'Kalkberg' K‐Bentonite

Home , Angochitina, Lochkovian, Waltham Model 1857

View metadata, citation and similar papers at core.ac.uk brought to you by CORE

provided by Ghent University Academic Bibliography

A new, high-precision CA-ID-TIMS date for the ‘Kalkberg’ K-bentonite (Judds Falls Bentonite)

NEO E.B. MCADAMS , MARK D. SCHMITZ, MARK A. KLEFFNER, JACQUES VERNIERS, THIJS R.A. VANDENBROUCKE, JAMES R. EBERT AND BRADLEY D. CRAMER

McAdams, N.E.B., Schmitz, M.D., Kleffner, M.A., Verniers, J., Vandenbroucke, T.R.A., Ebert, J.R. & Cramer, B.D. 2018: A new, high-precision CA-ID-TIMS date for the ‘Kalkberg’ K-bentonite (Judds Falls Bentonite). Lethaia, Vol. 51, pp. 344–356.

The numerical calibration of the base of the Devonian is poorly constrained due to several factors. Few precise radioisotopic age determinations are available from the late Silurian and Early Devonian, and the limited published data carry large error bars from older analytical methodologies. Volcanic ashfalls suitable for dating occur in the Lower Devonian of the Appalachian Basin, but have not been precisely correlated into the global chronostratigraphical scheme because of limited bio- and lithostratigraphical information. Here, we report a new U-Pb zircon radioisotopic age determination of 417.61 Æ 0.12(0.23)[0.50] Ma and improved chronostratigraphical context, including revised biostratigraphy, for an ash bed in the New Scotland Formation, Helderberg Group, from the Lochkovian Stage that was previously identiﬁed as the Kalkberg K-bentonite. This new information helps to integrate the classic New York Appalachian Basin succession into global Siluro-Devonian stratigraphy, reﬁne the calibration of the Silurian–Devonian boundary and more precisely estimate the duration of both time periods. □ Chitinozoans, chronostratigraphy, conodonts, Lochkovian, U-Pb geochronology.

Neo E.B. McAdams ✉ [[email protected]], and Bradley D. Cramer [[email protected]], Department of Earth and Environmental Sciences, Univer- sity of Iowa, 115 Trowbridge Hall Iowa City, IA 52240, USA; Mark D. Schmitz [[email protected]], Department of Geosciences, Boise State University, 1910 University Drive Boise, ID 83725, USA; Mark A. Kleffner [[email protected]], School of Earth Sciences, The Ohio State University at Lima, 4240 Campus Drive Lima, OH 45804, USA; Jacques Verniers [[email protected]], Thijs R.A. Vandenbroucke [[email protected]], Department of Geology (WE13), Ghent University, Krijgslaan 281/S8 9000 Ghent, Belgium; James R. Ebert [[email protected]], Department of Earth and Atmospheric Sciences, State University of New York, College at Oneonta, Oneonta, NY 13820, USA; manuscript received on 24/04/2017; manuscript accepted on 27/07/2017.

The late Silurian to early Devonian is a dynamic The stratigraphically lowest radioisotopic date transitional period of Earth history. It includes available from the Devonian System is derived from sharp sea-level fall (Tippecanoe–Kaskaskia a K-bentonite in the Helderberg Group that was ter- sequence boundary of Sloss 1963), the origin of med the Kalkberg K-bentonite (Tucker et al. 1998) the Old Red Sandstone Continent, the Acadian in reference to the formation from which it was orogeny, the Klonk carbon cycle perturbation and reported. Whereas this age determination provides the ﬁrm establishment of life on land (Labandiera the anchor for the calibration of the Silurian–Devo- 2005; Becker et al. 2012; Melchin et al. 2012). nian boundary in the Geologic Time Scale 2012 Our understanding of each of these events is lim- (Schmitz 2012a), reinvestigation of the K-bentonite ited by a general lack of precise radioisotopic age is necessary because the original determination of determinations that can provide accurate dura- the date used methodology that did not sufﬁciently tions and timings of these events. Recent work account for lead loss and/or inheritance in zircons, incorporating new radioisotopic dates from the and used tracers and gravimetric standards with Wenlock and Ludlow (Cramer et al. 2012, 2015; lower levels of metrology and traceability than those Cooper et al. 2014) demonstrates that integration available currently. These factors resulted in large of geochronometric and biostratigraphical meth- error bars attached to the date that can be improved ods can discern events with durations of less than with modern analytical techniques. Problems with 1 Myr in the stratigraphical record. However, no the utility of the date are compounded by changes in such data from the Pridoli to Lower Devonian are the chronostratigraphical framework of the New currently available. York Devonian succession, which indicate that the

K-bentonite is chronostratigraphically higher than A originally reported (Kleffner et al. 2009; Bevington Rd

et al. 2010). New lithostratigraphical investigation of Canajoharie Creek n Valkenburgh the Helderberg Group shows that the dated ben- 32 Va Judds Falls tonite occurs within the New Scotland Formation, Salt Springville Rd which overlies the Kalkberg Formation (Ebert et al. 20 2007). Conodonts and chitinozoans are rare in both the Kalkberg and New Scotland formations and no biostratigraphically informative graptolites have 166 been reported. However, integration of recent (Ebert St Butler Rd & Matteson 2003; Kleffner et al. 2009; Bevington et al. 2010) and new (this paper) conodont and 200 ft chitinozoan data suggest that the strata surrounding the bentonite belong to the middle Lochkovian, not B 76° W 74° W the basal Lochkovian Stage. e tud lati Low Land Here, we provide a new, high-precision, chemical aeo abrasion isotope dilution thermal ionization mass 30° S pal

d Rochester Utica spectrometry (CA-ID-TIMS) radioisotopic age 43° N Syracuse Low Lan n Cherry determination for a new sample from the ash bed Valley Lagoo Build-ups sin Albany dated by Tucker et al. (1998), which is constrained Ba nter by updated litho- and biostratigraphical data for Depoce

roximal 42° chronostratigraphical correlation. The bentonite dis- P tics N Lime mudstone-wackestone, Clas stromatolite-stromatoporoid Cherty, Silty Limestone cussed in this paper will be referred to as the ‘Kalk- fauna berg’ K-bentonite (KKB) for simplicity, although Crinoidal grainstone Calcareous Siltstone d an several other names have been proposed previously 010100 L kilometres (see Discussion). Fig. 1. A, roadmap showing location of the measured section (indicated by grey star) on US Route 20, near Cherry Valley, New York State. Sprout Brook Road section of Kleffner et al. Geological background (2009) is indicated by black circle. Lower right, diagram of New York showing outline of Otsego County, with area of roadmap indicated by grey square. B, palaeogeographical reconstruction of Palaeogeography New York State in the Lower Devonian and depositional environments during Helderberg Group deposition. Palaeolatitude The Palaeozoic succession of New York State inferred from Domeier & Torsvik (2014); lithologies from includes strata encompassing the Silurian–Devonian Laporte (1967) and Diedrich & Wilkinson (1999); basin geome- try adapted from Isaacson & Curran (1981) and Brett et al. boundary (Helderberg Group; Hall et al. 1859). (1990). These units were deposited in a shallow shelf environment in the Appalachian foreland basin during the Acadian orogeny (Bradley et al. 2000; Ebert & Becraft, Alsen and Port Ewen formations (Fig. 2). It Matteson 2003; Ver Straeten 2004, 2009). At that is underlain by the Rondout Formation and overlain time, New York was positioned along the southeast- by the Oriskany or Glenerie Formation of the Tris- ern margin of Laurentia, approximately 30° south of tates Group. Deposition of the Helderberg Group the palaeoequator (Fig. 1). The lithology is domi- was interrupted by a number of major unconformi- nated by carbonates, but some units in the middle ties (Kleffner et al. 2009; ﬁg. 2, and references and upper Helderberg Group show increased silici- therein), and it was terminated by the Wallbridge clastic input, and also episodic volcanic input from Unconformity, which is a regionally angular uncon- the active margin (Ver Straeten 2004). Helderberg formity that marks the Tippecanoe–Kaskaskia Group strata crop out in a narrow belt in central sequence boundary in the Appalachian Basin (Sloss New York, extending from just west of Syracuse to 1963; Hamilton-Smith 1993). Albany and then southward towards the New Jersey– The Helderberg Group includes a general repeti- Pennsylvania border. This is part of the classic New tion of facies (skeletal limestones–cherty carbonates– York Devonian which has been studied since the increasingly shaly carbonates) in the six formations mid-19th century (e.g. Hall et al. 1859; Rickard above the Manlius Formation. The Manlius Forma- 1962; Laporte 1969). tion is a mosaic of very shallow water, peritidal car- In New York, the Helderberg Group is composed bonates with some stromatoporoid build-ups, of the Manlius, Coeymans, Kalkberg, New Scotland, except for the informal ‘Green Vedder Member’ (i.e. 346 McAdams et al. LETHAIA 51 (2018)

