EXAMPLES OF FIELD PROJECT ASSIGNMENTS

IN SEDIMENTARY GEOLOGY AT SUNY ONEONTA

 

James R. Ebert

Earth Sciences Department

SUNY College at Oneonta

Oneonta, New York 13820-4015

(607) 436-3065; Ebertjr@oneonta.edu

 

1992

A) Anatomy of an Unconformity

B) Microstratigraphic Correlation of Closely Spaced Outcrops and K-Bentonites

1997

Facies Change or Unconformity?

1999

Ripples in the Howe Cave Quarry

2001

Contacts and Correlation of upper Helderberg formations from Schoharie to Sharon Springs

2003

Microstratigraphy and Depositional Environments of the Manlius Formation in the Howe Cave Quarry

2005

Depositional Environments and Stratigraphic Markers in the Lower Helderberg Group ♦ ♦

NOTE: Sections under these headings are the actual assignment sheets given to the students. Lists of references originally accompanied these assignment sheets, but in the interest of conserving space, they have been omitted.

= Presented at Northeast GSA. Reference to abstract follows project description.

 

 

1992 A: ANATOMY OF AN UNCONFORMITY

 

INTRODUCTION

 

             Without question, the most significant geologic boundary in central New York is the Devonian - Pleistocene unconformity. Approximately 380 to 400 million years are missing at this surface. This includes: parts of the Devonian Period, the Carboniferous and Permian periods, the entire Mesozoic Era and, most of the Cenozoic Era. Erosion along this surface began sometime in the late Paleozoic or early Mesozoic and continued through much of the Pleistocene Epoch. The majority of this erosion was from fluvial and mass wasting processes that included the continued destruction of the Acadian Orogen and subsequent dissection of parts of the Catskill Clastic Wedge. During the Pleistocene glaciations, glacial scour was added to these erosional processes.

 

            Following glacial erosion, the surface was buried beneath glacial and glacio-fluvial and glacio-lacustrine sediments. It is likely that some of these sediments were removed and additional erosion took place during multiple glacial advances. The final glaciation blanketed the unconformity surface with a thin to absent veneer of sediments in upland regions and along valley walls and a much thicker accumulation in valleys. Clearly, there is a great deal of relief on this unconformity surface. Although the general geometry of the unconformity is known (to some extent it mirrors present topography), specific details are sparse because the surface is buried beneath Pleistocene and Holocene sediments.

 

DEVONIAN - PLEISTOCENE UNCONFORMITY IN THE ONEONTA AREA

 

            On the east end of Oneonta, Devonian bedrock is dramatically exposed in the faceted spur that is opposite the entrance to the Pyramid Mall. Indeed, this mall takes its name from the rock exposure: Pyramid Rocks. Less than one kilometer west of Pyramid Rocks, Devonian rocks are also clearly exposed in Glenwood Creek. It seems likely that little erosion of the bedrock has taken place since the last glacial retreat, some 10,000 years ago. If we accept this simple assumption, the present topography north of Route 7 and east of Glenwood Creek approximates the unconformity surface.

 

            South of Route 7, the geometry of the unconformity is much less clear. In Neahwa Park, several kilometers west of the study area, a well was drilled that encountered bedrock at a depth of 400 feet beneath the present valley floor. Closer to the proposed study area (Fig.1), Cohen (1991) conducted a gravity survey which placed bedrock at 350 to 378 feet beneath the surface in a traverse along East End Avenue (Figs 2,3). Whereas Cohen's data is accurate, his correction factors are in error and bedrock may, in fact, be considerably shallower (Kucewicz, personal communication; Palmer, personal communication, 1992).

 

            During the summer of 1991, John Kucewicz and associates conducted resistivity and seismic studies near our proposed study area. The results of these studies (Kucewicz, 1992) suggest that the depth to bedrock is much shallower than indicated by Cohen (1991) immediately south of Route 7 and that it may even be expressed topographically in the form of a terrace-like feature on the wall of the valley and perhaps in the form of sinuous ridges on the south side of this terrace-like feature. Conventional interpretations of these landforms ascribe a glacial origin and imply that bedrock is hundreds of feet below the surface.

