UNIVERSITY OF CINCINNATI
______, 20 _____
I,______, hereby submit this as part of the requirements for the degree of:
______in: ______It is entitled: ______
Approved by: ______Sequence Stratigraphy and Event Correlations of upper Black River and lower Trenton Group Carbonates of northern New York State and southern Ontario, Canada.
A thesis submitted to the
Division of Graduate Studies and Research of the University of Cincinnati
in partial fulfillment of the requirements for the degree of
MASTER OF SCIENCE
in the Department of Geology of the College of Arts and Sciences
2000
by
Sean R. Cornell
B.S., Univesity of Rochester, 1998
ABSTRACT
Successions of carbonate to mixed carbonate/siliciclastic rocks of Middle Ordovician age were deposited in New York State and Ontario, Canada on the passive edge of the westward advancing Taconic foreland basin. The transition from carbonate to siliciclastic sedimentation is thought to record the critical change from a passive to active tectonic margin. In addition to tectonic change, it has been suggested that this stratigraphic interval also records an overall transgressive series (Tippecanoe megasequence Sloss, 1963) which is interrupted by shorter duration sea-level fall events (Holland & Patzkowsky, 1996, 1998). Holland & Patzkowsky
(1996, 1998) delineated 6 sequences for the Mohawkian and correlated these sequences in the southern Appalachians, Nashville Dome, and Cincinnati Arch. However, the succession in New
York and Ontario have not been equally evaluated within this framework. Herein, the upper
Black River to lower Trenton groups are investigated in order to help understand the event and cyclic stratigraphic relationships of units recognized throughout the outcrop belt from southern
Ontario, Canada, to northern New York State and to place these rocks into a sequence stratigraphic framework. Through the use of correlated event beds including K-bentonites, and other marker horizons it has been possible to delineate a series of 2 depositional sequences, with distinctive systems tracts, and small-scale parasequences (or PACs) that are correlatable across the New York-Ontario region. By establishing these correlations it has been possible to provide objective criteria for defining a new position for the Black River/Trenton Group lithostratigraphic boundary in this region, such that it also represents a significant chronostratigraphic boundary as well. In addition to establishing local to regional correlations, through the association of K-bentonites it has also been possible to infer the positions of two of
Holland and Patzkowsky’s (1996) sequences in the study region. Although the association of
ii Holland and Patzkowsky’s M4 and M5 sequences is preliminary, several key issues are raised that support the need for a revision of the North American chronostratigraphic nomenclature as applied outside the New York/Ontario type region.
iii ACKNOWLEDGEMENTS
The author wishes to recognize first and foremost, his wife, Angel Cornell. She has been patient, supportive and ever compromising even through the most difficult times. In addition, the support of several other individuals and organizations is gratefully acknowledged. I wish to thank Dr. Carlton Brett, my primary advisor, for his assistance in all aspects of this research and for his never ending enthusiasm for field work. This thesis would not have been possible without the assistance of Dr. Warren Huff and Dr. Thomas Algeo, who offered their assistance with editing previous drafts of this thesis. This manuscript has benefited greatly from their constructive comments. In addition to the faculty on the M.S. committee, I would also like to recognize assistance and discussions from Dr. Gordon Baird and from several students who aided the research through their assistance in the field. They include Heather Ellington, Alan
Turner, and Patrick McLaughlin.
Lastly, I would like to acknowledge the Geological Society of America’s student grants program for supporting two summers of research on this project as well as the University of
Cincinnati, Department of Geology, Caster Fund for providing additional summer support.
iv TABLE OF CONTENTS
PAGES I. INTRODUCTION P. 5
II. GEOLOGIC SETTING P. 15
III. PREVIOUS WORK P. 20
IV. STUDY AREA & METHODS P. 25
V. HISTORY AND GENERAL STRATIGRAPHY OF THE BLACK RIVER AND LOWER TRENTON GROUPS IN NEW YORK AND ONTARIO P. 28
VI. STRATIGRAPHIC CORRELATION USING LITHOLOGIC BOUNDARIES: P. 35 A. FACIES DISLOCATIONS AND EROSION SURFACES P. 35 1. THE PAMELIA-LOWVILLE CONTACT P. 35 2. THE BASAL COBOCONK CONTACT P. 37 3. THE WATERTOWN-LERAY (MOORE HILL) CONTACT P. 40 4. THE BASAL KINGS FALLS (LOWER KIRKFIELD) TO NAPANEE CONTACT P. 46 5. INTERPRETATIONS P. 48 B. FLOODING SURFACES P. 48 1. MINOR FLOODING SURFACES P. 48 A. LOWER-MIDDLE COBOCONK CONTACT P. 51 B. BASAL GLENBURNIE CONTACT P. 51 C. WATERTOWN-SELBY CONTACT P. 52 2. MAJOR FLOODING SURFACES P. 52 A. GULL RIVER-MOORE HILL CONTACT/ LOWVILLE-HOUSE CREEK-LERAY CONTACT P. 55 B. SELBY-NAPANEE CONTACT P. 55 C. INTERPRETATIONS P. 58
VII. BIOSTRATIGRAPHY P. 61
VIII. CHRONOSTRATIGRAPHIC K-BENTONITE CORRELATIONS P. 66 A. HISTORY OF K-BENTONITE STRATIGRAPHY IN NEW YORK AND ONTARIO P. 66 B. BLACK RIVER AND LOWER TRENTON K-BENTONITE STRATIGRAPHY P. 70 1. THE MX K-BENTONITE P. 73 2. THE MH K-BENTONITE P. 75 3. THE HOUNSFIELD K-BENTONITE P. 78 4. THE MR K-BENTONITE P. 82 5. OTHER K-BENTONITES P. 84
1 IX. OTHER STRATIGRAPHIC MARKERS USED IN CORRELATIONS P. 85 A. EPIBOLE MARKERS P. 85 B. DISTINCTIVE LITHOLOGIC INTERVALS P. 87 C. DISTINCTIVE LITHOLOGIC PATTERNS P. 88
X. REVISED STRATIGRAPHY OF THE UPPER BLACK RIVER GROUP TO LOWER TRENTON INTERVAL P. 95 A. BLACK RIVER-TRENTON GROUP LITHOSTRATIGRAPHIC BOUNDARY P. 95 B. UPPER BLACK RIVER GROUP P. 100 1. LOWER LOWVILLE FORMATION – LOWER GULL RIVER FORMATION (B1-B2 SUB-MEMBERS) P. 100 2. HOUSE CREEK (LERAY) – MOORE HILL MEMBER P. 103 3. WEAVER ROAD BEDS P. 107 4. COBOCONK MEMBER (BOBCAYGEON FORMATION) REVISED P. 109 5. GLENBURNIE MEMBER P. 113 C. LOWER TRENTON GROUP 1. WATERTOWN FORMATION P. 116 2. SELBY FORMATION P. 120 3. NAPANEE FORMATION P. 123
XI. SEQUENCE STRATIGRAPHY OF THE UPPER BLACK RIVER TO LOWER TRENTON SUCESSION P. 126 A. SEQUENCE 1: LOWER LOWVILLE – HOUSE CREEK - GLENBURNIE IN NEW YORK, AND EQUIVALENT MIDDLE TO UPPER GULL RIVER, MOORE HILL, & COBOCONK SENSU STRICTO IN SOUTHWESTERN ONTARIO. P. 131
B. SEQUENCE 2: WATERTOWN-SELBY-NAPANEE IN NEW YORK, UPPER COBOCONK-MIDDLE BOBCAYGEON FORMATION SENSU STRICTO IN SOUTH WESTERN ONTARIO P. 134
XII. IMPLICATIONS OF REVISED BLACK RIVER TO LOWER TRENTON STRATIGRAPHY FOR TEMPORAL CORRELATION P. 138
XIII. SEQUENCE COMPARISONS WITH EQUIVALENT STRATA IN THE NASHVILLE DOME, SOUTHERN APPALACHIANS AND CINCINNATI ARCH P. 142
IXV. CONCLUSIONS P. 145
XV. BIBLIOGRAPHY P. 149
2 LIST OF FIGURES
Figure 1: Locality map p. 6
Figure 2: Stage terminology p. 7
Figure 3: Mohawkian sequences p. 9
Figure 4: Previous depositional models p. 11
Figure 5: Absolute age determinations for K-bentonites p. 13
Figure 6: Physiographic map for study region p. 17
Figure 7: Historical stratigraphic classifications schemes p. 21
Figure 8: Examples of recognized marker horizons p. 27
Figure 9a: Relative stratigraphic thicknesses of units in New York p. 29
Figure 9b: Relative stratigraphic thicknesses of units in Ontario p. 32
Figure 10: Pamelia-Lowville contact as exposed at Depauville, NY p. 36
Figure 11: Pamelia-Lowville contact as exposed at Dalrymple, Ont. p. 38
Figure 12: Basal Coboconk contact as exposed at Coboconk, Ont. p. 39
Figure 13a: Basal Coboconk contact as exposed at Brownville, NY p. 41
Figure 13b: Upper Black River Group as exposed in Black River Gorge at Glenn Park, NY p. 42
Figure 14: Exposure at Ingham Mills, New York p. 43
Figure 15: Gull River and lower Bobcaygeon Formations as exposed at Coboconk, Ontario. p. 45
Figure 16: Kings Falls-Napanee Formation Contact at Napanee, Ont. p. 47
Figure 17: Sequence boundary correlation diagram p. 49
Figure 18: Example of minor flooding surface p. 50
Figure 19: Watertown-Selby contact (minor flooding surface) p. 53
3 Figure 20: Example of major flooding surface p. 54
Figure 21: Major flooding surface (Maximum Flooding) Gull River-Moore Hill contact p. 56
Figure 22: Major flooding surface (Maximum Flooding) Selby – Napanee contact p. 57
Figure 23: Correlation diagram showing positions of K-bentonites p. 59
Figure 24: Examples of conodonts and scolecodonts p. 62
Figure 25: from Kolata et al. 1996, known K-bentonites in NY p. 68
Figure 26: from Kolata et al. 1996, known K-bentonites in Ontario p. 69
Figure 27: Schematic representation of K-bentonite correlations p. 72
Figure 28: K-bentonites in Black River Gorge, Brownville, NY p. 77
Figure 29: Stratigraphic correlation of Hounsfield K-bentonite interval p. 80
Figure 30: Stratigraphic correlation of MH K-bentonite interval p. 89
Figure 31: Example of epibole horizons p. 90
Figure 32: Outcrop example of lower Lowville cycles p. 92
Figure 33a: Outcrop examples of upper Lowville (Moore Hill) cycles p. 93
Figure 33b: Correlation diagram showing cycle patterns p. 94
Figure 34: Sequence stratigraphic delineations for sequences 1 & 2. p. 96
Figure 35: Photomosaic of sequence 1 components p. 128
Figure 36: Photomosaic of sequence 2 components p. 129
Figure 37: Correlation diagram showing all correlations p. 130
4 CHAPTER I.
INTRODUCTION
The late Middle Ordovician (Mohawkian Series) Black River and Trenton groups of the northeastern midcontinent consist of some 250 m of highly fossiliferous, well-preserved carbonates with some intervening shales. These rocks are exposed along an approximately east- west outcrop belt for more than 250 km in central New York and across the U.S./Canada border into neighboring Ontario, where they closely flank the Precambrian Grenville Province (Figure
1). The Black River Group is comprised predominantly of peritidal to shallow subtidal fine- grained carbonate facies, the classic “birdseye” limestone (fenestral calcilutite- micrites) of early workers (Vanuxem, 1838, Hall, 1847). The Trenton is composed almost exclusively of subtidal, shallow shelf calcarenites (pack- and grainstones), and deeper ramp calcisiltites, calcilutites
(lime wackestones and mudstones), and shales. As a broad generalization, these strata record an overall large-scale deepening from the Black River into the middle Trenton, associated with the early phases of the Tippecanoe Supersequence (Creek holostrome) transgression (Sloss, 1963).
The Black River and Trenton Groups, originally defined in central New York State
(Vanuxem, 1842), are among the best known and earliest formally designated stratigraphic units in North America. The names of these well-known intervals have also been applied to time-rock units (Figure 2). Thus, the term Trentonian Stage was formerly applied to the late part of the
Mohawkian Series, and the term Blackriveran is still in common use for the lower Mohawkian today. Not surprisingly, some researchers have discouraged the use of lithostratigraphic terms for time-rock terms, and there has been an effort to substitute Fisher’s (1977) term Turinian, named for exposures of the Black River Group near Turin, NY, for Blackriveran. The
Trentonian Stage, no longer widely used, is roughly equivalent to what is now termed the
5 Brechin Kirkfield Marmora Kingston Dalrymple Coboconk Napanee
Depauville
Brownville
Lowville 80° 75°
45°
Ontario
New York
80 kms
50 miles
40°
Figure 1: Ordovician outcrop belt for Ontario, Quebec, and New York (Shaded). Key localities are shown in relation to political boundaries and modern physiographic features. N.Am. Time Rock Europe Rock Terms A B C Rock Terms in NY midcontinent Fm. Falls
Kings Kirkfieldian ASHGILL Richmondian. Fm.
Maysv. Napanee Chatfieldian CINCINNATIAN Rocklandian Utica Group Edenian Fm.
Selby town Water- Glenburnie Millbrig K-bentonite Group Shermanian Chaumont Fm. Leray Trentonian Ki. Trenton CARADOC Ro. MOHAWKIAN Riveran Lowville Fm. River Gp. Turinian Black Black Ashbyan Pamelia Fm. Figure 2: Stratigraphic terminology applied to the lower Upper Ordovicican succession as defined in New York State and adjacent Ontario, Canada. Column A shows current lithostratigraphic terminology (with the exception that Chaumont(ian) has been sometimes used as a time rock term), Column B represents the time-rock classification proposed by Fisher (1977) while Column C shows the approximate position of the time-rock term, Chatfieldian, as proposed in the eastern midcontinent by Leslie and Bergström, (1995) based on the Millbrig K-bentonite. Chatfieldian Stage (Leslie and Bergström, 1995). However, the alternative stage classification, using Kay’s (1937) more precise subdivisions of the upper Mohawkian Series: the Rocklandian,
Kirkfieldian, and Shermanian stages, is still in common use. All of these terms, except
Chatfieldian, have their roots in the stratigraphy of northwestern New York State and adjacent
Ontario, Canada.
It is surprising, therefore, that the stratigraphic details of the Black River and Trenton groups are still poorly known in these widely studied areas. For example, the precise position of the Black River/Trenton boundary, historically synonymous with top Turinian or base
Rocklandian in the type area, is still poorly defined after over a century of debate (Kay, 1937;
Fisher 1962; Titus & Cameron, 1976; Cameron & Mangion, 1977). Moreover, the base of the newly proposed Chatfieldian, at the stratigraphic level of the widespread Millbrig K-bentonite, has not been established with respect to litho- or sequence stratigraphy in the type Trenton/Black
River area, despite recent recognition of the Millbrig K-bentonite in New York (Adhya et al.,
2000).
Furthermore, while the Black River/Trenton-equivalent interval has recently become the focus of study from the standpoint of sequence stratigraphy and cyclicity in other parts of North
America, similar studies have not been undertaken in the type area. Holland and Patzkowsky
(1996, 1998) have identified and correlated six Mohawkian depositional sequences (M1-M6) throughout the southern Appalachians and eastern Midcontinent area (Figure 3). As yet, these sequences and their components have not been recognized or studied in the classic New York-
Ontario sections.
Likewise, numerous studies have demonstrated the widespread development of carbonate sequences and cycles, especially during Cambro-Ordovician time, and many have also
8 Age Seq
Stage (Ma) N. Am. Europe tropical rare C6 carbonates phosphate C5 445 C4
Ashgill C3 high C2 terrigenous Cincinnatian flux cool water abundant C1 450 Eden. Mays. Rich. carbonates phosphate
M6 M5 Chat.
M4 M3 455 Caradoc low Mohawkian M2 tropical rare terrigenous carbonates phosphate
Turinian flux M1
Figure 3 : Mohawkian and Cincinnatian third-order sequences, time scale and paleoclimatic indicators. Note three distinct climatic/sedimentologic regimes, the boundary of one occurs at the M4-M5 boundary and is coincident with the transition out of the Black River Group and into the overlying Trenton Group. (Modified from Holland & Patzkowsky, 1993) documented the correlation of parasequence sets within a framework of larger-scale sea-level fluctuations across wide (>250 km) platforms (Read & Goldhammer, 1988; Osleger, 1991;
Montanez & Osleger, 1992; Read, 1994; Pope & Read, 1995). Yet, these concepts have not been fully applied in some of the best known carbonate successions in New York and Ontario. In fact, the Black River Group and, to a lesser extent, the Trenton Group, exhibit typical parasequence stacking patterns and were among the first units used to demonstrate the concept of punctuated aggradational cycles (PACs), thin 1-5 m upward shallowing cycles separated by surfaces of non-deposition produced by apparent rapid base-level rise (Anderson et al., 1978;
Goodwin & Anderson, 1985; Goodwin et al., 1986). However, previous, rather limited, attempts at correlation of the Black River and overlying Trenton strata suggested that these PAC parasequences were not recognizable from one locality to another, much less across the entire outcrop region (Walker, 1973; Goodwin & Anderson, 1985). In fact, many workers supported the view that this interval was composed of a mosaic of diachronous facies (Figure 4). With this view, the nature of the Black River Group and the overlying Trenton came to be interpreted under a facies mosaic model. This view was supported by the work of Fisher (1965, 1977);
Textoris (1968); and Walker (1973), in New York, as well as that of Winder (1960) working separately in Ontario. Fisher (1965) even implied that Black River peritidal lithologies were, in part, time-equivalent to parts of the lower Trenton, which is of deeper marine origin.
A number of studies have investigated the local stratigraphic and sedimentologic characteristics for this interval. These studies were undertaken by Textoris (1968), Johnsen
(1971), and Walker (1973) for the New York region, and by Liberty (1969) for the Lake Simcoe region, and more recently by Noor (1989) and McFarlane (1992). Collectively, the results of these studies indicated that correlation was at least possible on a local scale using key marker
10 Figure 4: Three depositional models for Black River to lower Trenton groups as taken from Walker (1973). The series of models shows an evolution from a “layer cake” model to a more time- transgressive model; the latter views each unit as being largely laterally equivalent facies distributed across the Mohawkian Ramp. horizons. Yet, up to this time, there has been little effort to establish correlations across the entire outcrop belt in New York and Ontario. This region represents a very critical reference interval for North American stage nomenclature to which other similar sections are compared, and it is also a key interval for interpreting the early Paleozoic tectonic history of the Laurentian margin. Therefore, it is necessary that a well established set of correlations be made across the study region.
This process has been hampered by the low resolution of conodont biostratigraphy and a lack of other diagnostic index fossils. However, the presence of a number of K-bentonites and other event beds distributed throughout the succession may provide the basis for establishing more regional correlations. K-bentonites are generally deposited instantaneously, with respect to geologic time, over a very large region and, as such, are profoundly useful in establishing chronostratigraphic correlations. One of these key K-bentonites, the Hounsfield has also been equated with the well-known and very widespread Millbrig K-bentonite (Adhya et al., 2000), recognized in many coeval sections by Haynes (1994), and Kolata et al. (1996) (Figure 5). Other types of unique marker beds used to establish regional high-resolution correlations include a variety of event beds such as sharp facies disjunctions, fossil beds, stromatolite beds, epiboles, unique lithologic units, and distinctive patterns of bedding. Collectively, such a variety of distinctive marker units/beds can provide the discriminating stratigrapher a variety of tools from which detailed correlations can be based.
The intent of the present research is to investigate the upper Black River to lower Trenton groups in order to help understand the event and cyclic stratigraphic relationships of units recognized throughout the outcrop belt from southern Ontario, Canada, to northern New York
State and to place these rocks into a sequence stratigraphic framework. The specific goals of this
12 Zircon ONT NY Biotite U/Pb Ar/Ar
MR
Trenton Group
453.1 +/- 0.65 Ma Hounsfield 448.0 +/- 1.8 Ma = Millbrig
MH
454.5 +/- 0.25 Ma MX/ Barriefield 449.9 +/- 2.4 Ma Hill (Deicke?)
Black River Group
Pre-Cambrian
Figure 5: Absolute age comparison of the Deicke and Millbrig K-bentonites from Min, Renne, and Huff (2001). The relative position of K-bentonites present in Ontario and New York State is based on data presented herein. study are: a) to describe the physical stratigraphy and correlatable horizones of the upper Black
River and lower Trenton groups in the type area and adjacent Ontario, b) to identify and physically correlate K-bentonites and other unique marker beds, c) to establish a framework of regional tie-lines for correlation of upper Black River – Trenton from NY to Lake Simcoe,
Ontario, d) to provide objective criteria for defining the Black River/Trenton Group lithostratigraphic boundary in this region, e) to determine if depositional sequences, systems tracts, and small-scale parasequences (or PACs) are correlatable across the New York-Ontario region, f) to identify the positions of Holland and Patzkowsky’s (1996) sequences and their component systems tracts, if possible, and g) to briefly compare the New York-Ontario successions with those of other regions in eastern North America.
14 CHAPTER II
GEOLOGIC SETTING
The interval of time embraced by the Black River and Trenton groups spans late Middle to early Late Ordovician time, as previously defined. It should be noted that the IUGS
Subcommission on Ordovician Stratigraphy has recently recommended that much of the interval previously termed Middle Ordovician and Upper Ordovician Llandeilo-Ashgill stages (hence the
Black River-Trenton interval) be assigned to Upper Ordovician. As noted previously, the Black
River and Trenton groups comprise most of the North American Mohawkian Provincial Series
(see Figure 2). The Black River Group lies almost completely within the Turinian Stage. The
Trenton Group is almost entirely included within the broadly applied Chatfieldian Stage, although beds assigned to the uppermost Trenton actually fall into the base of the Cincinnatian
Series. The rocks of the lower Trenton interval that are discussed in this study lie mostly within
Kay’s (1937, 1960) Rocklandian Stage.
In the British classification this entire interval is assigned to the Caradoc Series (now in emended use as the Caradocian Global Stage) (see Figure 2). This is a relatively long time period which has only recently been divided into stages that are not well calibrated with the
North American standards. However, the basal boundary of the Burrellian Stage (of Britain) is approximately coincident with the basal Turinian Stage of the Mohawkian Series in North
American time stratigraphic terminology (Webby, 1998).
Absolute age dating for this interval has become a more realistic endeavor in recent years as multiple K-bentonites have yielded datable phenocrysts (Haynes, 1994; Kolata et al., 1996,
Samson et al. 1988, Min et al., 2001). Two widely dispersed K-bentonites, the Deicke and
Millbrig, have been dated by a number of geochronometric systems (see Figure 5). The resulting
15 ages range from 449.9 +/- 2.4 Ma (for 40Ar/39Ar dates of biotites with 100% concordance between samples) to 454.5 +/- 0.25 Ma (for U/Pb dates of zircon) for the Deicke K-bentonite; and 448.0 +/- 1.8 Ma (Ar/Ar dates of biotites) to 453.1 +/- 0.65 Ma (for U/Pb dates of zircon) for the Millbrig (Min et al., 2001).
The interval of interest for this study lies above a widespread discontinuity surface below the suspected Deicke K-bentonite (see Figure 5). The interval continues into younger strata above the Millbrig, now proposed to be equivalent to the Hounsfield of Kay (1929) by Adhya et al., (2000). Hence the duration of deposition for the upper Black River Group spans a period of about 1.5 to 2 Ma estimated for the Deicke to Millbrig interval based only on U/Pb and Ar/Ar dates, respectively. The entire study interval including lower Trenton beds probably spans close to 3 Ma.
The Black River to lower Trenton Group carbonates were deposited on the eastern margin of Laurentia during the early phases of the Tippecanoe Sequence (Sloss 1963). They rest unconformably on older rocks that range in age from mid-Proterozoic (Grenville) to Middle
Ordovician (Chazy) which are predominantly shallow-marine craton-derived clastics (Potsdam) and minor carbonates (Potsdam, Theresa and Ogdensburg) of the Cambrian to early Ordovician
Sauk Sequence.
During the late Middle Ordovician, the majority of ancestral North America (Laurentia) was covered by shallow tropical seas. The eastern portion of Laurentia was rotated approximately 90 degrees clockwise relative to its present configuration, and the study area was located approximately 20 º south of the equator (Scotese et al., 1994). The only exposed areas were portions of the modern Canadian shield and areas along the Transcontinental Arch that were in general of very low relief (Figure 6). Presently, the Middle Ordovician outcrop belt of
16 Transcontinental Arch L a u r e n t i a Equator
Sebree Trough
Taconic Foreland Basin 30˚ S I a p e t u s O c e a n
St. Lawrence Platform
Peterborough Arch Lake Ontario Frontenac Arch
Adirondack Dome/ Adirondack Arch
Figure 6: Above: Paleogeographic map of Laurentia and various physiographic features present during the Middle Ordovician. The inset (bottom) shows several key features that most likely played important roles in the distribution and deposition of sediments during Black River-Trenton time. southern Ontario, Canada, and New York State extends approximately northwest-southeast. At the time the Black River rocks were being deposited, this transect would have been oblique to the shoreline.
Exposures along the outcrop belt in southern Ontario show Precambrian basement rocks exposed as inliers, surrounded and onlapped by the carbonate rocks of both Black River and
Trenton affinities. This suggests that there were some small islands of granitic basement exposed near the shore of eastern Laurentia (Brookfield, 1988). The general lack of siliciclastic sediments in the almost pure carbonate succession of the Black River indicates very little transport and introduction of terrigenous craton-derived sediments into the local depositional regime. Therefore, this suggests a very low elevation and broadly peneplained configuration for the Grenville Shield. Initially, however, the relatively flat, low-lying shield complex allowed the deposition of discontinuous siliciclastic-dominated sediments in topographically low-lying areas.
