SU Master's the- the Upper Cretaceous of the Western Interior Seaway (Kirschbaum sis. Many thanks to Richard Bambach for supervising the project. We and Hettinger, 2004: McLaurin and Steel, 2000), and argues against a thank colleagues Shane Prochnow and Henry Posamentier for many true greenhouse setting in the Foreknobs Formation. thoughtful discussions and to Fred Read for providing insightful ideas while in the field. We also thank Kurt Cuffey for crucial information on 10. Conclusions glacioeustasy, as well as John Dennison, Andrew Bush, Katharine Lee Avary, Ron McDowell, Brian Willis, Andrew Kulpecz, Jessica Poteet, The Foreknobs Formation consists of 14 lithofacies, in four and James Bishop for their help during various stages in the preparation facies associations, recording the following depositional settings: of the manuscript. Thanks also to Paul McCarthy, Jason Mintz, Stacy 1) storm-dominated distal to proximal offshore to shoreface (facies as- Atchley, Jeffrey Over, Ashton Embry, James MacEachern, and anonymous sociation A); 2) sharp-based conglomeratic shoreface (facies associa- reviewer #1 for reviewing earlier versions of the manuscript. Finally, tion B); 3) fluvial redbeds (facies association C); and 4) incised-valley McClung and Cuffey thank Chevron USA Inc. for giving us permission to fill (facies association D). publish this paper. The identification and characterization of paleosols are critical to the sequence stratigraphic interpretation of the Foreknobs Formation Appendix A. Location details of Foreknobs Formation measured because they record hiatuses in the rock record related to sea-level sections lowstands and can be equated with interfluve settings corresponding with 4th-order sequence boundaries. 1. AUGUSTA, WV, Hampshire Co., Rt 50 immediately west of Rt 50 and Vertical juxtaposition of lithofacies and stacking patterns permits Rt 29N intersection, 1.8 mi east of Augusta: Lat 39.299768, Long − recognition of short-, intermediate-, and long-term scales of cyclicity, 78.607242. which are interpreted to be 5th-, 4th-, and 3rd-order, respectively, 2. BAKER, WV, Hardy Co., Rt 55, 1.0 mi west of Rt 29/259 Baker exit: based on their inferred duration. Based on the juxtaposition of facies as- Lat 39.049685, Long −78.754206. sociations, we infer sea-level amplitude fluctuations of 10–15 m, 25– 3. SHENANDOAH MTN, WV, Pendleton Co., Rt 33, 3.2 mi east of 35 m, and up to 35–45 m, respectively. Brandywine: Lat 38.599264, Long −79.17984. The 5th-order cycles are represented by coarsening-upward and 4. BRUSH MTN, VA, Botetourt/Craig Co., Rt 606, 0.35 mi north of coun- shoaling-upward parasequences of storm-dominated offshore marine ty line: Lat 37.547160, Long −79.975364. facies in distal settings, corresponding to repeated high frequency se- 5. BRIERY GAP, WV, Pendleton Co., Co. Rd 33/4 1.2 mi west of Rt. 33: quences of sharp-based aggradational fluvial redbed strata overlain by Lat 38.729012, Long −79.465442. offshore marine strata, and bounded by unconformities, in proximal 6. ROMNEY, WV, Hampshire Co., Rt 50 and Rt 10 intersection, 1.3 mi settings. east of Romney: Lat 39.328123, Long −78.732469. The 4th-order cycles are represented by unconformity-bound se- 7. SCHERR, WV, Grant Co., Rt. 42, 1.3 mi west of Scherr: Lat 39.196343, quences comprised of multiple repetitions of 5th-order cycles, in some Long −79.184303. cases exhibiting stacking patterns indicative of increasing or decreasing 8. ELKINS, WV, Randolph Co., Rt 33, intersection of Rt 25 (Kelly Mtn. accommodation space. The 4th-order cycles are delineated by a RSME at Rd.), 3.0 mi east of Elkins: Lat 38.914344, Long −79.782457. the base of sharp-based conglomeratic shoreface sandstones in the dis- 9. DURBIN, WV, Pocahontas Co., Rt 250, 0.3 mi east of Durbin: Lat tal setting, corresponding with paleosols in the proximal setting. 38.547142, Long −79.814644. The larger amplitude sea-level fall associated with 4th-order se- 10. MARLINTON, WV, Pocahontas Co., Rt 39, 2.2 mi west of Huntersville: quence boundaries steepened the gradient on the alluvial plain causing Lat 38.213401, Long −80.069175. transportation of gravel to the distal offshore setting during lowstand, thus explaining the origin of conglomeratic facies encased within offshore shaly strata. References The 3rd-order cycles are delineated by stacking patterns of the Allen, J.R.L., 1964. Sedimentation in the modern delta of the River Niger, West Africa. In: 4th-order cyclicity and large-scale progradational facies trends within Van Straaten, L.M.J.U. (Ed.), Deltaic and Shallow Marine Deposits. Elsevier, Amster- the Foreknobs Formation; 3rd-order sea-level trends reflected in the dam, pp. 26–34. Foreknobs Formation are nearly identical to world-wide sea-level curves. Allen, J.R.L., Friend, P.E., 1968. Deposition of the Catskill facies Appalachian region, with fi notes on some other Old Red Sandstone basins. Geological Society of America Special Incised-valley lls are present at one of the 3rd-order cycle boundaries, Paper 106, 21–74. associated with greatest sea-level fall. Allen, G.P., Posamentier, H.W., 1993. Sequence stratigraphy and facies model of an incised “Prograding muddy shoreline motifs” are re-interpreted to be multi- valley fill: the Gironde estuary, France. Journal of Sedimentary Petrology 63, 378–391. fl Ayrton, W.G., 1963. 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