 

FIELD METHODS AND DATA COLLECTION

 

            Over the next several weeks, we will conduct various geophysical surveys in the field area in an attempt to discern the geometry of the Devonian - Pleistocene unconformity. Gravimetric and seismic surveys will be the primary tools that we will use. Surveying techniques will also be employed to accurately locate data points and to enable formulation of various correction factors, particularly for the gravimetric survey. Results of the gravimetric survey will be directly comparable to the results of Cohen (1991) if we can accurately tie our base station to his.

 

            If time permits, we will also attempt a resistivity survey which will allow us to compare directly to the work of Kucewicz (1992) in adjacent areas. Following collection and analysis of geophysical data, we will also examine samples from a well drilled within the study area and use this data as a test on the accuracy of our geophysical data.

 

            The compilation of geophysical data, well data and perhaps data from Cohen (1991) and Kucewicz (1992) will provide the basis for interpretation of the geometry of the unconformity in the study area. We will also discuss processes responsible for this geometry if the data is sufficiently intriguing. A final report comprising all raw and corrected data, cross sections, maps and narrative will serve as the basis for evaluation of this project. If the results warrant, we will prepare an abstract for submission to the Northeastern Section of the Geological Society of America. The abstract deadline is November 24 and the meeting will be held March 22 - 24, 1993 in Burlington, Vermont.

 

NOTE: This project resulted in an oral presentation at a Northeast GSA Conference. Undergraduate co-authors are underlined and boldfaced.

 

Kucewicz, J., Jr., Ebert, J., Rasquin, C., Sherman, R., Nethaway, R., Gardner, J., Milunich, K., Weber, J., Wohlford, T., Franz, J., Brillon, S.,1993, Unusual Configuration of the Devonian-Pleistocene Unconformity in the Susquehanna Valley, Oneonta, New York: Evidence for a Subglacial Meltwater Inlet to Glacial Lake Otego: Geological Society of America, Abstracts with Programs, v. 25, no. 2, p. 65.

 

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1992 B: MICROSTRATIGRAPHIC CORRELATION OF CLOSELY SPACED OUTCROPS AND K-BENTONITES

 

Recent studies have documented multiple K-bentonite beds in the Kalkberg Formation (Helderberg Group, Lower Devonian) at Cherry Valley, New York. Smith, Berkheiser and Way (1988) report three K-bentonites, in comparison to the one originally recognized by Rickard (1962). They correlate these to the Bald Hill Bentonites of the Corriganville and Mandata formations in Pennsylvania, Maryland and West Virginia. Six (currently 7) K-bentonites were recognized by Ebert, Applebaum and Finlayson (1992) which were tentatively correlated to the New Scotland Formation at Schoharie, New York.

 

Lower Helderberg strata are exposed in a series of roadcuts along U.S. Route 20 and Sprout Brook Road, north of the village of Cherry Valley (see also Liebe and Grasso, 1990; and Gurney and Friedman, 1986). The K-bentonites of Ebert, et. al. (1992) occur in two nearly continuous outcrops along Rt. 20. A smaller, as yet unmeasured, outcrop on Sprout Brook Road may contain these or additional K-bentonites. Detailed measurement of these exposures and lithostratigraphic correlation will be undertaken in this project to determine if the strata exposed on Sprout Brook Road repeat the section on Rt. 20 or represent another stratigraphic interval which may contain previously unreported K-bentonites.

 

Reporting and Evaluation: The compilation of measured sections and their correlation will constitute the final report for Project 2. A brief one to two page paper which discusses the correlation should also be included.

 

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1997: FACIES CHANGE OR UNCONFORMITY?

 

INTRODUCTION

 

For decades, the Devonian strata of New York have served as the standard reference section for the Devonian System in North America. A list of geologists that have studied these rocks reads like a Who's Who of North American geology and would include such names as: James Hall, Amadeus Grabau, G.H. Chadwick, Carl Schuchert, Ebenezer Emmons, Lardner Vanuxem, Rudolph Reudemann, G.A. Cooper, Winifred Goldring and many others. Despite this illustrious history, many aspects of these rocks are still poorly understood.