The subsequent deposition of very broad and extensive shelf carbonates demonstrates a very stable, passive continental margin during the deposition of the lower to middle Black River
Group.
Offshore, a small volcanic island complex called the Ammonoosuc Arc (Rowley & Kidd,
1981) was beginning to migrate towards the northeastern margin of Laurentia, and could conceivably have been responsible for the deposition of a number of key volcanic ashes of the same age, including the well-known Deicke and Millbrig K-bentonites. Another potential site of explosive volcanism, the Blue Ridge Microcontinent, was beginning to be accreted onto the
Laurentian margin at this time (Stanley & Ratcliffe, 1985; Ettensohn, 1991). This event, referred to as the Blountian tectophase, caused the rapid subsidence of the Sevier foreland basin in the southern Appalachians, into which siliciclastic sediments poured beginning in early Black River
18 time. The Vermontian tectophase, a later arc collision, was active during the deposition of the middle Trenton Group and affected deposition of the shallow shelf carbonates and the Flat Creek
Shales in the Utica trough to the north in Pennsylvania and New York State. Thus, overall, the
Black River and Trenton Groups record the transition from passive to active tectonism in eastern
Laurentia.
19 CHAPTER III
PREVIOUS WORK
The Black River and Trenton rocks have been studied since the late 1800s and a great deal of headway has been made in understanding the limestone-dominated strata of these North
American series and stage type sections (Kay, 1937; Walker, 1973; Fisher, 1977). In the last few decades intense work has focused on the stratigraphy of upper Mohawkian rocks (Trenton
Group) and their relationship to lower Cincinnatian rocks (Utica Group) in the region of New
York (Cameron & Mangion, 1977; Cisne et al., 1982; Goldman et al., 1994; Mitchell et al.,
1994; Brett et al., 1992; Brett and Baird, in press; Baird and Brett, in press).
Much early work was done on the lower Mohawkian (Black River Group) and its relationship with the overlying Trenton Group in both the Lake Simcoe district of southern
Ontario (Okultich, 1939; Caley and Liberty, 1967; Liberty, 1969; Winder, 1960) and southeastern Ontario to northern New York State (Cushing et al., 1910; Kay, 1929; 1931, 1935;
Young, 1943; Walker, 1973; and Fisher, 1977). Yet, due to the variety of approaches used to define and address questions regarding the nature and position of stratigraphic boundaries within the Black River and Trenton, only broad generalized correlations were made between Ontario and New York State. Many complications arose in the literature regarding the lithostratigraphic, chronostratigraphic, and biostratigraphic relationships of these units, and the depositional environments under which these rocks were deposited. These complications have essentially been unresolved up to the present. Figures 7 a & b demonstrate graphically the variety of names and the position of stratigraphic boundaries assigned by previous workers to these units. It is evident that no clear consensus has been reached regarding the stratigraphic nomenclature used in either New York or Ontario.
20 Clarke & Cushing & Cameron & Vanuxem, Emmons, Vanuxem, Hall, Kay, Schuchert, Ruedemann, Mangion, 1838, ‘40 1840 1842 1847 1929,’35,’37 1899 1910 1977 Napanee Napanee
Mohawk Base of Water- Rock. Selby Selby Ls. Trenton Black River Black town Watertown Ls. Ls. River Glenburnie Watertown Mohawk Ls. Chaum. Leray
Black River Ls. Leray House Creek Birdseye Lowville Lowville
Ls. Black River Ls. Birdseye Mohawkian Series. Ls. Lowville Birdseye Ls. Lowville Ls. Birdseye Ls. Depeauville Waterlime Pamelia Pamelia Pamelia
Figure 7 a. Classification of Black River and lower Trenton rocks in northwestern New York State and southeastern Ontario, Canada
Liberty, et al. Vanuxem, Logan, Ami, Johnston Raymond Kay, Okulitch 1950,’52,’53 1842 1863 1903 1911-’14 1914 1929,’35,’37 1938 ‘55, ‘60, ‘64 Napanee Kirkfield M. D
Rockland Rock. Base of Trenton Trenton Selby Upper Watertown Trenton Ls. Ls. Ls. Gonioceras Glenburnie Coboconk Bobcaygeon L. C 1-2 Coboconk Chaum. Zone. Leray Black Black Upper Leray River River Moore Hill U. B 3 Lowville Ls. Ls. Lowville Lowville
Black River Ls. M. B 1-2 Birdseye Gull River Birdseye Ls. Birdseye Lower Upper Ls. Ls. Lowville Pamelia Gull River L. A 1-4 Lower Pamelia Shadow Lake Rideau Basal Ser. Pamelia Shadow Lake Basal Group
Figure 7b: Classification of Black River and lower Trenton rocks in southwestern Ontario, Canada (Lake Simcoe District). The lack of detailed stratigraphic subdivision was due to the seemingly monotonous lithologic character, the lack of distinctive fossils, and the predilections of investigators whom did not recognize the importance of diastemic horizons for use in correlation. Perplexing facies changes fueled views that these rocks were deposited in a diachronous mosaic of discontinuous tidal flat to lagoonal environments (see Figure 4), and that detailed correlations of lithostratigraphic units could not be integrated into time-parallel sequences over any significant distance.
To date, very little progress has been made regarding specific high-resolution correlations across the study region. However, relatively detailed stratigraphic syntheses have been carried out in the Lake Simcoe and Mohawk Valley areas for the overlying Trenton Group, upon which the current study is built. First, recent detailed studies of graptolite and conondont biostratigraphy, regional K-bentonite correlation, and sequence stratigraphic studies in the
Trenton Falls to the Black River Valley region of New York State have resulted in a refined chronostratigraphic framework for the upper Trenton Group (Goldman et al., 1994; Mitchell et al., 1994; Brett et al., 1992; Brett and Baird, in press; Baird and Brett, in press). However, the
Black River and the lower portion of the Trenton have not, as yet, received similarly detailed analyses.
The other region that has recently received a substantial amount of study is the Lake
Simcoe area of Ontario (Armstrong et al., 1994; Melchin et al.,1994; Brookfield and Brett, 1988;
Noor, 1989; Brookfield and El Gadi, 1998; El Gadi, in prep). Again, this work has established a stratigraphic framework, yet this stratigraphic framework has not been related in detail to that of
New York State nor, for the most part, to that of southeastern Ontario.
22 Some progress has been made in the past few years in very local regions around the study area. For instance, in the Kingston area of southeastern Ontario, R. B. McFarlane (1992) was able to demonstrate the correlation of a series of six depositional packages within the lowest
Black River Group (Pamelia Formation) and several in the overlying Lowville to Watertown
Formations based both on statistical analysis of faunal assemblages and on a series of marker horizons. However, McFarlane limited his correlations to the immediate region of Kingston,
Ontario and did not extend them into New York State or into the Lake Simcoe area.
In the Lake Simcoe region recent work by Noor (1989) and Melchin et al.(1994) has provided an initial stratigraphic framework based in part on Liberty’s nomenclature for the region. This framework has been used in the mapping of the Black River and Trenton Groups in that area. However, specific stratigraphic boundaries have not been identified, and only general lithologic associations were used to assign positions of stratigraphic intervals. More recently, El
Gadi and Brookfield (2000) have attempted to provide local correlations based on microfacies associations in the region of Lake Simcoe. They have recognized four shallowing-upward
“cycles” for the Black River to lower Trenton interval (Shadow Lake-Gull River-Bobcaygeon
Formations) that, despite local facies variability, are distinctive in character. These cycles can be used for correlation in the region of Lake Simcoe, and they have been tentatively related with those of McFarlane in the Kingston area.
Some recent work was also done on the equivalent rock sections in the Ottawa embayment region located to the northeast of the study region across the Precambrian outcrop belt of the Frontenac Arch by Salad Hersi and Dix (1999). These researchers were able to confirm the presence of rhythmically bedded carbonate-dominated units in this region, and, like
McFarlane, they were able to identify a series of high-order units [shallowing-upward cycles]
23 within the succession which were easily correlated from Ottawa to Montreal a distance of some
200 km. They also made an initial attempt to compare their successions with those sections of
McFarlane (1992) in the Kingston region, as well as with a section at Roaring Brook, in the
Black River valley of New York State. They were perplexed, however, that the rhythmicity apparent in the lower Black River seems to disappear upward into the overlying units. They attributed this to the net increase in accommodation space created by tectonic downwarping of the Laurentian margin during the initiation of the Taconic Orogen. By so doing, Salad Hersi and
Dix are the first to suggest that tectonic effects of the Taconic Orogeny in this region occurred much earlier than previously accepted.
Outside of this recent stratigraphic work, most other work during the 1970-1990 interval focused on the environmental sedimentology of the Black River Group and resulted in very specific interpretations regarding the depositional environments of these units (Grimwood et al.,
1999; Noor, 1989; Textoris, 1968; Johnsen, 1971; Cameron & Mangion, 1977; Titus and
Cameron, 1976). Most previous authors agree that these carbonates were deposited in a series of shallow carbonate settings on a wide passive continental margin. Whether platform or slope margin, however, is a matter of contention.
24 CHAPTER IV
STUDY AREA & METHODS
In order to address this research topic and its main goals including delineating event and cyclic stratigraphic relationships of rocks exposed in the Middle-Upper Ordovician outcrop belt of New York State and Ontario, Canada, both literature and field research was integral. In order to understand important stratigraphic concepts pertinent to these strata, it was important to investigate and understand established details of the stratigraphy, and sedimentology as presented by previous workers. Furthermore, once a working knowledge or at least a basic familiarity with the rocks was established detailed high-resolution outcrop analyses were conducted at relatively closely spaced outcrops across the study region. Successive outcrops were compared and correlations were established using a variety of tools discussed herein, with the result that a new, well-defined stratigraphic correlation chart was produced for the entire study region.
One of the first steps in this research process involved the collection of critical literature related to the Black River and Trenton groups of Canada and New York State, particularly primary literature regarding the physical description of these rock units. Using these references, a list of localities was assembled, with special attention paid to type sections and descriptions of specific and unique horizons.
The study area encompases a relatively narrow outcrop belt (10-20 km wide) extending approximately 250 km east-to-west within which some 30-35 outcrops were examined, primarily quarries, road cuts, and stream exposures. The study includes outcrops from Brechin, Ontario
(just east of Lake Simcoe), eastward to Kingston, Ontario and thence southeastward into New
York State to the position of Watertown, New York (Figure 1). Correlations have been extended
25 further southeast to the position of Lowville, New York based primarily on the work of Walker
(1973).
The field approach involved, first, establishing a series of well-described, highly-detailed reference sections in the two end regions using available stratigraphic information from previous authors and my own field measurements. Then using the end-member localities for reference, correlations were extended to intervening localities across the region. Stratigraphic layers/beds in each reference section were measured to the nearest centimeter. All beds were described in detail, with a particular emphasis on recognition of distinctive stratigraphic marker intervals, particularly K-bentonites, unique corrosion surfaces, hardgrounds, complex shell and coral beds, unique lithologies, and stratal patterns. The thickest and most complete sections were compared using key marker beds. Key marker beds could be classified into a series of sub-categories and are reviewed in figure 8 a & b. Representative lithologies were sampled for more detailed sedimentologic analysis, and an effort was made to collect bulk samples of all known and suspected clay horizons. The use of a digital camera and laptop computer in the field proved to be a major advantage allowing comparisons between outcrop exposures in the field in order to establish similar patterns between outcrop exposures.
Measured sections were drafted for correlation and were compared to those published in the literature. In some instances, it was necessary to revisit key sections in order to clarify particular aspects of the stratigraphy.
26 Sequence Components: Unique Patterns (cycles):
Flooding Surfaces: Sequence Boundaries: Unique but characteristic repetition of beds with facies dislocation, erosive and undulatory different scales of repetition and different hardgrounds, sed. surfaces, conglomerate recurrence intervals for particular lithologies starved horizons - horizons. pyrite, phosphate and glauconite lags.
Event Horizons: Faunal Markers:
volcanic Ash (K-bentonites), coral and stromatoporoid biostrome development, storm beds, domal stromatolite build-ups, brachiopod and salinity events - evaporite mineral laths, bivalve occurrences. seismic events.
Distinctive Lithologies
Unique carbonate and siliciclastic units, e.g. white lutites, green mudstones, blue- gray shales, chert horizons, etc.
Figure 8 a: Examples of useful markers for correlation of Black River and Trenton strata in New York State and Ontario, Canada.
K-bentonite Flooding Surfaces Sequence Boundaries
Stromatolitic units
Dark Platy shales Evaporite Mineral Molds
Pyritic-Phosphatic lag horizons
Figure 8 b: Outcrop pictures of some key marker horizons used herein for correlation of Black River and lower Trenton limestones in New York State and Ontario, Canada. CHAPTER V
I. HISTORY AND GENERAL STRATIGRAPHY OF THE BLACK RIVER AND
LOWER TRENTON GROUPS IN NEW YORK AND ONTARIO.
The Black River Group, as originally defined in the upper Black River Valley near
Watertown, north central New York State, is about 60 m thick and has been subdivided on the basis of lithostratigraphy into three formations: the Pamelia (40 m), Lowville (17 m) and the
Watertown limestone or upper Chaumont (3 m) formations (Fisher, 1977) (Figure 9 a).
Additional units were subsequently named based primarily on biostratigraphic criteria and came to take on a chronostratigraphic connotation. Hence the term Chaumont, originally used for medium to thick bedded carbonates with distinct faunas typified by a wide variety of brachiopods and cephalopods present in the area of Chaumont, Jefferson County, New York, was replaced in part by the lithostratigraphic term Watertown, and was modified to the time rock term Chaumontian Stage (Kay, 1937). This term is little used at present.
Unfortunately stratigraphic boundaries between these units were not always well defined if at all, nor were they well explained in the literature. Also little effort was made to trace these units laterally from their type sections. Hence the stratigraphy of the Black River came to be viewed as a mosaic of facies, with little to no continuity of units over long distances and, therefore, only broad facies associations were applied to these units. Thus, these strata were once viewed as time transgressive facies, with component facies grading laterally to each other (see
Figure 3). This model has been tested in the present study on the basis of K-bentonite and other marker horizon correlations and found to be largely incorrect.
28 7 m Napanee Formation
3 m Selby Formation 3 m Watertown Formation
Study Interval 17 m Lowville Formation Group Trenton
40 m Pamelia Formation Black River
Figure 9 a: Schematic representation of basic lithology and average thickness of the Black River to lower Trenton Group interval as present in New York State. The study interval is focused on strata lying just below the historical Lowville-Pamelia Formation boundary through the top contact of the Napanee Formation, thus encompassing approximately 40 meters of strata. (Based largely on Cameron & Mangion, 1977) As the interval of interest for the present study is in the upper Black River Group, details of the Pamelia Formation are omitted. Previously, the Lowville was subdivided into a lower member, about 13 m of sparsely fossiliferous, fenestral dove gray micrites and minor shales and an upper House Creek member (also called the Leray Member of the lower Chaumont
Formation) comprising about 4-5 m of medium gray burrow mottled, locally cherty wackestone to packstone. The latter commonly contains abundant Tetradium, tabulate corals, stromatoporoids, and associations of gastropods and bivalves. Locally, the upper portion of the
House Creek/Leray Member contains a thin interval of dark gray shales, platy micrites and domal stromatolites, herein designated the Weaver Road Member for an outcrop in the Town of
Lyme, very near Chaumont and about 3 miles south of Depauville. An unnamed 0.5-l m bed of crinoidal carbonates separates these shales from a higher 0.5 to 1 m shale and thin nodular limestone interval with a distinctive fauna which Kay (1929) termed the Glenburnie Shale
(middle member of the Chaumont Formation). In the type area, a 2 to 3.5 m horizon of sharply- based, massive, ledge-forming packstone to grainstone interval with a distinctive coral, algae and cephalopod fauna has been termed the Watertown Limestone (Cushing et al., 1910). This unit has generally been assigned to the Black River Group, although Conkin (1991) argued that this unit should be assigned to the Trenton Group. In the Watertown, New York to Kingston,
Ontario, area the massive and often coarse grained Watertown limestone is overlain by about 0.5 to 3 m of thinner bedded argillaceous to bituminous dark gray limestone, termed the Selby
Limestone. Finally, these beds are overlain by thin bedded, platy calcisiltites and shales assigned to the Napanee Formation. Collectively, the Selby and Napanee by definition have been assigned to the Rocklandian Stage.
30 In the Lake Simcoe area of southwestern Ontario, Canada, a different set of stratigraphic terms were employed to describe the equivalent age rock successions. Okulitch (1939) pioneered one of the first classifications in Canada for this interval of rocks, with a belief that specific intervals of the succession were separated by “slight nonconformities.” Liberty (1969), modified the Black River/Trenton classification of Okulitch, and argued that the rocks in the area of Lake
Simcoe did not demonstrate significant differences between the Black River and Trenton when compared to New York. He therefore lumped all of these Middle Ordovician carbonates into the
Simcoe Group. This unit, was used for the sequence of carbonate rocks above the basal siliciclastics of the Shadow Lake Formation and ranged in age from Blackriveran to Maysvillian.
Within the Simcoe Group, Liberty expanded Okulitch’s (1939) Gull River downward to include the upper part of the Shadow Lake Formation and introduced the term Bobcaygeon Formation for rocks above the Gull River. Both units are, in general, equivalent to the upper Black River and lower Trenton Groups of the New York nomenclature. Liberty (1969) further divided the
Gull River into two informal members. He believed them to be roughly equivalent to the
Lowville Formation of New York.
In the Lake Simcoe area of Ontario, the equivalent lower Mohawkian interval is about 45 m thick and includes the Shadow Lake, Gull River and lower Bobcaygeon formations (Figure 9 b). Collectively these units compose the lower portion of the Simcoe Group and are equivalent to the Black River and lower Trenton Groups in New York and southeastern Ontario. Liberty
(1969) subdivided the Gull River Formation into a series of 3 informal members (lower (A), middle (B), and upper (B3)), and submembers (A1 to A4, and B1 to B2). The Shadow Lake and the lower (A) member of the Gull River Formation is not considered in this discussion as it is
31 Lower Kirkfield Fm. 6 m (middle Bobcaygeon Fm.)
7 m Coboconk Member (lower Bobcaygeon Fm.) Study Interval
Simcoe Group Gull River Formation 26 m
Shadow Lake 8 m Formation Basal Gp. PreCambrian Grenville Province
Figure 9 b: Schematic representation of basic lithology and average thickness of the Simcoe Group, Black River to lower Trenton Group equivalent interval as present in the Lake Simcoe area of Ontario. The study interval is focused on strata lying just above the lower-middle Gull River Formation boundary through the top contact of the middle Bobcaygeon (lower Kirkfield) Formation, thus encompassing approximately 35 meters of strata. (Based largely on Liberty, 1969) thought to be roughly equivalent to the upper Pamelia Formation of New York and not part of the study interval.
Overlying the Gull River Formation stratigraphic scheme are coarser grained skeletal limestones designated the Bobcaygeon Formation by Liberty (1969). The contact between the
Gull River and Bobcaygeon Formation, as presently defined is ambiguous and not easily recognized, at least in some localities. Liberty (1969) designated this boundary as occurring at the transition from lithographic, semi-crystalline limestone into argillaceous limestone and calcarenite. The Bobcaygeon is about 20 m thick and comprises a variety of different lithologies. Liberty (1969) subdivided the Bobcaygeon into three informal members including: the lower, or unit C (6-7 m thick), the middle, unit D (5-6 m) , and an upper, unit E (10-11 m).
Liberty’s lower member (his C member) is equivalent of the Coboconk of Okulitch (1939). The lower member was also thought to be time equivalent to the Chaumont (Leray) to Rockland
(Selby-Napanee) interval in the biostratigraphic nomenclature of the New York area.
Furthermore, the upper member of Liberty’s Bobcaygeon was believed equivalent to the
Rockland-Kirkfield interval as applied in New York and southeastern Ontario. Subsequently,
Melchin et al. (1994) divided the interval into Coboconk (lower) and Kirkfield Members, resurrecting the older terminology of Kay (1935). They further subdivided the Kirkfield into a lower, thinner bedded, shaly and Dalmanella rich submember, (essentially equivalent to
Liberty’s middle (D) member of the Bobcaygeon) and an upper crinoidal grainstone submember equivalent to Liberty’s upper (E) member, which is approximately equivalent to the Hull
Limestone of eastern Ontario. In the present study only the lower or Coboconk Member and middle member (unit D) of Liberty’s Bobcaygeon Formation will be discussed. Member C is now thought to be a composite unit and is considered here in detail.
33 The terminology and proportional subdivisions of the Ontario units initially suggested little similarity with the New York section and consequently, Liberty believed little difference existed between the Trenton and Black River lithologically, so he included them in one single group – the Simcoe Group. However, recent work indicates instead that very close similarites exist between these areas, so that the challenge has been to find key markers to establish detailed stratigraphic correlation, and additional criteria upon which to separate the Black River/Trenton interval lithologically.
34 2. STRATIGRAPHIC CORRELATION USING LITHOLOGIC BOUNDARY
SURFACES
In the present study, particular emphasis has been placed upon the recognition and tracing of sharp facies changes that may relate to key sequence stratigraphic surfaces. These facies shifts are sharp contacts of two basic types: a) sharp contacts that show evidence for subaerial erosion and b) contacts which superimpose more offshore, typically finer grained lithofacies abruptly over shallower ones. The latter are typically also facies dislocations. That is, they show superposition of shallower facies over deeper ones and may be interpreted as small scale sequence boundaries. In the following sections key surfaces of each type are discussed in some detail.
A. Facies Dislocations and Erosion Surfaces
Particular emphasis has been placed upon recognition of sharp contacts at which evidence of at least minor subaerial erosion or facies dislocations occur. Erosional evidence includes: a) sharp, planar to slightly undulatory surfaces, b) local or regional truncation of underlying units, and/or c) incorporation of clasts of older units in the beds overlying the surfaces. There are four such surfaces of particular importance in correlating units throughout the northern New York
State- southern Ontario area.
1. The Pamelia-Lowville Contact: The lowest of these surfaces in New York lies about 2 meters below the historical boundary between the Pamelia and Lowville Formations (Figure 10).
This distinctive horizon has been recognized by the sharp transition from a massive, buff weathering, dolostone, to a green, quartz rich mudstone. Often the dolostone contains a rust stained surface resulting from the weathering of pyrite present at the contact. Additionally, the
35 MX K-bentonite “Green Marker Bed” Lowville Formation
Pamelia Formation
Figure 10: Pamelia-Lowville Contact as exposed at Depauville, New York (route 12 road cut) located just north of the village of Depauville. The contact (as defined herein) between the Pamelia Formation and the overlying Lowville Formation is shown by the lower white line, and has some degree of relief along the outcrop. The “Green Marker Bed” marks the base of the Lowville Formation and is overlain by the Barriefield Hill K-bentonite of Conkin (1991) or MX K-bentonite of Liberty (1969). A second K-bentonite (the MH) occurs just at the top of this cut. overlying green mudstone often has a coarse basal quartz rich lag – which in some localities is more of a sandstone than a mudstone, and in some cases is conglomeratic especially in the vicinity of Lowville, Lewis County, New York.
In the Lake Simcoe area a comparable surface can be found within the Gull River
Formation (Figure 11). This surface lies at the contact between Liberty’s A4 and B1 submembers of the Gull River and is again most recognizable because of the superposition of a green, quartz rich marker bed above the contact. This surface has previously been identified and traced locally by Noor (1989) and is known as the “upper green marker bed” by Melchin et al.,
(1994), and El Gahdi & Brookfield (2000). Present work indicates that this is a critical, major sequence boundary throughout the study area.
2. The Basal Coboconk Contact: In Lake Simcoe a second subtle facies dislocation occurs higher in the section at the base of the Coboconk Member of the Bobcaygeon Formation
(Figure 12). This horizon was described in detail by Okulitch (1931) and appears as a sharp transition from bioturbated tetradium rich, slightly argillaceous and rubbly weathering wackestones of the Moore Hill (upper Gull River Formation) into stromatoporoid and coral bearing, crossbedded, crinoidal grainstones of the Coboconk Member.
The equivalent position in the more eastern half of the study interval, occurs in the
Chaumont Formation and more specifically within the Leray Member or upper House Creek
Member of the Lowville. This contact also places coral-bearing crinoid grainstones abruptly over shaly carbonates herein referred to as the Weaver Road member. This is a sharp, slightly wavy surface that appears locally to truncate the upper Weaver Road beds. Occasional rip up clasts of the underlying units are found within the basal coarse skeletal hash bed, especially in sections near Watertown and Lowville, New York.