Sys- Se- with the New Scotland Formation partially equiva- Formation Member lent to the Becraft Formation, the Becraft partially

tem ries Stage Group equivalent to the Alsen Formation and the Alsen

Pr. Port partially equivalent to the Port Ewen Formation Ewen (Rickard 1962; ﬁg. 27). However, new interpreta- tions of the lower Helderberg Group, including the Alsen recognition of the extensive Mine Lot Falls, Clock- ‘Upper’ (massive) ville, Terrace Mountain, Howe Cave and Punch Kill Becraft unconformities in the Manlius–Kalkberg formations ‘Lower’ (interbedded) (Ebert & Matteson 2003; ﬁg. 2 in Kleffner et al. 2009), suggest that none of these formations are lat- New erally equivalent (Fig. 3A). Although the upper Lower Scotland Helderberg Group formations are not separated by Devonian

Lochkovian such laterally and temporally extensive unconformi-

Broncks Lake ties, and some formational contacts appear to be Kalkberg Hannacroix gradational, they are also not laterally contiguous equivalents and likely reflect different sequence Coeymans Ravena / Deansboro stratigraphical packages (Ebert & Matteson 2013). Helderberg Jamesville Clark Reservation Chronostratigraphy Elmwood Dayville The Silurian–Devonian boundary most likely occurs Olney within the lower Helderberg Group (e.g. Rickard Manlius 1962; Ebert & Matteson 2003; Kleffner et al. 2009), but it is difficult to locate with certainty because of ??? Green Vedder laterally complex facies arrangements (particularly in the Manlius Formation), laterally and sometimes temporally extensive unconformities and the dearth Thacher of biostratigraphically informative fossils. The Pridoli Silurian Rondout Chrysler boundary is correlated globally based on the first occurrence of the graptolite Monograptus uniformis Fig. 2. Stratigraphy and chronostratigraphy of the Helderberg uniformis Pribyl 1940 (Jaeger 1977). No graptolites Group and underlying Rondout Formation. Current best-supported position of the Silurian–Devonian boundary at the Punch are known from the Helderberg Group. The first Kill Unconformity (Kleffner et al. 2009) indicated by dashed line. appearance of the conodont Icriodus hesperius Klap- Lower dashed line with question marks indicates stratigraphically per & Murphy 1974 approximates the boundary lowest supported position of the Silurian–Devonian boundary within the ‘Green Vedder Member’ of the Manlius Formation position (Carls et al. 2007), but it too is unknown (Kleffner et al. 2009; Ebert & Matteson 2013; Ebert 2015). from the Helderberg Group. The onset of the Klonk Figure modified from Ebert & Matteson (2013). [Colour figure d13C excursion also occurs just below the boundary can be viewed at wileyonlinelibrary.com] level (Saltzman 2002; Buggisch & Mann 2004), but no unequivocal evidence (i.e. an isotopic shift con- the upper thin-bedded Thacher Member of Barnett strained by precise biostratigraphy) for the Klonk et al. 2006), which may represent a deeper, open- excursion has been recovered from the Helderberg shelf environment (Wilson & Ebert 2009). The Group at Cherry Valley (Kleffner et al. 2009). The Coeymans and Becraft formations are skeletal pack- same biostratigraphical problems (i.e. lack of diag- to grainstones; the Kalkberg and Alsen formations nostic fossils) continue throughout the upper are cherty, argillaceous wacke-packstones; and the Helderberg Group and also obfuscate the position of New Scotland and Port Ewen formations are argilla- the Lochkovian–Pragian boundary (Ver Straten & ceous carbonates and calcareous shales (Rickard Brett 2006), although it is likely within the Port 1962; Diedrich & Wilkinson 1999). Ewen Formation (Johnson et al. 1985; Kirchgasser & In the classic concept of the Helderberg Group Oliver 1993; Kirchgasser 2000). The uncertain posi- (Rickard 1962, 1975; Laporte 1969, Fig. 3B), the tion of both of these boundaries hinders the correla- Manlius, Coeymans, Kalkberg, and New Scotland tion of the KKB into the global formations (lower Helderberg Group) were consid- chronostratigraphical scheme. ered to be a continuous spectrum of diachronous Historically, the Silurian–Devonian boundary has facies partially or wholly equivalent to one another, been placed in a variety of positions in New York: at LETHAIA 51 (2018) ‘Kalkberg’ CA-ID-TIMS 347

Orisk. Oriskany Fm ? A Glenerie Fm

Connelly Fm Wallbridge Unconformity

Port Ewen

Terrace Mountain Unconformity Alsen

Becraft

New Scotland Clockville Unconformity Kalkberg Punch Kill Unconformity Clark Reservation Deansboro Ravena Jamesville Elmwood Howe Cave Unconformity Olney Dayville Green Vedder Thacher Minelot Falls Unconformity Rondout

Syracuse Cazenovia Hamilton Utica Oneonta Cherry Valley Schoharie Albany Ravena Catskill Kingston Port Jervis

West East North South Northeast Southwest

Mv OF Dv SSv CV ShS SCH ThP Rv Rt. 23 Ki NpQ

NEW SCOTLAND Deansboro El- Cr- Jm KALKBERG Ravena Olney Dayville COEYMANS

MANLIUS Thacher

RONDOUT Cb 20m ORDOVICIAN SALINA SALINA 0 50 km B Fig. 3. A, schematic diagram showing relationships of Helderberg Group and bounding strata with respect to unconformities in the succession at various locations in New York State. Modified from Ebert & Matteson (2013). This is a schematic representation of one possible solution to the underdetermined problem of time and stratigraphy in the Helderberg Group. B, traditional conception of Helderberg Group stratal relationships. CV in bold is the Cherry Valley section. Modified from Ebert & Matteson (2003). [Colour figure can be viewed at wileyonlinelibrary.com]

Fig. 4. A, exposure of New Scotland Formation along south side of US-20, facing west towards railroad overpass. Position of K-bentonite bed CV-2 (KKB) indicated by white arrow. B, closer view of K-bentonite bed. [Colour ﬁgure can be viewed at wileyonlinelibrary.com] or near the base of the Manlius Formation (Rickard et al. 2009). Conodont fossils are scarce in the 1962), within the underlying Rondout Formation Helderberg Group (Kleffner et al. 2009). However, (Rickard 1962; Barnett 1970), at the Howe Cave some reported diagnostic species provide age control Unconformity (Ebert & Matteson 2003), within the to parts of the succession. The underlying Rondout ‘Green Vedder Member’ of the Manlius (Kleffner Formation contains the conodonts Ozarkodina con- et al. 2009; Matteson & Ebert 2011; Ebert 2015) or ﬂuens (Branson & Mehl 1933), Zieglerodina rem- just above the Punch Kill Unconformity (Kleffner scheidensis (Ziegler 1960) and Kockelella variabilis 348 McAdams et al. LETHAIA 51 (2018)