 

Prominent exposures of Lower and Middle Devonian rocks occur across much of east central New York along the Helderberg escarpment. These exposures are typified by the large road cuts located at Cherry Valley. Although the rocks exposed at these locations have long been described, mapped, correlated and classified, some nagging problems of detail remain across this area.

 

For the next several weeks, we will be measuring stratigraphic sections at Cherry Valley and other locations in order to address some of these problems of detail. In particular, we will attempt to describe and interpret the nature of the contact between the Manlius Formation (various members) and the Coeymans Formation (Ravena, Dayville and Deansboro members). Although there was considerable debate in the first half of this century as to the nature of this contact, it has been interpreted as a gradational facies change since the seminal work of Rickard (1962). Subsequent interpretations (e.g. Laporte, 1967; 1969) of Helderberg paleoenvironments have been predicated on this interpretation and have become textbook examples of transgressive carbonate sequences.

 

ASSIGNMENT

 

Working in small teams, you will measure the stratigraphic sections at Cherry Valley and one or more additional sections, paying particular attention to the nature of contacts between units.

 

Although field measurements and observations will be garnered as teams, each of you will be responsible for submitting correlations and reports as individuals. Measured sections should include descriptions of: lithology, texture, sedimentary structures, biogenic structures, fossils, bedding thickness and geometry, prominent lithologic breaks and designations of stratigraphic units of formational or smaller rank. Your data for each location should be summarized in the form of neatly drafted columnar sections at a vertical scale of 1:50, that is, one centimeter on the paper will represent 50 centimeters of outcrop. Lithologies should be indicated by standard symbols.

 

Once the sections are drafted, you will prepare a correlation of the sections. The columns should be spaced proportionately to their actual geographic distance. Note that horizontal scale need not have any direct relationship to the vertical scale of the columns.

 

A brief written report should also accompany your correlation. Reports should include a description of the stratigraphic changes between sections, a section that focuses specifically on the nature of contacts between units and a discussion of any difficulties encountered in correlation and interpretations of the geologic history that is recorded at and between these sections.

 

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1999: RIPPLES IN THE HOWE CAVE QUARRY

 

FIELD PROJECT: Depositional Processes in the Thacher Member of the Manlius Formation (Helderberg Group, Upper Silurian – Lower Devonian) in the Howe Cave Quarry

 

            The Siluro-Devonian Helderberg Group (Přídolí – Lochkovian) has been widely cited as an archetype for Paleozoic carbonate sequences (e.g., Laporte, 1967, 1969) and deposition in epeiric seas (e.g., Prothero, 1990). Despite this illustrious history, there are many questions that remain unanswered from this fascinating interval. Current research by Ebert and Matteson (in progress) is indicating that there may be a need to revise the classic stratigraphic framework of Rickard (1962). Because this stratigraphic reconstruction laid the groundwork for Laporte’s (1969) interpretations of depositional environments of the lower Helderberg Group and the Manlius Formation in particular (Laporte, 1967), opportunities may exist to further refine Laporte’s interpretations in a new context.

 

            The inactive Howe Cave Quarry, located near Cobleskill, New York exposes most of the Thacher Member of the Manlius Formation, all of the Coeymans Formation and a small portion of the Kalkberg Formation near the top of the quarry’s highwall. Although the walls of this quarry are nearly vertical, they are accessible in parts of the quarry where debris is piled near the highwall. In addition to this marvelous exposure, one of the most unique features of the quarry is the extensive exposure of bedding planes in the quarry floor. Such extensive outcrops of bedding planes are most rare in natural outcrops. Therefore, the Howe Cave Quarry provides an unparalleled opportunity to examine sedimentary structures over a wide area (approximately 90,000 square meters!).

 

            For the next couple of months, we will conduct field studies in the Howe Cave Quarry with special emphasis on the Thacher Member of the Manlius Formation. After one or two weeks of making preliminary observations and formulating questions based on these observations, we will define research projects that will attempt to answer some of these questions. As you are formulating your questions, try to think of what types of data must be collected to address these questions. Our focus will be on sedimentary processes and depositional conditions, so you should pay particular attention to sedimentary structures. However, don’t discount the significance of lithology, lithologic changes and the fossils in the outcrop.