37 Bobcaygeon Formation
Gull River Formation Moore Hill Member/ Upper Member
MH K-bentonite
Gull River Formation Middle Member MX K-bentonite ” “Green Marker Bed
Gull River Formation Lower Member
Figure 11: Outcrop exposed at Miller Paving Quarry near the village of Dalrymple, Ontario (Lake Simcoe District). The yellow line at the base of the “Green Marker Bed” denotes the contact between Liberty’s lower and middle Gull River Formation, and the position of two prominent K-bentonites are shown in this figure. The positions of the MX and the MH are denoted by the two white lines. Two additional K-bentonites have been located within the traditional Bobcaygeon Formation, the uppermost of which occurs very near the cap of the quarry, and has been called the MR by Liberty, (1969). Bobcaygeon Formation Upper Coboconk Member
Bobcaygeon Formation Lower Coboconk Member
Gull River Formation Moore Hill Member/
Figure 12: Road outcrop as exposed along Hwy 35 just south of the village of Coboconk, Ontario. Coarse coral-bearing grainstone of the Coboconk Member of the Bobcaygeon Formation, sits sharply over the finer -grained, bioturbated wackestones of the Moore Hill Member of the Gull River Formation. This surface cannot truly be called a facies dislocation as it actually superimposes more offshore shoal grainstone facies over peritidal stromatolitic mudstones. Nonetheless, because there is some evidence for local erosion at this contact it is considered to be a combined lowstand erosion surface and transgressive ravinement surface.
3. The Watertown-Leray (Moore Hill) contact: The most important newly recognized surface occurs at the base of the “7 foot tier,” the massive bed identified previously as the
Watertown member of the Chaumont Formation or, more commonly now, as the Watertown
Formation (Fisher, 1977). This is a sharp, nearly planar or very gently undulatory contact between the massive grainstones, and packstones of the Watertown and a variety of underlying lithologies (Figure 13 a & b). In some areas, basal beds of the Watertown typically contain rip- up clasts of lithologies comparable to the immediately subjacent beds and may locally carry clasts of other units. From the Watertown type area to Kingston, Ontario, this surfaces juxtaposes the Watertown on shaly, thin ribbon bedded fossiliferous limestones referred to by
Kay (1929) as the Glenburnie Shale Member of the Chaumont Formation (separates the
Chaumont above and the Leray below). As the Watertown is traced southward, its basal contact has been observed to overstep successively the Glenburnie, which is absent south of Watertown,
NY, the underlying grainstone, and the Weaver Road member which is missing south of
Lowville, New York. Near Newport and Middleville, New York (eastern Mohawk Valley) the
Watertown rests directly on the cyclic beds of the Leray or House Creek member of the Lowville
Formation. A recent study of the classic Inghams Mills section on East Canada Creek, a tributary to the Mohawk River, (Cornell and Brett, 2000) indicates that the same erosion surface is recorded at this more proximal section by an sharp irregularly channeled erosion surface which
40 Chaumont Formation grainstone/ Watertown Member wackestone couplet
Glenburnie Shale
Chaumont Formation Leray Member
“Weaver Road Beds” Lowville Formation House Creek Member
Figure 13 a: Outcrop exposure along County Route 54, Town of Brownville, Jefferson County, New York State. This outcrop occurs just north of the intersection with Dexter-Brownville Road, and shows the upper portion of the Lowville Formation and the lower portion of the Chaumont Formation. The Glenburnie Shale is present in this locality as a 20 cm thick interval and includes at its base the Hounsfield K-bentonite of Kay (1929). This locality is very near the type section for the Hounsfield, as described by Kay. Kings Falls Formation
Napanee Formation
MR K-bentonite Selby Formation
Chaumont Formation Watertown Member Hounsfield Glenburnie Shale Leray Member K-bentonite
“Weaver Road Beds”
Lowville Formation House Creek Member
Figure 13 B: Exposure of the upper Black River to lower Trenton Groups exposed along the Black River at Glenn Park, New York, Town of Brownville. Note the sharp base to the Watertown limestone above the Glenburnie Shale. Napanee Formation
Selby Formation
Chaumont Formation Watertown Member
Lowville Formation House Creek Member
MH K-bentonite? Lowville Formation Lower Member
Figure 14: Outcrop on West Canada Creek at Inghams Mills, Herkimer County, New York. This outcrop displays a very interesting channeled surface between the dark gray bioturbated wackestones of the House Creek Member of the Lowville Formation, and the overlying white weathering Phytopsis burrowed Watertown limestone. Just over the crest of the falls the Selby Formation is present (although thin compared to northern New York). The Napanee Formation is also present, and displays its characteristic inter-bedded shales and fine grained carbonates. has removed about half of the Leray/House Creek member (see Figure 14). In this case peritidal
Phytopsis burrowed micrites of the Watertown fill channels the channels.
Similarly, to the west of the Kingston area, the sub-Watertown erosion surface appears to truncate beds of the Glenburnie shale which are thin or absent west of Marmora on the
Peterborough Arch. Furtherwest in the Lake Simcoe region, the Glenburnie has not been formally recognized. All of this indicates that the basal contact of the Watertown is a significant regional unconformity. Because of the strong evidence for regional beveling of units below this contact it is regarded as a major sequence boundary and is discussed in more detail below.
A comparable, but subtle surface exists within the lower Bobcaygeon (Coboconk) succession of the Lake Simcoe-Peterborough area, although its presence has only been hinted at in the past. In particular, Liberty (1969, p. 41) noted the presence of a conglomerate bed in the base of the C2 submember of the Bobcaygeon Formation at Silver Lake and Bobcaygeon just west of Peterborough, Ontario. Liberty also noted that this basal conglomerate bed contains clasts of lower Gull River and C1 submember like lithologies, although he did not comment further on the significance of this horizon. However, this may be highly significant in that Gull
River micritic beds lie about 5-6 m below the C1-C2 contact at this locality. This implies that at some unknown nearby location, the erosion surface had cut out a considerable thickness of lower
Coboconk and Moore Hill beds to the level of Gull River (Lowville-equivalent) micritic beds, supporting interpretation of this level as a major erosion surface. Its presence within the
Coboconk was also anticipated by Okulitch (1939) who noted that the upper portion of his
Coboconk Member was set off from the rest by a sharp contact (Figure 15). His notes show a discrepancy in thickness of underlying beds in nearby sections by about 40 cm suggesting very local truncation. Okulitch also suggested, on the basis of the fauna, particularly algae, corals,
44 Bobcaygeon Formation Upper Coboconk Member Bobcaygeon Formation lower Coboconk Member
Gull River Formation Moore Hill Member/ Upper Member
Figure 15: Left: Outcrop exposed at Coboconk Quarry just southeast of the village of Coboconk on the east side of Hwy. 35. Top Right: Road outcrop as exposed along Hwy 35 just south of the village of Coboconk, Ontario. Bottom Right: detail of coarse coral bearing grainstone of the Coboconk Member of the Bobcaygeon Formation, which sits sharply over the finer grained, bioturbated wackestones of the Moore Hill Member of the Gull River Formation. and various cephalopods, present in this upper bed, that it might in fact represent the Watertown interval of New York.
4. The Basal Kings Falls-Napanee/ lower-upper Kirkfield Contact: The highest surface of major significance in this study, lies at the base of the Kings Falls Limestone in the
Watertown region. The sharp juxtaposition of fossil rich cross bedded crinoid grainstones over the characteristic Napanee lithology signals the contact (Figure 16). This sharp contact locally contains pebbles of the underlying Napanee Formation and the Kings Falls appears to overstep the Napanee to the southeast outside of the study region. Local remnants of Napanee interbedded shaly calcisiltites, less than 0.5 m thick, have been found at an abandoned quarry and at Muhltanner Creek southeast of Middleville, Herkimer County, New York, but the Kings Falls appears to rest directly on mudcracked micrites of the Lowville nearby at City Brook. Further east, at Inghams Mills on east Canada Creek about 4.5 m of Napanee shales and calcisiltites are present. However a pebble bed including clasts of Napanee as well as Black River (Lowville) lithologies occurs at the base of the Kings Falls. Furthermore polymict conglomeratic crinoidal grainstones in the lower half-meter of the Kings Falls contain clasts of Precambrian Grenville quartzites and gneisses. This suggests an erosion surface of considerable relief, but the details of this region remain to be worked out.
In the Simcoe area a comparable and probably correlative surface lies at the sharp base of the upper Kirkfield grainstones and rests sharply on the underlying lower Kirkfield shaly beds
(unit D of Liberty, 1969). It is not clear if there is erosion at this contact but it does represent a sharp facies dislocation. As noted below, the correlation of a joint trilobite-conodont zonal boundary across the study area (Ludvigsen, 1978; Barnes et al. 1978; Noor, 1989), occurs at this
46 Sugar River Fromation
Kings Falls Formation =Upper Kirkfield
Napanee Formation =Lower Kirkfield
Kings Falls Formation basal bed of Kings Falls
Figure 16: The outcrop at Napanee, Ontario (Hwy 1) just east of downtown, shows the contact of the Napanee Formation (Rocklandian) with the Kings Falls Formation (Kirkfieldian). The contact shows coarse grainstones of the Kings Falls Formation sharply overlying the fine-grained calcisiltites with shaly interbeds of the Napanee (top). The surface exposure (bottom) shows the basal bed of the Kings Falls as exposed at Inghams Mills in the Mohawk Valley of New York State. This horizon demonstrates a rather well developed polymictic conglomerate within a carbonate grainstone, and herein is thought to be a rather important sequence stratigraphic horizon. sharp junction and provides strong support to the synchroneity of the sharp Napanee-Kings Falls contact with the middle-upper Bobcaygeon (lower-upper Kirkfield) boundary.
Interpretation: These sharp facies dislocations and regional erosion surfaces are herein interpreted as one small and three larger scale sequence boundaries, and are significant horizons for correlation across the New York State/Ontario region (Figure 17). Furthermore, it is believed that as they are such widespread horizons they might represent eustatic sea-level adjustments and might well be found in even more widespread settings.
B. Flooding Surfaces
A number of sharp contacts in the upper Black River and lower Trenton seem to record flooding surfaces, i.e. abrupt superposition of deeper or more offshore facies on shallower ones.
Noor (1989) referred to such surfaces in the Simcoe Group as inundites. However, this is an incorrect usage of that term which is meant to imply single event storm flood deposits (Seilacher,
1991). These horizons seem to occur on a variety of scales and are considered herein as either minor or major flooding surfaces based on their similarity to surfaces described in the sequence stratigraphic literature (Doyle & Bennett, 1998).
1. Minor Flooding Surfaces: Distinct bedding planes spaced within the Black River
Group at about 0.5 to 1 meter apart are considered to be minor flooding surfaces (Figure 18).
These surfaces are usually high frequency and are particularly prominent in the Moore Hill beds in Ontario and their correlatives in the House Creek/Leray member of New York State. They are generally planar contacts marked by thin shaly or clay rich seams, some of which appear to be K- bentonites. Close inspection of these surfaces indicate that in several cases they occur at
48 250 km 200 km 150 km 100 km 50 km 5 km
West 150 miles 100 miles 50 miles 0 miles East Napanee, Ont. Glenn Park, NY. Kings Falls Formation
SB-3 Kirkfield Member Brechin, Ont. (upper Bobcaygeon Fm.)
? ? Napanee Formation
Dalrymple, Ont. Brownville, NY. Rte 54 cut. Middle Member (middle Bobcaygeon Fm) MFS-2 ? Selby Formation
Lowville, NY.
(Walker, 1973) Kingston, Ont. Coboconk, Ont. Marmora, Ont. ? Coboconk Member Watertown Formation (lower Bobcaygeon Fm.) (upper Chaumont Fm.)
SB-2 Glenburnie Shale Weaver Road Beds Leray limestone Moore Hill Member (lower Chaumont Fm.) (upper Gull River Fm.) House Creek Member Depauville, NY. ? (Lowville Formation) Cycle6 MFS-1 ? Middle Member (Gull River Fm.) 3 m ? ?
Lower Member (Lowville Fm.) Lower Member Brechin Kirkfield Marmora Kingston (Gull River Fm.) Dalrymple Coboconk Napanee
Depauville
Brownville SB-1 Lowville 80 ° 7 5° Pamelia Formation Marker Horizons Lithology argillaceous mudstone stromatoporoids major flooding surfaces crinoid rich packstone with thin carbonate Stromatocerium sp. interpreted as maximum to grainstone interbeds flooding surfaces dark greyish-blue 45° chert in lenses, nodules micritic lime mudstone shaly nodular carbonate and some layers. sharp facies transition with birdseye fenestrae often stromatolitic large domal Tabulate surfaces often with visible head corals, mostly erosional relief interpreted . coarse crinoidal Foerstephyllum as sequence boundaries laminated dark shale grainstone Ontario Tabulate upright branching coral colonies, multiple minor flooding surface species of Tetradium between the Watertown bioturbated coral-rich K-bentonite seams and the Selby Formation wackestones Domal to LLH stromatolites New York previously viewed as the Black River-Trenton calcarous green ostracod rich lime Ostracodes, mostly boundary mudstone with minor mudstone with Leperditid type. quartz sand fragmented coral clasts 80 kms Hardgrounds, green quartz grainstone dolomitic lime 50 miles often vertically bored often with conglomerate mudstone base Evaporite mineral crystal buff weathering lath molds bioclastic packstone 40° dolostone
Figure 17: Stratigraphic Cross Section From Brechin, Ontario, Canada to Lowville, New York State. Diagram shows position of the largest and most distinctive facies dislocation surfaces and regional erosion surfaces. Herein they are interpreted to represent either important sequence boundary horizons or at least minor flooding surfaces as is the case with the Watertown-Selby contact. As indicated green lines represent sequence boundaries while yellow lines indicate maximum flooding surfaces for each sequence. Figure 18: Examples of a minor flooding surface as recognized herein. Left: a series of several cyclic beds (0.5-1 m thick) within the Moore Hill as exposed at Marmora (route 7) Right: Bioturbated shaly-nodular wackestones overlie bioturbated mudstones-packstones at a knife sharp contact. Often these sharp contacts display characteristic hardground development, and or evidence of minor corrosion. corrosion surfaces or hardgrounds on underlying carbonates. Several such horizons seem to be fairly distinctive across the study region.
A. Lower-Middle Coboconk contact. The first minor flooding surface is the contact associated with the lower – middle Coboconk. This horizon marks the transition from the well developed crinoidal grainstones of the lower Coboconk into the more shaly nodular wackestone of the middle Coboconk interval (see Figure 15). This particular interval is thickest in the region of Coboconk, Ontario and thins toward the east, where the association of these two facies is generally sharp. In fact exposures of this interval near Kingston, Ontario, and in northern New
York State often show a couplet of sharply juxtaposed crossbedded crinoidal grainstones overlain by bioturbated shaly nodular wackestones (see Figure 13 A). This couplet of beds has not been distinctly recognized west of Coboconk, Ontario, and in the Kingston to northern New
York State region, the couplet of beds occurs in the uppermost Leray member of the Chaumont.
B. Basal Glenburnie Contact: A second such minor flooding surface has been recognized at the base of Kay’s Glenburnie Shale Member of the Chaumont Formation (see Figure 13 A &
B). This particular flooding surface superimposes fossiliferous shaly packstones of the
Glenburnie overtop of the crinoidal rich grainstone-wackestone couplet of the lower-middle
Coboconk described above. Although the Glenburnie is relatively thin (only ~1.5 m maximum) it signifies a substantial deepening relative to lower intervals based on the nature of its more open marine bryozoan and brachipod faunas. In New York State, the contact appears to be a well developed hardground surface, which often has black staining and deeply convoluted surfaces in which the Hounsfield K-bentonite of Kay (1929) has been preserved.
As the Glenburnie has not been recognized west of Marmora, Ontario, the equivalent interval in the Lake Simcoe region has only been drawn on the presence of the Hounsfield K-
51 bentonite which is present at the base of the Glenburnie wherever the Glenburnie is present. The sections in Brechin and Dalrymple demonstrate a discontinuous surface which is locally truncated by overlying beds – but in some areas, the Hounsfield K-bentonite is preserved, again mainly as lenses of unctuous clay in topographically low areas.
C. Watertown-Selby contact: The third and final minor flooding surface considered herein is that between the Watertown and the overlying Selby Formation (Figure 19). In the
Watertown region and to some degree toward the south (outside of the study region), this particular surface appears generally as a sharp fairly well defined contact between the massive
“upper tier” of the Watertown into the shaly nodular facies of the Selby. However, in Ontario, where the massive beds of the Watertown tend to be less distinctive the contact with the Selby is not as sharp and can be described as transitional to gradational. This contact appears to transpose deeper water (shaly nodular limestones) onto the more bioturbated packstone to grainstone associations of the Watertown, and is thought to represent a minor flooding surface, contrary to the views of other workers (Cameron & Mangion, 1977).
2. Major Flooding Surfaces: In major flooding surfaces, hardground development is accompanied by the development of sharply defined burrows/borings which, at these contacts, pipe sediment from overlying units downward into underlying carbonates (Figure 20). In most cases the sediments below these contacts appear to be distinctly different from those that overlie them. In some cases the underlying beds are burrowed calcilutites with fenestral fabrics; these may be overlain by skeletal packstones or grainstones. In other cases, shaly micritic facies may be superimposed over bioturbated packstones or grainstones. In these situations, the flooding surfaces are regionally widespread and are very distinctive both in terms of the lithologies that
52 Selby Formation
Chaumont Formation Watertown Member
Napanee Formation
Selby Formation
Chaumont Formation Watertown Member
Figure 19: Top: Exposure of the Watertown-Selby contact as exposed along Hwy 133 at Camden East, Ontario. Bottom: Exposure of the Watertown, Selby and Napanee formations along the Black River at Great Bend, New York just southeast of Watertown. The Selby- Watertown contact is occasionally gradational as at Camden or can be rather sharp as occurs along the Black River, in New York State. Figure 20: Obvious burrowed/bored hardground surface from Inghams Mills, New York. This surface is well developed and shows typical vertical oriented burrows that are filled with sediment piped down from the overlying unit. In this case this particular horizon is interpreted to demarcate a surface of major flooding and delimits the contact between the lower and upper Lowville (House Creek) members. compose them, but also in their appearance and development, and hence are excellent marker horizons useful for correlation.
A. Gull River-Moore Hill Contact; Lowville-House Creek Member “Leray” contact: One of the most readily recognized surfaces over the entire study area is that between the pale gray weathering fenestral and occasionally Tetradium bearing micrites and medium dark brownish gray coral and stromatoporoid dominated, burrow mottled wackestones (Figure 21). In Ontario, this boundary corresponds to the Gull River-Moore Hill contact of Okulitch (1939) or the B2-B3 submember contact of the Gull River Formation in the scheme of Liberty (1969).
In New York State a very similar contact (one which was not previously emphasized) exists at approximately the contact of the lower Lowville with the House Creek “Leray” member. In older literature, much confusion exists as to the relationship of the Leray to the
Lowville, but based on recent field observations it is thought that “Leray” is approximately equivalent to the House Creek.
B. Selby-Napanee/ contact: One of the most important and regionally widespread contacts is that between the Selby Formation and the overlying Napanee (Figure 22). In most cases this is a razor sharp boundary between thin to medium bedded, shaly nodular to burrow mottled, dark gray, coral- nautiloid-bearing wackestones and brownish gray shales and pale cream weathering fossiliferous calcisiltites and calcilutites.
This contact appears comparable and correlative with that between the C2 submember
(Coboconk sensu lato) and the middle (D) member of the Liberty’s Bobcaygeon Formation of the Lake Simcoe region. In this region, the shaly nodular horizon is less well developed but its presence is noted by the increased shale content overlying the grainstone interval of the
55 Gull River Formation Gull River Formation Moore Hill Member Moore Hill Member
MH K-bentonite MH K-bentonite
Gull River Formation Middle Member
Gull River Formation Middle Member
Figure 21: Left: Outcrop as exposed at Brechin Quarry, Brechin, Ontario. Right: Outcrop as exposed at Marmora, Ontario (Hwy 7). Highlighted in these photos is the contact between the Middle and Upper Gull River (Moore Hill) members. This interval shows the position of the MH k-bentonite of Liberty (1969), and demonstrate the position of a unique bed that occurs above the MH k-bentonite across the study region. Napanee Formation
Selby Formation
Figure 22: Exposure of the Selby-Napanee Formation contact as exposed at Napanee, Ontario. The contact shows a clay rich seam on top of a more massive nodular horizon where it transitions into the base of a more thin bedded and argillaceous unit. This contact where exposed and well weathered demonstrates a recessive weathering notch and the uppermost contact of the Selby often demonstrates evidence of a condensed phosphatic lag containing abundant conodont, and scolecodont apparati as well as the K- bentonite presented herein as the MR of Liberty (1969). Coboconk. Furthermore, recognition of the contact is facilitated by locating the MR K- bentonite, which is present at this contact across the study region (Figure 23).
C. Interpretation: These contacts seem to define flooding surfaces at the tops of small and large scale cycles which probably range in order from 3rd to 5th order cycles. The presence of hardgrounds with phosphatic staining and very minor concentrations of phosphatic and glauconitic grains, sand grains, and corroded skeletal material at these contacts suggests that they represent at least minor breaks in sedimentation. The abrupt superposition of deeper/more offshore facies over these contacts indicates that they are associated with pulses of deepening.
It is particularly notable in this context that all of the major K-bentonites: MX, MH,
Hounsfield and MR, occur at just these sorts of surfaces. Indeed, as noted above, the, Hounsfield and MR were found to rest on hardgrounds at several localities, and show some evidence for concentration of locally derived resistant detrital grains (magnetite (?) and quartz grains) and conodonts in the case of MR (see below).
Moreover, several other abrupt contacts are marked by very thin, recessive weathering sticky clays that may represent bentonites although they were not possible to sample (Figure 23).
It is thus highly significant that volcanic ash beds appear to be associated with diastems and probable flooding surfaces. This phenomenon has been recognized elsewhere, see Huff et al.
(1999) for review. It suggests that ash beds may become concentrated during times of reduced sedimentation. This may also imply that at least some of the K-bentonites may be composite, time-rich concentrates rather than single instantaneous inputs of ash (See Huff’s Kinnekulle paper). On the other hand, the presence of distinctive lithologies and phenocryst suites in the major K-bentonites indicates that they are still time-specific. Furthermore, one may conclude
58 250 km 200 km 150 km 100 km 50 km 5 km
West 150 miles 100 miles East Napanee, Ont. Glenn Park, NY. Kings Falls Formation
SB-3 Kirkfield Member Brechin, Ont. (upper Bobcaygeon Fm.)
? ? Napanee Formation
Dalrymple, Ont. Brownville, NY. Middle Member Rte 54 cut. (middle Bobcaygeon Fm) ? MFS-2 MR Selby Formation
Lowville, NY. Coboconk, Ont. Kingston, Ont. Marmora, Ont. ? (after Walker, 1973) ? Hounsfield Coboconk Member ? K-bentonite Watertown Formation (lower Bobcaygeon Fm.) ? (upper Chaumont Fm.)
? SB-2 Glenburnie Shale Weaver Road Beds
? ? ? Leray limestone Moore Hill Member ? ? ? (lower Chaumont Fm.) (upper Gull River Fm.) House Creek Member Depauville, NY. (Lowville Formation) MH Unnamed (recognized by Walker, 1973) MFS-1
Middle Member
(Gull River Fm.) 3 m
MX
Lower Member Barriefield Hill (Lowville Fm.) Metabentonite Lower Member Brechin Kirkfield Marmora Kingston (Gull River Fm.) Dalrymple Coboconk Napanee
Depauville ?
Brownville SB-1 Lowville 80° 75° Pamelia Formation Marker Horizons Lithology
stromatoporoids argillaceous mudstone crinoid rich packstone Stromatocerium sp. with thin carbonate to grainstone interbeds dark greyish-blue 45° chert in lenses, nodules micritic lime mudstone shaly nodular carbonate and some layers. with birdseye fenestrae often stromatolitic large domal Tabulate head corals, mostly coarse crinoidal Foerstephyllum. laminated dark shale grainstone Tabulate upright branching Ontario coral colonies, multiple K-bentonite correlations species of Tetradium established on the basis of stratigraphic position bioturbated coral-rich K-bentonite seams wackestones Domal to LLH stromatolites New York calcarous green ostracod rich lime Ostracodes, mostly mudstone with minor mudstone with Leperditid type. quartz sand fragmented coral clasts 80 kms Hardgrounds, green quartz grainstone dolomitic lime 50 miles often vertically bored often with conglomerate mudstone base Evaporite mineral crystal lath molds buff weathering bioclastic packstone 40° dolostone
Figure 23: Stratigraphic Cross Section From Brechin, Ontario, Canada to Lowville, New York State. Diagram shows position of known K-bentonites, as reported in the literature and as newly identified herein. K-bentonite nomenclature used includse the MX, MH, and MR of Liberty (1969), the Hounsfield of Kay (1931), the Barriefield Hill of Conkin (1991), and an unnamed K-bentonite recognized by Walker (1973). Stratigraphic correlation, based mainly on stratigraphic position, shows that these K-bentonites can be related through 4 main horizons (the MX and the Barrifield Hill are believed to by synonymous, as are the MH and the unnamed K-bentonite of Walker). In addition to these main K-bentonites three additional horizons have been located that appear less regularly and are not as well developed. that many of the widespread shaly partings are probable flooding surfaces which record approximately isochronous and geologically brief intervals of sediment starvation.
60 CHAPTER VII
BIOSTRATIGRAPHIC CORRELATION
Biostratigraphic correlations of the Black River and lower Trenton have been hampered historically by the absence of zonally diagnostic taxa from the shallow carbonate platform during the Turinian and early Chatfieldian. Most coral and brachiopod species are clearly facies controlled and are of relatively little time significance. However, conodonts have been obtained from some samples of these carbonates from southern Ontario (Barnes, 1964, 1967), Manitoulin
Island (Barnes et al., 1978) and the Ottawa region (Winder et al., 1975). These were used by
Barnes et al. (1978) to assign the bulk of the Black River in southwestern Ontario to conodont assemblage zone 7 of Sweet & Bergström (1976), and Sweet (1984). A boundary with zone 8 based on the appearance of Phragmodus undatus was established for the upper Coboconk
Member equivalent in Manitoulin Island (Barnes et al., 1978). Noor (1989) compiled these data and suggested that this boundary could be extended eastward of Lake Simcoe with a position generally lying within the lower Bobcaygeon Formation. Interestingly, the lower boundary of P.
