Description, Deposition and Bounding Units of the Venango 3rd Oil Sandstone

Daniel Coyne; Zachary Hartin; Cody Lewis

Edinboro University of Pennsylvania

Abstract

The purpose of this paper is to define the environment that the Venango 3rd Oil Sandstone was

deposited in. This sandstone is rich in oil, giving it its name and order of sandstone. The

sandstone is in the Venango Formation, right above the Chadakoin Formation. The time period

that it was deposited in is the upper Devonian. We went on field trips through a Field Methods

class at Edinboro University of Pennsylvania, a total of 4 weeks of research. We collected data

(body and trace fossils, sedimentary structures and stratigraphic columns) and then researched

what it all meant. Horizontal burrows and different species of brachiopods were collected and

examined. Using Walther’s Law, we also looked into the Chadakoin formation and examined

data throughout it. The contact of the Chadakoin and the Venango formation was at an elevation

of 1135 feet above sea level. Most of the fossils found were deposited in shallow waters, giving

us the belief that the Venango 3rd oil sandstone was deposited in a shallow-marine environment.

Introduction

The Venango Third Oil Sand formations is historically prominent for the use of the first

successful drilling rig on a well drilled especially to produce oil in 1859(Bates, 2000). The

original outcrop in Venango County, Pennsylvania, was formally named by Lesley, and

originally proposed by Carll. The Venango Third Oil Sand is one of three formations in the

Venango Oil Sand group. The other two formations are called the Venango First Oil Sand

formation and the Venango Second Oil Sand Formation. (Harper et al., 1998)

This paper will primarily concentrate on the oldest of the three Venango Oil-Sand

formations, the Venango Third Oil Sand. This particular formation is linked to the late Devonian

period (Harper et al., 1998) and subsequently linked to the rise of the Kaskaskia cratonic

sequence and the erosion of the Acadian Mountains. The Venango Third Oil Sand is located in

Northeastern Ohio, Northwestern Pennsylvania, and Southwestern New York.

Description of the Venango 3rd Oil Sandstone

The Venango 3rd oil sand is a sandstone located right above the Chadakoin Formation.

As the name of it states, there is oil located in the sandstone, giving it the smell of oil or a dirt

floor in a barn. This oil sand is classified as the Panama Conglomerate Member. This sand stone

was deposited in the Devonian age and is known as the Catskill Formation (Marshall, 1911). The

Catskill Formation is part of a larger geological unit often referred to as the Catskill Delta, a

complex of Middle to Late Devonian alluvial, deltaic and marine deposits produced by the

erosion of the Acadian Orogeny. This is why we find these sands were they are in their

bounding units.

The Venango 3rd oil sand is light gray in color and when wet, a dark shade of gray which

is typical for sandstones. The Venango 3rd oil sandstone is also classified as “white to tan, oil-

bearing, quartz sandstones with interbedded cray to reddish-brown shales and silty shales”

(Harper et al., 1998) (See Figure 1). There was also iron staining on these rocks, allowing us for

interpretation that water flows through this sandstone and precipitates iron. This iron was a dark

red staining, which we noted. This unit was around 10 to 15 meters thick and had a definite oil

smell. Between the oil sands, which there are three total, there are siltstone and shale units.

The structure of this 3rd oil sand has hummocky bedding, which is clearly seen in Figure

2. On the top of the 3rd oil, there were Horizontal burrows 10 centimeters long and 2 centimeters

in diameter (See Figure 3). In other places, we see vertical burrows throughout the top 1 meter

of the sandstone. Some other body fossils that were found include Camarotoechia brachiopod

(See Figure 4) and Camarotoechia clams (See Figure 5).

Description of Bounding Units

Walter’s law is a simple but important tool when understanding the depositional

environment of bounding units as the moved through space and time. Walter’s law uses the

vertical layering of rock to show when and how these rocks where moved and deposited. For

instance, a layer of sandstone with beach characteristics may have a bounding layer above it with

shelled organisms and other marine pieces of evidence which if using Walter’s law, would

insinuate that there was a rise in sea level when it was deposited and the marine environment

overtook the beach over time. Though our studies of the Venango third oil sand, Walter’s law is

important to use as we search for clues to what environment the third sand was deposited in. The

bounding units of the Venango third sand are the contact to the Chadakoin formation below and

the Venango second sand above. The third sand is at the very base of the Venango formation

meaning it is the oldest rock in the formation.

