Abstract

(EDITOR'S NOTE: The manuscript from which this abstract has been made is a thesis submitted by Mr. Dille' for the degree of Master of Science, 1956, at the University of Oklahoma. The thesis was recommended by Dr. Carl C. Branson for publication in the Digest. It is of course much more informative than is the abstract, and carries illustrations, tabulations and a long bibliography for which we do not have space. However, the abstract does put before the members of the Society the various factors brought out by the thesis in an area of general interest to all Oklahoma geologists.)

Petroleum reserve possibilities exist in the Arbuckle Group, Reagan sandstone and granite wash of northeastern Oklahoma. These potential horizons are all significantly influenced by the paleotopography of the Precambrian surface. The area covered by this study extends from Range 1 East to the Arkansas line and from Township 10 North to the Kansas line. It includes about 16,281 square miles.

The surface features of the area are related to major drainage patterns and rock type variations in the outcrops. The major drainage is that of the Arkansas, Verdigris, Salt Fork, Cimarron, North Canadian, Illinois and Neosho Rivers. The Neosho River drains into the Lake O' The Cherokees (Grand Lake) which is within the area.

The Precambrian surface has been mapped from subsea datums in wells which penetrated this surface. No estimated tops have been used. In contouring this map some control was provided by the relationship of the Precambrian surface and post-Precambrian faulting and folding. Portions of the area are entirely without well control and in such portions the attitude of the overlying beds was taken into account. The large size of the area involved and the small number of wells drilled made the search for data difficult; full use was made of Oklahoma Geological Survey publications and available sample, electric and drillers' logs.

shows the general nature of the stratigraphic relationships in the northeastern and southwestern portions of the area of study. No attempt was made to divide the Mississippian limestones; they are predominantly Osage in age but may include some younger sediments. The top of the Mississippian is an erosional surface but many of its structures reveal the paleotopography of the Precambrian, as shown in cross sections which are not presented with this abstract.

The thickness of the Kinderhookian Chattanooga and its subsurface equivalent, the Woodford shale, is quite consistent across northeastern Oklahoma, and it covers the entire area except where absent due to erosion or non-deposition. The Misener sand may appear below the Woodford at the basal unconformity, but the occurrence is sporadic.

The Siluro-Devonian section is represented by the Hunton, which is crystalline in the upper part, dolomitic and darker in color in the middle and at the base more sucrosic, porous and dolomitic. In the Ordovician section the Sylvan shale in the part of the area in which it is present conformably underlies the Hunton. In turn the Viola conformably underlies the Sylvan, but it has an unconformity between its two divisions, the Fernvale and the underlying Trenton.

In northeastern Oklahoma the Simpson group in descending order consists of the Simpson "Dense" limestone and Simpson dolomite, "2nd Wilcox" sandstone, Tyner formation, and the Burgen sandstone. The Simpson "Dense" and Simpson dolomite are a series of brown or gray sandy dolomitic limestones interstratified with some green shale and thin sandstone members. A near thickness of 140 feet is found in the vicinity of Stroud, Oklahoma, where the series is composed almost entirely of a light brown dolomite, with about five feet of sand at its upper contact.

The "2nd Wilcox" sandstone is made up of angular to sub-angular, fairly well sorted fine grains of sand in northeastern Oklahoma. Many of the individual grains have a frosted appearance which has been attributed to wind abrasion. The "2nd Wilcox" varies considerably in thickness due to post-Simpson erosion. The basal portion of the formation in parts of this area may be of Tulip Creek age.

The Tyner formation consists of sandy green shales, thin sandstones and a few scattered thin beds of dolomitic limestone. Both surface and subsurface samples are similar except that in the subsurface red shales occur in the middle of the formation. South of Tulsa the sand content of the Tyner formation increases, whereas the green shales decrease. Northwest of Tulsa, however, the base is more dolomitic.

The Burgen varies from a loosely cemented, angular to well rounded sand to a glassy quartzitic sandstone much coarser than the overlying "2nd Wilcox". The color varies from very light gray to yellowish brown. A few partings of green shale may be present along with pyrite. The Burgen is believed to be basal Oil Creek in age.

