Turritellid gastropods are among the most widespread, abundant, and diverse mollusks in Plio-Pleistocene deposits of the Atlantic coastal plain and Florida, with at least 46 species and subspecies described over almost two centuries. Yet the systematic status of these common fossil species and their phylogenetic relationships—to each other and to turritellids living today in the western Atlantic—have never been investigated in detail. We make use of recent molecular phylogenetic work on living turritellids and new analyses of shell characters to review the group from this time interval to the present in a comprehensive phylogenetic analysis and assessment of their evolutionary history in the region. We conclude that 20 fossil and two Recent species are valid. Four of these species are placed in the genus Torcula Gray, 1847; five in Caviturritella new genus, and eleven in “Turritella” sensu lato. We identify Torcula perattenuata as the likely direct ancestor of one of the two turritellid species living today off the southeastern U.S. coast, Torcula exoleta, and we elucidate the fossil record of the other extant species, “Turritella” perexilis (senior synonym of Turritella acropora). We show that Caviturritella was extirpated from the United States Gulf and Atlantic coastal plains in the Early Pleistocene but is still represented in the western Atlantic by the living species C. variegata in the southern Caribbean. We also present the first detailed treatment of Plio-Pleistocene turritellid fossils from Georgia. Our analysis shows that the Plio- Pleistocene Pinecrest beds of Florida contain 18 co-occurring turritellid species, which is the highest turritellid species diversity in one formation known in the fossil record.
Late 18th to early 19th century reports on the rocks of the Catskill Mountains in eastern New York were followed by over 180 years of geological and paleobiological studies of the Devonian terrestrial succession, in the state and up and down eastern North America. Yet, nearly 230 years later these estimated ca. 2.4 km- (1.5 mi-) thick, homogenous strata remain a largely unknown frontier in many ways. Studies of Devonian terrestrial strata in New York over the last century include two different stratigraphic frameworks. The first, by George Chadwick (1930s–1940s), focused on the Catskill Front to the vicinity of Slide Mountain, highest peak in the Catskills. The second, by Fletcher and Rickard in the 1960s to mid-1970s, attempted to create a broader, more geographically inclusive chronostratigraphic nomenclature throughout the entire Catskills outcrop belt. Recent work indicates that in the field this latter model, based on thick lithosomes of red and gray rocks and conglomerates, is problematic. It can be seen as representing a “second draft” stratigraphic framework, in need of additional work and refinement. At this time, however, too little is known as to how to better ground the existing stratigraphy, or to propose a sound alternate stratigraphic framework for the Catskills succession. Other major foci in the Devonian terrestrial of New York include paleobotany (1950s–today), petrography (1960s–1980s), fluvial systems (1970s–1990s), and terrestrial arthropods (1980s–2000s). Broader paleobiological studies, in part associated with the Red Hill site in northern Pennsylvania, burgeoned in the 1990s and continue today. Recent Catskills terrestrial research of impact is perhaps largely paleobiological and includes the first complete Eospermatopteris (“Gilboa”) tree, mapping of well- preserved forest floors, and increasing research on paleosols. Difficulties in research of Devonian terrestrial strata in New York include: the lateral discontinuity of terrestrial facies and the lack of documented, distinctive marker beds for correlation; little biostratigraphic and geochronologic control; extensive cover in sometimes rugged terrain; too few researchers, and a need for greater cross-disciplinary perspectives and communication. The purpose of recent and ongoing research by the author is multifold. First to systematically gather various data, such as event deposits, petrography, detrital zircon dating, and palynological biostratigraphy, top to bottom through the succession, initially in the classic Catskill Front to the vicinity of Slide Mountain, in the New York State Department of Conservation “Slide Mountain Wilderness” of the Catskill Park. Second within that succession, to better document depositional history, provenance, and biostratigraphy, and to know the succession more closely. Through this, the larger goal is to test the existing stratigraphic framework and try to ground that stratigraphy in the regional rock record better, or to develop a new stratigraphic framework. Key issues that remain largely unresolved in Devonian terrestrial strata of New York include: lack of a well-tested, viable, and correlatable stratigraphic framework; a general lack of chronostratigraphic data from palynological/microvertebrate biostratigraphy and radiometric ages from altered air fall volcanic tephra beds; and no systematic documentation of the vertical Catskill succession. Other future studies could include lateral, interstate/province comparisons of variations in provenance/drainage evolution along the Acadian (Acadian-Neoacadian) Foreland Basin and its subbasin known as the Appalachian Basin, via petrography, detrital mineral dating and other methods.