Walliser 1957; which indicate assignment to the Cherry Valley, Otsego County, New York (Fig. 1). Ludlow/Pridoli stages (Johannessen et al. 1997). The first discovered and most studied of the ben- Conodont collections from throughout the overlying tonites is commonly referred to as the Kalkberg K- Manlius Formation contain the species Ozarkodina bentonite (KKB) (Fig. 4). It was first observed by remscheidensis eosteinhornensis (Walliser 1964; now New York State palaeontologist D.W. Fisher in 1955 known as Genus W eosteinhornensis sensu Murphy after road construction exposed outcrops assigned to et al. 2004), O. confluens (Branson & Mehl 1933) the Kalkberg Formation (Rickard 1962; Fisher 1987). and Oulodus elegans detortus (Walliser 1964), which Rickard (1962) was the first to publish the discovery demonstrates that the Manlius Formation correlates of the bentonite and its use as a lithostratigraphical with a position no higher than the Pridoli Stage correlation tool. In an abstract, Miller & Senechal (Ebert & Matteson 2003). These occurrences, (1965) reported an 87Rb-87Sr date of 395 Æ 5Ma although awaiting formal systematic discussion from a biotite crystal, presumably from the KKB because no specimens have yet been illustrated in material sent to Miller by Fisher in 1957 (Miller & published literature, combined with the presence of Senechal 1965; Fisher 1987). Unfortunately, the date Icriodus postwoschmidti-group conodonts (sensu was never formally published. Conkin & Conkin Carls et al. 2007) in the Kalkberg/New Scotland for- (1984) named the bed reported by Rickard (1962) mations (Kleffner et al. 2009), indicate that the Sil- the Judds Falls Metabentonite. Smith & Way (1988) urian–Devonian boundary most likely occurs above established the name Bald Hill Bentonite Beds (A, B the Thacher Member of the Manlius Formation, and and C) for a series of bentonites in Pennsylvania, and below the New Scotland Formation. Kleffner et al. stated that Rickard’s bentonite is equivalent to their (2009) attempted to locate the Silurian–Devonian Bed A. Tucker et al. (1998) reported a radioisotopic boundary using a combination of conodont bios- date for a bentonite that was collected from ‘the well- tratigraphy and carbon isotope chemostratigraphy. studied exposure of a single ash bed’ near Cherry The Coeymans Formation contains no evidence of Valley that is also the ash reported by Rickard. the Klonk-positive carbon isotope excursion (fig. 2 We sampled a stratigraphical section on US of Kleffner et al. 2009) and therefore is unlikely to Highway 20, northeast of Cherry Valley, NY correlate with the boundary, but this correlation (Figs 1, 4), which preserves the KKB as studied by cannot be confirmed due to the lack of biostrati- Rickard (1962), Conkin & Conkin (1984) and graphically informative conodonts, and the Coey- Tucker et al. (1998). The KKB lies within unequiv- mans Formation is erosionally truncated. The ocally Devonian (Lochkovian) strata, as it is above absence of evidence of an isotopic excursion is also the Punch Kill Unconformity and below the Port not diagnostic. The best-supported position of the Ewen Formation. The KKB was originally reported boundary given the current evidence places it most to be from the Kalkberg Formation (Rickard likely just above the Punch Kill Unconformity 1962), but recent analysis of the onlap of the Kalk- (Fig. 3; fig. 2 of Kleffner et al. 2009) at Cherry Val- berg and New Scotland formations onto the Punch ley, as indicated by the first appearance of I. post- Kill Unconformity from the Hudson Valley to woschmidti-group conodonts (Kleffner et al. 2009), Cherry Valley (Fig. 3) shows that only a few as they are definitively Devonian. It is possible, how- metres of the Broncks Lake Member of the Kalk- ever, that the boundary occurs lower in the section, berg are present at Cherry Valley and that the in the ‘Green Vedder Member’ of the Manlius For- rocks containing the KKB belong to the silty lower mation (Matteson & Ebert 2011). Biochemostrati- New Scotland Formation (Ebert et al. 2007). The graphical investigation of more complete upper New Scotland Formation is truncated by the Wall- Ravena–Kalkberg sections is required to confirm the bridge Unconformity at Cherry Valley and overlain position of the boundary, as are improved diagnoses by the Oriskany Sandstone. We chose this section and stratigraphical ranges for Icriodus woschmidti- specifically to sample the same bentonite that was group and I. postwoschmidti-group conodonts. dated by Tucker et al. (1998) and to improve the biostratigraphical context in order to correlate the History of study of the ‘Kalkberg’ K-bentonite new radioisotopic age determination into the global time-scale. The Helderberg Group contains several K-bentonite beds resulting from volcanism at the active margin as Previous Pb-Pb zircon date of the ‘Kalkberg’ Avalonia and Meguma collided with Laurentia dur- bentonite ing the Acadian orogeny (Van Staal et al. 2009; Ver Straeten 2009). The K-bentonite beds are well Tucker et al. (1998) analysed 10 multigrain zircon exposed in the roadcuts on US-20 northeast of samples from the KKB. One sample was rejected LETHAIA 51 (2018) ‘Kalkberg’ CA-ID-TIMS 349 due to obvious inheritance. The remaining analyses et al. (1971) and values of 235U/205Pb = 100.2329 resulted in a weighted mean 207Pb/206Pb age of and 233U/235U = 0.99506 for the EARTHTIME 417.6 Æ 1.0 Ma (1r). New methods (CA-ID- ET535 spike. Other details of analytical parameters TIMS) for obtaining high-precision dates from sin- can be found in the notes to Table S1. Uncertainties gle zircon grains that are suitable for the geological are based upon non-systematic analytical errors, time-scale are now available. These methods mini- including counting statistics, instrumental fractiona- mize lead loss (Mattinson 2005) and can produce tion, tracer subtraction and blank subtraction. These age determinations with <0.1% uncertainty. Tucker error estimates should be considered when compar- et al. (1998) assigned the bentonite to the upper ing our 206Pb/238U dates with those from other I. woschmidti Zone based on the reported first laboratories that used tracer solutions calibrated occurrence of I. woschmidti Ziegler 1960 (or sub- against the EARTHTIME gravimetric standards. species in that complex), 20–30 m below the ben- When comparing our dates with those derived from tonite, and the presence of conodonts indicating other decay schemes (e.g. 40Ar/39Ar, 187Re-187Os), the Kimognathus delta (Klapper & Murphy 1980) the uncertainties in tracer calibration (0.05%; Con- Zone in the Becraft and Alsen formations else- don et al. 2007) and U decay constants (0.108%; Jaf- where in New York. fey et al. 1971) should be added to the internal error During the construction of The Geological Time in quadrature. Sample ages are thus reported as Æ X Scale 2012, Schmitz (2012a,b) recalculated all (Y) [Z] Ma, where X is the internal error, Y is the reported radioisotopic ages from the original data internal plus tracer calibration error and Z is the sources, using the revised U decay constant ratio of internal plus tracer plus decay constant uncertainty. Mattinson (2010) to standardize the ages. The recalculation resulted in a younger age than originally Biostratigraphical methods reported, and much expanded uncertainty. The nine multigrain zircon fractions from the sample yielded Conodont and chitinozoan samples from this study a recalculated weighted mean 207Pb/206Pb age of are labelled with metres above the base of the US-20 415.48 Æ 0.97 (2r without k)orÆ2.71 (2r with k). section (0–4 m). Biostratigraphical samples from These data include a cluster of four concordant frac- Kleffner et al. (2009) are labelled with metres above tions with a recalculated weighted mean 206Pb/238U the base of the Sprout Brook Road section (0– age of 415.99 Æ 1.93 Ma (95% confidence interval 29 m). An unknown thickness of the Kalkberg and including geologic scatter). The recalculation lowest New Scotland Formation lies above the demonstrates that a high-precision radioisotopic Sprout Brook Road section of Kleffner et al. (2009) date is needed, and new biostratigraphical data from and below the US-20 section of the present study. the section containing the bentonite are necessary to However, the US-20 section definitely lies above the correlate the new date into global Devonian highest putative Silurian–Devonian boundary posi- chronostratigraphy. tion (just above the Punch Kill Unconformity; Kleff- ner et al. 2009). Conodont samples were processed at The Ohio State University at Lima using the dou- Methods ble-buffered formic acid method (Jeppsson & Ane- hus 1995). Chitinozoan samples were processed at CA-ID-TIMS methods Ghent University using the standard method of Paris (1981). Figured conodont specimens are stored in U-Pb geochronology methods for isotope dilution the University of Iowa Palaeontology Repository in thermal ionization mass spectrometry follow those the Department of Earth and Environmental previously published by Davydov et al. (2010). Zir- Sciences (Iowa City, Iowa, USA) with specimen con crystals were subjected to a modified version of number prefix SUI. Figured chitinozoan specimens the chemical abrasion method of Mattinson (2005), are stored at the Department of Geology, Ghent reflecting a preference to prepare and analyse care- University, Belgium. fully selected single crystal fragments. All analyses were undertaken on crystals previously mounted, polished and imaged by cathodoluminescence (CL), Results and discussion and selected on the basis of zoning patterns (see image mosaic with selected crystals highlighted in Sample CV-2 Fig. S1). U-Pb dates and uncertainties for each analysis were calculated using the algorithms of Schmitz Sample CV-2 of the ‘Kalkberg’ K-bentonite (KKB) & Schoene (2007), the U decay constants of Jaffey yielded a large homogeneous population of glass and 350 McAdams et al. LETHAIA 51 (2018) mineral-inclusion-rich, nearly equant to highly elon- Corriga 2012). The lowest occurrence of any species gate prismatic zircon grains from 100 to 200 lmin of Ancyrodelloides is in the A. carlsi Zone, which is long dimension. CL images display fine oscillatory equivalent to the upper part of the Ozarkodina zonation in the majority of grains, which vary in eurekaensis Zone and the lower part of the K. delta luminescence from bright cores to darker rims Zone in the biostratigraphical scheme of Ogg et al. (Fig. S1). Some equant grains contain cores with (2008), and equivalent to the upper O. eurekaensis more intense zoning and internal complexity absent and lower Lanea omoalpha zones in the scheme of from elongate grains. Eight grains of varying shape Murphy & Valenzuela-Rıos (1999) (fig. 4 of and CL-zoning character were selected for CA-ID- Corradini & Corriga 2012). The first occurrence of TIMS. Two grains yielded slightly older U-Pb dates Ancyrodelloides species also marks the base of the interpreted as biased by older inherited zircon cores. middle Lochkovian (Slavık 2011; Corradini & Six grains yielded concordant and equivalent U-Pb Corriga 2012). Species of Ancyrodelloides do not dates with a weighted mean 206Pb/238U age of occur any higher than the trigonicus Zone (=top of 417.61 Æ 0.12 (0.23) [0.50] Ma (n = 6; MSWD = former K. delta Zone). The range of Ancyrodelloides 0.66; probability of fit = 0.6556), which is inter- species in terms of the biostratigraphical scheme in preted to estimate the eruption and depositional age GTS 2012 (fig. 22.10 in Becker et al. 2012) is upper of the volcanic deposit (Fig. 5, Table S1). Caudicriodus postwoschmidti to upper A. trigonicus zones (sensu GTS 2012), based on correlation from Biostratigraphy the scheme of Murphy & Valenzuela-Rıos (1999). It should be noted that the names of the Lanea Conodont samples surrounding the KKB yielded no eleanorae and Lanea transitans zones are reversed in conodonts indicative of specific biostratigraphical the GTS (fig. 22.10 in Becker et al. 2012). It should zones and half of the samples yielded no conodonts also be noted that these biostratigraphical zones are at all (Fig. 6). However, two taxa (Fig. 7) allow typically referred to by specific epithet only, in part bracketing of the zonation of the bentonite. Ozarko- due to taxonomic disagreements on generic assign- dina planilingua (Murphy & Valenzuela-Rıos 1999) ments (e.g. Corradini & Corriga 2012). occurs at 1.75–1.85 m in the US-20 section. Its pres- The stratigraphically highest sample processed for ence indicates that this horizon falls between the top chitinozoans in this study is located at 26.7 m in the of the Pridoli lower Oulodus elegans detortus Zone Sprout Brook Road section (Kleffner et al. 2009), and the top of the Lochkovian Ancyrodelloides transi- just above the Punch Kill Unconformity (Broncks tans Zone in the biostratigraphical scheme proposed Lake Member of the Kalkberg Formation), approxi- by Corradini & Corriga (2012). The presence of Pb mately at the favoured Silurian–Devonian boundary elements assigned to Ancyrodelloides sp. at 2.35– position of Kleffner et al. (2009). It yielded chitino- 2.40 m (just below the KKB) restricts this horizon to zoans that may be assigned to Urnochitina urna a position no lower than the base of the Ancyrodel- (Eisenack 1934) or to Eisenackitina bohemica (Eise- loides carlsi Zone and no higher than the upper part nack 1934) (Fig. 8). The overall morphology of the of the Ancyrodelloides trigonicus Zone (Corradini & species is nearly identical, but E. bohemica bears