Undatus zone has been extended downward with the recognition that P. undatus could be recognized below the Deicke K-bentonite and therefore is found within most of the Black River deposits (Leslie & Bergström, 1995b).
The only contribution of the present study toward biostratigraphic correlation was the recognition of abundant conondont elements in the MR K-bentonite from several localities across the study region (Figure 24). A number of species of conodonts have been recognized in this ash, including Dreapnoistodus suberectus, and possibly some partly broken Erismodus sp.
(S. Leslie, pers. com) from Napanee, Ontario, and Phragmodus undatus (M element), Plectodina aculeata, Drepanoistodus suberectus, and Panderodus gracilis from the same horizon at Miller
61 AB
C
Figure 24: Digital images above show a number of skeletal elements of conodonts and scolecodonts as collected from samples of the MR K-bentonite. A: shows samples from Miller Paving Quarry, Dalrymple and include Phragmodus undatus, Plectodina aculeata, Drepanoistodus suberectus & Panderodus gracilis. B: shows an unidentified scolecodont jaw apparatus C: a sample from Napanee, Ontario includes Drepanoistodus suberectus & some broken Erismodus sp. Paving Quarry in Dalrymple, Ontario. These fossils suggest assignment to the long-ranging
Phragmodus undatus Zone, or assemblage zone 8 of Sweet and Bergström (1976). This is in line with previous studies that placed much of the lower Bobcaygeon, Coboconk Member, within
Zone 8 (Noor, 1989).
Two distinctive megafossil assemblage zones have also been recognized in shaly intervals of the upper Black River-lower Trenton interval. The “Glenburnie fauna” of Kay
(1929) includes a varied assemblage of ostracodes (Aparchites, Eridoconcha, Primitia spp.,
Schmidtella, Tetradella), and bryozoans (Escharopora suberecta Ulrich, Hemiphragma erasum
Ulrich, and two species each of Pachydictya and Rhinidictya). The brachiopods Camarella sp.,
Rhynchotrema sp., and Strophomena sp., the corals Columnaria and Streptalasma, the trilobite
Bathyurus spiniger Hall, and the bivalve Ctenodonta are also abundant. Kay (1929) drew
attention to the similarities of this fauna with that of the lower or Spechts Ferry Member of the
Decorah Shale in the upper Mississippi Valley. Kay also believed that the Hounsfield K-
bentonite of New York was equivalent to the Millbrig ash of the upper Mississippi Valley and
supported correlations of this interval from New York to Wisconsin and Minnesota. It should be
noted that the Spechts Ferry was recently found to contain the Millbrig K-bentonite (Kolata et
al., 1994) while the Glenburnie Shale carries the Hounsfield K-bentonite (= Millbrig?)
suggesting that this faunal assemblage may indeed have time significance. This assemblage has
been traced from the type Glenburnie, near Kingston into northern New York. Some aspects of
the fauna may also be present in shaly beds equivalent to the middle Coboconk westward of
Marmora and the Peterborough Arch. However, as yet it has not been identified in the Lake
Simcoe region and correlations are made on the basis of the presence of the Hounsfield K-
bentonite. This lack of Glenburnie faunas may be due to biofacies change associated with a
63 lateral lithofacies change of the Glenburnie into the middle Coboconk Member toward the west.
Or in some areas, such as Coboconk, Ontario, just west of the Peterborough Arch (Noor, 1989), where the Coboconk is strongly dominated by crinoidal grainstones, most of the Glenburnie interval may have been cut out at the erosion surface below the upper Coboconk (Watertown).
A second faunal assemblage zone is represented in the upper Watertown–Selby and lower
Napanee beds of the Watertown, New York to Kingston, Ontario region. This assemblage, typifying Kay’s Rocklandian stage, is distinct from that of the Glenburnie and contains the brachiopods Doleroides ottawanus, Dalmanella sp., Hesperorthis tricenaria, Triplesia cuspidata, Parastrophina hemiplicata, Sowerbyella sericea and Sowerbyella curdsvillensis and others. Significantly, elements of this fauna have also been identified in submember C2 of the
Coboconk Member in the Peterborough, Ontario region, while some members of the fauna – including Hesperorthis tricenaria show up in the underlying C1-B submember. Again this fauna may have broader significance. Some elements have been identified in lower Chatfieldian
(~Rocklandian) age strata elsewhere as in the Ion Member of the Decorah (Kay, 1929) and the
Curdsville Member of the Lexington limestone of Kentucky (Cressman, 1972).
Another biostratigraphic scheme was proposed by Ludvigsen (1978) who divided the
Ordovician of Ontario into eleven trilobite faunas which D, E and F of are importance here. The boundary between his fauna E and F coincides approximately with Sweet and Bergström’s conodont zones 8 and 9 near the Rocklandian-Kirkfieldian Stage boundary. In terms of lithostratigraphy, this boundary occurs near the Napanee-Kings Falls boundary in New York and the middle-upper Bobcaygeon Formation (lower-upper Kirkfield member of Melchin et al.
1994), in southern Ontario.
64 In addition to formal biostratigraphic zonation, informal brachiopod and coral abundance zones have been recognized in the past (Liberty, 1969). These include the Onchometopus
(lower Gull River) beds, Tetradium cellulosum (generally upper Lowville member and corresponding Moore Hill beds in Ontario), Columnaria (Coboconk) beds, Gonioceras anceps,
(Selby-Napanee – middle Bobcaygeon), and the Dallmanella (middle to upper Bobcaygeon / upper Napanee) beds. But caution is to be heeded as these represent only maximum abundances rather than ranges for these particular taxa and most are present in other horizons within the interval.
65 CHAPTER VIII
CHRONOSTRATIGRAPHIC K-BENTONITE CORRELATIONS
A. History of K-bentonite stratigraphy in New York and Ontario.
The Black River and Trenton groups of New York and Ontario, Canada have been, in the past, the subject of research regarding the nature of peculiar clay seams (Kay, 1935, 1937; Cisne
& Rabe, 1978, Cisne et al. 1982; Walker, 1973; and Mitchell et al., 1994). Probably the most cited research on this topic was that of Kay (1929, 1931), who described a particular horizon that he termed the Hounsfield Metabentonite and correlated it around the eastern mid-continent of
North America. He asserted that it was equivalent to what later came to be known as the
Millbrig K-bentonite of the upper Mississippi Valley. Kay believed this metabentonite to be an altered volcanic ash, which had been deposited in a widespread blanket over much of eastern
Laurentia at this time. This provided, he believed, the opportunity to correlate widely spaced equivalent strata. Soon after this assertion was made in the literature, many other workers identified multiple similar horizons with which the Hounsfield could correlate, and subsequent debates occurred regarding the correct correlation throughout the mid-continent.
In the Lake Simcoe region, a number of horizons had been identified in the subsurface
(Forman and Lake, 1954) and in outcrop exposures that were described as persistent clay seams, because they consisted of predominantly illite clays (Liberty, 1969). Were these layers that were traced laterally for over 200 km, just persistent clay seams, or were they altered volcanic ash layers?
This debate went largely unresolved until the early 1980’s when advances in chemical fingerprinting by Huff (1983), Kolata et al. (1986), Delano et al. (1994), and Haynes (1992,
66 1994), enabled relatively accurate means of identifying and correlating individual altered bentonites. The Ontario, and New York sections have been recently reconsidered in regard to these K-bentonites (Kolata et al., 1996), and based on correlations of several well-known beds in the eastern mid-continent region by wireline logs, only general correlations were made to some of the New York and Ontario K-bentonites. Specifically, Kolata et al. (1996) indicated the presence of an ash near the top of the lower Lowville in New York just below the base of the
House Creek, which was previously recognized by Walker (1973), and that of the Hounsfield at the base of the Watertown per Kay (1931) (Figure 25). These authors associated these K- bentonites with the Deicke and Millbrig respectively. However, they were unable to explicitly detail the correlation of these K-bentonites with these well-known ashes (Huff, pers. comm..).
In the Lake Simcoe region, Kolata et al. (1996) also equated several of Liberty’s (1969)
“persistent clay seams,” to the well-known K-bentonites of the eastern mid-continent region
(Figure 26). Specifically, Liberty’s (1969) MX, MH, and MR horizons were equated by Kolata et al. (1996) to the Ocoonita, Deicke, and Millbrig, respectively. Present evidence, however, indicates that these correlations may not be entirely correct.
Since the Kolata et al. (1996) study, only limited research has been performed to ascertain the exact correlations that were proposed by these researchers. However, one significant abstract was recently published by Adhya et al. (2000), who proposed that the
Hounsfield K-bentonite is equivalent to the Millbrig K-bentonite based on the composition of apatite pheonocrysts. Some ambiguity exists, however, due to the deterioration of the type section for the Hounsfield, such that sampling this horizon is difficult. Furthermore, Conkin
(1991) indicated that Kay’s Hounsfield K-bentonite lies within the Selby and above the
Watertown, not below it. Finally, the issue concerning whether the Hounsfield is correlative
67 Booneville
K Fall North Section Nap
Trenton Group Sel Wat Hounsfield
Study unnamed K-bentonite Interval
Lowville Fm. Black River Group
Pamelia Formation
Figure 25: Schematic representation of basic lithology and position of K-bentonites as reported by Kolata et al. (1996), for the New York State Black River to lower Trenton outcrop belt. These authors claimed that these particular K-bentonites could not be confidently correlated with the Deicke and Millbrig K-bentonites. Interval Study bentonites werenotknown, andarethusconsideredherein. K-bentonite, betweenthe MHandtheMR,alongwithacoupleofotherregional K- Millbrig K-bentonitesthrough thesubsurfaceofOhio.However,position ofanother reported thattwoofthese particularK-bentonitescouldbecorrelatedwith theDeickeand reported byKolataetal.(1996),fortheLakeSimcoe region,outcropbelt.Theseauthors Figure 26:Schematicrepresentationofbasiclithology andpositionofK-bentonitesas
PreCambrian Basal Gp. Simcoe Group
Grenville Province S. Lake Gull River Bobcaygeon MX MH =Deicke MR =Millbrig = Oconita with the MR in Ontario as suggested by Kolata et al. (1996), has not been resolved. Herein the stratigraphic position of the Hounsfield is established as is that of the MR. By nature of its higher stratigraphic position, the MR is not the Hounsfield equivalent, and therefore it is probably not equivalent to the Millbrig as previously proposed.
One possible additional erratum in correlation of these K-bentonites concerns the questionable position of the Deicke K-bentonite. In New York, Kolata et al. (1996) suggested that the unnamed ash of Walker (1973) is the equivalent of the MH ash of Ontario, which based on lithostratigraphic correlations of this study is most likely accurate. They also showed the
Hounsfield and the MR to be the next higher K-bentonites and viewed the MR as equivalent to the Millbrig. However, based on comparison to outcrop exposures in the Jessamine Dome area of central Kentucky, there is another as yet unnamed ash in between the Deicke and Millbrig.
This unnamed K-bentonite appears approximately in the same stratigraphic position as the MH in the study region. Thus the inferences might be made that the MX, located below the MH, is the appropriate equivalent of the Deicke, the MH is equivalent to the unnamed K-bentonite in the
Jessamine Dome (between the Millbrig and Deicke), and the Hounsfield, which lies high in the
Black River Group may be the equivalent of the Millbrig. These inferences are supported by the sequence stratigraphic position of all three of these K-bentonites as reported by Holland and
Patzkowsky (1996, 1998), and are similarly positioned herein.
B. Black River and lower Trenton K-bentonite stratigraphy
Within the study region, most outcrops of the Black River Group were found to contain several distinctive recessive weathering, unctuous clay beds, ranging from a few millimeters to
70 almost 20 cm in thickness. Other additional clay horizons have been recognized low in the overlying Trenton Group (Figure 27).
Most of these horizons, including the MX, MH, MR, Hounsfield and Barriefield Hill beds, have been sampled, wet sieved, and subjected to powder X-Ray Diffraction analysis.
Nearly all were observed to contain component clay mineralogy with mixed illite/smectite clays.
Moreover, examination of larger grains extracted from the samples indicates the presence of distinctive volcanogenic phenocrysts in most of these horizons. These properties suggest that the four most prominent clay layers in the upper Black River Group and lower Trenton are indeed K- bentonites. Another smaller subset of local clay horizons also demonstrate some evidence of illite/smectite clay composition and possibly minor volcanogenic phenocrysts – but at this time they are not recognized consistently across the study interval.
In contrast, four major K-bentonites appear consistently in well-constrained stratigraphic intervals (see Figure 27). Furthermore, these K-bentonites appear to be fairly distinctive and recognizable across the study region with respect to their stratigraphic position. These particular horizons maintain the greatest thickness and most consistent appearance in outcrop and core.
Additionally, each of these beds is located near conspicuous lithologic boundaries, which aids in their field recognition.
Based on the work of Liberty (1969), the lower two conspicuous K-bentonites have been called the MX and the MH and are referred to herein by this classification. Furthermore, the highest laterally continuous metabentonite appears to represent Liberty’s MR clay seam and is defined by its stratigraphic position. However, a newly discovered horizon, several meters below the MR and about 4 meters above the MH, occurs near the top of strata mapped as Moore
Hill in Ontario and House Creek in northern New York State (see Figure 23). It does not appear
71 ONT NY
Napanee
MR Bobcaygeon Selby
Watertown
Hounsfield = Millbrig
Moore House Hill Creek
MH
Gull River Lowville
MX Barriefield Hill (Deicke?)
Gull River Pamelia Shadow Lake
Pre-Cambrian
Figure 27: Schematic representation of K-bentonite correlations between the Lake Simcoe area and northern New York State. Herein, we suggest that the MX is equivalent to Conkin’s (1991) Barrifield Hill K-bentonite, and the Hounsfield lies between the MH and the MR. to have been previously recognized in Ontario but, as noted below it appears to correlate with the
Hounsfield K-bentonite of southeastern Ontario and New York State, based primarily on its stratigraphic position.
At least two, K-bentonites have been recognized in the Black River Group in eastern
Ontario and the northern New York region and appear to correlate with those recognized by
Liberty (1969). Specifically, the MX K-bentonite of Liberty (1969) was termed the Barriefield
Hill Metabentonite by Conkin (1991) who was unaware of the probable correlation.
Additionally, the MH of Liberty (1969) is thought to be equivalent to the basal House Creek unnamed ash first recognized by Walker (1973) even though Walker was not aware of the correlation. The overlying Trenton Group contains a prominent clay layer that appears to correspond to the MR bed of the Simcoe area (Liberty, 1969; see below). These prominent clay beds stand out among many other such horizons identified by previous workers in the middle to upper Trenton group as exposed in the central Mohawk Valley of New York. For the purposes of correlation within this study, the four most easily recognized K-bentonites are discussed in detail.
1. The MX K-bentonite: The lowest K-bentonite horizon observed in the study interval was initially recognized in subsurface well cuttings in the vicinity of Lake Simcoe, Ontario
(Forman and Lake, 1954). This particular altered ash is located low in the Gull River Formation which is roughly equivalent to the basal Lowville Formation of the New York nomenclature.
Conkin (1991) described a similar horizon and applied the term Barriefield Hill to this particular metabentonite seam for exposures near Kingston, Ontario. In this region the Barriefield Hill metabentonite is recognizable in exposures as a sticky clay layer immediately above the distinctive greenish gray, silty dolomitic mudstone. In the Lake Simcoe region, Liberty (1969)
73 also located a distinctive horizon with a persistant clay seam at the top of the A-4 submember of his lower Gull River Formation and applied the reference name MX. In the present investigation, a distinctive greenish gray, clay rich seam and the subjacent green marker bed have been observed from four main localities: Dalrymple, Ontario (Miller Paving Quarry);
Marmora, Ontario (Bethlehem Steel Quarry); Kingston, Ontario (Division Street Quarry); and
Depauville, New York route 12 road cut spanning a distance of about 250 km.
Based on the correlation of the Pamelia-Lowville/Lower – Middle Gull River contact, and the green marker bed, the Barriefield Hill and MX horizons are believed to lie in the same stratigraphic position in the study area. Thus the MX and Barriefield Hill are thought to be one in the same horizon. Additional support for this assessment is based on sedimentologic characteristics (see below) of these horizons. Herein, the MX term takes precedence on the basis of historical priority, and it is used here in place of the Barriefield Hill K-bentonite.
Previous to this study, the MX K-bentonite was not previously identified, in New York.
However, careful observations of the stratigraphic interval revealed the presence of a similar clay layer also associated with a greenish dolomitic mudstone in the section at Depauville, New York.
In this locality the MX K-bentonite is located approximately 1.5 m above the contact of the
“green marker bed” with the massive buff dolostones of the Pamelia Formation. This horizon sits below the historical uppermost limit of the Pamelia dolomitic interval, which was drawn arbitrarily where the limestone dropped to less than 10% dolomitic limestone. Herein, it is recommended that the Pamelia-Lowville contact be drawn below the first birdseye limestones, and at the base of the green marker bed for reasons highlighted below.
The MX- K bentonite, has its maximum thickness in the Lake Simcoe region where it is generally between 2-3 cm thick and it thins considerably toward the east. In the sections near
74 Depauville, New York, (route 12 road cut) the MX K-bentonite is only between 0.5 – 1 cm thick,
except in small depressions on the surface of the underlying bed, where the thickness then can be
over 3 cm.
Samples of the MX (Barriefield) K-bentonite were collected from three localities and are
generally light to dark green in color, and interestingly, are often very similar in color to the
underlying green slightly dolomitic mudstones and siltstones upon which they sit (at all
localities).
2. The MH K-bentonite: As originally defined in the Lake Simcoe region (Liberty,
1969), the MH K-bentonite is a prominent clay layer that lies between 0.4 and 0.6 meters below
the contact of the Moore Hill tetradium beds (B3 submember of Liberty) and the underlying B2
submember of the Gull River Formation. Thus, the MH K-bentonite is located very near the top
of Liberty’s “middle member” of the Gull River Formation and some 3-4 m above the MX K-
bentonite. In the quarries at Brechin and Dalrymple, Ontario, the MH measures 0.15 m and 0.10 m respectively and are very easily collected in the unweathered quarry sections.
Based on its stratigraphic position, the MH horizon appears to be coextensive with a K- bentonite that was described by Walker (1973) near the boundary of the lower Lowville – upper
Lowville House Creek Tetradium beds, in the southern Black River Valley. In this region, the
MH- K-bentonite also lies about 0.3 – 0.4 m below the sharp contact between the birdseye
micrites of the lower Lowville and the bioturbated wackestones of the overlying House Creek or
“Leray” member. In this region, it is approximately 10 m above the MX horizon (Figure 23).
The MH bed appears in a recessive notch at the top of the Route 11 road cut at
Depauville, New York where the characteristic birsdeye limestone of the Lowville changes
abruptly into the bioturbated wackestones of the House Creek/Moore Hill interval. At the
75 Barrett Paving quarry off route 37 just northeast of Watertown, New York a similar notch- forming clay is present near the base of the locally cherty Leray limestone, but it has been considerably weathered and inaccessible from the quarry floor. In the section at Glenn Park on the Black River (just west of Watertown), the basal House Creek/Leray interval is generally submerged below the river level and thus the bentonite is not observable. However, exposures further downstream show the basal House Creek/Leray member exposed above water level adjacent to the paper plants in Brownville, New York. Water issues from the gorge wall along the contact where the MH has presumably been eroded away (Figure 28).
Thus, the MH K-bentonite is a very conspicuous K-bentonite and can be traced, mainly on its stratigraphic position, across the study region from Lake Simcoe area to Watertown, New
York and further south into the region of Lowville as supported by Walker (1973) (see Figure
23). Multiple samples of this K-bentonite were collected for this study at localities including:
Brechin Quarry, Brechin Ontario; Miller Paving Quarry, Dalrymple, Ontario; Provincial Route
35 road cut just south of Coboconk, Ontario; Provincial Highway 7 road cut west of Marmora,
Ontario; Bethlehem Steel Mine, Marmora Ontario; Provincial Route 2 road cut just east of
Napanee, Ontario (below the highway department); QEW Highway 401 road cut at Montreal
Street exit, Kingston, Ontario; State Route 12 road cut at Depauville, New York; Barret Paving
Quarry, State Route 37, Leray, New York; Mill Creek section; Lowville, New York. Out of all of the sampled horizons this K-bentonite is again most well developed in the Lake Simcoe region where it attains a maximum thickness of 15 cm. At Depauville and Watertown the thickness of the MH is much less, approximately 3 cm.
The MH clay ranges in color from a greenish blue hue at Uhthoff and Brechin to a more characteristic rusty-yellow color near Dalrymple and eastward. In sections in northern New
76
Watertown Formation Watertown Notches (arrows) below the side tributary falls. the MH and Hounsfield K-bentonites. Although they are not easily sampled, their presence is indicated by water flow out of Road bridge and top right is facing east (toward Watertown) from the same bridge. In this section it possible to see po Brownville, New York, where top left image is facing west Figure 28: Photographs of the northern side Black River gorge at Lowville House Creek
Watertown Formation MH K-bentonite MH
Hounsfield K-bentonite Glenburnie Shale Glenburnie sition of both recessed from Mill York State, the MH maintains the same characteristic yellow color, although in more weathered samples the color becomes more greenish gray. In the Barrett Paving Quarry in Watertown, the
MH is also generally inaccessible, but samples have been collected from fallen blocks and generally these samples are whitish in color.
3. The Hounsfield K-bentonite: The Hounsfield K-bentonite was originally defined as a thin clay layer occurring at the contact of the Watertown Limestone with the underlying Leray
(Chaumont Formation) at a small quarry about 1 mile east of Dexter, NY and ~4 miles south of
Depauville, New York (see Figure 1). Although some of Kay’s correlations outside of the region may have been incorrect (Kolata et al. 1996), the position of this bentonite was explicit in his sections. He placed the Hounsfield K-bentonite in his Glenburnie Shale Member below the
Watertown Limestone (Kay, 1931). Some confusion about the placement of this bed resulted from the work of Conkin (1991) who considered Kay’s placement of the Hounsfield to be in the
Selby and not at the base of the Watertown. This was, in part, because there are two shaly zones within the upper Black River to lower Trenton interval (see Figure 13 B). Moreover, another K- bentonite occurs in the base of similar appearing shaly limestones of the Napanee Formation, above the Watertown. This is especially confusing where the massive “upper tier” of the
Watertown becomes less distinctive and can be thinner bedded in well weathered outcrop exposures.
Similar to the underlying ashes, the Hounsfield has a wide-ranging color spectrum. In the
Lake Simcoe region, the ash is generally blue gray and it grades eastward into a yellow gray color by Kingston, Ontario. In northern New York the Hounsfield is usually yellowish orange especially in the thickest pockets.
78 In its type area, the Hounsfield is a thin (0.5-1 cm), unctuous clay bed that lies above bioturbated crinoidal packstones and wackestones. This interval is typically assigned to the upper Lowville or Leray limestone, but herein is correlated with the lower Coboconk interval in
Ontario (Figure 29). It is the basal bed of a 2-3’ (<1 m) interval of shales and shaly limestones correlated by Kay (1931) with the Glenburnie Member which he had defined in Ontario. This position is about 3-4 m above the MH marker and the base of the House Creek interval. In recent fieldwork the author has recognized a clay rich seam in the type Glenburnie section (north of Kingston, Ontario) where it occurs at the base of a fossiliferous shale and above a distinctive couplet of coarser grained beds. The position of the ash bed and the Glenburnie Shale itself was previously confused with the somewhat lower stromatolitic shale and platy limestones of the
Weaver Road beds of this report (see Figure 13 B). But the latter interval appears to be distinctly set off from the Glenburnie and lacking distinctive bentonites.
In the present study, the Hounsfield K-bentonite has been traced westward from Dexter based on its stratigraphic position, and has been tentatively located in sections as far as the Lake
Simcoe region. Its position is believed to be equivalent to a clay rich horizon within the
Coboconk member of the Bobcaygeon Formation which is found from Marmora west to Brechin,
Ontario. As with the type Hounsfield, this clay bed occurs about 3 to 4 m above the MH marker and slightly below a sharp erosion surface, herein identified as the base of the Watertown limestone. Here the equivalent Hounsfield bed occurs within the middle, slightly shaly and rubbly weathering portion of the Coboconk Member at Marmora, and Coboconk. This horizon is slightly more fossiliferous than underlying bioturbated limestones and thus seems to correspond to the base of the Glenburnie Shale of the northern New York to Kingston area. Although the
Hounsfield was previously suspected of being coextensive with the MR K-bentonite of the Lake
79 Brechin, Ont. Coboconk, Ont. Napanee, Ont. Dalrymple, Ont. Marmora, Ont. Kingston, Ont.
? ? shale
mudstone packstone
grainstone
/
wackestone ? 3 m ? 100 km 50 km 5 km
50 miles 0 miles Brownville, NY. key marker horizons located around the Hounsfield Kingston, Ont. Glenn Park, NY. K-bentonite Lowville, NY. (after Walker, 1973) Watertown Limestone Glenburnie Shale
? Wackestone Marker- Hounsfield ? upper part of couplet K-bentonite Grainstone Marker- lower part of couplet 3 m Weaver Road Beds ? Upper Moore Hill Beds (cyclic interval)
Figure 29: Detailed correlation of marker horizons around the Hounsfield K-bentonite (used here as the datum). Notice that the Weaver Road through Glenburnie interval has a variable thickness across the region and the Glenburnie is sharply overlain by the more massive Watertown limestone. The contact shows evidence for sub-aerial erosion and is classified herein as the Black River-Trenton SB. Simcoe area, (Kolata et al., 1996), the present survey and work by Liberty (1969) shows the stratigraphic position of the MR to be a separate bed some 5 m above the position of this particular clay seam. Thus, the position of the Hounsfield, when traced across the study interval appears to show a consistent stratigraphic position near the top of the Black River Group in the base of the Glenburnie Shale interval, and corresponds to a stratigraphic interval, where, in the
Lake Simcoe region no other K-bentonite has previously been identified.