The upper Frasnian and Famennian Devonian stratigraphy in central and western New York State is comprised of the upper Frasnian West Falls and Java groups and the Famennian Canadaway, Conneaut, and Conewango groups. The Devonian stratigraphic correlation chart compiled by Rickard (1975) has been the general standard for the Frasnian and Famennian section in central and western New York. However, Rickard’s (1975) chart predates sequence stratigraphy, more sophisticated biostratigraphic and δ13Corg studies, and the recognition of numerous faults that offset the “layer-cake” stratigraphy. Our detailed field studies at over 2,000 sites that involved sedimentology, sequence stratigraphy, structure, and ichnology promoted the identification and tracing of key marker beds in central and western New York State. These studies encouraged a revision and refinement of the units and correlations that were represented in the Rickard (1975) stratigraphic chart. Revisions to Rickard’s (1975) Devonian stratigraphic chart include: abandoning the Perrysburg and Forty Bridge formations; reinstating units that Rickard (1975) omitted in his compilation, including the South Wales, Canaseraga, Rushford, Machias and Cuba formations, as well as the Salamanca Member; and proposing new East Sixtown, Gorge Dolomitic, Higgins, and West Lake members of the Caneadea Formation. We revised seven other units; fifteen units remain unchanged. A consequence of this new stratigraphy is a more robust depositional history for the Upper Devonian in central and western New York State. The Upper Devonian stratigraphic units of New York State record the transition from deeper-water shales and turbidite sandstones to terrestrial sands and shales as the Acadian Foreland Basin filled and the shoreline moved farther westward through time. The westward march of the shoreline was not steady, however, and was controlled by the usual interplay of 1) basin subsidence and fault block motion, 2) sediment supply, and 3) eustatic variation. The last of the Devonian black shale deposition occurred in the Frasnian/Famennian. The Frasnian is typified by offshore deposition, including turbidities. In contrast, the sedimentary structures and ichnofacies observed indicate the Famennian stratigraphy represented a shallower, offshore-to-nearshore depositional environment. The occurrence of storm influenced/modified bedding becomes ubiquitous in units of the upper Canadaway, Conneaut, and Conewango groups. Exposures of the Conneaut and Conewango typically are comprised of the thicker, fine sandstone packets. Fewer outcrops upsection result in less definitive correlations. Correlations in the Conneaut and Conewango are dependent on the presence of marker beds that contain distinctive lithologies such as red shales and beds containing white quartz pebbles.