419.0

U ‘Kalkberg’

0.06715 238 K-bentonite 418.8 ranked Pb/ (CV-2) 418.6 206 418.4

0.06705 206

418.2 Pb/ 418 238

0.06695 U date (Ma) 417.6 417.8

417.2 0.06685 CV-2 417.61 ± 0.12(0.23)[0.50] Ma 417.4 n = 6; MSWD = 0.66 416.8 207Pb/235U 0.06675 417.0 Fig. 5. Concordia diagram of sample CV-2. Single zircon 206Pb/238U dates and concordia diagram for the CV-2 K-bentonite. Ellipses represent 2r error for each data point. [Colour ﬁgure can be viewed at wileyonlinelibrary.com] LETHAIA 51 (2018) ‘Kalkberg’ CA-ID-TIMS 351

US-20 Section Fm.

Stage A C Series m 4 sp. sp. 3 D Pseudooneotodus Ancyrodelloides Ancyrodelloides Cingulochitina ervensis Eisenackitina bohemica 2 Margachitina catenaria Gotlandochitina sp. Ozarkodina planilingua Wurmiella excavata Wurmiella Ancyrochitina sp.

Lochkovian B Lower Devonian

New Scotland Formation 1

0 Conodont sample Mudshale bed Fig. 7. Conodonts from the Cherry Valley section. See Fig. 6. All Calcareous siltstone bentonite CV-2 specimens were imaged by taking a series of stacked photographs putative bentonite with a Canon EOS 60D (65-mm lens) at 759 magnification, and the photographs were stacked using Zerene Stacker software. A, Fig. 6. Stratigraphical column of US-20 measured section at Ozarkodina planilingua Murphy & Valenzuela-Rıos 1999, oral Cherry Valley. The first putative bentonite layer (CV-1) occurs at view of Pa element, SUI 144575, 1.75–1.85 m. B, O. planilingua 1.70–1.75 m, but no zircons were recovered from the sample. – Murphy & Valenzuela-Rıos 1999, lateral view of Pa element, SUI The dated bentonite layer, CV-2 (KKB), occurs at 2.40 2.45 m. 144576, 1.75–1.85 m. C, Ancyrodelloides sp., Pb element, SUI The section yielded the conodonts Wurmiella excavata and 144577, 2.35–2.40 m. D, Anycrodelloides sp., Pb element, SUI Ozarkodina planilingua at 1.75–1.85 m, Ancyrodelloides sp. at – – – 144578, 2.35 2.40 m. [Colour figure can be viewed at wileyonli- 2.35 2.40 m, and Pseudooneotodus sp. at 2.45 2.55 m. Three nelibrary.com] samples below CV-1 did not yield conodonts. Chitinozoan data from Bevington et al. (2010), reported as collected between the lower putative bentonite bed and sampled bentonite CV-2 (1.75– at least in sample 26.7 represent abraded E. bohem- 2.40 m). [Colour figure can be viewed at wileyonlinelibrary.com] ica, or it is possible that the Silurian–Devonian boundary lies between 26.7 and 27 m in the section. spines and has a less-developed mucron. These Asselin et al. (2004) also figured spineless Devonian spines are small and delicate and therefore relatively chitinozoans from the Gaspe Peninsula, Quebec, easily removed through taphonomic processes. The that they assigned to several morphotypes of E. bo- specimens from our sample are not very well pre- hemica. It is possible that our specimens belong to served, so taphonomic spine removal cannot be similar Devonian age morphospecies. ruled out. However, it is conservative to assign our Bevington et al. (2010) collected chitinozoans spineless specimens to U. urna in the absence of from the upper Helderberg Group at a thicker sec- positive evidence that they may belong to E. bohem- tion on US-20 near Cherry Valley that includes our ica. Urnochitina urna is indicative of the Pridoli, as measured section. At Cherry Valley, they reported its FAD is earliest Pridoli, and its LAD is latest Pri- the index-species E. bohemica in the New Scotland doli (Paris in Paris 1986; Verniers et al. 1995), Formation, in beds directly below as well as 2.75 m whereas E. bohemica is the name-bearer of the low- above the KKB. In the bed directly below the ben- est chitinozoan zone in the Lochkovian (fig. 22.10 in tonite, it reportedly co-occurs with Cingulochitina Becker et al. 2012). Similar specimens occur in a ervensis and Margachitina catenaria. All three species sample at 26.6 m, located just below the Punch Kill are very long-ranging, with overlapping ranges in Unconformity in the uppermost Coeymans Forma- the Lochkovian (Paris et al. 2000). These occur- tion. A sample at 27 m in the Sprout Brook Road rences, although they are currently unpublished out- section yielded I. postwoschmidti-group conodonts side of the Bevington et al. (2010) abstract and are (Kleffner et al. 2009) so it is certainly of Devonian awaiting formal systematic discussion, suggest that age. Therefore, it seems likely that the chitinozoans the KKB interval of the New Scotland Formation 352 McAdams et al. LETHAIA 51 (2018)

