Criner Hills Research Articles

Geochemical characterization of the Devonian-Mississippian Woodford Shale from the McAlister Cemetery Quarry, Criner Hills Uplift, Ardmore Basin, Oklahoma

Abstract It has been estimated that technically recoverable reserves from shales in the continental U.S. are believed to be approximately 24 billion barrels of oil (BBO) and 750 trillion cubic feet (Tcf) of gas. In Oklahoma the most important hydrocarbon source rock is the Woodford Shale, proposed to be the source of some 70% of the state's liquid hydrocarbon reserves. Such a regionally widespread source rock provides potential for both academic study and industrial opportunities. In this study representative samples of the Woodford Shale from the McAlister Quarry outcrop have been characterized by a variety of geochemical techniques. TOC values range from 0.07 to 15.6 wt% and, based on Rock-Eval Pyrolysis, most of the samples plot within the Type I/II kerogen range, with several low TOC samples plotting in the Type III kerogen range. TOC and biomarker parameters, suggests that two sections of the Upper Woodford are immature paleosols, having been subaerially exposed due to abrupt episodes of sea level fall during the Late Devonian. Evidence for these zones of paleoweathering includes highly depleted TOC, increased oxygen index (OI) values, loss of n-alkanes, decreases in the aryl isoprenoid ratio (AIR), sesquiterpenoids, cheilanthanes, hopanoids, and decreases in many of the polycyclic aromatic hydrocarbons (PAHs). The values of several paleoenvironmental proxies for samples immediately following the Frasnian-Famennian (F–F) Stage extinction boundary within the Upper Woodford suggests that a large influx of weathered terrigenous material occurred at that time. The presence of pyrogenic compounds implies that paleowildfires were widespread throughout the Middle and Late Devonian in the North American midcontinent. It is possible that these influxes of weathered terrestrial organic material stimulated algal blooms that led to the anoxic water column conditions often attributed to the F–F Stage extinction event. Investigation of the stratigraphic framework of these source rocks assists in evaluating their potential as hydrocarbon producers and/or unconventional reservoirs. Integration of geochemical data adds another powerful dimension to this approach. It has been proposed that the Woodford Shale was deposited during a 2nd order depositional sequence. The lower member represented the transgressive systems tract (TST), the Upper member the highstand systems tract (HST), and the Middle member bridging the transition between the two. Numerous 3rd order parasequences were also identified as being part of the overall 2nd order sequence and could be correlated to the Devonian sea level curve. The major objectives of the study were: While this study focuses locally on the McAlister Quarry samples, it is also of regional importance. The Woodford is a prolific source rock throughout the Anadarko Basin and has been the subject of extensive exploration and production efforts, particularly in the past decade with the development of horizontal drilling and hydrofracturing techniques. Continued investigation of the heterogeneity of the shale will greatly enhance the ability to predict more productive facies within the formation throughout the basin.

A new family of trepostome bryozoans from the Ordovician Simpson Group of Oklahoma

A new family, Bimuroporidae, is proposed for a clade of Ordovician trepostome bryozoans. The family is united by several characteristics, including a zooidal ontogenetic progression from mesozooid to autozooid and an integrate wall structure. Discriminant and cladistic analyses of colonies from the Ordovician Simpson Group outcropping in the Arbuckle Mountains and Criner Hills of south-central Oklahoma permit the recognition of eight species belonging to this family. Four species assigned to the new genus Bimuropora are described: B. dubia (Loeblich), B. pollaphragmata n. sp., B. conferta (Coryell), and B. winchelli (Ulrich), as well as four species assigned to the genus Champlainopora Ross: C. chazyensis (Ross), C. ramusculus n. sp., C. pachymura (Loeblich), and C. arbucklensis n. sp.