Strata between the middle Givetian Moscow Formation and the newly recognized Givetian-Frasnian zonal stage boundary, at or near the top of the Lodi Member (Penn Yan Formation of the Genesee Group), include limestone-dominated strata of the Tully Formation and coeval siliciclastic deposits of the Gilboa Formation, overlain by progradational, siliciclastic deposits of the Gen- eseo Formation-Lodi Member succession. The Tully and Gilboa formations, the type expression of the North American provincial Taghanic Stage, correspond to the Polygnathus ansatus–“Ozarkodina” semialternans international conodont zones, and the Global Taghanic Biocrisis interval. The lower, pre-Frasnian part of the Genesee Group, corresponding to the successive hermanni (former hermanni-cristatus Zone), disparilis, and norrisi conodont zones, recorded the onset of a major Acadian tectophase (Tectophase 4; see Ver Straeten, 2023a [Vol. 1, Ch. 1]), timed with coincident deepening of the Devonian foreland basin and major global sea level-rise. The Tully Formation limestone in western and central New York State is an anomalous deposit of dominantly fine grained, medium to dark gray limestone that contrasts greatly with underlying Hamilton Group siliciclastic deposits and overlying pro- gradational siliciclastic facies of the Genesee Group. Tully Formation deposits in western and central New York accumulated on a shallow platform. However, these deposits grade eastward and southward into the equivalent thicker siliciclastic Gilboa Forma- tion, preserved within a structural trough or, possibly, a small-scale orogen-ward migrating basin, in eastern New York and central Pennsylvania that served as a “clastic trap” for siliciclastic sediments which failed to reach the platform. Diachronous basal Geneseo deposits record the westward regional onlap of basinal black mud deposits onto an east-sloping submarine ramp. The Geneseo Formation recorded geologically rapid subsidence and development of a shelf-slope break that imparted a strong control on sedi- mentary magnafacies. The Tully Formation largely displays distinctly clean carbonate deposits in central New York; the Gilboa Formation is herein applied to coeval eastern (shoreward) siliciclastic facies. Post-Gilboa, Geneseo-equivalent onshore divisions, which include the Unadilla Formation, Sherburne Formation, Otego Formation, and Otselic Formation, are, herein, delineated. Most member-scale units of the Tully- and Geneseo-correlative formations, described herein, correspond to divisions based on discontinuity-floored marine sequence and subsequence concepts.
Frasnian strata of New York are within the Genesee (in part), Sonyea, West Falls, and Java (in part) groups, consisting of strata that grade from terrestrial clastics in the east to offshore dark-colored shale and pelagic limestone in the west. These strata contain tephra beds, brachiopods, conodonts, goniatites, spores, and other flora and fauna that allow global correlation and recognition of zonal and stage boundaries. Five third-order cyclic packages are recognized by distinct black shale to gray shale groups that are recognized within corresponding strata of the Burket and Harrell shale formations in Pennsylvania, the Flynn Creek and Dowelltown members of the Chattanooga Shale Formation in the southern Appalachian Basin, the Blocher and Selmier members of the New Albany Shale Formation in the Illinois Basin, and the Squaw Bay Limestone Formation and Norwood and Paxton members of the Antrim Shale Formation in the Michigan Basin.
Middle to upper Lower Devonian strata in New York are comprised of seven formations, in four distinct vertical packages. They were deposited over an interval of approximately 18.2 million years. The lowest strata (lower Pragian-age Port Jervis Limestone) occur only in the Tristates area, southeastern New York. Overlying upper Pragian-age units are the largely co-eval Oriskany Sandstone, Glenerie Cherty Limestone, and Connelly Conglomerate. Overlying synorogenic siliciclastics of the Esopus Formation (lower Emsian-age) are restricted to eastern to east-central New York. Overlying upper Emsian strata of the correlative Schoharie and Bois Blanc formations comprise mixed siliciclastic-carbonate and carbonate strata, respectively, with some quartz arenites, especially across central New York. These New York units, and their correlatives across the Appalachian Basin outcrop belt, are examined and summarized. In nearly all of New York, some to all of these strata are absent at an erosional unconformity. The Tristates area at the meeting of New York, New Jersey, and Pennsylvania is the only area of the outcrop belt where deposition was continuous through this time. To the overall north and west, a major Paleozoic sea level lowstand ± crustal flexure during the Acadian orogeny led to development of an amalgamated series of unconformities, focused around the sub-Oriskany Wallbridge Unconformity. Maximum development of the unconformity in New York occurs in the west-central part of the state. In terms of sequence stratigraphy, the entire succession comprises six or seven major, third-order sequences. This includes two likely Pragian sequences, and five distinct Emsian-age sequences, all of which appear to be global. A series of altered airfall volcanic tephras occur in the lower part of the Esopus Formation; a few additional discrete airfall tephras are known from the Schoharie Formation. Faunal differences distinguish the four vertical packages of strata. Too little biostratigraphic data, however, continues to limit the accuracy of pinpointing stage boundaries in the New York and Appalachian Basin strata.