ABC

Fig. 8. Chitinozoans assigned to Urnochitina urna (Eisenack 1934), from sample 04MK1–26.7 (basal uppermost Kalkberg or basal New Scotland), located just above the Punch Kill Unconformity (likely Silurian–Devonian boundary) at the Sprout Brook Road section of Kleffner et al. (2009; not refigured herein). Magnifications: A, 9520. B, 9360. C, 9360. falls no lower than the E. bohemica chitinozoan of uncertainty and imprecision on the biostrati- Zone (Fig. 9), which is early to mid-Lochkovian (fig. graphical, and therefore chronostratigraphical, cor- 22.10 in Becker et al. 2012). These data provide no relation of the KKB, and consequently any derived better precision than the conodont data presented ability to calibrate the base of the Devonian System above, and therefore, we can constrain the position from this date. Additional biostratigraphical data of the bentonite only to the latest early Lochkovian from the Manlius–New Scotland interval is required to middle Lochkovian (Fig. 9). to confirm the position of the Silurian–Devonian boundary and other Lower Devonian biozone Recent recalibration of the boundary boundaries relative to the dated ash fall beds. Husson et al.(2016) recently attempted a recalibra- Nomenclature tion of the Silurian–Devonian boundary based on new radioisotopic dates from bentonites from east- It is now clear that ‘Kalkberg K-bentonite’ is not an ern North America. As part of their study, they dated appropriate name, and its usage should not be zircons from the KKB using single-grain CA-ID- upheld. Firstly, the bentonite in question has never TIMS methods and their radioisotopic age determi- formally been named the Kalkberg K-bentonite, but nation of 417.68 Æ 0.21(0.27)[0.52] Ma that was has consistently been placed in the context of occur- derived from their youngest closed-system single zir- ring in the Kalkberg Formation. This practice began con agrees very well with our weighted mean deter- with its discovery by Fisher in 1955 (Fisher 1987) mination of 417.61 Æ 0.12(0.23)[0.50] Ma. and has continued until recently (e.g. GTS 2004, Whereas Husson et al. provide valuable high-quality GTS 2012). Tucker et al. (1998, p. 176–177) referred chemostratigraphical and radioisotopic data, their to their dated ash bed as ‘K-bentonite, Kalkberg For- data lack the necessary chronostratigraphical con- mation (Helderberg Group)’, in contrast to the trols to reliably calibrate the base of the Devonian named ‘Tioga K-bentonite’ of Ebright et al. (1949). System. In particular, they lack biostratigraphical The bentonite has also been referred to as part of control on any of their samples and rely instead the Bald Hill Bentonite Beds (Smith & Way 1988), exclusively on chemostratigraphical correlation that which were named for a series of three bentonites is then combined with stratigraphical thickness and (A, B and C) that appears in multiple stratigraphical assumed constant rates of sedimentation, even sections in Virginia, West Virginia, Maryland, Penn- across identified stratigraphical hiatuses, to provide sylvania and New York. Smith and Way initially a ‘stretching factor’. It is never described in their investigated the bentonite reported by Rickard manuscript how this is derived or precisely how it is (1962) from Cherry Valley (KKB), but ultimately applied to their data; however, they then use this placed the type section of the Bald Hill bentonites at ‘stretching factor’ to extrapolate a presumed date for Bald Hill, PA, to avoid conflict with the name Kalk- the base of the Devonian from their data. Rather berg Formation (Smith et al. 2003). Use of the term than following their less-than-transparent methodol- ‘Bald Hill’ to refer to the KKB and the other associ- ogy to derive a presumed level of precision for the ated beds has been adopted by recent authors (e.g. calibration of the base of the Devonian, we have cho- Ver Straeten 2004, 2009; Ver Straeten et al. 2012). sen here to illustrate more precisely the actual level However, there are several problems with this usage. LETHAIA 51 (2018) ‘Kalkberg’ CA-ID-TIMS 353

Ep- grapt- cono- chitin- were excluded as outliers. A more thorough finger- Age s.s. Ma och olite dont ozoan printing study, similar to that of, for example, Ray N. hercynicus Urochitina et al. (2011), should be conducted to confirm equiv- trigonicus simplex eleanorae alence of the beds across the outcrop area. Ver Strae- M. prae- transitans 417.61 ± 0.12 hercynicus ten (2009) stated that there are up to 15 closely omoalpha Fungochitina 415 lata spaced bentonites in the Bald Hill suite, so many different exposures of three beds could potentially be Caudicriodus postwoschmidti identified as A, B and C. Ver Straeten (2009, p. 19, Early M. uniformis fig. 11a) also figured an outcrop from Cherry Valley

Lochkovian Eisenackitina Early Middle Caudicriodus bohemica in which a bed appearing identical to the KKB was hesperius labelled ‘Bald Hill K-bentonite C’. There is some confusion over the identities of the lettered Bald Hill O. elegans M. transgrediens - beds outside of their type area. Most importantly, 420 Pr2 detortus M. perneri Angochitina superba Bald Hill Bentonite Beds is a junior synonym in the case of the KKB. M. bouceki ‘O.’eost. s.l. I.Z.

Pridoli Pr1 M. lochkovensis - Margachitina elegans Conkin & Conkin (1984) proposed the name M. loch. branikensis Ne. ult./parult. Fungochitina kosovensis 422.91 ± 0.07 Lu3 M. formosus O. crispa Eisenackitina Judds Falls Metabentonite and speciﬁed that the type Lu2 Ne. kozlowskii / O. snajdri barrandei Po. podoliensis I.Z. section is the roadcut near the railroad bridge near Bohemograptus Eisenackitina 424.08 ± 0.20 Cherry Valley, New York (i.e. the bentonite sampled Po. siluricus

Lud. philipi Lu1 Sa. leintward./ by Tucker et al. (1998) and sampled herein). They 425 Sa. linearis A. ploeckensis Angochitina speciﬁed that the Judds Falls Metabentonite is the Lo. elongata Go2 K. v. vari- scanicus abilis I.Z. bed identiﬁed in Rickard (1962) and did not recog- not zoned nize any other bentonites in the section. The obscu-