To start, the Chadakoin formation below was studied in depth for the first two weeks of

our field studies. The formation is Devonian age rock with a lithology consisting of inter-

fingered sandstone, siltstone, and even shale. As we studied this formation, we discovered a wide

abundance of brachiopod shelled organisms and ripple marks.

One of the most prevalent sedimentary structures we found was ripple marks. These

ripple marks appeared to have the same slope on each side of the peak which characterizes them

as symmetrical. They were extremely prevalent on the creek floor and were also found in the

outcrop of both weeks of research. These marks are formed from steady equilateral movement of

waves back and forth. The most common place to find this movement is in tidal action areas such

as shallow marine environments.

Another fossil found in our research at Howard Falls was a type of extinct brachiopod,

named Brachiopoda strophomenata chonetes (See Figure 6). Chonetes lived in the Devonian

period (between Late Ordovician to the Middle Permian) in Pennsylvania and were known as the

longest lived group of the productid brachiopods (Brittannica.com). “The shell is small, one half

concave in form and the other moderately convex. The horizontal margin of the shell bears short,

angled spines that the animal used in anchoring or attaching itself.” (Brittannica.com). Chonetes

environment was stationary low-level epifaunal suspension feeder (Fischer de Waldheim, 1830).

This fossil was discovered in the Chadakoin Formation insitu in the outcrop.

The Venango second sand is the bounding unit above the Third sand. The formation has

many similarities to the third oil sand. One of the first pieces of evidence we found was the large

hummocky cross-stratification in the outcrop above Howard falls and at Goodban run in

Fairview, PA. Hummocky bedding is a sign of storm waters being the environment of deposition

for the second sand. Many times strong thunder storms or hurricanes are prevalent in the

environment of deposition when hummocky bedding is found. Strong storms will have this affect

usually in shallow marine environments when the movement of the water from storms will most

effect the sand below. Another great find was the glass sponge, Titusvillia drakei. This fossil was

found at Goodban run in Fairview, PA. It is a fossil from about 300 million years ago in the

Devonian period. Its environment is believed to be an inland shallow marine that existed during

this time in northern Pennsylvania and parts of New York (Modified from Cornell University,

1999).

Interpretation of Depositional Unit of Venango 3rd Oil Sandstone

In our studies of Goodban Run in Fairview, PA, we discovered a species of brachiopod in

the order of Rhynchonellida (See Figure 7). This brachiopod was extremely abundant in the

Mesozoic period with over 250 genera, many of which went extinct but some still exist today.

The brachiopod is distinctly identified through is physical attributes. Its shell consists of strong

radiating ribs that peak sharply, this most likely helped regulate the flow of water in and out of

the shell (modified from Monks and Owen). This order brachiopod has a fold located in the

brachial valve. This means that the commissure, the line between the two valves or shells, is

zigzagged, a distinguishing characteristic of this group. The prominent beak of the pedicle valve

usually overlaps that of the brachial valve, in order to allow the shell to open and close (Modified

from Monks and Owen). This is a very common order of brachiopod but does give us a little

insight to the third oils depositional environment.

The environment related to the Rhynchonellida brachiopod is obviously marine but

through research, not much is known about the specifics of the environment. This order is just

known to live in shallow to medium depth waters. Following along with all of our other

evidence, this discovery also points to the third oil sand being deposited as a shallow marine

environment.

Horizontal Burrows were littered throughout the Venango 3rd oil sand and in lower and

upper units. These burrows were on average around 2 centimeters in diameter and 6 inches in

length (See Figure 3). These burrows are known to be located in shallow marine environments

in this region, which is the upper Devonian (Miller 1979). When looking at horizontal burrows,

we predominantly see burrows and trails of the Cruziana ichnofacies (including Teichichnus,

Planolites, Palaeophycus, Cruziana and Zoophycus) in the uppermost part of the sandstone

(Craft and Bridge, 1987). When looking at vertical burrows, we see the Skolithos ichnofacies

(including Diplocraterion, Arenicolites, and different varieties of Skolithos) in sandstones and

siltstones. The ichnofacies of Cruziana and Skolithos are known to burrow in a shallow marine

environment in loose or softground (Sandstone). Cruziana ichnofacies tend to be horizontal,

while the Skolithos ichnofacies tend to be vertical.