The Devonian strata in New York State were the standard section for North America for over 100 years, and remain a significant reference for regional to global correlation and research. Since publication of L. V. Rickard’s (1975) New York Devonian correlation chart, various higher-resolution stratigraphic analyses have been employed, sometimes at bed-by-bed scale. These include sequence-, bio-, event-, chemo-, and other -stratigraphic approaches, along with increasingly finer-resolution geochronologic dating of airfall volcanic tephras. Results have led to many new interpretations and insights of the succession. The purpose of this three-volume work is to produce a new Devonian stratigraphic synthesis for New York State, and to record, often in detail, current knowledge of the succession, and various other geologic and paleontologic aspects of it for current and future research and discussion. The purpose of this chapter is to provide overviews of the Devonian Period, the Devonian of North America (“Laurentia”), the Devonian of eastern Laurentia, and the Devonian of New York State. Furthermore, this review extends beyond the sedimentary rock and paleobiological record, and beyond the United States, Canada, and northern Mexico, to also summarize aspects of Devonian orogenesis, metasedimentary foreland basin fill, silicic igneous activity, complexities of terranes of Mexico and Central America, and Appalachian faunas that extended into South America. The Devonian Period as a whole encompasses 60 million years of time, approximately 419 to 359 million years ago. During that time, shallow seas covered large continental areas; climate was warmer globally than our current climate, during the late stage of a global greenhouse climate. By the end of the Devonian, that warm climate was descending into a time of global icehouse conditions, with widespread glaciation. The positions of modern continental masses were much different. During the Devonian Period, Life first fully colonized the land, led by primitive spore-bearing plants, small arthropods, and apparently by the Middle Devonian, the first tetrapod (“four-legged”) animals, which evolved from bony fishes. Decimeter-tall plants at the beginning of the period had evolved to tree-size forms by the Middle Devonian, approximately 30 million years later, and Earth’s first forest ecosystems arose. Devonian strata are widespread around the ancient continent “Laurentia,” which approximately corresponds to modern North America). At that time, Laurentia straddled the equator, with New York State and the Appalachian region somewhat north of 30° south latitude. Shallow epicontinental seas covered large but varying amounts of the continent over the period. Mountain belts formed on the eastern, northern, and western margins of Laurentia, due to plate tectonic collisions with smaller continental masses, exotic terranes, and volcanic island arcs. Through the Early to Middle Devonian, seas in western and eastern Laurentia were separated by a “transcontinental arch,” and generally had distinctly different marine faunas. In the latest Middle Devonian, sea level transgressed over the land barrier of the Laurentian Transcontinental Arch and the Canadian Shield, and those marine faunas mixed, leading to a more global cosmopolitan fauna in the Late Devonian. Anomalously, however, Early and Middle Devonian Laurentian shallow marine faunas are found in Devonian rocks in Central and South America, which were part of the southern Gondwana continent, generally thought to be separated from Laurentia by oceanic water depths at that time. During the Devonian, eastern Laurentia was an active tectonic margin, related to continent-continent collisions with various terranes/smaller continental masses. The Caledonian, Acadian, and Neoacadian orogenies resulted in compressional and some transpressional tectonics, and the uplift of an extensive mountain belt from east Greenland to Alabama and Georgia. Crustal loading of the orogen in eastern Laurentia led to subsidence and formation of a retroarc Acadian-Neoacadian Foreland Basin, which was initially filled with marine waters, followed by gradual overfilling to above sea level by massive volumes of synorogenic sediments from the east. The resulting lands were the site of some of the earliest forests on Earth, preserved at several sites in New York State, and forest ecosystems. Large-scale deformation, seismic activity, and metamorphism in the mountain belt were accompanied by igneous processes, including explosive eruption of felsic volcanic ash and other material, collectively termed “tephra,” also sometimes termed ash or tuff layers, or if diagenetically altered, sometimes termed bentonite, K-bentonite, metabentonite, or tonstein layers. These explosive Devonian eruptions sent volcanic tephra high into the atmosphere, and easterly winds spread airfall volcanic “tephra layers” across the eastern United States. Meanwhile, rock decay in the mountains