In the region to the south of the study interval, considerable amounts of upper Black
River strata are removed successively southward, such that by the position of Lowville, New
York the Glenburnie, the lower Coboconk, and Weaver Road Members are lost, and the
Watertown rests on the House Creek/Leray beds (see Figure 17). As a result, the Hounsfield K- bentonite is not present from Lowville to the Mohawk Valley region, and presumably was removed by erosion at the base of the Watertown (see Figure 14). The Hounsfield was previously reported in the Middleville, New York, area, some 75 km to the southeast in the
Mohawk Valley (Kay, 1931). However, the section at Middleville juxtaposes a substantially thinned interval of the distinctive Selby and Napanee lithologies on the Watertown limestone, which in turn, sits on evenly bedded bioturbated wackestones of the lower House Creek interval.
Thus, the clay rich seam that Kay (1931) interpreted as the Hounsfield is located on top of the
Selby limestone, at the base of the Napanee Formation, and therefore the stratigraphic position of this 2-3 cm thick clay bed is probably equivalent to the MR K-bentonite, but this is not yet confirmed (author pers. observation).
The Hounsfield K-bentonite is perhaps the most distinctive K-bentonite in the entire
Black River to lower Trenton. This K-bentonite has a very diverse and complex mineralogy, with the well preserved forms. Presumably the fact that this horizon was deposited during a
81 rather rapid, yet minor flooding event (into the Glenburnie Shale) helped to preserve the pristine glass. In outcrops across the region the thickness of this bed varies quite dramatically, (from 1 to
10 cm) especially in those regions where the thickest portions of the K-bentonite lie on a convoluted surface interpreted to be a hardground. In the County Route 54 cut in the Town of
Brownville very near the type section of the Hounsfield, recent road widening exposed the bedding plane upon which the ash rests. In this outcrop it was possible to collect a large sample from a small lens over 8 cm deep. Throughout the rest of the study area, the thickness of this interval is usually less than 1-2 cm and inconspicuous, although it is sometimes easily recognized in quarries such as that at Dalrymple, Ontario where iron stained rocks below alert its presence.
The Hounsfield K-bentonite was recently proposed to be equivalent to the Millbrig K- bentonite of the southern Appalachians and mid-continent area on the basis of apatite phenocryst geochemistry (Adhya et al., 2000). The very nature of this work presents the opportunity for some very interesting correlations outside of the study region, and will be discussed in a later section.
4. The MR K-bentonite: The MR K-bentonite, as described by Liberty (1969), is located just above the top of the C-2 submember of the Bobcaygeon Formation in the base of the overlying D submember. Based on present lithostratigrapic correlations herein, this position is thought to be stratigraphically equivalent to the Selby – Napanee Formation contact recognized farther east.
The MR K-bentonite, in most weathered outcrops is inconspicuous in its appearance and has not generally been identified in surface exposures in the past. Fortunately, this horizon was
82 identified by workers (Forman and Lake, 1954) in well cuttings in the subsurface near the base of the sublithographic interval of the middle Bobcaygeon.
The MR horizon has been recognized in the Miller Paving quarry at Dalrymple, Ontario where the ash rests on a distinctive bored hardground surface. The bentonite here seems to have directly blanketed articulated echinoderms on the hardground. The bentonite and immediately overlying shales are extensively burrowed and the burrow fillings have been preferentially cemented forming three dimensional tubes that weather out on the surface of the outcrop.
Although this particular preservational style is unique, the MR appears to be developed on a hardground at several localities including several in eastern portions of the study region.
When traced eastward across the outcrop interval from the Lake Simcoe region, the position of the MR appears to correlate with a clay bed exposed near Napanee, Ontario, Highway
1 road cut, at the base of the Napanee, in a position about 3-4 m above the Hounsfield horizon.
Recent Department of Highway “calving” work presented excellent new faces in the road cut of Highway 2 just east of Napanee, Ontario. In this newly faced cut, the light brown to yellow clay of the MR K-bentonite can be observed in recessed lenses along the cut. It reaches a maximum thickness of around 1 cm, but is more commonly less than 0.5 cm. This particular horizon has not been located at Kingston (due to the lack of exposures in this stratigraphic interval). It does, however, appear to be the equivalent of a recessed notch about 2 m above the top of the upper tier in the Black River Gorge section at Glenn Park.
Additionally, when this distinctive stratigraphic interval is traced toward the southeast into New York State a similar horizon is found through to the Mohawk Valley. The position of the K-bentonite at Middleville (referenced in Kay, 1931) is correlative with this horizon.
Fortunately, only a thin (less than 2’) interval of Napanee Formation, with its characteristic
83 brachiopod fauna, remains above this position before the sharp transition into the overlying
Kings Falls Formation.
Again, as described previously, this contact is shown to superimpose well developed deep shelf shales and interbedded carbonates on top of more shallow shelf carbonate of the Selby
Formation. This contact is thought to behave as a sediment starved surface with very little sedimentation occurring, except the deposition of the volcanic ash. The result is a condensed interval, which is accentuated by the presence of a high number of conodonts in the sample.
5. Other K-bentonites: Although these four main K-bentonites have been the focus of this investigation – several other less distinctive clay seams occur within the stratigraphic complex studied herein and although they are not continuously exposed there presence is at least deserving of a note (see Figure 23).
The first of these minor horizons occurs near the middle of the middle Gull River (B3 submember), i.e. within the Moore Hill/House Creek interval as previously described. This particular clay seam has been observed in four localities including the Coboconk Rte. 37 road cut, Marmora (Rte 7) road cut, Kingston (Hwy 401) road cut and at Brownville (County Rte. 54) road cut. This horizon is consistently 1.5 – 2 m above the MH and usually about 2 – 2.5 m below the Hounsfield.
The second such horizon occurs in the basal Watertown and is usually a clay-shale parting ~30 cm above the base of the Watertown. In Kingston and Marmora a minor 1 cm thick clay seam has been collected. It shows minor characteristics of a K-bentonite, but analysis has not been completed on these samples.
84 CHAPTER IX
OTHER STRATIGRAPHIC MARKERS AND CORRELATION TOOLS
In the discussion thus far, I have mostly detailed common event style marker horizons including: stratigraphic boundaries such as facies dislocations and flooding surfaces and associated features, and K-bentonites. However, a few other marker horizons have also proven useful for correlation at least locally and include: faunal epibole style markers (like stromatolite buildups, bivalve occurrences, and coral and stromatoporoid development), as well as lithologically distinct intervals and patterns of lithologic succession (cycles).
A. Epibole Markers
While the Black River and lower Trenton group are not renowned for such horizons, they do occurr and can be used at least on local scale for correlation. The most distinctive of these markers is a widespread domal stromatolite horizon (usually between 1-2 m) at the top of the
House Creek Member of the Lowville Formation, herein assigned to the Weaver Road beds (see
Figure 29). This particular horizon forms a distinctive marker tool for correlation of the uppermost terminus of the House Creek Member from Napanee, Ontario eastward into northern
New York State (~ 100 km).
Such stromatolite occurrences have been used in the Paleozoic record to illustrate the concepts of a biological event or epibole, and have been useful in correlation over wide areas
(Grotzinger, 1986, Liddell (1997). In addition to its unique and well constrained stratigraphic interval (the uppermost high frequency cycle of the House Creek) this horizon, with its associated lithofacies including capping shaly mudcracked associations, suggests a regressive phase for the upper House Creek, a pattern that is also useful for correlation.
85 A second epibole style marker that may be significant – consists of widespread stromatoporoid and tabulate coral horizons – which in a few cases could be considered biostromal. This kind of a marker occurs twice in the study interval. The first occurrence – and less biostromal of the two, shows up in the base of the second cycle of the Moore Hill/House
Creek interval, about 3-4’ above the MH K-bentonite. Large 30-40 cm Foerstephyllum
(Favositid) corals can be found in most localities where this horizon is exposed. In particular – they are usually found in the Brechin and Miller Paving Quarries in Lake Simcoe, and can be found in similar positions at Napanee, Kingston, and Glenn Park sections. More recently, they have also been seen in the same position in the section at Inghams Mills in the Mohawk Valley, over 150 km to the southeast.
The second and more distinctive biostrome, occurs within the upper Coboconk Member of the Bobcaygeon in the vicinity of the Peterborough arch from Coboconk to Marmora and again in the vicinity of Glenn Park to Lowville near the base of the probable equivalent
Watertown Formation. In particular this interval yields abundant Stromatocerium coenostea interspersed with both tabulate and ruguse coral assemblages. The dominance of stromatoporoids is unique to this interval. Interestingly, they are commonly associated with silicified brachiopods, and nodular chert horizons. Where the Stromatoporoid horizons are absent (as in the Kingston region) the Watertown equivalent lacks chert.
A third epibole – that is of more local importance for correlation is an interval rich in the bivalve Ctenodonta. The main horizon for highly concentrated bivalve associations occurrs within the Moore Hill/House Creek interval of southeastern Ontario (Marmora to Kingston). In this region, the Moore Hill cycles appear much shalier than in either the Lake Simcoe area or northern New York. Within this region, Ctenodonta bivalve associations (with minor gatropod
86 development) usually are preserved as recrystallized shells, and casts. They occur in great numbers in the bioturbated wackestone caps of the highly cyclic Moore Hill/House Creek interval, and appear to contribute to the bioturbation and homogenization of these beds.
B. Distinctive Lithologic Intervals
This category of marker horizon has played only a limited role in this study compared to other distinctive tie lines, however several significant intervals include the upper green marker bed, of the Lake Simcoe region, evaporite crystal lath horizons, Tetradium/Ostracode wackestones, and rubbly weathering, shaly mudcracked horizons.
The “upper green marker bed” has been used in conjunction with the MX K-bentonite as described above, to provide the basal anchor for correlations in this study. This unique quartz rich green mudstone horizon is distinctive and can be recognized across the study region. In the immediate vicinity of Kingston, and Napanee, as well as in the Lake Simcoe region – similar horizons occur lower down in the Black River strata within the Pamelia or Shadow Lake
Formations, and are thus not considered herein.
Occasionally, in the lower Lowville – lower Gull River B1 submember, a certain dolomitic mudstone demonstrates a so called “chicken wire” texture. This unique pattern is the product of evaporite mineral crystal impressions within the fine matrix of the rock. In the study region, the mineral crystal impressions only occur within a narrow interval within the basal portion of the Lowville. As of now, they are only known in outcrop at Marmora, Ontario,
Kingston, Ontario, and Depauville, New York. They have not been found in equivalent sections in other areas, and presumably imply a minor restriction with hypersaline brine development in this region during the deposition of the lower Lowville.
87 The Tetradium/Ostracode wackestone bed is a unique horizon (Figure 30). This unique bed commonly has a thickness of nearly 60 cm at several locations in the region around Uhtoff and Brechin, Ontario. It marks, essentially the transition from the Lower Gull River (B1 and B2 submembers) into the middle Gull River (B3 or Moore Hill Member), and separates the MH K- bentonite from the Moore Hill interval wherever the MH is exposed (see Figure 21). This wackestone bed contains abundant Tetradium and Ostracode fragments. The bed generally thins toward northern New York State, and may be differentiated into several thinner beds – mutually seperated by thin shales.
The final marker horizon in this category is a rubbly weathering shaly limestone unit at the top of the Moore Hill/House Creek succession (Figure 31). This interval has been referred to herein as the Weaver Road beds, and is distinctive as mention above for its domal stromatolite horizon – but additionally, the unique occassionally platy gray shales and calcisiltites have been found to contain a preponderance of desiccation cracks. This particular interval is useful for correlation and although the papery shale component is lost west of the Peterborough Arch, the desiccation cracked calcisiltites remain and help to tie sections in southeastern and southwestern
Ontario together lithologically.
C. Distincive Lithologic Patterns
This particular correlation tool refers to the use of predictable successions of unique patterns to associate rock units from different locations. The Black River Group, like most
Cambro-Ordovician passive margin carbonate successions, demonstrate cyclically stacked parasequences on a number of different scales.
88 Brechin, Ont. Coboconk, Ont. Napanee, Ont. Dalrymple, Ont. Marmora, Ont. Kingston, Ont.
? shale
packstone ? mudstone
grainstone
/
3 m
wackestone
Lowville, NY. Brownville, NY. key marker horizons located (after Walker, 1973) around the MH K-bentonite Kingston, Ont. Depauville, NY. Glenn Park, NY. Moore Hill Beds (bioturbated wackestones) ? “60 cm bed” -ostracode wackestone. 3 m MH K-bentonite
Upper Lowvile (birdseye micrites)
Figure 30: Detailed correlation of marker horizons around the MH K-bentonite (used here as the datum). Notice that the upper Lowville (birdseye micrite) transitions rather abruptly into the Moore Hill above the buff colored bed called informally the “60 cm bed,” as it is typically about 60 cm thick in the outcrop region. Note also that the contact shows evidence for sharp transition to a more off-shore (and deeper water facies). This surface has been interpreted herein to be a maximum flooding surface. Figure 31: Top: Shows a the Weaver Road Beds from their reference locality in the Town of Lyme. Bottom: the same horizon located in the Chaumont Quarry (County rte. 179) where the shaly interbeds are reduced and the mass of the stromatolite becomes more domal and amalgamated. The Lowville to House Creek succession is the most distinct and most predictable for the development of such successions. In successions where the entire Lowville is exposed (from the
MX K-bentonite up to the MH, usually 6 (2 – 2.5 m) cycles can be discerned (Figure 32). The equivalent lower Gull River succession has not been fully evaluated in the Lake Simcoe area – but the succession at Marmora demonstrates several of these parasequences and presumably all 6 may be present, in this location. The Moore Hill/House Creek interval also contains several parasequence-scale cycles which are usually between 0.5 to 1.0 m maximum thickness. These particular horizons, in the Lake Simcoe region, are highly distinctive and most sections easily show between 8 and 10 of these cycles (Figure 33 a). The corresponding interval in more eastern areas also show a characteristic 9-10 cycles for the Moore Hill/House Creek interval. The succession, referred to herein as the Weaver Road beds, also shows an additional 2 to three cycles. Thus leading up to the Hounsfield K-bentonite, the number of parasequences ranges from 17-19 for the middle to upper Black River Group.
Such small scale cycles are less obvious in outcrops for strata above the Hounsfield K- bentonite. However, if the Napanee interval is considered the alternation of shales, calcisiltites and fossiliferous packstone to grainstone beds appear to demonstrate a similar pattern of rhythmicity. In this case at least 7-8 cycles appear in the Napanee and by extrapolation downward, an additional 7-8 occur in the Selby to Watertown interval. Thus for the entire study interval, the number of cycles (observed or extrapolated) appear to be on the order of between 17 and 19 for the upper Black River Group, and 15 to 16 for the lower Trenton interval (Figure 33 b).
91 Cycle 6 MH K-bentonite Lowville Formation Cycle 5
Cycle 4
Cycle 3
Cycle 2 Cycle 1 Pamelia Formation
Figure 32: Outcrop of lower Lowville showing the reduction in capping dolostone (overall deepening) with each successive cycle. In total there are approximately, 6 cycles present in this part of the Lowville. 1. 2. 3. 4. 13 7 12
11 13 11 12 6 10 10 11 10 5 9 9 8 9 4 7 8 8 6 7 7 3 5 6 6 5 4 4 5 2 3 4 3 3 1 2 2 2 1 1 1 ?
Figure 33 a: Images show four outcrop exposures for the MH K-bentonite (white line) and the overlying beds of the Moore Hill /House Creek interval. The localities show are from left to right: 1. Brechin Quarry, Brechin, Ontario, 2. Miller Paving Quarry, Dalrymple, Ontario, 3. Division Street Quarry, Kingston, Ontario, and 4. Black River Gorge south gorge wall at Glenn Park, New York. These outcrop images are used here to demonstrate the continuity of small scale cycles within the Moore Hill/House Creek interval. The vertical scale for these cycles is generally between 0.5 to 1.0 m. Cycle numbering shows the relative number of cycles in each section. 250 km 200 km 150 km 100 km 50 km 5 km
West 150 miles 100 miles 50 miles 0 miles East Napanee, Ont. Glenn Park, NY. Kings Falls Formation
Cycle8 SB-3 Cycle7 Kirkfield Member Brechin, Ont. (upper Bobcaygeon Fm.) Cycle 6 Cycle 5 ? Cycle 4 ? Napanee Formation Cycle 3 Dalrymple, Ont. Cycle 2 Brownville, NY. Cycle 1 Rte 54 cut. Middle Member Cycle8 MFS-2 (middle Bobcaygeon Fm) ? Cycle7 Cycle 6 Selby Formation Cycle 5 Cycle 4 Lowville, NY. Cycle 3 (Walker, 1973) Kingston, Ont. Coboconk, Ont. Cycle 2 Marmora, Ont. ? Cycle 1 ? Coboconk Member Watertown Formation ? ? (lower Bobcaygeon Fm.) (upper Chaumont Fm.) Cycle 3 Cycle 2 SB-2 Cycle 1 ? Glenburnie Shale Cycle10 ? Cycle9 ? Weaver Road Beds Cycle8 ? Cycle7 Leray limestone Moore Hill Member ? ? Cycle 6 ? ? ? (lower Chaumont Fm.) (upper Gull River Fm.) ? Cycle 5 Cycle 4 ? House Creek Member Cycle 3 Depauville, NY. (Lowville Formation) Cycle 2 ? ? Cycle 1 ? Cycle 6 MFS-1 ? Cycle 5 Middle Member ? (Gull River Fm.) 3 m ? ? Cycle 4 ?
Cycle 3b ? Lower Member (Lowville Fm.) Cycle 3a ? Lower Member Brechin Kirkfield Marmora Kingston Dalrymple Napanee (Gull River Fm.) Coboconk ?
Depauville Cycle 2 ?
Brownville Cycle 1 SB-1 Lowville 80 ° 7 5° Pamelia Formation Marker Horizons Lithology argillaceous mudstone stromatoporoids major flooding surfaces crinoid rich packstone with thin carbonate Stromatocerium sp. interpreted as maximum to grainstone interbeds flooding surfaces dark greyish-blue 45° chert in lenses, nodules micritic lime mudstone shaly nodular carbonate and some layers. sharp facies transition with birdseye fenestrae often stromatolitic large domal Tabulate surfaces often with visible head corals, mostly erosional relief interpreted . coarse crinoidal Foerstephyllum as sequence boundaries laminated dark shale grainstone Ontario Tabulate upright branching coral colonies, multiple K-bentonite correlations species of Tetradium established on the basis bioturbated coral-rich of stratigraphic position K-bentonite seams wackestones Domal to LLH stromatolites New York minor flooding surface calcarous green ostracod rich lime Ostracodes, mostly between the Watertown mudstone with minor mudstone with Leperditid type. and the Selby Formation quartz sand fragmented coral clasts previously viewed as the 80 kms Hardgrounds, Black River-Trenton green quartz grainstone dolomitic lime boundary 50 miles often vertically bored often with conglomerate mudstone base minor flooding surfaces Evaporite mineral crystal correlations are intended buff weathering lath molds to show similarity of pattern bioclastic packstone 40° dolostone across the outcrop belt
Figure 33 b: Key marker horizons are shown and dashed lines indicate the approximate correlations of small scale cycles (PAC’s?) between outcrop sections. Each cycle is not recognized as a specific cycle but pattern and similarity in sequencing suggests lateral continuity of these horizons. Note that the 6 cycles in the lower Lowville have on the order, 2 times the thickness of the cycles in the Moore Hill/House Creek interval. Assuming all small scale cycles, of which there are 19-20 between the MX and Hounsfield K-bentonite, are of the same temporal scale a simple calculation results in a time averaged cycle duration of approximately 100,000 years per cycle (1.6-2 my between the K-bentonites). CHAPTER X
REVISED STRATIGRAPHY OF THE UPPER BLACK RIVER GROUP TO LOWER
TRENTON INTERVAL
The following sections synthesize results of the author’s new field study (Figure 34) with previous work to provide an integrated view of lithostratigraphy of the upper Black River and lower Trenton groups in the type area and in southern Ontario. These results also point to the need for a complete revision of Black River and Trenton stratigraphy and terminology.
However, this project will be the subject of future studies.
A. Black River-Trenton Group Lithostratigraphic Boundary
As noted above, there has been ongoing controversy as to where to place the Black River-
Trenton boundary and, in fact Liberty (1969) argued that no natural break exists between these units; he therefore combined both intervals into an all-encompassing Simcoe Group. At this stage it may be useful to inquire as to whether or not a lithostratigraphic boundary distinction between the units is justified or useful. Both names are so deeply entrenched in the literature of
North American Ordovician stratigraphy that little useful purpose would be served by lumping these into a single unit. Both groups, as presently recognized in New York, are dominated by carbonates and in both cases lithologies are relatively diverse. However, on the whole, the rocks assigned to the Black River Group are more dominated by pinkish gray, to pale gray weathering, relatively pure sparsely to moderately fossiliferous, micritic limestones and minor dolostones, with fenestral fabrics (“birdseye structures”) common. Fossils tend to be dominated by
95 Napanee, Ont. Glenn Park, NY.
Brechin, Ont. SB Brownville, NY. Dalrymple, Ont. Rte 54 cut. MFS-2 Lowville, NY. Kingston, Ont. Coboconk, Ont. Marmora, Ont. (after Walker, 1973) SB
Depauville, NY. MFS-1 TST-1 HST-1 TST-2 HST-2 Black River Gp.Gp. Trenton SB 3 m ?
250 km200 km 150 km 100 km 50 km 5 km
150 miles 100 miles 50 miles 0 miles
Figure 34: Sequence stratigraphic framework for sequences 1 and 2. Datum used is the position of the MH K-bentonite (yellow line) which is located just below MFS-1. Notice that in both sequences the TST’s appear to level out at the MFS which are fairly flat across the outcrop region, where as the HST appear to terminate at the uneven sequence boundary surfaces. This sequence framework is based on the presence of 3 newly recognized sequence boundaries which show considerable erosional relief across the New York/Ontario outcrop belt. The middle sequence boundary, at the base of the Watertown limestone, is proposed herein as the appropriate contact to which the Black River-Trenton Group boundary should be applied. Tetradium corals, ostracods, and mollusks. Conversely, Trenton Group rocks contain far more abundant skeletal carbonates, packstones and grainstones. Moreover, as a whole, the Trenton limestones are thinner bedded, more argillaceous and tend to weather medium gray to brownish gray. As a whole they represent more offshore, open shelf facies. Hence, there are both lithological and faunal differences and the appearance of the two units is sufficiently distinctive that most outcrops can be readily assigned to one or the other of these units.
Moreover, there is currently a tendency to define groups as clusters of genetically related formations set off from one another by important discontinuities. In short, many groups approximate depositional sequences or supersequences.
The problem then is to define an objective and meaningful lithostratigraphic boundary, ideally at a sharply defined and readily recognized contact. In the past the boundary between the
Black River and Trenton Groups was drawn lithologically and applied generally. In this regard, the Trenton was characterized by “Blue Foetid limestones” and the Black River by the “birdseye limestone”. After these initial distinctions were made by Vanuxem (1838, 1840, 1842), other workers recognized the need to draw boundaries more specifically and many resorted to a combination of lithostratigraphy and biostratigraphy (Kay, 1935). Thereafter, the boundary was assigned at the top of the Chaumont Formation although it was recognized that portions of the
Leray Member were Black River-like and the Watertown was Trenton-like.
This particular boundary position was supported by work of Titus and Cameron (1976), who documented their belief that the boundary should be applied at the base of the Rocklandian
Selby Formation based on faunal evidence. In contrast, Cameron and Mangion (1977) revisited the boundary issue and opted for a boundary at the top of the Selby (base of Napanee) as they recognized two things a) the Selby seemed to be transitional from the Watertown in most
97 locations, and b) they believed there was physical evidence at the base of the Napanee for subaerial exposure and erosion. This exposure surface (and hence erosional unconformity) existed only in the Mohawk Valley region and closed successively northwestward, and therefore was not regionally widespread.
More recently Conkin (1991), when illustrating his concept of a “paracontinuous unconformity,” suggested that the true boundary between the Black River and Trenton should be placed at the base of the Watertown Formation. He based his argument on the belief that a more widespread and correlative sequence break existed at the base of the Watertown – across New
York and Ontario. He viewed the Watertown as Trenton.
Thus, up to this point the boundary between the Black River and Trenton has been placed at no less than three distinct horizons a) the base of Napanee, b) the base of Selby, and c) the base of Watertown – each of which is supported by different lines of evidence. In deciding among these options it is worth considering strengths and weaknesses of each.
Historically, the basal Selby to Watertown contact has probably been the most frequently cited Black River-Trenton boundary in the type area. There is no doubt that, in places, relatively abrupt facies and faunal changes occur at this contact. However, there were also problems with this boundary. First, the contact between the Selby and Watertown is not always clearly defined as in Napanee, Ontario. Also, in places the Selby is generally thinned so that it appears that the
Napanee rests unconformably on the Watertown. More importantly, where the section is more complete, in the type area, the Watertown-Selby-Napanee succession forms a conformable succession with only a minor diastemic break at the Watertown-Selby contact as noted previously.