 

            Presentation of the results of your investigations will be in the form of a written report which details your descriptions and interpretations. You will share a brief summary of your report with the rest of the class and we will discuss your results. Be prepared to defend your interpretations!

 

Depending on the outcomes (if any!) of your projects, we may prepare one or more abstracts to submit for presentation at the annual meeting of the Northeast Section of the Geological Society of America. The abstract deadline is near the end of the semester, but the conference is in the spring (mid-March). Because GSA is in the semester that follows completion of this course, participation in any GSA-related activities (abstract submission, preparation of poster or PowerPoint for talk and presentation at the conference) will be strictly voluntary. Please keep in mind that your project may be worthy of publication so you should strive for excellence and thoroughness!

 

NOTE: This class project resulted in presentation at the 2000 Northeast GSA conference with all students in the class as co-authors on the abstract (student names are boldfaced).

 

Ebert, J.R., Deats, M.D., Chartier, M.G., Houston, S.D., McDaniel, B.L. and Miller, Z.D., 2000, Orientation of ripple crests and early cementation in the ribbon facies (intertidal) of the Thacher Member (Manlius Formation, Helderberg Group) in the Howe Cave Quarry: Geological Society of America Abstracts with Programs, v. 32, no. 1, p. A-15.

 

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2001: CONTACTS AND CORRELATION OF UPPER HELDERBERG FORMATIONS FROM SCHOHARIE TO SHARON SPRINGS

 

INTRODUCTION

 

            The Siluro-Devonian Helderberg Group (Přídolí – Lochkovian) has been widely cited as an archetype for Paleozoic carbonate sequences (e.g., Laporte, 1967, 1969) and deposition in epeiric seas (e.g., Prothero, 1990). Despite this illustrious history, there are many questions that remain unanswered from this fascinating interval. Recent stratigraphic work in the lower Helderberg Group (Ebert and Matteson, 2001a,b) has called into question the traditional stratigraphic framework of Rickard (1962) which served as a central foundation for Laporte’s (1969) interpretations of depositional environments. The work of Ebert and Matteson suggests that contacts between stratigraphic units are unconformable rather than gradational changes of facies as Rickard suggested. If these recent stratigraphic reinterpretations are correct, then a need exists to re-examine all stratigraphic relationships in the Helderberg Group.

 

            The Becraft Formation, a coarse crinoidal grainstone in the upper Helderberg Group, is one of the most distinctive units within the group (Ebert, 1983, 1987). The Becraft is well exposed in two large road cuts on opposite sides of Rickard Hill Road near the village of Schoharie. Immediately underlying this unit is an extremely fossiliferous unit which Rickard assigned to the Kalkberg Formation, despite the fact that the usually superjacent New Scotland Formation occurs below this unit. We will examine these units at Rickard Hill Road with special attention to the contacts between units in an attempt to evaluate the competing hypotheses of gradational vs. unconformable contacts. To further test these hypotheses, we will also examine an outcrop which should display similar stratigraphy along U.S. Rt. 20 near Sharon Springs, New York. In order to accomplish this testing, you should pay special attention to any distinctive sub-units or beds which we may be able to correlate between outcrops and which could serve as reference horizons to determine changes in the positions of contacts.

 

            Results from your field investigation may be supplemented by analysis of samples collected from the outcrops. If samples require processing (e.g., cutting, polishing, making thin sections, etc.), I will assist you in this preparation and in the laboratory examination of your samples.

 

            Presentation of the results of your investigations will be in the form of a correlation of the measured sections of the two outcrops. This correlation will be accompanied by a written report which details your descriptions and interpretations. Depending on the originality of your results and the strength of the data supporting your interpretations, we may prepare abstracts to submit for presentation at the annual meeting of the Northeast Section of the Geological Society of America. Because GSA meets in March, well after the end of this course, participation in any GSA-related activities (abstract submission, preparation of poster or talk and presentation at the conference) will be strictly voluntary. Your projects may culminate in publication and presentation, so you should set and maintain the highest standards for your work!