Origin and Genesis of Fracture Porosity in Viola Limestone (Ordovician): ABSTRACT

Analysis of surface exposures of the Viola Limestone is important to understanding Viola oil and gas production trends in the Marietta basin of southern Oklahoma. Surface exposures of the Viola Limestone in the Arbuckle Mountains and Criner Hills of Oklahoma indicate a critical dependence of fracture development on structural position and lithology. Maximum fracturing occurs in tensional zones along fold crests, rather than in areas characterized by intense compressional stress. Fracturing also appears to be related to lithology. The basal, cherty unit has a fracture density approximately two to four times greater than that of the upper, more calcareous units. These relationships could be important to understanding oil and gas occurrence in the Viola Limestone, because th same controls may dictate distribution of fracture porosity in the subsurface. End_of_Article - Last_Page 411------------

Late Mississippian Epeirogeny and the Wichita Orogeny in the Mid-Continent: ABSTRACT

Widespread epeirogeny in Late Mississippian time uplifted elements of the Transcontinental arch and bordering regions. Late Mississippian deposition in the Mid-Continent was confined to the Anadarko, Ardmore, and Arkoma basins where maximum thicknesses of 5,000, 3,000, and 2,000 ft of sediments (respectively) accumulated. Erosional processes accompanied regional uplift and continued after the cessation of Late Mississippian deposition. Consequently, over the Mid-Continent an erosional surface was etched on a terrane of predominately carbonate paleozoic sediments and igneous Precambrian rocks. A maximum thickness of 4,000 ft of Morrowan (Early Pennsylvanian) sediments was deposited in the Anadarko basin. From there, northward to southwestern Nebraska, Morrowan beds onlap the Late Mississippian erosional surface and truncate rocks ranging in age from Late Mississippian to Precambrian. This depositional onlap accounts for the limits and much of the thinning of the Morrowan Series from the Anadarko basin toward the north and northeast. Morrowan rocks on the order of 3,000 ft and 5,000 ft in thickness were deposited in the Ardmore and Arkoma basins, respectively. In these basins Morrowan sediments lie on Late Mississippian rocks with minor unconformity. The post-Morrowan, pre-Atokan Wichita orogeny brought the aligned Criner Hills-Amarillo-Wichita uplift-Cimarron arch into existence through strong vertical uplift accompanied by high-angle faulting with an estimated 10,000-15,000 ft of maximum vertical displacement. Concurrently a foredeep began to form in the Arkoma basin which would subside rapidly and receive phenomenal thicknesses of Atokan rocks--12,000 ft in the western Arkoma basin and 19,500 ft in the eastern part of the basin. Meanwhile, an area on the western margin of this developing Atokan foredeep became mildly positive, possibly in response to the strong downwarping of the foredeep. From the Criner Hills this area trends northward across the Ardmore basin and the Arbuckle uplift, and turns northeastward toward the Ozark uplift, a distance of approximately 175 mi. This belt was about 125 mi wide and it encompassed the southeastern flank of the Anadarko basin and the northwestern flank of the Arkoma basin. Morrowan rocks were eroded from this positive area with the exception of those in the Ardmore basin, those on the southeastern flank of the Anadarko basin, and those on the northwestern margin of the Arkoma basin. These rocks exhibit an angular, unconformable relation with overlying Atokan or Desmoines an beds. Elsewhere in the Arkoma basin, and in the Anadarko basin and on its shelf area, the contact of Morrowan and Atokan rocks is nonangular and probably disconformable. In western Oklahoma, western Kansas, and southwestern Nebraska, the depositional limit of Morrowan sediments is overstepped eastward by Atokan beds, and the depositional limit of Atokan beds is in turn overstepped eastward by Desmoinesian rocks. The uninterrupted advance of these sediments eastward toward and onto the Nemaha ridge and the Cambridge arch-Central Kansas uplift is evidence that the age of these features is pre-Morrowan (Late Mississippian) rather than post-Morrowan, pre-Atokan (Wichita orogeny) as often claimed. In addition Atokan and Desmoinesian rocks of these areas do not exhibit lateral facies changes involving the influx of coarse clastic sediments End_Page 646------------------------------ from the east that would be expected if the Nemaha ridge and the Cambridge arch-Central Kansas uplift experienced post-Morrowan uplift. End_of_Article - Last_Page 647------------

Articulate Brachiopods of the St. Clair Limestone (Silurian), Arkansas, and the Clarita Formation (Silurian), Oklahoma