98 The basal Selby to Napanee contact as proported by Cameron & Mangion (1977) certainly represents a significant diastemic surface and in the Mohawk Valley may also be associated with limited truncation of the Selby. However, in the context of the stratigraphic succession and the deep shelf lithologies of the Napanee, this particular boundary may only be locally truncated by submarine dissolution at a flooding surface rather than an exposure surface.
This flooding surface is therefore believed to be a component of the same submergence episode of the underlying Selby, and most definitely within the Trenton sequence.
The basal Watertown position for the group boundary also has its pros and cons.
Watertown Limestone matrix more closely resembles the typical Black River lithology and indeed, Hall’s original conception, but not Vanuxem’s, of the Black River limestone was essentially equivalent to the Watertown. However, in some senses, the Watertown boundary has several key positive features: a) throughout New York State and much of Ontario this is a sharp, distinctive contact, b) as documented herein, this is a regional discontinuity, c) this discontinuity appears to correspond to a widespread unconformity interpretable as an important sequence boundary, the M4-M5 boundary of Holland and Patzkowsky (1996, 1998). Hence, placing the
Black River – Trenton boundary at this position aligns lithostratigraphy and sequence stratigraphy. d) This position is nearly coincident with the horizon of one of the most stratigraphically significant marker, the Hounsfield or Millbrig K-bentonite. As this marker has also been used to define the Turinian-Chatfieldian Stage boundary it also places the Black River-
Trenton Group boundary of the type area at an important chronostratigraphic boundary.
Moreover, this brings the Turinian-Chatfieldian Stage boundary of other regions into close alignment with the Blackriveran-Rocklandian Stage boundary of earlier workers. Therefore, it is
99 proposed that the sharp base of the Watertown Formation be designated as the Black River-
Trenton group boundary.
B. Upper Black River Group
1. Lower Lowville Formation- lower Gull River Formation (B1-B2 sub-members)
Definitions: The Lowville Formation was named for exposures of the “birdseye limestone” in the vicinity of Lowville, Lewis County, New York (Clarke and Schuchert, 1899).
It is clear in the original description by Cushing et al. (1910), that his concept of Lowville included two main components of the Lowville. The lower Lowville was the birdseye limestone of the early workers on the basis of its most characteristic lithology – fenestral micrites. The upper Lowville, later renamed the House Creek member, was substantially coarser and more fossiliferous. At present the lower, typical “birdseye micrite” remains unnamed and will be referred to simply as the lower Lowville member.
In southwestern Ontario, the lower Lowville member appears on the basis of the MX and
MH to be equivalent to much of Liberty’s (1969) middle or B member (B1 and B2 submembers, but not B3) of the Gull River Formation.
Distribution and Thickness: The Lowville Formation and its equivalents in Ontario have a very widespread distribution and nearly identical facies can be observed from the eastern
Mohawk Valley of central New York State through the westernmost part of the study area.
The formation has a fairly uniform thickness across most of the outcrop belt of northern
New York and southern Ontario and ranges between 10 and 14 m (30 and 45’). It thins in the
100 southeastern most portion of its exposure area where at Inghams Mills only about 12-15’ is exposed. Outside of the study region, namely in the eastern Mohawk Valley region, the
Lowville has been demonstrated to thin very drastically and it has been truncated completely beneath a complex unconformity in that area. Beyond the Mohawk Valley the Lowville reappears in the area around Amsterdam, New York.
The lower Lowville Member reaches its maximum thickness in the region just east of
Marmora, Ontario where it also shows its greatest range in facies variability. Typical birdseye micrites also have well developed shales in portions of small scale cycles.
The equivalent Gull River B1-B2 beds as bracketed by the MX and MH K-bentonites, also thin toward the west of Lake Simcoe. In this region the B1 submember has been measured at about 4.5 m (14’) at Orillia, and the upper submember (B2) measures about 6 m (20’) in the
Coldwater quarry, very near Orillia. The total thickness for the Lowville is then about 10 m
(34’) in thickness in this region and matches very nearly the thickness in more eastern portions of the study region.
Contacts: The Lowville Member lies above the Pamelia Formation with the boundary originally drawn at the top of the highest development of dolostone (Cushing et al. 1910).
However, the highest development of dolostone lies above the position of the first well developed birdseye micrites, and in fact the dolostones above this point have only relatively minor cycle cap development. Young (1943) provides a more concrete position for the contact of the Lowville with the Pamelia. In the region of Roaring Brook, he describes the contact as
“disconformable” and notes that the basal Lowville shows conglomerate character within lenses of soft greenish mudstone to shale. This horizon marks a more concrete stratigraphic horizon
101 and can be used as a stratigraphic marker for correlation across the study region and is coincident with the green marker bed discussed previously.
In Ontario, the contact between the Pamelia/Lowville coincides to approximately lower- middle Gull River contact, slightly below the MX K-bentonite. This basal contact is sharp and well defined by the change from massive buff dolostones often with a red stained pyritic top to a very sandy quartz rich green mudstone which often contains variable sized clasts of Pamelia carbonates. In those regions where the Lowville oversteps the underlying Pamelia, the basal contact shows the basal green mudstone with well rounded quartz, feldspar, and granitic pebbles and cobbles typical of the Precambrian deposits.
The upper contact of the lower Lowville (B1-B2 submember of the Gull River) and
House Creek/Moore Hill (B3 submember) members is a very distinctive horizon that can be recognized from the central New York region through to southwestern Ontario. The contact is a well developed sharp transitions from fine grained wackestones/packstones of the House
Creek/Moore Hill (see below).
Lithology-Petrology: The lower member of the Lowville is composed mainly of fine grained limestones. Young (1943), has defined the lower member of the Lowville as being composed primarily of thin to medium bedded, laminated dark gray to dove. Young defines the term as “light and medium purplish-gray, sublithographic limestones (micrites), most of which weather white or light gray.” Minor interbedded buff weathering carbonates which generally cap small apparently shallowing upward cycles occur in the lower half and are equivalent to
Liberty’s B1 submember. Occasional ooids, ostracodes, crinoid plates, trilobite fragments and bivalves make up the allochem component of the rocks and are generally more prevalent in the upper part. The spar fractions of most samples are present in either of two forms – void space
102 birdseye fillings or replaced calcite spars. The term birdseye comes from the numerous small, calcite spar filled vugs and burrows that are present in the fine cryptocrystalline matrix of the rocks. These features are either cross section views of Phytopsis tubulosa burrows, or are void space fenestral fillings; the later are generally considered to be birdseye structures (fenestrae) sensu stricto by modern carbonate sedimentologists.
In a more detailed description of the section, near the type Lowville area, Textoris (1968) describes the interval as being composed of interbedded pelmicrite, pelsparite, biopelmicrite, with lesser amounts of intramicrite, biopelsparite, and Tetradium biolithites. Occasionally in the lower Lowville thin beds of dolomitized micrite occur. Interestingly the majority of Textoris’ lithologic descriptions include the prefix pel-. He indicates the pellets seem to be fecal in origin, and are commonly merged laterally to produce a homogeneous micrite.
Similarly, in the Lake Simcoe District of Ontario the equivalent middle Gull River Fm. interval is composed of: lime mudstone (=pelmicrite; lithofacies 3 of Grimwood et al., 1999); peloidal bioclastic wackestone and packstone (=biopelmicrite; lithofacies 4); ooid grainstone
(oosparite; lithofacies 6); and intraclastic bioclastic wackestone and packstone (intramicrite; lithofacies 7).
Collectively, the Gull River and Lowville often show well developed, parallel laminations, rare wave ripples, well developed mud cracked horizons and graded bedding
2. House Creek (Leray)/Moore Hill Member
Definitions: In New York State, early workers (Cushing et al., 1910; Young, 1943) recognized an upper division of the Lowville Formation that was distinctive from the lower
Lowville. Ruedemann & Kemp (1910) named the upper Lowville the Leray Member for
103 sections near the town of Leray in northern New York. The Leray in the type section contained well bedded chert horizons which were subjacent to those of the Watertown Limestone. In regions outside of Watertown some similarity between the Watertown and the Leray led to confusion on the nature of the Leray. In this situation there was no acceptable resolution and so
Kay 1960) proposed the Chaumont Formation to encapsulate the two intervals. Many workers, under the assumption that Ruedemann’s Leray was only the basal part of the Watertown
Limestone as recognized outside of Jefferson County, New York, reverted to the definition of
Cushing (1910) where the upper limit of the Lowville was at a contact with the Watertown
Limestone and was much more concretely defined.
In more recent literature, Walker (1973) renamed the upper more massive division of the
Lowville the House Creek Limestone Member and distinguished the beds of the House Creek on the basis of their densely packed Tetradium and other corals content. He argued that without the chert as is present in the Leray in the vicinity of Watertown – the term “Leray” could not be applied to these successions. As it turns out – the characteristic Tetradium beds of this unit can be recognized over a very widespread area and together with the MH K-Bentonite demonstrate that this particular interval is equivalent to the Moore Hill (Tetradium beds) of Lake Simcoe.
The House Creek interval is very similar in lithology to the upper Gull River Formation –
B3 submember ( or Moore Hill) recognized in the Lake Simcoe area. The term Moore Hill
(Formation) was originally proposed by Okulitch (1939). In his work in the vicinity of
Coboconk (eastern Lake Simcoe District), he recognized a distinctive interval of medium- grained, dark gray limestones that were fossiliferous and distinctively more coarse grained and was lithologically distinguishable from underlying units.
104 Contacts: The lower contact is defined at the well-developed sharp transition out of the lower Lowville into the fine to medium grained wackestones/packstones of the House
Creek/Moore Hill. This contact consistently occurs at approximately 0.5 m above the distinctive
MH K-bentonite (after Liberty, 1969).
The upper contact of the cyclically bedded House Creek/Moore Hill interval is marked by the transition into, the informal Weaver Road beds. This transition is generally drawn at the base of a 0.75-2 m (2-6’) shaly zone. In the eastern portion of the study region (Kingston through northern New York State), the upper Moore Hill grades into the platy dark shales and interbedded domal stromatolitic wackstones of the Weaver Road beds. As this horizon is traced toward the west, the upper Moore Hill grades laterally into slightly less distinctive interbedded shales and more LLH style stromatolitic wackestones. In the Lake Simcoe distict, this same horizon is only recognized by a thin shaly nodular horizon that can display minor oncolitic development, at the base of the Coboconk Limestone.
In the Lake Simcoe region, this contact is drawn at the base of a 0.75 m thick, wavy bedded, greenish gray wackstone with interbedded dark shales. This horizon is developed over the typical massive bioturbated packstones and wackstones of the underlying Moore Hill
Member. In the region between Coboconk and Marmora, this same contact is developed again from the transition from the massive bioturbated beds of the underlying Moore Hill into thinner bedded wackstones and interbedded shales which often show well developed mudcracks.
Distribution and Thickness: The House Creek (Leray) is about 4.5 m (13-15’). The
Moore Hill also displays an astonishingly regular thickness of about 5 m (12-15’) across most of the outcrop belt. In the Lake Simcoe region, this interval shows slightly more thickness and can range up to 6 m. In the southeastern most exposures of the Mohawk Valley the thickness of this
105 unit varies but at Inghams Mills it is up to about 2.5 m (8’) at most as the upper portion appears to be truncated at the base of the Watertown Formation.
Lithology-Petrology: Okulitch (1939) states, “ the character of the rock changes abruptly
[from the Gull River] to bluish fine-grained to aphanitic limestone with numerous fossils.”
Within these beds a more diverse assemblage of corals (Tetradium, Lambeophyllum and
Foerstephyllum), brachiopods and stromatoporoids occur. They became known as the Tetradium beds in this regard. In addition to the skeletal fossil remains, a higher degree of bioturbation is evident. The bioturbation has given the massive beds of the Moore Hill a more or less mottled or swirled texture. The characteristic evenly bedded, rhythmically banded, burrow mottled, pelletal carbonates are very easily distinguished from the underlying lower Lowville and Lowville equivalent Gull River (B1-B2) birdseye micrites. An important characteristic of this unit is the presence of a large diversity of cephalopods, corals, and stromatoporoids which are generally not abundant in the lower Lowville, but are characteristic of the Moore Hill/House Creek interval.
These units demonstrate a much coarser signature than is present in underlying lithologies. Included in this interval are a series of repetitious beds showing argillaceous mudstone to wackestone associations. In most cases, these beds are churned and homogenized by bioturbation so that they appear in outcrop as a distinctive interval.
The petrographic study of Textoris (1968) in the central Black River Valley described this interval as being composed mainly of Tetradium biolithite, intrasparite, biopelsparite, with minor oolitic intrasparite. More recent work by Grimwood et al. (1999) describes this interval as being composed mainly of lime mudstone (which includes a distinctive burrow mottled bed), and intraclastic bioclastic wackestone and packstone. The later lithofacies seems to be the equivalent of the intrasparite, described by Textoris (1968). In their description, however, Grimwood et al.
106 did not highlight the importance of Tetradium in the Lake Simcoe region – except as a bioclasts within the lime mudstones and interbedded intraclastic bioclastic wackestone and packstone.
The Moore Hill cyclic interval is one of the most widespread of the Black River units and is distributed from the Lake Simcoe region of Ontario (and parts west) through to the Mohawk
Valley region
3. Weaver Road Beds
Definition: At the top of the House Creek/Moore Hill interval displays an interesting and unique interval of shales and interbedded stromatolitic boundstones. The interval is herein referred to as the “Weaver Road” beds. The Weaver Road interval is defined from a locality in a streambed in the Town of Lyme, northern New York State, where a small tributary to the Horse
Creek passes beneath Weaver Road, just to the southeast of the village of Chaumont. This interval is recognized also in the nearby Black River Gorge at Glenn Park, where the interbedded shales and domal stromatolites of this unit can be seen in relation to the underlying Moore Hill limestones and the overlying Watertown limestone. Noor (1989) also recognized this interval in drill core from the region south of Bath, Ontario, and named the equivalent interval the Bath submember of the Bobcaygeon Formation, although the thickness for this interval is much greater than that exposed in outcrop.
Distribution and Thickness: The Weaver Road interval has a limited thickness in the study area. In the reference locality, the Weaver Road is slightly under two meters in thickness it maintains this thickness through the Kingston region. The gray, papery shales component thickens towards Napanee, where it shows a maximum thickness of just over two meters.
Beyond Napanee, the Weaver Road beds thin substantially, yet are recognizable through
107 Marmora as a thin, shaly unit interbedded with thin calcisiltites that are typically desiccation cracked and vertically burrowed in a zone approximately 0.5 to 0.6 meter thick. Beyond
Marmora, near Coboconk, Ontario, the Weaver Road interval is recognized as an argillaceous and rubbly carbonate (~1.1 m thick) at the base of the overlying Coboconk. Farther west, in the region of Brechin quarry, the Weaver Road has not been explicitly documented, but the equivalent interval is approximately 1 meter thick.
In a section at Medonte, Ontario, (just northwest of Orillia and northwest of Lake
Simcoe), Kay (1931) recognized this same interval and described it to contain 3’8” of
“interbedded, fine textured, very light gray limestones and blue-gray, laminated, papery, tough shales, the latter containing leperditiid ostracods.” Although not explicitly observed by the author, this description is very similar to that seen in the Glenburnie road cut and quarry, as well as at Napanee in the Highway 401 cuts, and indicates that this restricted horizon is fairly continuous and similar in lithology across the region, although it is not as well developed in the
Brechin to Dalrymple region.
In the Lake Simcoe region, however, the interval is slightly more expanded and is thought to be equivalent to the lower part of Coboconk Member of the Bobcaygeon Formation.
To the south of the study region the shaly Weaver Road interval thins substantially with the loss of the stromatolitic wackstone component. The dark shales grade into thin bedded and laminated lutites (similar to the Lowville birdseye limestones) near Lowville. At Boonville, the
Weaver Road interval is no longer present and is thought to have been erosionally truncated.
Contacts: The upper contact of the Weaver Road is complex and is often a sharp horizon.
In the Lake Simcoe region, where the Weaver Road Member is limited to a bioturbated argillaceous nodular carbonate unit the contact with the overlying Coboconk is generally fairly
108 sharp. At several localities including Brechin Quarry it is delineated by the presence of a well developed hardground with Solenopora overlain by a much coarser (grainstone) which typically has abundant Stromatoporoids and appears in some locations to be biostromal. In contrast to the underlying fine grained calcisiltites and nodular limestones of the Weaver Road beds, the
Coboconk grainstones are fairly distinctive from Coboconk eastward across the study region.
Toward the eastern portion of the study area (at Glenburnie and Kingston), the upper contact of the Weaver Road interval is also sharp and is overlain by a ~ 0.5 m bed of strongly cross bedded grainstone. This same scenario repeats itself in northern New York State, where the lower Coboconk grainstone appears in the Black River Gorge at Glenn Park, and in the nearby county route 54 road cut at Brownville.
Lithology and Petrology: As the “Weaver Road” is only now recognized as a distinctive interval, previous detailed studies of the sedimentology of the unit are lacking. The Weaver
Road, at its reference locality in northern New York State, is physically defined as the succession of wave rippled bioclastic wackestones and packstones, with interbedded blue gray calcareous shales and stromatolitic boundstones. The stromatolitic boundstones toward the top of the succession are overlain by dark gray to black platy shales, which have well developed desiccation cracks in the uppermost few inches. The shale component of this facies association demonstrates a highly siliciclastic component, unlike any of the previous units of the Black
River.
4. Coboconk Member (Bobcaygeon Formation) (REVISED)
Defintion: Immediately above the Moore Hill/House Creek succession lies a unit called the “Coboconk Member” of the Bobcaygeon Formation in the Lake Simcoe district.
109 Historically, the equivalent interval in New York and southeastern Ontario, has been variously called the Chaumont Formation (Kay, 1929), or more recently, in part, the Watertown Formation
(Walker, 1973; Fisher, 1977). The Coboconk Member was originally proposed by W.A.
Johnston (1910) for “dark blue to gray nodular and chert limestones” in the region of Coboconk,
Ontario. It was originally assigned a formation status, and based on its lithological characteristics it was placed in the Black River Group by Okulitch (1939). Yet, because of the
Rockland type faunas present within the Coboconk, Kay (1937, 1939) viewed the unit as
Trenton. This debate was not officially resolved and the Coboconk was placed in the Simcoe
Group by Caley and Liberty, (1967), to help reduce ambiguity of the Black River/Trenton boundary designation.
Okulitch, detailed sections in the vicinity of Coboconk. In his work he recognized three main units within this interval, which he assigned to beds 14, 15, and 16. In his descriptions of the Coboconk it is possible to see multiple lithologies within the overall coarse grainstone interval of the Coboconk. This interval of the Coboconk Member was described by Okultich
(1939) as “medium to fine grained, grey to brownish grey limestone [which is] brown on weathering; irregularly fractured; and consisting of several irregular beds [unlike the underlying
Moore Hill].” Stratigraphically, the Coboconk contains several distinctive intervals that when traced eastward, and to some degree westward, expand open into several units.
In the present study the composite nature of the “Coboconk” as originally defined has been recognized to be fairly important. Okulitch (1939, p. 335) hinted at this when he suggested that the contact between his beds 15 and 16 represented a disconformity and he questioned
“whether all of the twenty feet [for beds 14, 15, & 16] can be retained in the Coboconk and whether it will not be necessary to restrict this formation to beds 14 and 15.” Thus as defined
110 herein, the term Coboconk is restricted in the type section to Okultich’s beds 14 & 15 totaling about 2.3 m (7’), leaving bed 16 which measures (13’) excluded from the Coboconk. The distinctive sharp contact noted by Okulitch sets massive bed 16 apart. That unit is herein assigned to the Watertown (see below), and the beds 15-16 contact is recognized as an erosion surface, and as the Coboconk (sensu stricto) to Watertown contact – the Black River-Trenton
Group contact – and an important sequence boundary. This contact is traceable eastward in
Ontario and forms the base of the Trenton Group throughout. The underlying unit, (equivalent to
Okultich’s bed 15, in part becomes more shaly and may pass eastward into the Glenburnie Shale by the position of Marmora, Ontario and certainly by Napanee, Ontario.
Contacts: As defined in Ontario, the Coboconk sensu stricto (C1 of Liberty) has its basal contact with the Moore Hill (B3 submember of Liberty) which puts a sharply based grainstone on the wackestone interval of the Moore Hill. In southeastern Ontario and New York State an as yet unnamed grainstone/wackestone couplet sharply overlies the shaly Weaver Road. In older literature this unit would have been considered to be part of the Leray Member and below the
Glenburnie and Watertown members of the Chaumont Formation. The sharp contact of this grainstone with the Weaver Road appears very similar to the basal contact of the Coboconk.
Herein it is suggested that these contacts are one in the same.
When considering the upper contact in the Lake Simcoe region it must be noted that recent field work shows the Coboconk of Okulitch and Liberty is a composite unit of multiple lithologies sandwiched together and within which occur a number of distinctive marker horizons which allow correlation eastward. The upper contact of the Coboconk (as defined by Liberty), occurs at the base of Liberty’s “Dalmanella beds” or unit D of the Bobcaygeon Formation herein correlated with the Napanee Formation. When considered toward the east as in the Napanee
111 region, this (C2-D) contact overlies Selby Formation. As such this warrants the need for revision of these units and a recalibrations between appropriate horizons.
Herein, the separation between Okulitch’s bed 14 and 15 of the Coboconk type section is marked by the transition to more fossil rich argillaceous and hackly weathering wackestone which contains the Hounsfield K-bentonite and is believed to be equivalent to the Glenburnie shale.
Also contained within the composite Coboconk is the contact between beds 15-16, which appears to truncate and remove significant amounts of bed 15 below the “upper tier” of the
Coboconk (submember C2 of Liberty). The presence of a conglomerate in the base of the C2 in nearby areas (Liberty, 1969) suggests this is a highly important horizon correlative of the
Watertown of more eastern areas.
Distribution and thickness. The Coboconk (sensu stricto), as now recognized, is well developed in the region around Coboconk, Ontario where two main sub-intervals occur within the Coboconk as described by Okulitch (1939). The cumulative thickness at the type section is therefore slightly more than 7’ (~2.5 m), again with the exclusion of bed 16.
As the Coboconk (sensu stricto) is traced westward into the Lake Simcoe vicinity, the
Coboconk becomes less coarse and is thought to be recorded by a thin interval of interbedded fine grainstones and shaly calcisiltites. This package as developed at Brechin Quarry is not more than 1 m (3.25’) thick and does not maintain the massive bedded grainstone appearance that is so characteristic of the interval. Eastward of Coboconk, toward Marmora, Ontario, the Coboconk
(sensu stricto) thickens slightly and changes in character mainly due to increased coral development in that direction. The strongly developed crinoidal grainstones and Stromatoporoid beds developed in the Coboconk region are replaced by poorly sorted ooid grainstones which are
112 interbedded with colonies of Tetradium, stromatoporoids, and favositid style tabulate corals, and are on the order of 10’ (3.5 m) thick. As the Coboconk is traced still farther east, the Coboconk
(beds 14, and 15) thins considerably and becomes a more obvious couplet of beds and the
Glenburnie shale. At Glenburnie, Ontario, the Coboconk is a thin (less than 0.5 m thick) bed with a basal coarse herringbone crossbedded grainstone with weakly developed climbing ripple marks. It is overlain immediately by an upper cap of wacke- to packstone lithology with a number of coral, brachiopods and bivalves and is in turn overlain by beds assigned to the
Glenburnie Shale.
Lithology and Petrology: The matrix of the Coboconk Member is somewhat similar to the bioclastic wackestone and packstone associations of the underlying Moore Hill, however, it is distinctive in that it contains a much greater abundance of colonial organisms (corals, stromatoporoids, bryozoans). In fact, in most horizons the basal Coboconk can be described as almost biostromal. Presumably corals were effective in trapping fine and medium grained sediments as the interval thickens where corals are abundant. In the region of the Peterborough
Arch, eastward toward Napanee, the Coboconk shows a greater abundance of ooids and
Tetradium.
5. Glenburnie Member
Definition: The type section for the Glenburnie is approximately 6 miles north of
Kingston, Ontario. In the road cut and nearby quarry, the 2’ dark shale of the Glenburnie overlies a grainstone wackestone couplet (noted above) and lies below a well developed intraclastic, conglomeratic grainstone. The Glenburnie, and the Hounsfield K-bentonite which was present at the base of the Glenburnie, was used by Kay, (1929) for correlation in the region
113 around Kingston and to a lesser extent westward into Lake Simcoe near Orillia, but was not recognized by him in New York. However, a locality near Three Mile Bay, New York was reported earlier by E.O. Ulrich (1910) to show a dark shaly interval which had well developed bryozoan faunas similar to those of the Decorah Formation of Iowa, Minnesota, and Wisconsin.
This same dark shale horizon has also been located to the west of Kinston at Napanee, however it is not distinctly recognized at Camden East (just west of Napanee). The dark Glenburnie shale and its typical brachiopod-bryozoan rich fauna are recognized further west at Marmora, and again in the Lake Simcoe region (at Brechin Quarry) where the interval has expanded both in thickness (up to 1.0 m) and lithological character.
Thickness and distribution: As mentioned above the Glenburnie is about 2’ thick in its type area and thins toward the east into New York State. Near Three Mile Bay only about 1’ of
Glenburnie is present. In the few miles between Three Mile Bay and the village of Chaumont, the Glenburnie is no longer recognized and only traces of the Hounsfield K-bentonite occur.