Gor. N. nilssoni / Go1 Lo. progenitor K. crassa rity of the journal in which this article was published Ho3 Col. ludensis K. ortus Sph. lycoper. 427.86 ± 0.32 Col. prae./deub. absidata 428.06 ± 0.21 Ho2 Pr. par./G. nas. O. boh. longa 428.45 ± 0.35 likely precluded later authors from recognizing that Conochitina Cy. lundgreni the KKB had been formally named with a type sec- Ho1 O. s. sagitta pachycephala Hom. Cy. rigidus / K. ortus ortus tion in the area from which it was originally 430 Sh3 Cingulochitina M. K. walliseri belophorous cingulata described. Although both ‘Kalkberg K-bentonite’ Sh2 O. s. rhenana M. riccarton. K. ranuli. S.Z. Margachitina and ‘Bald Hill bentonites’ have been widely used to Wenlock Ludlow Shein. Sh1 Cy. murchisoni procerus S.Z. margaritana Lland. Tely. Cy. centrifugus Pt. am. amorph. 431.83 ± 0.23 describe the KKB, neither of these names accurately and specifically describe the dated bed at Cherry Val- Fig. 9. Updated chronostratigraphy and radioisotopic age determinations with integrated dates and chronostratigraphical ley. We advocate for the use of the name proposed framework. Solid rectangle around date at right represents the by Conkin & Conkin (1984), amended to Judds Falls biostratigraphical range of conodont species assigned to Ancy- Bentonite Bed, in future publications discussing the rodelloides, which best constrains the chronostratigraphical position of the new radioisotopic age determination for the KKB. KKB. It is also appropriate to place the Judds Falls The age determination falls outside the expected chronostrati- Bentonite Bed in the context of the Bald Hill ben- graphical position as currently calibrated, and suggests that the tonite suite, but its equivalence with any of the Bald Lochkovian should be recalibrated. Silurian portion of chart based on GTS 2012 Gradstein et al. (2012) and Cramer et al. Hill beds should be further investigated. (2015). Devonian portion of chart based on Gradstein et al. (2012). [Colour figure can be viewed at wileyonlinelibrary.com] Conclusions As the Bald Hill bentonites are explicitly a suite of The following conclusions can be drawn. beds, the name does not specifically refer to the KKB, and it is useful to have a name for this • The KKB should be referred to as the Judds Falls chronostratigraphically important bed. The KKB Bentonite Bed, as this name has precedence over could be termed ‘Bald Hill Bentonite A’ (Smith & all others. The Judds Falls Bentonite Bed likely Way 1988; Smith et al. 2003), but it is not entirely represents one of the Bald Hill bentonites, but proven that these beds are the same (noted by Smith further analysis is required to determine precisely & Way 1988). Smith et al. (2003) performed a pre- to which bed it correlates. liminary chemical fingerprinting analysis of the Bald • The Judds Falls bentonite occurs in the New Scot- Hill suites in multiple sections, including the KKB, land Formation of the Helderberg Group, not in for TiO2 content and determined that Bed A con- the Kalkberg Formation. tains approximately 0.37% TiO2, but several samples • Conodont data from the New Scotland Forma- from other sections that were more enriched in TiO2 tion indicate that the Judds Falls Bentonite Bed 354 McAdams et al. LETHAIA 51 (2018)

occurs in the uppermost lower Lochkovian or the Carls, P., Slavık, L. & Valenzuela-Rıos, J.I. 2007: Revisions of conodont biostratigraphy across the Silurian–Devonian middle Lochkovian, not the basal Lochkovian as boundary. Bulletin of Geosciences 82, 145–164. previously thought. Preliminary chitinozoan data Condon, D., Schoene, B., Bowring, S., Parrish, R., McLean, N., are consistent with the conodont biostratigraphi- Noble, S. & Crowley, Q. 2007: EARTHTIME; isotopic tracers and optimized solutions for high-precision U-Pb ID-TIMS cal correlation. geochronology. Eos, Transactions, American Geophysical • Zircons from the Judds Falls bentonite yielded a Union 88, Abstract V41E-06. date of 417.61 Æ 0.12(0.23)[0.50] Ma, which is Conkin, J.E. & Conkin, B.M. 1984: Paleozoic metabentonites of North America: Part 1. – Devonian metabentonites in the east- in line with recently produced high-precision ern United States and southern Ontario: their identities, strati- dates from the Silurian (Ludlow). However, the graphic positions, and correlations. University of Louisville revised chronostratigraphical position of the Studies in Paleontology and Stratigraphy 16, 136 pp. Cooper, R.A., Sadler, P.M., Munnecke, A. & Crampton, J.S. Judds Falls Bentonite Bed presented herein 2014: Graptoloid evolutionary rates track Ordovician—Sil- demonstrates that the Silurian–Devonian bound- urian global climate change. Geological Magazine 151, 349– ary and the Lochkovian are older than currently 364. Corradini, C. & Corriga, M.G. 2012: A Prıdolı–Lochkovian con- recognized, and numerical recalibration of the odont zonation in Sardinia and the Carnic Alps: implications base Devonian is necessary. for a global zonation scheme. Bulletin of Geosciences 87, 635– 650. Cramer, B.D., Condon, D.J., Soderlund,€ U., Marshall, C., Wor- Acknowledgements. – We are grateful for comments from three ton, G.J., Thomas, A.T., Calner, M., Ray, D.C., Perrier, V., anonymous reviewers that helped improve this manuscript, as Boomer, I., Patchett, P.J. & Jeppsson, L. 2012: U-Pb (zircon) well as Editor Peter Doyle. Alyssa Bancroft, University of Iowa, age constraints on the timing and duration of Wenlock (Sil- photographed the conodont specimens. Tiffany Adrain, Univer- urian) paleocommunity collapse and recovery during the ‘Big sity of Iowa, provided SUI collections numbers and curation Crisis’. Geological Society of America Bulletin 124, 1841–1857. assistance. Thomas Steeman, Ghent University, took SEM images Cramer, B.D., Schmitz, M.D., Huff, W.D. & Bergstrom,€ S. 2015: of the chitinozoans. Sabine Van Cauwenberghe, Ghent Univer- High-precision U-Pb zircon age constraints on the duration of sity, processed chitinozoan samples. This work was partially sup- rapid biogeochemical events during the Ludlow Epoch (Sil- ported by the American Chemical Society-Petroleum Research urian Period). Journal of the Geological Society, London 172, Fund Grant #53196-DNI8 to B.D. Cramer. This paper is a contri- 157–160. bution to IUGS/UNESCO International Geoscience Programme Davydov, V.I., Crowley, J.L., Schmitz, M.D. & Poletaev, V.I. (IGCP) Project 591: The Early to Middle Paleozoic Revolution. 2010: High-precision U-Pb zircon age calibration of the global Carboniferous time scale and Milankovitch-band cyclicity in the Donets Basin, eastern Ukraine. Geochemistry, Geophysics, Geosystems 11, Q0AA04. References Diedrich, N.W. & Wilkinson, B.H. 1999: Depositional cyclicity in the Lower Devonian Helderberg Group of New York State. Asselin, E., Achab, A. & Soufiane, A. 2004: Biostratigraphic sig- The Journal of Geology 107, 643–658. nificance of lower Paleozoic microfaunas from eastern Canada. Domeier, M. & Torsvik, T.H. 2014: Plate tectonics in the late Canadian Journal of Earth Science 41, 489–505. Paleozoic. Geoscience Frontiers 5, 303–350. Barnett, S.G. 1970: Upper Cayugan and Helderbergian stratigra- Ebert, J.R. 2015: Rising, falling, highstand or lowstand: eustasy at phy of southeastern New York and northern New Jersey. Geo- the Silurian–Devonian boundary. Geological Society of America logical Society of America Bulletin 81, 2375–2402. Abstracts with Programs 47, 631. Barnett, J., Greenemeier, R., Fulton, A., Matteson, D.K. & Ebert, Ebert, J.R. & Matteson, D.K. 2003: Distal stratigraphic effects of J.R. 2006: Stratigraphic, sedimentologic, and taphonomic the Laurentia – Avalon collision: a record of early Acadian insights from Schoharie, NY: Green Vedder Member, Manlius (Prıdolı – Lochkovian) tectonism in the Helderberg Group of Formation (Upper Prıdolı Helderberg Group). Geological Soci- New York State. Courier Forschungsinstitut Senckenberg 242, ety of America Abstracts with Programs 38, 64. 157–167. Becker, R.T., Gradstein, F.M. & Hammer, O. 2012: The Devo- Ebert, J.R. & Matteson, D.K. 2013: Preliminary multitaxa bios- nian period. In Gradstein F., Ogg J., Schmitz M., Ogg G. (eds): tratigraphy and sequence stratigraphy of the Prıdolı (late Sil- The Geologic Time Scale 2012, 559–601. urian) and Lochkovian stages (early Devonian) in the Bevington, K.S., Ebert, J.R. & Dufka, P. 2010: Early Devonian Appalachian standard succession of New York. Geological Soci- (Lochkovian) chitinozoan biostratigraphy of the lower Helder- ety of America Abstracts with Programs 45, 52. berg Group, Appalachian Basin, New York State, and the age Ebert, J.R., Johnson, E., Grimes, A., Routh, R., Pechenik, N., of the ‘Kalkberg’ K-bentonite. Geological Society of America McCredy, R. & Bowler, J. 2007: The Kalkberg Formation Abstracts with Programs 42, 136. (Helderberg Group, L. Dev., Lochkovian) at Cherry Valley, Bradley, D.C., Tucker, R.D., Lux, D.R., Harris, A.G. & McGregor, New York is actually New Scotland—preliminary results of D.C. 2000. Migration of the Acadian Orogen and Foreland Basin sedimentologic and stratigraphic investigations. Geological Across the Northern Appalachians of Maine and Adjacent Areas, Society of America Abstracts with Programs 39, 60. U.S. Geological Survey, Professional Paper 1624. 55 pp. Ebright, J.R., Fettke, C.R. & Ingham, A.I. 1949: East Fork— Branson, E.B. & Mehl, M.G. 1933: Conodonts from the Bain- Wharton gas field, Potter County, Pennsylvania. Pennsylvania bridge (Silurian) of Missouri. Conodont Studies Number 1. Geological Survey, 4th ser., Bulletin M30, 43 pp. The University of Missouri Studies: A Quarterly of Research 8, Eisenack, A. 1934: Neue Mikrofossilien des baltischen Silur III. 39–52. Und neue Mikrofossilien des bohmischen€ silurs. Pal€aontolo- Brett, C.E., Goodman, W.M. & LoDuca, S.T. 1990: Sequences, gisch Zeitschrift 16,52–76. cycles, and basin dynamics in the Silurian of the Appalachian Fisher, D.W. 1987: Lower Devonian limestones, Helderberg Foreland Basin. Sedimentary Geology 8, 191–244. escarpment, New York. In Roy , D.C. (ed.): Centennial Field Buggisch, W. & Mann, W. 2004: Carbon isotope stratigraphy of Guide. Geological Society of America Centennial Field Guide— Lochkovian to Eifelian limestones from the Devonian of cen- Northeastern Section, volume 5, 119–122. tral and southern Europe. International Journal of Earth Gradstein, F., Ogg, J., Schmitz, M. & Ogg, G. (eds) 2012: The Sciences 93, 521–541. Geologic Time Scale 2012. Elsevier, Waltham, MA, 1176 pp. LETHAIA 51 (2018) ‘Kalkberg’ CA-ID-TIMS 355