The St. Clair Limestone and Clarita Formation contain large, Upper Silurian (Wenlockian) brachiopod faunas. The St. Clair Limestone crops out in two areas in north-central Arkansas; one is the type area near Batesville, in parts of Independence, Stone, and Izard Counties, the other is near Gilbert, Searcy County. The Clarita Formation, Fitzhugh Member, crops out in the Arbuckle Mountain region and Criner Hills of south-central Oklahoma. The articulate brachiopod fauna of the St. Clair Limestone comprises 45 species and subspecies referred to 35 genera and subgenera, and that of the Clarita Formation, Fitzhugh Member, comprises 23 species and subspecies referred to 22 genera and subgenera. The combined St. Clair-Clarita fauna totals 51 species and subspecies, of which 17 are new; 40 genera and subgenera are represented, of which 9 are new:Orthostrophella, Onychotreta(Eilotreta),Onychotreta(Lissotreta),Placotriplesia, Boucotides, Leangella(Opikella),Virginiata, Dicamaropsis, andHomoeospirella.The faunas of the St. Clair and Clarita are remarkably similar; all but six of the Clarita species are present in the St. Clair, and the two formations are closely related in age. Strata of this age are probably widely distributed in the Midcontinent area of the United States, although the brachiopod evidence for this is meager. The generic suite represented in the St. Clair-Clarita brachiopod faunas is similar to that of the Wenlock of Great Britain and the Slite and Mulde Marlstones of Gotland; the stage of development represented by the St. Clair species ofDicoelosiais also similar to that ofD. bilobafrom the Wenlock Limestone and Slite and Mulde Marlstones. The St. Clair-Clarita brachiopod fauna does not show any marked similarity to brachiopod faunas known to be in the Silurian of Bohemia, and, in fact, correlation with the Czechoslovakian Silurian section is at present uncertain.

Stratigraphy of Deeper Marietta Basin in Oklahoma and Texas: ABSTRACT

The Marietta basin is in southern Oklahoma between the Muenster arch on the southwest and the Criner Hills uplift on the northeast; it extends from Love County, Oklahoma, southeastward through Cooke and Grayson Counties, Texas, the deepest part being known as the Gordonville trough. The folded and faulted buried ridge (mid-basin ridge) on which the Southeast Marietta field is located has a more southward strike than the present basin axis, and divides the basin into two parts. The thickest sections of Atoka and older sediments were deposited north of the ridge. The Gordonville trough developed in Late Mississippian End_Page 193------------------------------ or Early Pennsylvanian time from a gentle downwarp into a deep, relatively narrow trough with steep, commonly faulted sides, growing progressively as it received up to 5,000 feet or more of sediments of Atoka, Morrow, and possibly Springer (Goddard?) ages. The Atoka and Morrow boundaries are indefinite on the basis of present knowledge. Some geologists place the top of the Atoka at the base of the Davis Sand (Grayson County, Texas). The writer has placed the top at an oolitic limestone (Lester?) midway between the Baker and Davis Sands. Westheimer believes the sand in the Ardmore basin Dornick Hills correlates with the Hartshorne Sandstone of the Arkoma basin and the Davis Sand of Grayson County. The sandstone correlated as Davis or micaceous in the Southeast Marietta field is several hundred feet higher stratigraphically than the Davis Sand of Grayson County. A thick section of pre-Atokan appears northward as well as eastward from the mid-basin ridge. This is believed to be mostly Morrowan-lower Dornick Hills, Springer (Goddard?), and Caney. The boundaries are indefinite and based on electric-log characteristics, related to early sample work. More qualified determinations are necessary in samples from later wells. Post-Atokan Dornick Hills also thickens eastward and northward in Grayson County, but thins and disappears southwestward against the lower faulted margin of the Muenster uplift. The same components may be noted in the Des Moines or Strawn (Deese), although the thickening here may be more related to the development of the present Gordonville trough by foundering and filling during erosional destruction of the Ouachitas. More intense folding and thrust faulting, even deep within the basin, complicate considerably the development of structure and stratigraphy because of the loss of section (a loss which is not the result of depositional factors). End_of_Article - Last_Page 194------------