One exception is at Brownville, where the bentonite and portions of the Glenburnie are present
In occasional depressions, up to 4-5 cm of the K-bentonite can be present. Without the
Glenburnie, the succession appears to be nearly continuous from the grainstone/wackestone couplet of the Coboconk (sensu stricto) up into the massive “upper tier” of the Watertown
Formation. However regional study shows that this interval actually contains a cryptic unconformity.
In the region west of Kingston, Ontario, the Glenburnie shale is present through Napanee, where it is still overlain by the basal intra-clastic conglomerate, although it too has been reduced in character. By the position of Camden and Highway 401, the Glenburnie is not formally recognized although a minor well-weathered recess does occur in the approximate position.
114 Further west in the vicinity of Marmora, a thin dark shale with well developed brachiopod and bivalve faunas is present and is capped again by an excellently developed intra-clastic conglomerate such as is developed at Kingston and Glenburnie. Intriguingly, some faunal elements associated with the Glenburnie Member can be seen in an interval of interbedded shales, and silty carbonates in the region of Dalrymple and Brechin as described previously.
Contacts: The lower contact of the Glenburnie is marked across the study region by the
Hounsfield K-bentonite of Kay (1929). In the eastern portion of the study region, Kay, recognized the Glenburnie shale as being present, more or less as a lens of black shale with distinctive open marine faunas, from the region west of Kingston to northernmost New York
State. It is recognized in the region from Three Mile Bay, New York to Glenburnie, Ontario, and further toward the west, the Glenburnie overlies beds of the lower Coboconk Member and composes a rubbly-shaly interval recognized by Okultich (in his interval #15). In addition, Noor
(1989) has recognized the same interval from core and has included this interval in the Bath
Member of the Bobcaygeon Formation. In the core, however, Noor shows the interval to be much thicker than in outcrop. The Bath appears to be partly synonymous with Kay’s (1929) older term Glenburnie and partly to the Weaver Road beds used herein.
The Hounsfield K-bentonite is found near the base of this interval and has been found through Brechin, Ontario. However, in some instances, as in the Miller Paving Quarry at
Dalrymple, Ontario, the K-bentonite can be seen as discontinuous. In this one outcrop the K- bentonite and its associated notch can be observed in the eastern quarry wall, while it is absent in the adjacent (northern) and western walls. However, the approximate position is marked by fossiliferous shales interbedded with minor wackestone – packestones which appear similar to the Glenburnie
115 The upper contact of the Glenburnie with the overlying Watertown is distinctive. At the type section, the contact is knife sharp and when traced laterally along the outcrop it shows local angular truncation of the Glenburnie on the order of 0.10 – 0.2 meters. Due to the recessive nature of the weathered shales the overlying Watertown ledges out and is immediately recognizable as having a well developed intra-clastic conglomerate with a variety of carbonate lithologies represented within it (see below). This same horizon is very well developed in the
Highway 401 cuts at Kingston and westward into Lake Simcoe.
In the sections near the village of Three Mile Bay, New York, where the Glenburnie is thin, the contact is equally well formed; it appears to have truncated the upper beds of the
Glenburnie.
Lithology and Petrology: The Glenburnie shale appears as a highly siliciclastic (shale) dominated interval and is variously interbedded and cemented by carbonates. The usual appearance of this shale is as a dark gray papery shale with interbedded calcisiltites and minor bioclastic wackestones. Occasionally the Glenburnie demonstrates a black color. More often the
Glenburnie shows evidence of bioturbation and abundant fossils in the calcisiltites and wackestones.
C. The lower Trenton Group (REVISED)
1. Watertown Formation
Definitions: The Watertown Limestone of northern New York State and southern
Ontario, Canada, was originally defined from exposures in the Black River Valley near
Watertown, New York. This rather thick and massive limestone unit was recognized by James
116 Hall (1847), and was called the Black River Limestone by him, and was approximately equivalent to the so-called “Seven-foot tier” of the quarry industry. However, as many workers, before and after, used the term Black River more broadly for the carbonate rocks in the region, another name was needed for this “upper tier.” Cushing et al. (1910) proposed the term
Watertown Formation to encompass this unit and approximately 8-9’ (2.5-3.0 m) of underlying dark limestones which included the Glenburnie shale and the Leray limestone. The term
Watertown is herein redefined and restricted to massive bedded cephalopod rich limestone above the Glenburnie shale, and is equivalent to bed 16 of Okultich (old upper Coboconk).
Distribution and thickness: The Watertown limestone and its equivalents has a widespread occurrence in New York and Ontario. The Watertown reaches a maximum thickness of approximately 5 m (15’) (although it is more commonly close to 3 m (10’)). South of the study region, in the southern Black River Valley, the Watertown begins to thin and establishes itself at Boonville as a very standard 7-8’ (where it received its fame by quarry workers as the
“7’ tier”, and by the position of the eastern Mohawk Valley, the Watertown has thinned substantially to about 4-5’ of strata. In the Kingston to Napanee area of the study region – the massive, single bed character of the Watertown breaks up and most exposures show much more grainstone rich intervals, and in some cases oolitic horizons, especially in the Napanee region.
The chert horizons mentioned earlier seem to be well developed throughout the Watertown and its equivalent units toward the west, and can be used as general marker horizons.
Contacts: The lower contact of the Watertown seems to be sharp and planar to slightly irregular at all localities in north central New York. The basal Watertown comprises a very coarse packstone to cross-bedded grainstone interval. According to Liberty (1969), in many places this particular horizon (his basal C2 submember) shows clasts of a variety of lithologies
117 derived from the underlying Gull River Formation. These clasts range in size from a few centimeters in length up to a decimeter, and in outcrop generally weather recessive in contrast to the coarse grainstones within which they occur.
The contact of the Watertown Formation with the overlying Selby Formation appears to be gradational in northern New York and Ontario, and only appears sharp in the southeastern portion of the study area (Watertown to Lowville) because of the amalgamated nature of the massive “7 foot tier” of the Watertown Formation. In the region farther to the south (Boonville), and in the Mohawk Valley region, the contact with the Selby has previously been described as being unconformable, but it appears to be gradational and similar to minor flooding surfaces seen elsewhere in the lower succession.
Lithology and Petrology: In the original description of the Watertown, Cushing et al.
(1910) described 13’ of dark gray to black, fine textured, hackly fracturing, semi-crystalline limestone. These authors also indicated that the majority of the thickness was made up in two massive beds, which generally contain excellently developed nodular black chert horizons across most of northern New York State. In most cases, as in the section at the Black River Gorge at
Glenn Park, the Watertown appears as a single massive bed, however, at the route 54 road cut in
Brownville, it appears as two distinctive beds. In addition to the distinctive chert horizons, the
Watertown is typified by its fauna, and is renowned specifically for the diverse and very large
(up to 10 m long) cephalopods that can be found within the unit. However, in Ontario, the massive bioturbated wackestone “upper tier” changes slightly and becomes thinner bedded and more grainstone rich.
The Watertown Formation in the vicinity of its type locality in the northern Black River
Valley demonstrates a highly variable set of lithofacies. In the more eastern portion of the study
118 region, a basal grainstone is developed from highly fragmented echinoderm, bivalve and brachiopod shell material. In most cases, this basal calcarenite interval shows a gradual change upward into finer grained material. At Watertown, the basal grainstone is overlain by very massive, bioturbated fossiliferous wackestones. These dark gray to black limestones contain beds with black chert nodules about 3-4 cm in diameter and are often elongated parallel to bedding.
The medium textured, massive gray wackestones and packstones resemble the House
Creek/Moore Hill beds – except that they contain well developed cephalopod faunas and are much more massive. For this reason, much confusion has resulted from trying to identify the
Watertown limestones in regions outside of northern New York State. Without the recognition of the sharp contact with the Glenburnie shale at its base, the Watertown would appear to be part of a continuous succession..
Toward the west, especially in the Coboconk region, the probable Watertown equivalent
(Okulitch’s, 1939, bed #16) is generally more thin bedded than those sections in the eastern portions of the study interval. Instead of being a well bioturbated wackestone interval, the
Watertown in the region of Coboconk is dominated by coarser sediments, which often contain bioclastic crinoidal debris. In this region (on the Peterborough Arch) the upper Coboconk
(Watertown equivalent) also contains well developed dark black nodular chert horizons. In more westerly sections, e.g, at Coboconk, the Watertown equivalent shows well developed oolite horizons mixed with cross bedded, medium to coarse grained limestones
Fauna: The fauna of the Watertown Formation is distinctly more diverse than those of the underlying units. While many of the same coral species, and a few small invertebrates are shared with the underlying Leray/Moore Hill beds, a variety of new taxa, including a number of cephalopods and various algae are introduced rather abruptly in the Watertown limestone
119 (although some bryozoan and brachiopod taxa first appear in the Glenburnie). For this reason,
Kay (1929) promoted the idea that this interval was more closely related to the Trenton and
should be included with that interval, a view that is supported herein (see below).
According to Cushing et al. (1910) the Watertown “is essentially a cephalopod facies.”
The nautiloid Gonioceras anceps, Hormotoma tenuifilum (a gastropod), and several species of
Endoceras can be found in just about every outcrop where there is a flat bedding plane exposed.
Such a horizon in the Town of Brownville, very near the type section of the underlying Weaver
Road Member, exhibits well over 70 cephalopods (including Gonioceras and Endoceras sp.) on a bedding plane approximately 20 m by 15 m in width. In this case the majority of the straight shelled cephalopod shells showed similar alignment orientations – roughly northeast - southwest.
Western Watertown equivalents contain a variety of algae (including Receptaculitids), crinoids, corals (both colonial and solitary), and a variety of brachiopod and bivalve forms.
Stromatoporoids occur in moderate abundance at this position as well.
2. Selby Formation
Definition: The Selby was first named by Kay (1937) as the lower member of the
“Rockland Formation,” based upon an incomplete type section located on Selby Creek (Lennox
and Addington county, Ontario) just north of Napanee. However, he was not the first to identify
the unit as a distinctive interval. In fact, Cushing et al. (1910) recognized an interval of about 2’
of knotty (nodular), impure dark gray limestone with a variety of brachiopods and trilobites
immediately on top of the 7’ tier at Watertown. Cushing et al. (1910) viewed this interval as
being very similar to the underlying Watertown and included it therewith. However, it wasn’t
until work by Kay (1937) that the Selby was excluded from the Watertown and included as a
120 member of his Rockland Formation. Kay defined the unit on the presence of the distinctive brachiopod Doleroides ottawanus (Wilson), which occurs above the Black River Group, and below the Napanee. The Napanee contrasted lithologically from the underlying Selby and had abundant Dalmanella rogata (Sardeson) and Sowerbyella curdsvillensis (Foerste).
In more recent work, Cameron and Mangion, (1977) again recognized, the Selby as being more similar lithologically to the Watertown and it was again thought to be part of the underlying sequence. Addtionally, these authors believed that an unconformity existed at the top of the Selby, thus separating it from the overlying Napanee. They further went on to say that this
Selby-Napanee unconformity is only obvious in the Mohawk Valley region, and as it is traced toward the northwest, it is not discernable by the region of Lowville.
Thickness and distribution: The Selby Formation has been shown to be present in the
Mohawk Valley region as a thin interval less than 1 m (3’) and has been recognized to thicken from that point northwestward into southern Ontario, where it has its type section. Although the type section is not a complete exposure- nearby exposures at Camden East road cut along Hwy
133 (junction with Hwy 401), show a thickness for this interval of approximately 2.5 m (7.5’)
Presumably the interval is present west of Napanee, but due to the limited exposures the Selby has not been explicitly identified in the Lake Simcoe region (except in the subsurface).
However, in the section at Brechin quarry, a thin interval above the Watertown equivalent and below Liberty’s “ D submember”, can be observed to contain fine grained packstones and grainstones that are bioturbated to irregular nodular, beds and is tentatively correlated with the
Selby in more easterly regions. Additionally, this particular interval does demonstrate a diverse brachiopod assemblage, although Doleroides ottawanus (the characteristic brachiopod of the
Selby) has not been identified.
121 Across its known outcrop region, the Selby Member(?) varies in its thickness. In the
Mohawk Valley region, the Selby is limited to only a few 10’s of centimeters in thickness, while in more northerly regions, the thickness can reach up to about 2 m in thickness. The thickest
Selby is measured at the Camden East sections, as just over 2 m (7’).
Contacts: The lower contact of the Selby can be described as abrupt but conformable over much of the outcrop belt. In some locations, this contact appears to be more gradational upward out of the underlying Watertown, and occassionally the Selby appears tabular (bedded) like the Watertown. More often, however, the Selby grades into more nodular bedded wackestones and packstones. Where this occurs, the contact is more often sharp.
The upper contact of the Selby Formation is much more distinctive than the lower contact. The Selby is sharply overlain by the Napanee Formation. The contact superimposes interbedded fossiliferous dark shales and barren lenticular to semi-planar calcisiltites on the
Selby Formation. This rather dramatic change is easily recognized wherever the contact is exposed across the entire study region. This particular horizon was noted previously by
Cameron and Mangion (1977) to represent a critical change in the deposition of the Laurentian shelf and therefore assigned this contact as the Black River– Trenton Group boundary.
However, as discussed above, this study has shown a more critical and pervasive disconformity at the base of the Watertown and we have placed the Black River/Trenton Group boundary there.
Lithology and Petrology: The Selby Formation was defined by Cushing et al., (1910) as a
“black, knotty, impure, dark limestone,” while Kay (1937) described the same interval to be
“dark-gray to black, medium to fine textured petroliferous limestone in thin beds, weathering buff, and having a jointed splintery fracture.” In their survey of the Black River and Trenton
Groups, Cameron and Mangion (1977) describe it as being composed of argillaceous, burrow-
122 reworked, fine-grained calcarenites (biopelmicrites), which are occasionally nodular and chert bearing. These authors add that the “ fine-grained micritic calcarenites increase in coarseness and frequency toward the top of the unit where biosparites, sometimes ruditic, become common.”
The description of Cameron and Mangion, (1977) is fairly accurate for this particular unit. The sediments can be much coarser than that of the underlying upper Watertown, and even in the upper few feet of the member, display small scale ripples and cross lamination.
Additionally, the upper meter of the Selby Member shows evidence of being extremely fossiliferous and probably is condensed. At Camden East road cuts near Highway 401 in
Ontario, the Selby Member is extremely fossiliferous and shows especially in the upper few feet of the section, densely packed molluscan and brachiopod assemblages.
Fauna: Regarding the fauna, the Selby was defined by Kay, (1937) to contain the distinctive brachiopod Doleroides ottawanus Wilson, and was separated from the Napanee on the basis of abundant Sowerbyella curdsvillensis and Dalmanella rogata within the Napanee. In addition to its distinctive brachiopod D. ottawanus, the Selby also displays a number of other brachiopods including some that are present in the overlying Napanee. In many exposures where the Selby is more argillaceous and nodular, the Selby appears to be abundant in cephalopods
(Gonioceras sp.), multiple forms of gastropods (including Hormotoma), as well as crinoids, and trilobites (Calymene, Isotelus).
3. Napanee Formation
Definition: The Napanee Formation, like the underlying Selby Formation was originally described from localities in southeastern Ontario. The term Napanee was also proposed by Kay
123 (1937) to delineate the upper member of the “Rockland Formation” which had been described
from the region of the Ottawa Embayment. In particular, Kay intended the Napanee to include
those beds overlying the Selby, and underlying the Hull Formation (now known as the Kings
Falls or uper Bobcaygeon formation). The Napanee was defined on the presence of the
brachiopod Triplecia cuspidata (Hall), and the absence of the Parastrophina hemiplicata (Hall) which were common in the overlying beds. Lithologically, the Napanee was also defined as “ gray-blue, medium textured, rather heavy-ledged limestone with shaly partings” (Kay, 1937).
Thickness and Distribution: Overall, the Napanee has a fairly even thickness, although it
has its thickest development in the region of southeastern Ontario. At Napanee, Kay, (1937)
reports the thickness for this interval to be 11 m (34’) although the author has measured this
section to be no more than 8 m (25’). Slightly less than this thickness is present in the Black
River Gorge at Glenn Park, New York where it has been measured to be close to 7 m (20’) thick.
In this locality the Napanee overlies the Watertown, and a thin Selby interval 1 m (~3’ thick).
The Napanee in turn is overlain above by grainstones of the Kings Falls limestone high in the
gorge wall. In the section at nearby Great Bend (upstream from Watertown and Glenn Park), the
Napanee has also been measured, at just under 9 m.
Westward from Napanee, the thin-bedded nature of the Napanee has enabled it to be
pealed up from the top of the massive Black River limestones by Pleistocene glacial activity. In
this region, therefore, very few exposures exist for detailed study until the region of Lake Simcoe
where a number of large quarries show vertical sections through the lower Trenton and Black
River. Although the Napanee has not been explicitly recognized from these sections previously,
an interval of thin interbedded calcisiltite limestones and dark shales show very similar
characteristics to the Napanee of southeastern Ontario. This particular interval is close to 6.5 m
124 (20’) thick and is equivalent to the middle (D) member of Liberty’s (1969) Bobcaygeon
Formation. And although Liberty uses a different descriptive nomenclature for the rocks, the lithologic descriptions are nearly identical. In addition, Liberty has identified the MR-K- bentonite as occurring slightly above the contact between his C2-submember and the D member of the Bobcaygeon Formation. Assuming a minor thickness of Selby is present in the Lake
Simcoe region, the position of the MR, should be very near the Selby-Napanee contact in eastern areas. This is indeed the case and at Napanee, Ontario the MR sits near the sharp contact of the
Selby/Napanee.
Contacts: The lower contact of the Napanee with the underlying Selby Formation has been discussed above (in sections regarding the MR K-bentonite) as well as in the discussion of the upper contact of the Selby.
The Napanee has a distinctive upper surface over most of the study interval and in the region of the Mohawk Valley. This contact has been described by Kay (1937) as the highest development of the brachiopod Triplecia cuspidata, but it also can be described lithologically.
The coarse, often cross-bedded crinoidal grainstones of the Kings Fall Formation sit sharply on the fine grained Napanee Formation. This particular horizon is very distinctive across the study region, and into the Mohawk Valley. This contact is often very undulatory and usually demonstrates a sharp facies dislocation from finer to extremely coarse-grained carbonates.
Further west, in the Lake Simcoe region, the equivalent interval also demonstrates the sharp juxtaposition of very coarse, cross-bedded crinoidal grainstones of the upper Bobcaygeon –
Kirkfield member on the middle Bobcaygeon.
Lithology and Petrology: The Napanee Formation has received little direct study under the petrographic scope. In the literature, the Napanee has only been described from outcrop
125 exposures and hand samples. In these descriptions, the Napanee has been referred to as fairly thin bedded, fine grained limestones, which often ledge out in outcrop because of the weathering of the interbedded dark shale horizons. In most places the Napanee demonstrates fairly fossiliferous shales and less fossiliferous calcisiltite limestones, except where the upper bedding planes show bryozoan or brachiopod faunas. Most often the thicker (0.06-0.1 m) calcisiltites demonstrate minor normal graded bedding especially toward the top of the formation where the calcisiltites are sometimes replaced with fine grainstones and packstones. Toward the top of the
Napanee fossils become more abundant and a number of hardground surfaces are often developed.
126 CHAPTER XI
SEQUENCE STRATIGRAPHYOF THE UPPER BLACK RIVER TO LOWER
TRENTON SUCCESSION
Using the correlations between New York State and southwestern Ontario proposed herein, it is possible to also relate these packages within a modern sequence stratigraphic framework. Moreover, by establishing the position of key marker horizons including K- bentonites, these successions might be related on a broader scale to those already established for other regions of eastern North America (e.g. Holland & Patzkowsky, 1996) (see Figure 3).
The following discussion will outline the particular features of each stratigraphic unit that contribute to an understanding of their sequence stratigraphic position. Key marker horizons and sequence boundaries already discussed are integrated into the following discussion in order to delineate each depositional sequence, and its components.
For the upper Black River to lower Trenton groups, two prominent large-scale sequences can be delineated (see Figure 34). The first is composed of the lower Lowville – House Creek –
Glenburnie succession, middle to upper Gull River, Moore Hill, and lower to middle Coboconk formations (Figure 35), and the second of the Watertown – Selby – Napanee, upper Coboconk –
Middle Bobcaygeon formations (Figure 36). Each particular sequence has prominent sequence boundaries, distinguishable maximum flooding surfaces, and well-developed systems tracts.
127 Hounsfield (Millbrig) K-bentonite SB
HST
MFS & MH - K-bentonite
TST
MX K-bentonite
SB
Figure 35: Sequence components for upper Black River sequence for the New York to Ontario region. SB=sequence boundary, HST= highstand systems tract, TST= transgressive systems tract, MFS= maximum flooding surface. SB
HST
MFS
MR-K-bentonite
TST
SB
Figure 36: Sequence components from uppermost Black River to lower Trenton sequence. Herein it is believed that the sequence boundary at the base of this sequence actually should represent the Black River-Trenton Group boundary. SB=sequence boundary, HST= highstand systems tract, TST= transgressive systems tract, MFS= maximum flooding surface. 250 km 200 km 150 km 100 km 50 km 5 km
West 150 miles 100 miles 50 miles 0 miles East Napanee, Ont. Glenn Park, NY. Kings Falls Formation
Cycle8 SB-3 Cycle7 Kirkfield Member Brechin, Ont. (upper Bobcaygeon Fm.) Cycle 6 Cycle 5 ? Cycle 4 ? Napanee Formation Cycle 3 Dalrymple, Ont. Cycle 2 Brownville, NY. Cycle 1 Rte 54 cut. Middle Member Cycle8 MFS-2 (middle Bobcaygeon Fm) ? Cycle7 Cycle 6 Selby Formation Cycle 5 Cycle 4 Lowville, NY. Cycle 3 (Walker, 1973) Kingston, Ont. Coboconk, Ont. Cycle 2 Marmora, Ont. ? Cycle 1 ? Coboconk Member Watertown Formation ? ? (lower Bobcaygeon Fm.) (upper Chaumont Fm.) Cycle 3 Cycle 2 SB-2 Cycle 1 ? Glenburnie Shale Cycle10 ? Cycle9 ? Weaver Road Beds Cycle8 ? Cycle7 Leray limestone Moore Hill Member ? ? Cycle 6 ? ? ? (lower Chaumont Fm.) (upper Gull River Fm.) ? Cycle 5 Cycle 4 ? House Creek Member Cycle 3 Depauville, NY. (Lowville Formation) Cycle 2 ? ? Cycle 1 ? Cycle 6 MFS-1 ? Cycle 5 Middle Member ? (Gull River Fm.) 3 m ? ? Cycle 4 ?
Cycle 3b ? Lower Member (Lowville Fm.) Cycle 3a ? Lower Member Brechin Kirkfield Marmora Kingston Dalrymple Napanee (Gull River Fm.) Coboconk ?
Depauville Cycle 2 ?
Brownville Cycle 1 SB-1 Lowville 80 ° 7 5° Pamelia Formation Marker Horizons Lithology argillaceous mudstone stromatoporoids major flooding surfaces crinoid rich packstone with thin carbonate Stromatocerium sp. interpreted as maximum to grainstone interbeds flooding surfaces dark greyish-blue 45° chert in lenses, nodules micritic lime mudstone shaly nodular carbonate and some layers. sharp facies transition with birdseye fenestrae often stromatolitic large domal Tabulate surfaces often with visible head corals, mostly erosional relief interpreted . coarse crinoidal Foerstephyllum as sequence boundaries laminated dark shale grainstone Ontario Tabulate upright branching coral colonies, multiple K-bentonite correlations species of Tetradium established on the basis bioturbated coral-rich of stratigraphic position K-bentonite seams wackestones Domal to LLH stromatolites New York minor flooding surface calcarous green ostracod rich lime Ostracodes, mostly between the Watertown mudstone with minor mudstone with Leperditid type. and the Selby Formation quartz sand fragmented coral clasts previously viewed as the 80 kms Hardgrounds, Black River-Trenton green quartz grainstone dolomitic lime boundary 50 miles often vertically bored often with conglomerate mudstone base minor flooding surfaces Evaporite mineral crystal correlations are intended buff weathering lath molds to show similarity of pattern bioclastic packstone 40° dolostone across the outcrop belt
Figure 37: Key marker horizons are shown and dashed lines indicate the approximate correlations of small scale cycles (PAC’s?) between outcrop sections. Each cycle is not recognized as a specific cycle but pattern and similarity in sequencing suggests lateral continuity of these horizons. Note that the 6 cycles in the lower Lowville have on the order, 2 times the thickness of the cycles in the Moore Hill/House Creek interval. Assuming all small scale cycles, of which there are 19-20 between the MX and Hounsfield K-bentonite, are of the same temporal scale a simple calculation results in a time averaged cycle duration of approximately 100,000 years per cycle (1.6-2 my between the K-bentonites). A. Sequence 1: Lower Lowville – House Creek – Glenburnie in New York, and equivalent middle to upper Gull River, Moore Hill, and Coboconk sensu stricto in Ontario
The lower Lowville Member is here found to be laterally equivalent in part to the Gull
River Formation (submembers A4 and B1-B2) of the Lake Simcoe region. Collectively these two units show similar changes upward above the basal sequence boundary described previously at the base of the “green marker bed”. The successions show stepwise transgression out of the restricted dolostone-dominated carbonates of the Pamelia/lower Gull River Formation into more intertidal to shallow subtidal laminated and fenestral micrites. Additionally, the Lowville
Formation demonstrates a much wider distribution than the underlying Pamelia Formation and, as noted previously, is exposed from the Mohawk Valley and points east to Lake Simcoe. The presence of successively deeper parasequences, although almost entirely dominated by the decreasing proportion of supratidal dolostones and increased proportion of intertidally deposited fenestral limestones, demonstrate a sequentially rising sea-level. This succession is interpreted as representing the transgressive systems tract (TST) of the first sequence.