led to the erosion, transport, and deposition of massive volumes of clays, silt, sand, and gravel into the Acadian-Neoacadian Foreland Basin, and beyond. Devonian rocks in New York are found at or just below the surface across approximately 40% of the state (~50,500 km2/19,500 mi2). The strata are generally undeformed and gently dipping, and while often covered by soil, glacial sediments, and vegetative cover, are relatively widely found in natural and man-made exposures. Three relatively thin intervals of carbonates are accompanied by eastward thickening wedges of synorogenic mudrocks, sandstones, and minor conglomerates. The history of geological and paleontological observation and study in New York began in the late 18th century. The first professional geologists appeared in the early 19th century. Since the advent of the first geological survey of New York State in 1836, the Devonian Period (nearly termed the “Erian Period” for New York’s Devonian-age rocks) has been the focus of a great volume of research which continues today. The Devonian succession in New York includes strata from all seven stages of the period, with erosional gaps of small to major significance. In addition to a range of marine facies, nearly one quarter of the entire area of Devonian bedrock in the state was deposited in terrestrial settings, with massive volumes of siliciclastic sediments shed off of Acadian-Neoacadian highlands to the east, that also feature the fossils of Earth’s oldest known forest ecosystems. The stratigraphic philosophy in New York has long evolved toward a hybrid classification, wherein groups, formations, and bed-level units are largely time-rock/allostratigraphic to occasionally chronostratigraphic, with lithostratigraphy often ascribed to member-level divisions (e.g., Pragian to Givetian strata, middle Lower to upper Middle Devonian). However, in some intervals, such as Frasnian strata (lower Upper Devonian), group-level units are time-rock units, and formation-level units within groups are largely lithostratigraphic. Forty-eight years of research since Rickard’s (1975) New York Devonian correlation chart permits development of a new, more refined chart (forthcoming), and also permits a new synthesis of Devonian rocks and fossils in New York, presented in this work of twelve chapters, with additional digital appendices.
Lower Middle Devonian strata (Eifelian to lower Givetian stages) of New York are identified under the names Onondaga and Marcellus. As has been New York practice for over 80 years, they represent time-significant allostratigraphic units, which to some degree cut across lithologic boundaries. The Onondaga Formation is a relatively tabular, limestone-dominated unit throughout New York. Strata thin from both east and west into more basinward facies in the central part of the state. In contrast, the (revised) “Marcellus subgroup” forms an eastward-thickening and coarsening wedge of siliciclastic-dominated facies. Marcellus-equivalent strata range in thickness from less than seven meters in the western New York subsurface to an estimated maximum thickness of 580 meters in the Hudson Valley, eastern New York. Few stratigraphic revisions have been proposed for the Onondaga Formation since 1975, beyond minor revisions to two members associated with the abandonment of the informal, former Clarence member, chert-rich facies in western New York. In contrast, the term “Marcellus” has been raised in New York State from formation to subgroup status, with three formation-level units: a lower Union Springs and coeval upper Marcellus Oatka Creek and Mount Marion formations. The latter two represent correlative basinal dark shales and proximal dark shales to shoreface sandstones, respectively. Overall, following Cooper’s classic 1930s stratigraphy of one formation with 11 members, 13 members are now recognized in the Marcellus subgroup; two in the Union Springs Formation and 11 in the upper Marcellus Oatka Creek and Mount Marion succession. Onondaga and Marcellus strata form three third-order depositional sequences, which feature three very distinct faunas. The sequences, termed Devonian Sequences Ic, Id, and Ie (alternatively Eif-1, Eif-2, and Eif-Giv) consist, respectively of 1) lower to middle Onondaga; 2) upper Onondaga and Union Springs; and 3) coeval Oatka Creek and Mount Marion formations, except where upper Mount Marion strata are not yet clearly distinguished form lower Skaneateles equivalents in eastern New York. The fossil assemblages of the Eifelian to lower Givetian have been subdivided into three “faunas” or ecological-evolutionary subunits. The oldest of the three faunas, the Onondaga Fauna, is succeeded by the Stony Hollow Fauna in shallow facies of the upper Union Springs and lowermost Mount Marion-Oatka Creek formations. The Stony Hollow Fauna is, in turn, succeeded by the classic Middle Devonian Hamilton Fauna throughout the remainder of upper Marcellus strata and Hamilton strata above.