Hall, J., Simpson, G.B. & Clarke, J.M. 1859: Palaeontology of Matteson, D.K. & Ebert, J.R. 2011: Where does the Devonian New-York: Containing Descriptions and Figures of the Organic begin in the Appalachian standard succession? Recognition of Remains of the Lower Helderberg Group and the Oriskany Sand- the Silurian–Devonian boundary event in the Helderberg stone, 1855–1859 [pt. 1 Text (1859); pt. 2 Plates (1861)] Vol- Group of New York State. Geological Society of America ume 3. C. van Benthuysen, 532 pp. Abstracts with Programs 43, 97. Hamilton-Smith, T. 1993: Stratigraphic effects of the Acadian Mattinson, J.M. 2005: Zircon U-Pb chemical abrasion (‘CA- orogeny in the autochthonous Appalachian basin. In Roy TIMS’) method: combined annealing and multi-step partial D.C., Skehan J.W. (eds): The Acadian Orogeny: Recent Studies dissolution analysis for improved precision and accuracy of in New England, Maritime Canada, and the Autochthonous zircon ages. Chemical Geology 220,47–66. Foreland. Geological Society of America Special Papers, vol- Mattinson, J.M. 2010: Analysis of the relative decay constants of ume275, 153–164. 235U and 238U by multi-step CA-TIMS measurements of Husson, J.M., Schoene, B., Bluher, S. & Maloof, A.C. 2016: Che- closed-system natural zircon samples. Chemical Geology 275, mostratigraphic and U-Pb geochronologic constraints on car- 186–198. bon cycling across the Silurian–Devonian boundary. Earth and Melchin, M.J., Sadler, P.M. & Cramer, B.D. 2012: The Silurian Planetary Science Letters 436, 108–120. period. In Gradstein F., Ogg J., Schmitz M., Ogg G. (eds): The Isaacson, P.E. & Curran, H.A. 1981: Anatomy of an Early Devo- Geologic Time Scale 2012, 525–558. nian carbonate buildup, central New York. Journal of Paleon- Miller, D.S. & Senechal, R.G. 1965: Age determinations in New tology 55, 1225–1236. York state. Volcanology, Geochemistry, and Petrology Abstracts, Jaeger, H. 1977: Graptolites. In Martinsson A., (ed.): The Silurian Transactions American Geophysical Union 46, 173. —Devonian Boundary. International Union of Geological Murphy, M.A. & Valenzuela-Rıos, J.I. 1999: Lanea new genus, Sciences, Series A, volume 5, 337–345. lineage of Early Devonian conodonts. Bollettino della Societa Jaffey, A.H., Flynn, K.F., Glendenin, L.E., Bentley, W.C. & Paleontologica Italiana 37, 321–334. Essling, A.M. 1971: Precision measurements of half-lives and Murphy, M.A., Valenzuela-Rıos, J.I. & Carls, P. 2004: On classifi- specific activities of 235U and 238U. Physical Review C 4, cation of Pridoli (Silurian)-Lochkovian (Devonian) Spathog- 1889–1906. nathodontidae (Conodonts). University of California, Riverside Jeppsson, L. & Anehus, R. 1995: A buffered formic acid tech- Campus Museum, Contribution 6,1–25. nique for conodont extraction. Journal of Paleontology 69, Ogg, J.G., Ogg, G. & Gradstein, F.M. 2008: Devonian period. In 790–794. Ogg J.G., Ogg G., Gradstein F.M. (eds): The Concise Geologic Johannessen, K.M., Natel, E.M. & Ebert, J.R. 1997: An upper Sil- Time Scale,65–72. urian, conodont-rich facies from the Rondout Formation of Paris, F. 1981: Les chitinozoaires dans le Paleozo€ıque du sud- central New York: approximating the Ludlovian-Prıdolıan ouest de l’Europe (cadre geologique- etude systematique- boundary and a note on possible diagenetic influences on con- biostratigraphie). Memoire de la Societegeologique et mineralo- odont color alteration indices (CAI). Geological Society of gique de Bretagne 26,1–496. America Abstracts with Programs 29, 55. Paris, F. 1986: 6.4 Chitinozoa. In Kriz J., Jaeger H., Paris F., Johnson, J.G., Klapper, G. & Sandberg, C.A. 1985: Devonian Schonlaub€ H.P. (eds): Pridoli—the Fourth Subdivision of the eustatic fluctuations in Euramerica. Geological Society of Amer- Silurian System. Jahrbuch der Geologischen Bundesanstalt vol- ica Bulletin 96, 567–587. ume 129, 337–338. Kirchgasser, W.T. 2000: Correlation of stage boundaries in the Paris, F., Winchester-Seeto, T., Boumendjel, K. & Grahn, Y. Appalachian Devonian eastern United States. Courier 2000: Toward a global biozonation of Devonian chitinozoans. Forschungsinstitut Senckenberg 225, 271–284. Courier Forschungsinstitut Senckenberg 220,39–55. Kirchgasser, W.T. & Oliver Jr, W.A. 1993: Correlation of stage Pribyl, A. 1940: Die Graptolithenfauna des mittleren Ludlows boundaries in the Appalachian Devonian, eastern United von Bohmen€ (oberes eß). Vestnik Statniho Geologickeho Ustavu States. Subcommission on Devonian Stratigraphy, Newsletter Ceskoslovenske 16,63–73. 10,5–8. Ray, D.C., Collings, A.V.J., Worton, G.J. & Jones, G. 2011: Upper Klapper, G. & Murphy, M.A. 1974: Silurian–Lower Devonian Wenlock bentonites from Wren’s Nest Hill, Dudley; compar- conodont sequences in the Roberts Mountains Formation of isons with prominent bentonites along Wenlock Edge, Shrop- central Nevada. University of California Publications in Geologi- shire, England. Geological Magazine 148, 670–681. cal Sciences 111,1–62. Rickard, L.V. 1962: Late Cayugan (Upper Silurian) and Helder- Klapper, G. & Murphy, M.A. 1980: Conodont zonal species from bergian (Lower Devonian) stratigraphy in New York. New the delta and pesavis zones (Lower Devonian) in central York State Museum and Science Service Bulletin 386, 157. Nevada. Neues Jahrbuch Fur€ Geologie und Pal€aontologie, Mon- Rickard, L.V. 1975: Correlation of the Silurian and Devonian atschefte 8, 490–504. rocks in New York State. New York State Museum Map and Kleffner, M.A., Barrick, J.E., Ebert, J.R., Matteson, D.K. & Karls- Chart Series 24, 16. son, H.R. 2009: Conodont biostratigraphy, d13C chemostratig- Saltzman, M.R. 2002: Carbon isotope (d13C) stratigraphy across raphy, and recognition of the Silurian/Devonian boundary in the Silurian–Devonian transition in North America: evidence the Cherry Valley, New York region of the Appalachian Basin. for a perturbation of the global carbon cycle. Palaeogeography, In Over D.J. (ed.): Conodont Studies Commemorating the 150th Palaeoclimatology, Palaeoecology 187,83–100. Anniversary of the First Conodont Paper (Pander, 1856) and the Schmitz, M.D. 2012a: Appendix 2: radiometric ages used in GTS 40th Anniversary of the Pander Society. Palaeontographica 2012. In: Gradstein F., Ogg J., Schmitz M., Ogg G. (eds): The Americana, volume 62,57–73. Geologic Time Scale 2012, 1045–1082. Labandiera, C.C. 2005: Invasion of the continents: cyanobacterial Schmitz, M.D. 2012b: Radiogenic isotope geochronology. In crusts to tree-inhabiting arthropods. Trends in Ecology and Gradstein F., Ogg J., Schmitz M., Ogg G. (eds): The Geologic Evolution 20, 253–262. Time Scale 2012, 115–126. Laporte, L.F. 1967: Carbonate deposition near mean sea- Schmitz, M.D. & Schoene, B. 2007: Derivation of isotope ratios, level and resultant facies mosaic: manlius formation errors and error correlations for U-Pb geochronology using (Lower Devonian) of New York State. AAPG Bulletin 51, 205Pb-235U-(233U)-spiked isotope dilution thermal ionization 73–101. mass spectrometric data. Geochemistry, Geophysics, Geosystems Laporte, L.F. 1969: Recognition of a transgressive carbonate 8, Q08006. sequence within an epeiric sea: Helderberg Group (Lower Slavık, L. 2011: Lanea carlsi conodont apparatus reconstruction Devonian) of New York State. In Friedman G.M. (ed.): Deposi- and its significance for subdivision of the Lochkovian. Acta tional Environments in Carbonate Rocks, a Symposium. Society Palaeontologica Polonica 56, 313–327. of Economic Paleontologists and Mineralogists, Special Publi- Sloss, L.L. 1963: Sequences in the Cratonic Interior of North cation, Tulsa, volume 14,98–119. America. Geological Society of America Bulletin 74,93–114. 356 McAdams et al. LETHAIA 51 (2018)