The lower Lowville Member reaches its maximum flooding at the top of the “60 cm bed” slightly above the MH K-bentonite. In contrast to the underlying Lowville, the House
Creek/Moore Hill cyclic interval contains between 8 and10 small 0.4 - 0.6 meter cycles also inferred to be parasequences. These cycles are recognized across the entire study region and although they demonstrate slight variations in component facies, the thickness of these cycles is remarkably similar. Each of these cycles are generally homogenized by bioturbation, but each cycle shows a gradual decrease in argillaceous content upward until the position of the Weaver
131 Road beds where the shales and interbedded ribbon limestones show the first signs of desiccation since the Lowville.
As Moore Hill deposition advanced, depositional cycles demonstrate gradual shallowing over time into the facies of the Weaver Road such that large coral colonies present in the lower
Moore Hill are replaced upward by Stromatocerium, ostracod and bivalve associations with smaller more fragmentary Tetradium corals. This successive shallowing is in stark contrast to the lower Lowville that demonstrates the opposite pattern. It is believed that the Moore Hill with its well developed cycles represents the early part of a sea-level high stand event, and their widespread nature demonstrates general stability of conditions across the region.
The Weaver Road interval is a thin interval near the terminus of the Moore Hill, and most likely represents the last two parasequences of the highstand (HST) event producing the Moore
Hill. Intriguingly, in the type section area, the Weaver Road interval is dominated by siliciclastic, dark black calcareous shales interbedded with stromatolitic boundstones and minor stringers of calcareous shale. Without the presence of large domal stromatolites and mudcracked horizons this interval might be considered a rather deepened interval, but as is the case, it is thought that the increased load of siliciclastic input is related to a rapid influx of siliciclastic sediments as a result of either temporary sea-level drop over the region, or progradation of terrestrial derived sediments during the late highstand.
The Weaver Road member is overlain sharply by the grainstone-wackestone couplet, equivalent to the lower and middle Coboconk Member of the Bobcaygeon Formation of Lake
Simcoe. The nature of the Coboconk Member is less well understood, and requires further investigation, however, in the eastern portion of the Lake Simcoe region, the lower Coboconk interval is a thin interval, approximately 1.5 m, of well-developed (almost) biostromal
132 wackestones and interbedded grainstones. This interval of coarse limestones is well developed on the Peterborough Arch, and is less well developed both toward the west (in the Lake Simcoe region) where the interval is represented by interbedded shaly limestones and crinoidal limestones, and toward the east by a single 0.5 m thick bed with a medium grainstone base and a bioturbated wackestone – packstone limestone cap.
The Glenburnie Shale Member of the Gull River Formation is a very interesting horizon, but is poorly understood. The lower contact of the Glenburnie appears to be fairly sharp and most likely represents a flooding surface, that is not everywhere as significant as it is in the eastern portion of the study region. The Hounsfield (Millbrig) K-bentonite sits on this horizon and assists in correlation of this unit across the region.
Collectively, with the underlying grainstone-wackestone couplet of the lower-middle
Coboconk, the Glenburnie with its offshore fauna probably represents a short lived 4th order sequence in its own regard, sandwiched between the other two larger scale 3rd order sequences.
Finally, sequence one is capped by a rather distinctive contact at the base of the
Watertown/upper Coboconk interval, which appears in many instances to truncate underlying units. This particular horizon demonstrates very widespread development and shows evidence in the Mohawk Valley for incisement, and karstification (Cornell and Brett, 2000) such that it probably represents a true sub-aerial exposure surface and sequence boundary. This particular sequence boundary in relation to the Millbrig (or Hounsfield K-bentonite) is equivalent to the
M4-M5 sequence boundary as defined by Holland & Patzkowsky (1996, 1998).
Thus sequence 1 (or sequence M4 in the scheme of Holland & Patzkowsky) has a) a prominent erosional sequence boundary approximately 5’ below the MX K-bentonite, and is defined as the contact between the Pamelia and Lowville Formations in New York
133 classifications. The same sequence boundary appears at the contact of the A3 submember with the overlying A4 submember of the lower Gull River, at the base of the “green marker bed.” b)
The lower Lowville successions appears to deepen upward to a maximum flooding surface at the contact with the overlying House Creek Member, and thus represents the TST of sequence 1. In
Ontario, the Gull River (submembers A4, B1, B2) demonstrates this same deepening and reach a maximum flooding very near the MH K-bentonite. c) The House Creek/Moore Hill components of the sequence demonstrate a back-stepping (or overall shallowing) into the restricted and mudcracked Weaver Road interval as typical of a HST. d) The additional appearance of the lower Coboconk to Glenburnie interval represents a small scale “mini sequence” inserted below the Black River/Trenton sequence boundary, and in part is truncated by the Black River/Trenton
(M4-M5) sequence boundary.
B. Sequence 2: Watertown – Selby – Napanee; in New York, upper Coboconk – Middle
Bobcaygeon Formation in Ontario
With the inclusion of the Watertown Formation, the succession of the lower Trenton
Group may be interpreted as a single genetically related sequence. The basal sequence of the
Trenton Group is herein defined to contain the Watertown, Selby and Napanee formations
(Figure 33). Each in their own right, representing a significant component of a single large scale sea-level oscillation. The nature of this particular sequence is discussed in detail in the section below.
The Watertown sharply overlies sequence 1 (M4 of Holland & Patzkowsky) strata. In most areas the upper shaly portion of the underlying Glenburnie Shale has been truncated and removed, with only the remnants of it preserved as clasts in the basal Watertown. This basal
134 contact represents a significant sea-level drop which resulted in erosional truncation and entrenchment at various places around the New York to Ontario region.
The massive unit overlying the sequence boundary (unit 16 of Okulitch, 1939) is a crinoidal grainstone to packstone unit with abundant Tetradium, Stromatocerium, and occasional chert nodules in the region of Coboconk. In the thousand islands or Kingston region of Ontario, and nearby New York, the equivalent unit is a massive, bioturabated wackestone - packstone, and sometimes cherty facies that was referred to in the past as the upper tier (Cushing et al.,
1910). These beds appear in the type Watertown area and are assigned herein to the Watertown
Formation proper. The Watertown is a more highly compartmentalized succession that demonstrates lagoonal (Adirondack Arch beginning near Boonville, NY) to shoaling facies on the top and flanks of the Peterborough Arch. Undoubtedly the Watertown shows discontinuous facies belts due to incisement during the previous lowstand, and as Watertown deposition went on – continued transgression of sea-level led to the deposition of the Selby Formation.
The Selby Formation is herein used for the more argillaceous, upward extension of the
Watertown Limestone. The change from the Watertown into the Selby is considered to lie at a fairly widespread flooding surface, although not the most maximum flooding surface of this particular sequence. This interval in the Napanee to Kingston, Ontario region reaches its maximum thickness, and is mostly composed of distinctively condensed shaly nodular limestones. An excellently preserved fauna characterizes this interval as belonging to the
Rocklandian Stage (of Kay, 1935), and is distinctive from both the overlying Napanee Formation and the underlying Watertown. It is demonstrably more condensed than the Watertown and shows a lesser degree of bioturbation. These observations help to characterize the Selby as representing a fairly deep-water (although not the deepest) shelf environment. The top of the
135 Selby is recorded by yet another sea-level flooding surface that juxtaposes the even deeper shelf facies of the Napanee on to mid shelf facies, with the contact marked by the MR K-bentonite and representing the MFS of sequence 2. As such the Watertown to Selby succession demonstrates the characteristics of a TST.
The Napanee, which has not been studied in great detail at present, shows a generally upward shallowing pattern, with thicker bundles and more richly fossiliferous limestones towards the top of the succession. In addition smaller scale cycles also appear to be present in the interval.
In the past the Napanee was interpreted as a lagoonal facies by Cameron and Mangion
(1977), however, it appears that this interval carries characteristics of off shore and deep water facies. With an offshore marine fauna, the Napanee is dominated by small brachiopods
(Dalmanella, Sowerbyella), small bryozoans, and fairly diverse trilobite faunas. In addition to the distinctive faunal characteristics of this unit, a number of sedimentological features characterize this unit as being deep water including: a rather significant amount of dark black fossiliferous shales, occassionally well developed HCS- style, crossbedding in the fine grained carbonates, and the lack of bioturbation, and some normally graded beds.
With such features, and characteristics the Napanee appears to have its deepest facies at the base with successively shallower facies toward the top, where they are in turn overlain sharply by yet another sequence boundary and an interval of very shallow grainstones of the
Kings Falls Formation. This thus fits into the sequence framework as the HST.
Thus sequence 2 (M5 of Holland & Patzkowsky, 1996) is also composed of well-defined sequence components. They are as follows: a) The Watertown and Selby formations demonstrate an overall deepening succession – each showing the transition from lagoonal to
136 shoaling facies upward into moderately deep shelf, and hence are interpreted as the TST of sequence 2. b) The MFS of this sequence lies at the contact of the Selby and Napanee
Formation, and can be traced across the study region on the basis of the MR K-bentonite which sits on the sediment starved – and highly condensed flooding surface. c) The Napanee demonstrates a thinning of shale interbeds and increased component of grainstones and packstones upward toward the overlying Kings Falls/Kirkfield limestones, that show winnowing and wave reworking of some shelly organisms – thus the Napanee represents the HST component of sequence 2. d) The final component of sequence 2 is the upper sequence boundary, which lies at the base of the Kings Falls limestone in New York and the Kirkfield
(upper Bobcaygeon Formation) in Lake Simcoe. This contact displays considerable relief across the study region and most likely represents a substantial sub-aerial exposure surface during the lowstand event. The amount of relief represented by this contact in the study area is usually on the order of 0.5 meter, however, in the Mohawk Valley region, the Napanee has been considerably truncated such that only 0.5 m of the strata are left at Middleville, and none of the
Napanee, or underlying Selby is found at Canajoharie.
137 CHAPTER XII
IMPLICATIONS OF REVISED BLACK RIVER TO LOWER TRENTON
STRATIGRAPHY FOR TEMPORAL CORRELATION
An objective redefinition and sequence stratigraphy of the upper Black River-
Trenton in northwestern New York and southern Ontario has important implications for the
North American standard terminology. After all, the terms Black River and Trenton were both derived out of the study region and the vicinity of the Mohawk Valley of New York. The
Rocklandian was named originally for strata that encompassed the Rockland Formation of
Wilson (1946) from the Ottawa lowlands of Ontario. These beds are approximately equivalent to the Selby and Napanee, and portions of the Watertown according to Kay (1935). The overlying Kirkfieldian was derived from the region of Kirkfield, Ontario where strata presently assigned to the upper Bobcaygeon Formation outcrop, and is most likely correlative with the
Hull of the Ottawa region and the Kings Falls Formation of northwestern New York. The
Shermanian Stage formed the upper part of the Mohawkian Series and was established for upper
Trenton Group strata in east central New York State.
The stage nomenclature of the Mohawkian Series has been a subject of debate for the last half century. For example, the term Black River Group and Black Riveran have been used for lithologic terminology and time-rock terms, a practice that was not highly regarded by many workers. So, Fisher (1977) proposed Turinian as a time-rock term for the lower Mohawkian, and allowed the Rocklandian, Kirkfieldian and Shermanian stages of Kay (1935) to stand. However, due to the difficulty of establishing Kay’s stage nomenclature outside of the New York/Ontario region, recent work by Leslie and Bergström (1995a) suggested that a new term be employed for
138 the upper Mowhawkian strata based on the correlation of the Millbrig K-bentonite of the Mid- continent. This new stage, known as the Chatfieldian, ironically, could not be concretely applied in the type sections for this series. However, the recent work by Adhya et al. (2000) suggests that the Millbrig is present in the study region and is equivalent to the Hounsfield K-bentonite. If this is the case, this helps to establish the Chatfieldian Stage within this region. Despite the establishment of the Chatfieldian Stage by Leslie and Bergström (1995), a number of workers still prefer to use the stage nomenclature of Kay, and when considered in light of recent discoveries, including those herein, perhaps their recognition in eastern Midcontinent regions is possible.
A second important means of subdividing the late Middle Ordovician into chronostratigraphic units is the system of sequences devised by Holland and Patzkowsky (1996,
1998). This partitioning is based upon the identification of prominent erosional unconformities, flooding surfaces and depositional systems tracts as recognized widely in the Appalachian Basin,
Cincinnati Arch, and Nashville Dome areas. At present, Holland and Patzkowsky recognize 6 depositional sequences within the Mohawkian, three in the Turinian (M1-M3) and three within the later Mohawkian, approximately equal to the Chatfieldian (see Figure 3).
As discussed previously, substantial evidence suggests that the two sequences delineated in New York/ Ontario are similar and equivalent in both timing and scale to two of those recognized by Holland and Patzkowsky (1996, 1998) (Figure 37). With these assessments made, and upon comparing these newly defined sequences of New York/Ontario, with the appropriate biostratigraphic stage names as applied by Kay to these rocks, an interesting dichotomy is observed. That is, in New York/Ontario, the lower sequence (sequence 1) of New York/Ontario consists of the Lowville – Glenburnie. It thus contains both the Deicke(?) and the Millbrig K-
139 bentonites, and by comparison with Holland & Patzkowsky, this should be their M4 (which they considered to be Rocklandian). The upper sequence, the Watertown-Selby-Napanee, physically defined makes up the majority of the Rocklandian Stage, and lies above the M4 sequence, established assuming the correlation of the Millbrig and Hounsfield K-bentonites is correct.
Thus, the M4 of Holland and Patzkowsky should not be equated with the Rocklandian Stage as defined in New York/Ontario, but instead with the Turinian (or, in their scheme, the Black
Riveran). By default, the M5 which these authors assign as Kirkfieldian and Shermanian, is also not in agreement with the New York/Ontario sections.
While the purpose of this paper is not to establish such widespread correlations, some problems associated with these correlations can be summarized. Firstly, the assertion that the
Millbrig is present in New York establishes the position of the M4 sequence in New
York/Ontario, where the sequence is not equivalent to Rocklandian strata but lies within the classic Black Riveran. Secondly, the next overlying sequence, the M5, is described as
Kirkfieldian to Shermanian by Holland and Patzkowsky (1998). If it correlates with the
Watertown – Napanee interval, as is suspected, then it is actually of Rocklandian age. However, if this cycle contains true Kirkfieldian to Shermanian faunas, then either another sequence containing the true Rocklandian sequence is absent by unconformity in the southern United
States, or the faunas delineating the Kirkfieldian-Shermanian stages demonstrate a much older first appearance in the south than is represented in classic New York/Ontario sections. In other words, at least some supposedly diagnostic Kirkfieldian and Shermainian species would actually appear in Rocklandian age sequence M5.
The implications then of these new observations can be summarized as follows. The bentonites in New York/Ontario, known as the MX, MH, and Hounsfield (Millbrig) are all
140 assignable to the upper portion of the Black River Group and thus are consistently within the
Turinian Stage (Blackriveran) in its type area, at least being assignable to the beds immediately underlying the Millbrig bentonite. Holland and Patzkowsky’s (1996, 1998) sequence M4 coincides approximately with the interval encompassed between the MX and Hounsfield
(Deicke and Millbrig) in New York/Ontario, and thus sequence M4 lies almost entirely within the Turinian, and not within the Chatfieldian (Rocklandian) as shown on most of Holland and
Patzkowsky’s recent charts. The critical M4-M5 sequence boundary lies close to, but slightly above the Turinian/Chatfieldian stage boundary except in central New York where the Millbrig is removed by the sequence boundary as defined by Leslie and Bergström in the eastern midcontinent. Holland and Patzkosky’s M5 sequence and their critical faunal change (M4-M5) sequence boundary lie within the classic Rocklandian and not within the Kirkfieldian stage.
141 CHAPTER XIII
SEQUENCE COMPARISONS WITH EQUIVALENT STRATA IN THE NASHVILLE
DOME, SOUTHERN APPALACHIANS AND CINCINNATI ARCH
As a result of this study, the Black River Group and lower Trenton Group as exposed in
northern New York State have been subdivided into two separate 3rd order sequences. These
sequences are superimposed upon a larger 2nd order sea-level rise event known as the Tippecanoe
Megasequence (Sloss, 1968). These sequences are equivalent to those recognized in the
Nashville Dome and Cincinnati Arch by Holland and Patzkowsky (1998). Based on the correlation of the Millbrig K-bentonite and tentatively on the basis of the Deicke K-bentonite, the lower sequence (lower Lowville-Moore Hill-Glenburnie) corresponds to their M4, and by extrapolation the other (Watertown-Selby-Napanee) is the M5 sequence.
Even though the Deicke and Millbrig K-bentonites constrain the correlation of the M4 of the Nashville Dome to sequence 1 of New York and Ontario sections, it is herein noted that there are remarkable similarities (as well as some differences) between these sequences from
Ontario/New York and those of Tennessee. Holland and Patzkowsky (1998) describe the nature of these Mohawkian sequences (with approximate durations of 1-3 my) with TST and HST components only. Furthermore, the sequences these authors describe are on the same order of thickness and have similarly styled sequence boundaries.
In the Frankfort, Kentucky area along the Cincinnati Arch and Jessamine Dome, sequence 4 as recognized by Holland & Patzkowsky comprises the Tyrone Formation. This consists of pale gray, fenestral micrites that is nearly identical to the lower Lowville of sequence
4 in New York State. A bright green shale and the Deicke K-bentonite near the base appear to
142 correspond to the green shale marker bed and the MX K-bentonite in New York. About midway through the interval a smaller yellowish K-bentonite, presently unnamed in Kentucky, appears to correspond to the MH K-bentonite of Lake Simcoe, Ontario. About 0.4 to 0.5 m above this position is a sharp change to Tetradium-rich, biotubated limestone that corresponds to the House
Creek/Moore Hill of NY/Ontario. The upper portion of this succession including the Millbrig
(Mud Cave) K-bentonite is locally truncated by a sharp erosive surface; Holland & Patzkowsky’s
M4-M5 sequence boundary.
The overlying M5 consists of a massive crinoidal pack- grainstone locally containing stromatoporoids and Tetradium known as the Curdsville limestone of the Lexington Formation.
Lithologically this interval is very similar to the Watertown-Selby interval in New York. An abrupt contact separates this unit from the overlying Loganna Member. This unit consists of dark brownish gray shales and interbedded calcisiltites, virtually identical to the Napanee. This is consistent with some other lines of evidence, such as the presence of Dalmanella rogata, and
Sowerbyella curdsvillensis in the Curdsville and Loganna formations, which appear to be correlative respectively with the Watertown, Selby and Napanee formations of the classic New
York/Ontario Rocklandian
In their work, Holland and Patzkowsky (1996, 1998) have established the presence of the
Deicke and Millbrig K-bentonites within their M4 sequence. The definitive presence of the
Millbrig (in the top of the upper Black River sequence of New York/Ontario), and the inferred position of the Deicke near the base of the Lowville Formation allows fairly secure one for one matching of the sequences. In the Nashville Dome, for instance, Holland and Patzkowsky
(1998) describe the systems tracts of the M4, or Carters Limestone, to be as follows: TST:
“retrograding from peritidal parasequences into highly bioturbated shallow subtidal facies”;
143 MFS: indistinct; and the HST as a “thick zone of aggradationally stacked bioturbated shallow subtidal parasequences, eventually passing upwards into parasequences with peritidal caps.” As noted previously, the sequence represented by the Lowville-House Creek- Coboconk-Glenburnie interval shows remarkably, almost this exact same pattern of facies modifications.
As for the M5 sequence of Holland and Patzkowsky, the Hermitage, Bigby-Cannon interval of Tennessee, again, shows similar patterns to the Watertown, Selby and Napanee associations of the New York/Ontario region. Shallow water lagoonal limestones of the
Watertown are missing in the region of Tennessee, yet are replaced by successively deepening hummocky siltstone facies which grade (deepen) upward into more shaly and calcisilt dominated strata of the Bigby-Cannon (= to Napanee Formation of New York). These intervals are remarkably similar (also to the Logana of Kentucky as well). The sequence boundary of the M5 sequence is described as being nearly planar with up to 7 m of regional relief, with an overlying coarse sand bed. Interestingly, the nature of this horizon most nearly matches the definition of the Gull River/Watertown Formation sequence boundary, and is in the right position with respect to the M4-M5 sequence boundary. With these similarities established, there appears to be some inherent problems with the direct correlation of the New York Sequences with those of the
Nashville Dome. However, because of the distinct similarities in facies patterns, it is believed that these “inherent problems” are most likely due to an error in the table produced for the
Holland and Patzkowsky (1998) publication. It is not believed, however, that these errata are based on the outcrop data although this is not confirmed.
144 CONCLUSIONS
The purposes of this research as stated previously were: 1) to describe the physical stratigraphy and correlatable horizons of the upper Black River and lower Trenton groups in the type area and adjacent Ontario; 2) to identify and physically correlate K-bentonites and other unique marker beds; 3) to establish a framework of regional tie-lines for correlation of upper
Black River – Trenton from NY to Lake Simcoe, Ontario; 4) to provide objective criteria for defining the Black River/Trenton Group lithostratigraphic boundary in this region; 5) to determine if depositional sequences, systems tracts, and small-scale parasequences (or PACs) are correlatable across the New York-Ontario region; 6) to identify the positions of Holland and
Patzkowsky’s (1996) sequences and their component systems tracts; 7) and to briefly compare the New York-Ontario successions with those of other areas.
In conclusion, it is documented herein that the Black River to lower Trenton units can be consistently recognized and correlated across the outcrop belt from Lake Simcoe to northern
New York State. Decades of previous work by a number of geologists have provided a substantial sedimentologic and stratigraphic literature that has been referenced herein. The detailed work of many of these early workers provided a basic understanding of the stratigraphy and sedimentology for given sections across the study region. From this foundation work, detailed high-resolution stratigraphic mapping has enabled the construction of a regional cross- section across the study area. A significant number of marker horizons have been identified for correlation in the construction of a two-dimensional stratigraphic model for the upper Black
River to lower Trenton interval, a task that was not previously deemed possible.
145 As mentioned above, a number of horizons have been used to help establish correlations across the study region. In particular K-bentonites, were expressly considered for their potential use in fingerprinted correlation, however, the K-bentonite correlations established herein are based mainly on their sequencing within the strata, and general lithologic appearance. With respect to chemical analyses of volcanogenic phenocrysts, more work is needed to help substantiate and or test the lithostratigraphic based correlations established here.
Interestingly, a number of other unique intervals were also identified and utilized in correlation from outcrop to outcrop. These unique correlation horizons helped to establish a lithologically based set of correlations for the upper Black River to lower Trenton interval. As such, these intervals, combined with K-bentonites, helped to not only establish correlations, but also enabled the testing of notions of synchroneity/diachroneity of these rocks across the region.
It appears from these correlations that most lithologic change was fairly synchronous and fairly widespread across the study region – suggesting a more external mechanism for change.
Now that this uniform stratigraphy is established, these strata suggest that it is possible to delineate two separate depositional sequences (at least 3rd order) for the upper Black River to lower Trenton interval. In addition, these sequences can be divided into well-defined sequence components or systems tracts bounded by erosional sequence boundaries. These sequences show consistently well-developed retrogradational (TST) packages overlain by well-defined flooding surfaces and aggradational (HST) packages. Moreover, these depositional sequences also demonstrate a series of high-order, internally consistent parasequence-scale packages that presumably indicate Milankovitch-band sea-level fluctuations. The remarkable similarity of these units across the study region can be demonstrated and again suggest they are isochronous rather than diachronous in this limited region.
146 Also of significance with respect to this work is the elucidation of a new critical erosional unconformity between the two depositional sequences discussed above. Historically, the position of the Black River-Trenton boundary has been debated many times in the past with little satisfactory resolution. As discussed, a number of critical observations are made that support an objective re-definition of the Black River-Trenton boundary at the base of the Watertown
Formation.
Therefore, the ability to recognize such well-defined and consistent chronostratigraphically based sequences across the study region, with an outcrop distance of
>250 km, suggests that the processes responsible for producing these patterns must be largely allocyclic in nature. This has led to the comparison of these sequences with those recognized in this same time interval elsewhere in the southeastern United States by Holland and Patzkowsky
(1996, 1998). Based on the position of the widespread Deicke and Millbrig K-bentonites, herein believed to be equivalent to the MX and Hounsfield K-bentonites, the study region can be related, and appear to be relatively synchronous with, the M4 and M5 sequences recognized by
Holland and Patzkowsky (1998). Futhermore, if these correlations are accurate, and the position of the Millbrig and Deicke can be substantiated more securely in New York/Ontario, then this work represents a substantial contribution in support of a revision of the Mohawkian stage nomenclature for eastern North America.
While future work must effectively test for the same sea-level fluctuation signal during this critical time in other regions of the world, this research strongly supports a global eustatic fluctuation that was effective in controlling the deposition and redistribution of sediments in time periods of between 1 and 3 million years duration. Furthermore, as suggested by the westward shifting of depocenters for the upper Black River and lower Trenton sequences, perhaps some
147 tectonic signal can be elucidated suggesting minor flexure of the passive margin during the onset of Taconic collision.
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