 

NOTE: Although this project did not result in publication, it did discover a new K-bentonite at the contact between two sub-units of the Becraft Formation.

 

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2003 – MICROSTRATIGRAPHY AND DEPOSITIONAL ENVIRONMENTS OF THE MANLIUS FORMATION IN THE HOWE CAVE QUARRY

 

FIELD PROJECT: Microstratigraphy and Depositional Environments of the Manlius Formation (Helderberg Group, Upper Silurian – Lower Devonian) in the Howe Cave Quarry

 

            The Siluro-Devonian Helderberg Group (Přídolí – Lochkovian) has been widely cited as an archetype for Paleozoic carbonate sequences (e.g., Laporte, 1967, 1969) and deposition in epeiric seas (e.g., Prothero, 1990). Despite this illustrious history, there are many questions that remain unanswered from this fascinating interval. Recent studies by Ebert and Matteson (2003a, b) has proposed a significant revision to the classic stratigraphic framework of Rickard (1962). Because Rickard’s reconstruction laid the groundwork for Laporte’s (1969) interpretations of depositional environments of the lower Helderberg Group and the Manlius Formation in particular (Laporte, 1967), opportunities may exist to further refine Laporte’s interpretations in a new context.

 

            The inactive Howe Cave Quarry, located near Cobleskill, New York exposes most of the Thacher Member of the Manlius Formation, all of the Coeymans Formation and a small portion of the Kalkberg Formation near the top of the quarry’s highwall. Although the walls of this quarry are nearly vertical, they are accessible in parts of the quarry where debris is piled near the highwall. The Sedimentary Geology class of 1999 studied the bedding planes exposed in the floor of this quarry and, in the process, shed some new light on depositional processes in the Manlius Formation (Ebert, et. al., 2000). We will attempt to extend this study by focusing on the stratigraphic section that is exposed in the quarry walls.

 

            For the next couple of months, we will conduct field studies in the Howe Cave Quarry with special emphasis on the Thacher Member of the Manlius Formation. Our focus will be on sedimentary processes and depositional conditions, so you should pay particular attention to sedimentary structures, lithology and the types and distribution of fossils in the Thacher. Results from your field investigation may be supplemented by analysis of samples that you collect. You will be instructed in the preparation of polished and/or etched slabs and thin sections as the need arises. Also, you will be guided in observation of these prepared samples with binocular and petrographic microscopes to supplement your field observations.

 

            Presentation of the results of your investigations will be in the form of a neatly drafted stratigraphic column with an accompanying written report which details your descriptions and interpretations. You will share a brief summary of your report with the rest of the class and we will discuss your results. Be prepared to defend your interpretations!

 

Depending on the outcomes (if any!) of your projects, we may prepare one or more abstracts to submit for presentation at the annual meeting of the Northeast Section of the Geological Society of America. The abstract deadline is near the end of the semester, but the conference is in the spring (mid-March). Because GSA is in the semester that follows completion of this course, participation in any GSA-related activities (abstract submission, preparation of poster or PowerPoint for talk and presentation at the conference) will be strictly voluntary. Please keep in mind that your project may be worthy of publication so you should strive for excellence and thoroughness!

 

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2005: DEPOSITIONAL ENVIRONMENTS AND STRATIGRAPHIC MARKERS IN THE LOWER HELDERBERG GROUP

 

FIELD PROJECT: Depositional Environments and Stratigraphic Markers in the Lower Helderberg Group

 

            The Siluro-Devonian Helderberg Group (Přídolí – Lochkovian) has been widely cited as an archetype for Paleozoic carbonate sequences (e.g., Laporte, 1967, 1969) and deposition in epeiric seas (e.g., Prothero, 1990). Despite this illustrious history, there are many questions that remain unanswered from this fascinating interval. Recent stratigraphic work (Ebert and Matteson, 2003a,b; 2005) has called into question the traditional stratigraphic framework of Rickard (1962) which served as a central foundation for Laporte’s (1969) interpretations of depositional environments. If the recent stratigraphic reinterpretations are correct, then perhaps the time is also ripe to re-examine the sedimentology of these classic stratigraphic units.