The Arbuckle group has been subdivided mainly on the basis of the dominant characteristics of the various formations and members. Insoluble residues and sequence of beds have been taken into consideration, but these characteristics are not infallible. The nomenclature within the group is based on the Missouri type section.

The Powell, the youngest unit of the Arbuckle group, has been removed by erosion in much of northeastern Oklahoma, but thicknesses up to 220 feet have been preserved in some places. The Cotter dolomite is the most widely distributed unit, and it maintains a thickness generally of about 125 to 180 feet, but thickens in Craig County. A sandstone bed called the Swan Creek zone often lies at the base of the Cotter; it is very uniformly fine grained and is usually about 20 feet thick. The underlying Jefferson City dolomite is 10 to 50 percent chert. At 60 to 100 feet below its top is a consistent oolitic bed with other minor oolitic zones below. Northeast of Vinita the Jefferson City has a thickness of 285 to 320 feet. Usually it is unconformably overlain by the Cotter, but post-Arbuckle beds may also directly overlie it.

The Roubidoux is marked by 20 to 40 percent brown quartzose oolites, with sand zones at the top, middle and base of the formation; the sands average 15 to 80 feet in thickness. Either the Roubidoux or Upper Gasconade are the oldest beds of the Arbuckle group that are present over the highland area on the Precambrian surface of northeastern Oklahoma. At the base of the Gasconade-Van Buren formation there is a sandy dolimite which marks the base of the Ordivician Section and which rests unconformably on the Cambrian section.

The Eminence dolomite at the top of the Cambrian section of the Arbuckle carries small amounts of pyrite, chert and oolites. Glauconite is present as the usual marker of the Cambrian portion but it is not abundant. The Bonneterre dolomite contains clastics which increase downward to a 20 to 40 foot basal sandstone which grades into the Lamotte-Reagan sandstone below.

It is now believed that the Reagan sandstone in northeastern Oklahoma is a "basal sandstone" overlying the Precambrian which is of Cambro-Ordovician age. It rests upon the Precambrian with great unconformity and grades upwards into the sandy dolomitic limestones of the Arbuckle group. In Kansas there is a transgressive basal sandstone lying on the Precambrian surface. Locally in the southeastern part of the state it is the equivalent of the Lamotte sandstone of Missouri. The Lamotte extends into northeastern Oklahoma as such a "basal sandstone" where it is thought to be the equivalent of the Reagan in that part of the state, especially in its basal part. This "basal sandstone", previously referred to as igneous detrital by Ireland, is according to well records a stratigraphic unit which underlies sediments of Bonneterre to Jefferson City age or, in other words, of Cambrian or Ordovician age. The "basal sandstone" therefore evidently transgresses time units. It is possible that the Reagan of northeastern Oklahoma will be correlated with the basal portion of the type Reagan of southern Oklahoma.

Erosion of the Precambrian of northeastern Oklahoma has produced a major unconformity. Besides the familiar coarse grained granite at Spavinaw and in well cuttings in northeastern Oklahoma, quartzite, schist and gneiss have also been identified in wells. The literature indicates that metamorphic rocks are more common in southern Kansas.

The only exposure of the Precambrian surface in northeastern Oklahoma is that near Spavinaw, where much investigation has been done by different geologists. Originally there was a question whether the outcrop represents a granite ridge on the Precambrian surface or a dike-intrusion. Now most geologists consider the Spavinaw granite outcrop to be a ridge, from the following evidence.

1. The granite shows no changes from its central portion outward to the contact zone.

2. Exposure is due to overlapping, truncation and erosion.

3. A strand line is indicated at the granite by the abundance of fossils near the contact with a decrease upward in the stratigraphic column.

4. There is no evidence of associated sills, dikes and metamorphism.

5. In the top of the overlying Cotter dolomite the material which occurs there appears to be depositional debris rather than brecciation due to intrusion.

6. Detrital feldspar, quartz and rounded pebbles of gray decomposed granite occur in the dolomite adjacent to the granite.

The paleotopography of the Precambrian surface of northeastern Oklahoma is the result of a long period of erosion preceding the deposition of Cambrian sediments. (map inserted in back of book) shows the contouring on this surface. Main features on this map are:

A major divide through the Spavinaw peak with southward and westward branches in the Claremore-Pryor area.