Upper Famennian strata, including a time slice from the international Palmatolepis marginifera conodont Zone to the Protognathodus kockeli conodont Zone, and part of the Cheiloceras ammonoid Zone, upward to the topmost Acutimitoceras ammonoid Zone at the Devonian-Carboniferous boundary, are well exposed in the southern part of the western New York Southern Tier region and in adjacent Pennsylvania and northern Ohio. This interval includes offshore marine to paralic deposits in the Conneaut and Conewango groups in New York and correlative Chadakoin and Venango formations in northwest Pennsylvania, as well as strata comprising parts of the Chagrin Member of the Ohio Shale in Ohio. Terrestrial deposits, time-equivalent to the Conneaut and Conewango groups, are represented by the Catskill Formation in north-central Pennsylvania. Offshore marine-to-paralic units in the post-Conewango Group–pre-Cuyahoga Group time slice are exposed mainly in northwest Pennsylvania and northern Ohio. In Ohio, they include, in ascending order, the Cleveland Member of the Ohio Shale, the Bedford Shale, and the Berea Sandstone. In northwest Pennsylvania they include the “Drake Well Formation,” Knapp Formation, Corry Formation and the newly proposed divisions within the expanded Berea Formation succession. Coeval terrestrial deposits in Pennsylvania are represented by a lower portion of the Huntley Mountain Formation and by the Spechty Kopf Formation. The Mississippian Subsystem commences with transgressive dark shale deposits of the Orangeville Formation of the Cuyahoga Group in Ohio. The post-Conewango Group time slice was dominated by major oscillations in climate during the global Dasberg Event and Hangenberg Biocrisis, with associated changes in sea level during the latest Devonian. In Ohio, the Dasberg transgression is marked by the overspread of oxygen-deficient, black shale facies recorded by the Cleveland Member of the Ohio Shale. It is marked by an upward change into non-red, nearshore marine and terrestrial deposits of the Oswayo, Huntley Mountain, and Spechty Kopf formations in New York and Pennsylvania. The aftermath of the initial Hangenberg Biocrisis is recorded by sparsely fossiliferous deposits of the Bedford and Berea formations. One or more subsequent episodes of glaciation produced deposits of diamictite in eastern Pennsylvania and Maryland and a major lowstand disconformity along the base of the Cussewago Sandstone- Berea Formation succession across Pennsylvania and Ohio. Mississippian deposits commence with the transgressive overspread of dark, offshore shales of the Sunbury Member of the Orangeville Formation in Ohio, which grade eastward (shoreward) into neritic marine deposits in the central Pennsylvania region.
The Frasnian-Famennian boundary interval is exposed in New York State in an outcrop belt that stretches from Lake Erie eastward to Steuben County, continuing into Pennsylvania. Recent biostratigraphic examination of brachiopods and conodonts suggested that the shallower water sections to the east have been miscorrelated with the deeper water sections to the west. Revised correlations place the Upper Kellwasser extinction event (Frasnian-Famennian boundary) within the Canaseraga Formation and the Lower Kellwasser extinction event (Pipe Creek Formation) above the Wiscoy Formation. We review these revised correlations and provide additional support based on δ13Corg profiles from several sections. We also define new members in the Wiscoy Formation (Rossburg Member) and Canaseraga Formation (Hornell, Elkhorn Creek, and Crooked members) that should facilitate discussions of faunal and paleoenvironmental changes associated with the Frasnian-Famennian extinctions in the Appalachian Basin.