 

            Several large road cuts on Interstate 88 just west of the Schoharie exit expose, almost completely, all the units of the Helderberg Group that are present in the Schoharie and Cobleskill valleys. The easternmost outcrop will be the focus of our investigations. This road cut exposes the Upper Silurian Brayman Shale at its base. The Brayman is disconformably overlain by the Cobleskill Limestone, which is, in turn, overlain by the Rondout Formation. Two distinctly different members of the Manlius Formation follow: The Rondout is overlain by the Thacher Member of the Manlius Formation which is succeeded by the Green Vedder Member (informal). The Green Vedder is bounded below by the Clockville Unconformity and is truncated above by the Terrace Mountain Unconformity. The Dayville Member of the Coeymans Formation overlies the Terrace Mountain Unconformity and is truncated above by the Howe Cave Unconformity. The highest unit in the outcrop is the remainder of the Coeymans Formation, which is mapped as Ravena Member, but may also include parts of the Deansboro Member. Other road cuts along I-88 expose the younger Kalkberg, New Scotland and Becraft formations of the middle and upper Helderberg Group. The Becraft is cut by the widespread Wallbridge Unconformity and is overlain by the Oriskany Sandstone and other units of the Tristates Group.

 

            For the next couple of months, we will conduct field studies at the I-88 east outcrop through the courtesy of the New York State Department of Transportation, from whom I have obtained a work permit to allow us to work along the interstate. You will be divided into teams of two, with three teams investigating the Thacher Member of the Manlius Formation and two teams examining the Coeymans Formation. You are to observe and record (via a graphic measured section) lithologies, sedimentary structures, biogenic structures, fossils, unique taphonomic occurrences and any other features that will assist you in interpreting the depositional processes and environments that are recorded by these units. In addition, you should also be on the lookout for any distinctive sub-units which may aid in regional correlation. Likewise, you should pay particular attention to contacts between major stratigraphic units and between any sub-units that you identify.

 

            Results from your field investigation may be supplemented by analysis of samples collected from the outcrop. You will be instructed in the preparation of polished and/or etched slabs and thin sections as the need arises. Also, you will be guided in observation of these prepared samples with binocular and petrographic microscopes to supplement your field observations.

 

            Presentation of the results of your investigations will be in the form of a written report which details your descriptions and interpretations and in a poster which will be shared with the class in an informal ‘poster session.’ Please note that if the results of your investigations are of sufficient merit, we may prepare abstracts to submit for presentation at the annual meeting of the Northeast Section of the Geological Society of America. The deadline for abstract submission is December 13, one day before our final exam/meeting. Northeast GSA meets in March in Camp Hill, Pennsylvania. Because this is clearly after the end of this course, participation in any GSA-related activities (abstract submission, preparation of poster or PowerPoint for talk and presentation at the conference) will be strictly voluntary. Because these projects may culminate in publication and presentation, you should set and maintain the highest standards for your work!

 

NOTE: This class project resulted in two poster presentations at the 2006 Northeast GSA conference with all students in the class as co-authors on the abstracts (student names are boldfaced). JPEG versions of the posters are available in a supplementary file.

 

Ebert, J.R., Miller, J., Nierenberg, D., Wilson, R., Weeks, B. and Matteson, D.K., 2006, Stratigraphic and sedimentologic insights from Schoharie, NY: Coeymans Formation (Lower Lochkovian, Helderberg Group): GSA Abstracts with Programs, v. 38, n. 2, p. 90.

 

Matteson, D.K., Taylor, B., Tracy, M., Franzi, A., Folino, A., Armbruster, J. Hoenninger, A. and Ebert, J.R., 2006, Stratigraphic and sedimentologic insights from Schoharie, NY: Thacher Member, Manlius Formation (Upper Prídolí, Helderberg Group): GSA Abstracts with Programs, v. 38, n. 2, p. 90.

 

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