Recent Developments in Marietta Basin: ABSTRACT

During the past 10 years, a new search for significant reserves swept the Texas part of the Marietta basin and resulted in several important discoveries. The Ordovician Oil Creek Sandstone and numerous Strawn sandstones of Pennsylvanian age were the primary objectives. The Marietta is primarily a Pennsylvanian basin, and oil occurrence is related closely to sedimentation and orogenies during this period. The presence of the southeast extension of the southern Oklahoma Criner Hills trend caused much deep exploration for Oil Creek gas-condensate production. The New Mag field was a significant result of this play. Much exploration remains to be done for fields of this type. The 20-yr-old Handy field, also on the Criner trend, was extended considerably and new pay zones were found in this multipay Strawn field. Reserves were increased several times. On the southwest side of the basin, the Bob K field in Cooke County was an important find. A combination of structural and stratigraphic entrapment created this very prolific multipay Strawn field. Histories of development and geological interpretations of these and other areas are presented. End_of_Article - Last_Page 196------------

Silurian and Early Devonian Carbonate Rocks of Oklahoma

A thin sequence of Silurian and Devonian carbonate strata (maximum thickness at the surface about 450 feet) crops out in the Arbuckle Mountains region, the Criner Hills, and in northeastern Oklahoma. In the Arbuckle Mountains region these strata are referred to six discrete depositional units which comprise the Hunton Group, the oldest being the Keel and Ideal Quarry Members of the Chimneyhill Formation of Early Silurian age (Alexandrian), and the youngest the Frisco Formation of Early Devonian age (Deerparkian); in northeastern Oklahoma (Sequoyah County) the Frisco Formation is locally overlain by the Sallisaw Formation of latest Early Devonian age (Esopusian). These depositional units are believed to be separated from one another by periods of time during which there wa induration and, in places, uplift and erosion. An unconformity separates the Silurian from the Devonian strata, and throughout much of the southeastern part of the Arbuckle Mountains region Early Devonian rocks (Helderbergian) rest on Early Silurian rocks (Alexandrian) and are within a few feet of the Ordovician strata. In Sequoyah County very latest Early Devonian strata (Esopusian) locally rest on late Niagaran strata.

Geologic Interpretation of Argillaceous Sediments: Part II. Clay Petrology of Upper Mississippian-Lower Pennsylvanian Sediments of Central United States

X-ray diffraction analysis of Upper Mississippian-Lower Pennsylvanian shales from the Ardmore and Anadarko basins indicates that the Meramecian Caney shales are characterized by the abundance of illite and the scarcity of chlorite and kaolinite, the Chester shales by the presence of illite and montmorillonite, the Springer shales by the presence of montmorillonite and the absence of illite, the Lower Pennsylvanian Morrow shales by an abundant illite content, and the Atoka shales by the relative abundance of mixed-layer clay. The Chester and Springer formations, which can be divided into three geographic provinces, are overlain by a 200±-foot mixed interval which consists of a mechanical mixture of the Morrow and underlying formation clays. The type of reworked Springer clay in the mixed interval can be used to identify the geographic province of the underlying Springer section. Both the Morrow and Atoka shales contain distinctive interfingering beds of reworked Springer shales which appear to be restricted to wells situated near the downthrown sides of faults. In the Ouachita geosyncline the Upper Mississippian Stanley shale is characterized by the presence of illite, chlorite, and feldspar, the Lower Pennsylvanian Jackfork and Johns Valley shales by the presence of mixed-layer clay and the relative scarcity of kaolinite and chlorite. Near the northern margin of the Ouachita area the lower Stanley shale is similar in composition to the Caney and Springer shales, indicating a transition between the two basins. The Stanley illite-chlorite shales and high-rank graywacke sandstones were deposited in a rapidly sinking eugeosyncline. The sediments were derived from a metamorphic-acid igneous complex on the south. The closely related Chester and Springer montmorillonitic shales and orthoquartzite-quartzose graywacke sandstones were deposited in a rapidly sinking intracratonic basin. They were probably derived from a broad, low-lying sedimentary-volcanic source north and south of the basin. The southern source area may have extended toward the east and partly separated the two depositional areas. The Pennsylvanian (Morrow) was ushered in by a major uplift and metamorphism in the southern part of the Ouachita eugeosyncline, and minor faulting along the southern flank of the Anadarko and Ardmore basins. The micaceous Jackfork shales (Ouachita basin) and orthoquartzite sandstones were derived from this Ouachita uplift. The micaceous Morrow shales (Ardmore and Anadarko basins) were derived in part from the Ouachita area and in part from the periodically uplifted montmorillonitic sediments along the south flank of the basins. At the beginning of Atokan time there was increased uplift along the south flank of the basins (the Wichita Mountains and Criner Hills) and as a result the Atokan shales are more montmorillonitic than the Morrow shales, and the sandstones are typical low-rank raywackes. Regionally the clay mineral suites in the Arkansas and Illinois basins and in the north Texas area can be related to those in Oklahoma. End_Page 272------------------------------