Smith II, R.C. & Way, J.H. 1988: The Bald Hill Bentonite beds: a Appalachian Basin – stratigraphic nomenclatural changes. Lower Devonian pyroclastic-bearing unit in the northern Northeastern Geology & Environmental Sciences 28,80–95. Appalachians. Northeastern Geology 10, 216–230. Verniers, J., Nestor, V., Paris, F., Dufka, P., Sutherland, S. & Van Smith II, R.C., Berkheiser, S.W., Way, J.H. 2003: Bald Hill Ben- Grootel, G. 1995: A global Chitinozoa biozonation for the Sil- tonites A, B, and C—history and new data since 1988. In Way urian. Geological Magazine 132, 651–666. J.H. et al. (eds): Geology on the Edge: Selected Geology of Bed- Walliser, O.H. 1957: Conodonten aus dem oberen Gotlandium ford, Blair, Cambria, and Somerset Counties, Guidebook, 68th Deutschlands und der Karnischen Alpen. Notizblatt des Hessis- Annual Field Conference of Pennsylvania Geologists, Altoona, chen Landesamtes fur€ Bodenforschung zu Wiesbaden 85,28–52. PA, 73–77. Walliser, O.H. 1964: Conodonten des Silurs. Abhandlungen des Stacey, J.S. & Kramers, J.D. 1975: Approximation of terrestrial Hessischen Landesamtes fur€ Bodenforschung 41, 106. lead isotope evolution by a two-stage model. Earth and Plane- Wilson, R.H. & Ebert, J.R. 2009: Sedimentology of the Green tary Science Letters 26, 207–221. Vedder Member (Manlius Fm.) and new questions regarding Tucker, R.D., Bradley, D.C., Ver Straeten, C.A., Harris, A.G., the stratigraphic evolution of the Helderberg Group. Geologi- Ebert, J.R. & McCutcheon, S.R. 1998: New U–Pb zircon ages cal Society of America Abstracts with Programs 41, 27. and the duration and division of Devonian time. Earth and Ziegler, W. 1960: Conodonten aus dem Rheinischen Unterdevon Planetary Science Letters 158, 175–186. (Gedinnium) des Remscheider Sattels (Rheinisches Schieferge- Van Staal, C.R., Whalen, J.B., Valverde-Vaquero, P., Zagorevski, birge). Pal€aontologisch Zeitschrift 34, 169–201. A. & Rogers, N. 2009: Pre-Carboniferous, episodic accretion- related, orogenesis along the Laurentian margin of the northern Appalachians. In Murphy J.B., Keppie J.D., Hynes A.J. (eds): Ancient Orogens and Modern Analogues, Geological Soci- Supporting Information ety London Special Publication. Ver Straeten, C.A. 2004: K-bentonites, volcanic ash preservation, and implications for Early to Middle Devonian volcanism in Additional Supporting Information may be found in the Acadian orogeny, eastern North America. Geological Soci- the online version of this article: ety of America Bulletin 116, 474–489. Ver Straeten, C.A. 2009: The classic Devonian of the catskill Fig. S1. Cathodoluminescence image of selected zir- front: a foreland basin record of Acadian orogenesis. In Voll- mer F. (ed.): New York State Geological Association, 81st cons from sample CV-2. Labelled zircons were Annual Meeting Guidebook, 7-1–7-54. annealed and chemically abraded following Mattin- Ver Straeten, C.A., Baird, G.C., Karabinos, P., Samson, S. & son (2005). Zircons z1 and z8 were excluded from Brett, C.E. 2012: Silicic Appalachian Magmatism During the Ordovician and Devonian: Perspectives from the Foreland Basin, the ﬁnal calculation of the radioisotopic age deter- and the Hinterland. New York State Geological Association, mination due to inheritance. 84th Annual Meeting Guidebook, A7-1–A7-59. Ver Straten, C.A. & Brett, C.E. 2006: Pragian to Eifelian strata Table S1. Data from radioisotopic age determina- (middle Lower to lower Middle Devonian), northern tion analysis.