The Middle Devonian (lower–middle Givetian) Hamilton Group of New York State is an iconic unit in North America, which has contributed many key concepts in stratigraphy, sedimentary geology, paleoecology, and evolution. This interval comprises a 100- to 1200-m-thick clastic wedge, shed westward from the Acadian Mountains, with thin but persistent carbonates. Despite the rich and diverse invertebrate fauna that consists of more than 300 species of corals, bryozoans, brachiopods, mollusks, echinoderms, and trilobites, the age of the Hamilton Group is rather poorly constrained in terms of chronostratigraphy owing to the rarity of biostratigraphically useful conodonts and goniatites. The upper part of the Hamilton Group that is the focus of this paper apparently belongs to the Polygnathus timorensis to middle Polygnathus ansatus Conodont chronozones. The middle to upper Hamilton Group in New York State comprises three formations—the Skaneateles, Ludlowville, and Moscow—each defined as an interval delimited with a sharply based fossiliferous limestone-calcareous siltstone; these formations are interpreted as containing condensed transgressive deposits overlain by thicker highstand to falling-stage shales, mudstones/siltstones, and sandstones. The eastern equivalents of these formations are dominated by fine-grained sandstones and siltstones and include two formations: the Panther Mountain Formation, equivalent to the Skaneateles and Ludlowville formations combined, and the Cooperstown Formation, equivalent to the Moscow Formation. In the present paper, we review, revise and update a hierarchical framework of lithostratigraphic subdivisions of these formations, including 24 members (four new), 50 submembers (more than half newly proposed or redefined; 14 informal at this time), and more than 80 named beds, both formal and informal. This refined lithostratigraphy provides an excellent framework for studying high-resolution sequence stratigraphy. As defined herein, members and most submembers represent high-frequency depositional sequences with basal shell-rich carbonates and abrupt flooding surfaces that mark the bases of highstand deposits. Not only are most of the members and submembers traceable across western and central New York, but also to a lesser extent into adjacent regions that include southern Ontario, Ohio, the Michigan Basin, and northeastern Pennsylvania. Nevertheless, much work on correlation remains to be done in eastern New York and central Pennsylvania, where local progradation of siliciclastics and expansion of successions obscures many of the finer scale features.
Historically, the Helderberg Group has been an important unit including some of the earliest paleontologic and stratigraphic studies in North America. Once interpreted as a series of coeval facies, most formations and even some members of the Helderberg Group are separated by disconformities and regionally angular unconformities. The Green Vedder Member (new) is defined within the Manlius Formation and the Dayville Member is reassigned from the Coeymans to the Manlius Formation. The name Ravena member of the Coeymans Formation is abandoned because it coincides entirely with the redefined Coeymans Formation. Two new members, Jefferson Heights and Leeds Gorge, are recognized within the New Scotland Formation. A cluster of tephra beds occurs in the Kalkberg Formation, the upper Jefferson Heights and lower Leeds Gorge members of the New Scotland Formation. Strata formerly described as an “upper tongue of the Kalkberg Formation” are referred to as the Old Stone Fort Member (new) of the Becraft Formation. The Deansboro, formerly a member of the Coeymans Formation, is raised to formational rank owing to its physical and biostratigraphic separation from the Coeymans Formation. Reef-bearing strata may still comprise a part of the Deansboro Formation or may be removed and referred to as the Mosquito Point Formation (new). Strata that overlie the Deansboro Formation in central New York that had been regarded as part of the Kalkberg Formation differ lithologically and are significantly younger than the Kalkberg. They are therefore redefined as the Buckley Mill Formation (new). Major unconformities occur between the Chrysler Member of the Rondout Formation and the Thacher Member of the Manlius Formation (Mine Lot Falls Unconformity), between the Thacher and Green Vedder members of the Manlius Formation (Clockville Unconformity), and between the Green Vedder Member and the Olney and Dayville members (Terrace Mountain Unconformity). The Columbia Center Unconformity separates the Olney from the overlying Dayville Member. The Howe Cave Unconformity marks the base of the Coeymans Formation and is basin-wide in its extent. The Punch Kill Unconformity caps the Coeymans Formation and is onlapped by four subunits of the Kalkberg Formation. The Getman Corners Unconformity marks the base of the Deansboro Formation and erosionally separates this unit from the Helderberg Group. The