A broad east-west valley north and northwest of Spavinaw.

A fault at Miami where wells indicate a difference of 574 feet in elevation in one mile on the Precambrian. Gunter sandstone overlies the Precambrian on the west side of the fault and Lamotte sandstone overlies it on the east side.

A narrow valley south of the Spavinaw peak. This narrow valley may be in part the result of Precambrian faulting.

A high Precambrian area northwest of Tulsa which has been severly dissected by post-Precambrian erosion. The name "Tulsa Mountains" has been applied to this range by Ireland.

A western slope of 30 to 50 feet per mile of the Precambrian surface begins in western Osage County; it is interrupted by isolated highs at intervals.

A deepening of the Precambrian surface southwest of Tulsa which is interrupted by occasional monadnock features. One of these, "Cushing Ridge", is of major importance.

There are probably many small features which are not evident because of lack of control.

Granite wash is recorded immediately above the Precambrian in 14 wells in northeastern Oklahoma. However, the information on such occurrences is meagre and some of the records are doubtful. The Reagan sandstone occurs in the major valleys of the Precambrian surface of northeastern Oklahoma as a flanking, sheet-like sandstone which pinches out over the prominent highs. Two principal accumulations are in the broad valley north of Spavinaw, where it extends as far west as the "Tulsa Mountains", and in the trough southeast of "Cushing Ridge".

Cross sections not here shown which include the pre-Pennsylvanian sediments illustrate different phases of the relationship of these sediments to the Precambrian surface. Many structures at least in part may be controlled by the Precambrian paleotopography; the thesis carries a list which is not given here. Some of the Precambrian highs have post-Arbuckle sediments of Simpson, Woodford or younger Mississippian age resting on the Precambrian surface.

The sediments first deposited upon the Precambrian surface are upper Cambrian in age. As the sea advanced to the north basal sandstones were progressively deposited along with the overlying sandy dolomitic Arbuckle limestone. At the end of Cambrian time the "Tulsa Mountains" and isolated Precambrian peaks formed islands in the sea. The Ordovician sea continued the overlap of the Precambrian surface and in Cotter time the Spavinaw peak was overlapped. A minor uplift in northeastern Oklahoma and the Ozark Mountains occurred in post-Arbuckle-pre-Simpson time, with accompanying slight southwest tilting and accompanying erosion. Simpson time brought a gradually encroaching sea with Simpson and following Viola, Sylvan and Hunton deposition. A period of south and southeastward tilting and accompanying erosion followed; to the northeast the Viola, Sylvan and Hunton formations were removed by the erosion, and peneplanation of the Simpson and Arbuckle took place, exposing a few isolated Precambrian peaks.

The Woodford was deposited in a wide spread shallow sea over most of the Midcontinent region. It was followed by the deposition of the younger Mississippian rocks. Following this, south and southeastward tilting resulted in a long period of erosion.

Lower Pennsylvanian sediments were deposited only on the south and east sides of the north central Oklahoma high area. Beginning with the middle Pennsylvanian the Ozark high was further uplifted, resulting in a tilting of northeastern Oklahoma, the final major movement of the area.

As to oil and gas prospects, many of the highs in Osage County reflect the paleotopography of the Precambrian surface. Many of them have not been tested to the Precambrian. Many of them have less than 300 feet of Arbuckle on top and oil or gas may be trapped in the Arbuckle or in the sediments above on their flanks. There are four unconformities which may form oil trans in the Arbuckle above the upper Gasconade, probably the oldest Arbuckle formation in the Osage County area. Porous zones in the sand, chert, dolomites and limestones may also form reservoirs.

The rest of northeastern Oklahoma is relatively untouched by drilling below the top of the Arbuckle. In such drilling the Powell and Cotter dolomites offer good possibilities in a certain stratigraphic sequence, and the Roubidoux may have oil and gas reservoirs in the sand zones it carries.

The past history of the Reagan in the Midcontinent indicates that it may be prospective in northeastern Oklahoma, probably on the flanks of the deep valleys. It might also produce on closure on Precambrian highs.

Granite wash occurrences, which have been reported at scattered points, are all located over Precambrian highs. Some shows have been reported in such occurrences.