Pre-Deese Paleogeography of Part of Ardmore Basin, Southern Oklahoma: ABSTRACT

The part of the Ardmore basin discussed in this paper includes the area south and west of the Arbuckle Mountains, east of the Cruce-Velma trend, and north of the Loco-Criner Hills area; it includes parts of Bryan, Marshall, Johnston, Love, Carter, Stephens, Grady, and Garvin counties. A small part of the Anadarko basin is discussed showing the onlapping of the Deese beds on older Pennsylvanian and pre-Pennsylvanian of the Pauls Valley uplift. In the Ardmore basin the Deese lies unconformably on top of beds from the Arbuckle to Dornick Hills age. The area of greatest pre-Deese truncation is the Healdton-Criner area. A large part of the basin has Permian beds and Cretaceous beds lying unconformably on Pennsylvanian and pre-Pennsylvanian rocks. A considerable part has Pennsylvanian beds at the surface. The only pre-Pennsylvanian beds exposed in the basin area are on the Mannsville anticline in Marshall County. There are pre-Pennsylvanian rocks cropping out in the Arbuckle Mountains on the north flank of the basin and in the Criner Hills area on the south side of the basin. The Deese has a maximum thickness of 8,000 feet, Dornick Hills 3,000, Springer 6,000, Caney shale 500, Sycamore 600, Woodford 700, Hunton 400, Sylvan 400, iola 1,100, Simpson 2,400, and Arbuckle 7,300 feet. These are maximum thicknesses and are probably not reached in any one place. Probably the greatest thickness of both the Pennsylvanian and pre-Pennsylvanian is in the area of Ardmore, Oklahoma. End_of_Article - Last_Page 425------------

Walnut Bend Pool of Cooke County, Texas: ABSTRACT

The Walnut Bend pool is the first major deep discovery in the Marietta-Sherman syncline, a northwest-southeast trending feature which extends from southwestern Carter County, Oklahoma, to southeastern Grayson County, Texas, parallel to the Criner Hills axis and the Muenster Arch. In this pool 1,000 feet of Comanche rocks overlie the 4,200 feet of Upper and Middle Pennsylvanian (Canyon and Strawn) sediments, and beds of lower Simpson (Oil Creek) age underlie the Pennsylvanian rocks. Pre-Pennsylvanian rocks show the Walnut Bend structure as an elongate anticline. This structure was formed on an arch folded in early Pennsylvanian (pre-Bostwick) time and the Marietta-Sherman syncline was formed in late Deese time by the downwarping of the middle part of this arch. Over one an one-half million barrels of oil have been produced from 6 sandstone zones between the depths of 4,100 and 5,100 feet, and from 2 dolomite beds in the Simpson group. Occurrence of oil in the sandstone zones at 4,900 and 5,100 feet is controlled by anticlinal structure over the closely folded Ordovician beds, Electrical log cross sections are presented to indicate that oil in the 4,100-, 4,600- and 4,700-foot zones occurs in a stratigraphic trap formed by gradation of standstone into shale. End_of_Article - Last_Page 941------------

Correction to Stratigraphy of Hoxbar Formation, Oklahoma: ERRATUM

Correction to Stratigraphy of Hoxbar Formation, Oklahoma: ERRATUM

Pre-Cretaceous Rocks Found in Wells in Gulf Coastal Plain South of Ouachita Mountains