Silurian–Devonian boundary interval (base of the Lochkovian Stage) occurs in the upper portion of the Green Vedder Member of the Manlius Formation. The co-occurrence of scyphocrinitid loboliths and a positive δ13C excursion (Klonk Event) in facies that represent deeper, dysoxic conditions characterize the boundary interval. The Judds Falls Bentonite Bed is constrained to the middle Lochkovian (upper bohemica Zone) by a somewhat diverse chitinozoan fauna. A mid- to late Lochkovian age for the Becraft and Alsen formations is indicated by chitinozoans. Additional chitinozoan data suggest that the Lochkovian–Pragian boundary occurs in the Port Ewen Formation. Pragian conodonts from the Deansboro Formation mark a maximum age for the bioherms that have been grouped with the Deansboro. A Pragian age is also likely for the Buckley Mill Formation that overlies the Deansboro Formation, but chitinozoan studies from this unit are not yet completed. Seven epiboles of various crinoids and cystoids are recognized and are important marker horizons in the revised stratigraphy. The sequence stratigraphic framework of the Helderberg Group suggests that the stratigraphic architecture is strongly controlled by episodic, tectonically-driven subsidence produced by crustal loading during a pre-Tectophase I episode of Acadian orogenesis. During deposition of the Thacher Member of the Manlius Formation, maximum subsidence occurred in the region around Cherry Valley, New York. During deposition of the overlying Green Vedder Member, a low arch developed in this region, separating two sub-basins. The Cherry Valley Arch disappeared during deposition of the Dayville Member of the Manlius Formation and maximum subsidence was centered near Columbia Center, New York. The Cherry Valley Arch was reactivated and broadened to extend between Cherry Valley and the area around West Berne during deposition of the Elmwood through Jamesville members of the Manlius Formation. The Cherry Valley Arch disappeared as subsidence increased during deposition of overlying Helderberg units. Post-Manlius formations document eastward migration of the axis of maximum subsidence and bathymetric axis of the basin through time. This pattern reversed during deposition of the lower part of the Becraft Formation in which deeper water facies (Old Stone Fort Member) were deposited in the Schoharie region and shallower environments developed in the Hudson Valley. This transposition was short-lived as maximum subsidence migrated into the Hudson Valley region once again and persisted during deposition of the upper Becraft and the overlying Alsen and Port Ewen formations. The newly developed sequence stratigraphy and biostratigraphy in the Appalachian Standard Succession (New York State) enable revised correlations within the Central Appalachian Basin.
Marine strata of the Middle Devonian Hamilton Group in eastern New York State consist of a thick succession of synorogenic ba- sinal to shoreface sediments. Initial basinal dark to black shales grade upward through increasingly coarse, sand-dominated facies. Beginning in Marcellus (early Givetian-age) strata in the Hudson Valley, these marine facies grade upward and laterally into ter- restrial strata. This major transition occurs diachronously with higher strata undergoing transition to terrestrial facies progressively further westward. Time-rock/allostratigraphic relationships in these rocks have long remained poorly understood. This chapter examines older and recent observations and presents new interpretations and hypotheses on the correlation of these strata. The purposes of this work are to: 1) better constrain the position of the marine to terrestrial transition in upper the Marcellus subgroup strata; 2) better constrain the contact “interval” of the marine Mount Marion-Panther Mountain formations; 3) present current knowledge and hypotheses about the Panther Mountain Formation; 4) discuss the presence of two intervals of unique fauna, each consisting of an epibole of the brachiopod Schizophoria King, 1850 in southern Albany County and northeastern Greene County together with correlation of these intervals southward into Ulster County; 5) discuss basal strata of the upper Hamilton Coo- perstown Formation through Schoharie to Greene counties; and finally, 6) present an overview of development of the Hamilton Group between Kingston, Ulster County and Port Jervis, Orange County, where New York, New Jersey, and Pennsylvania meet. Methods utilized include reviews of older reports, new findings, sequence stratigraphy, correlation of distinct marker units, some faunal assessment (e.g., Schizophoria fauna intervals and other faunal associations, including a coral-rich bed), and some lithologic indicators of relative depths (e.g., thin, decimeter-scale conglomerates). The synthesis and resulting interpretations presented in this chapter are more tentative than in some chapters; however, the authors attempt herein to lay the groundwork for future research.