The Cruziana ichnofacies represents the mid and distal continental shelf below normal

wave base (Benton and Harper, 1997) (See Figure 8). The makers of Cruziana are mainly

considered to have been trilobites and several specimens of Cruziana are commonly found

associated together at one sedimentary horizon, suggesting that they were made by populations

of trilobites, which would be the reason for multiple burrows (Wolfe, 1990).

The Skolithos ichnofacies was at first seen as occurring only in the intertidal zone, but it

is also typical of other shifting sand environments (Benton and Harper, 1997) (See Figure 9).

Some burrows have a helical form (Volohonskya, 2008). Skolithos is typically marine, but is

also known from freshwater lacustrine settings (Trewin and McNamara, 1995).

The Brachiopoda camarotoechia fossil that we found was located in the Venango 3rd Oil

Sand formation (See Figure 4). This Genus of Brachiopods has a fossil record that ranges from

about 460 million to 270 million years ago (Halle and Clark, 1893). This means it would have

appeared in the fossil record about half way through the Ordovician Period and survived through

the Silurian and Devonian Periods and disappeared in the rock record late in the Permian Period.

Brachiopods dominated the seafloor during the entire Paleozoic Era, and can be filed

under a slew of genus types. J. J. Veever states that there are five characteristics used to separate

the genus Camarotoechia from any other Brachiopod Genus. The characteristics Veever wrote

are first, “a thick, plicated shell”, second, “a ventral valve convex at the umbo, almost flat on the

flanks, rest of valve uniformly weakly convex along its length, transversely depressed into a

sulcus, which is drawn out dorsally into a tongue; with a small erect beak, a short interarea, and a

narrow, open delthyrium”, third, “a dorsal valve evenly convex in profile; median fold broad;

umbo broadly convex, tip protruded into delthyrium”, fourth, ”strong teeth supported by short

high dental plates”, and fifth, ”a broad hinge-plate, split or unsplit, supported by a short median

septum; crura short, parallel”( Veever, 1959).

The Camarotoechia has a limited range of habitats due to its sessile and benthic

ecology. Hall and Clarke designated the genus to “reef, buildup or bioherm, shallow subtidal ,

offshore, transition zone/lower shore face, deep subtidal shelf, deep subtidal, prodelta, shoreface,

offshore shelf, lagoonal, marginal marine, deep subtidal ramp, open shallow subtidal, coastal,

delta plain, deltaic, perireef or subreef, delta front, sand shoal, and slope enviroments” (Halle and

Clark 1893).

The evidence found through our weeks of field research point to the depositional

environment of the Venango 3rd oil sand being a shallow marine environment most likely

located in the Kaskaskia Epicontinental Sea. This inland sea over the North American craton

existed about 250 million years ago in the Devonian. With the evidence found in the field, the 3rd

oil sand was likely in a tidal region of the sea where there was much biodiversity and wave

action. This is the exact way the 3rd oil sand was deposited and why the evidence we found

concludes us to believe that the 3rd oil sandstone was deposited in a shallow marine environment

in the Kaskaskia Sea.

Figures and Diagrams

Figure 1

Figure 3

Figure 2

Figure 4 and 5

Description of Figures and Diagrams

Figure 1: Venango 3rd oil Sandstone

Figure 2: Hummocky Topography of

Venango 3rd oil Sandstone Unit

Figure 3: Horizontal Burrows

Figure 4: Smaller fossils are Camarotoechia

brachiopoda

Figure 5: Large fossil is Camarotoechia clam

Figure 6: Brachiopoda

strophomenata chonetes (Small

pock marks in rock)

Figure 7: Brachiopoda

Rhynchonellida in Venango 3rd oil

Sandstone

Figure 8: Diagram of Cruziana

ichnofacies

Figure 9: Diagram of Skolithos

ichnofacies

Figure 6

Figure 7

Figure 8

Figure 9

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