Deep wells that have been drilled in the part of the Gulf Coastal Plain south of the Ouachita Mountains have passed through gently inclined Cretaceous strata and entered Paleozoic rocks. The Paleozoic floor, which is relatively smooth, has a steep southerly dip; therefore, it has not been reached by wells at great distances from the mountains. It has, however, been reached at many places in a wide southwestward trending belt that extends from Oklahoma into Texas. The wells that are described in this paper include a few in southwestern Arkansas, a few in southeastern Oklahoma, and several in Grayson, Fannin, Lamar, and Red River counties, Texas. The Paleozoic rocks that have been penetrated by these wells are similar in character and age to the Paleozoic rocks exposed in t e Ouachita Mountains. Some of the wells in the counties adjacent to Red River in Texas have entered pre-Carboniferous rocks. Areas of such rocks are perhaps southwestward extensions of the exposure of rocks of this age in the Ouachita Mountains in Oklahoma. The other wells within the area described entered rocks that are assigned to the Carboniferous or simply to the Paleozoic. There seems to be no evidence that any of the wells entered pre-Cambrian rocks. The western boundary of the Ouachita Mountain facies of rocks seems to pass in a southerly direction through the western part of Grayson County, Texas. West of this boundary are Paleozoic rocks that are similar to those exposed in the Arbuckle and the Wichita Mountains and Criner Hills. This boundary, the writers believe, is marked by a southwestward continuation of the Choctaw fault from Oklahoma. The axis of the Ouachita geosyncline--the geosyncline in which the rocks of the Ouachita Mountain facies were deposited--has an east-west trend in Arkansas, but it swings toward the southwest in Oklahoma and crosses Red River into Texas. The part of the geosyncline extending from Arkansas across Oklahoma into Texas thus displays an arcuate form.

Permo-Carboniferous Orogeny in South-Central United States

This paper is a synopsis of the late Paleozoic orogeny in the south-central states of North America. Recent papers by American geologists and personal work of the writer and his collaborators are coordinated into as complete a treatise as present knowledge permits. Two independent mountain systems, the Wichita and the Ouachita, are distinguished. The Wichita system comprises the Wichita Mountains, the Criner Hills, the Arbuckle Mountains, the buried folds along Red River including the Muenster arch, and the buried Amarillo Mountains. These folds, though belonging to the Permo-Carboniferous phase, originated within an intra-continental pre-Middle Devonian geosyncline, in which the major accumulation of predominantly marine limestone sediments was pre-Devonian. This system strikes generally west and west-northwest. It meets nearly at right angles the front of the second complex, the considerably more important Ouachita system. The Ouachita system (in a wider sense) is a large arcuate feature of which only a small part of the widely overthrust outer rim of the northernmost loop is exposed in the Ouachita Mountains of southeastern Oklahoma and Arkansas. Most of this system is buried, though folds exposed in the Marathon uplift belong to the southwestern extension of the same system, which, as the writer believes, in Oklahoma and Arkansas is itself an extension of the Appalachians, which disappear in Alabama under the Cretaceous blanket of the Gulf Coastal Plain. Unlike the Wichita complex, the Ouachita ranges originate from an inter-continental Carboniferous geosyncline, with major post-Devonian deposition, principally in the latest Mississippian or earliest Pennsylvanian. The facies of the rocks is also intrinsically different. The exposed part consists of great overthrust masses, of a structural type that can best be compared with the northern front of the European Variscan system in France and Belgium. The principal phases of folding in both the Wichita and the Ouachita systems are Pennsylvanian; the final phase of the overthrusting of the Ouachitas is possibly Permian. Precursory Mississippian and older movements are indicated. End_Page 991------------------------------ Recent geological subsurface work makes possible the tracing of the rim of the buried Ouachita front range through east-central Texas, first by the characteristic, depressed early Pennsylvanian foreland basin, which exactly reproduces the coal basin foredeep of southeastern Oklahoma and southern Arkansas, and then by wells which actually have penetrated to the mountain front. The present Llano-Burnet uplift marks the existence of a resistant buttress in the foreland, causing a salient around which the chains turn, to reassume a southwest course in southwestern Texas and northern Mexico; here the folds reappear at Marathon, beyond which they disappear beneath the Cordillera in Mexico. The Hunton arch is another important buttress, causing the uplift of the folded foreland fault-slices of the Arbuckle Mountains. The character of the nappe (overthrust) structure of the Ouachita chains is discussed and compared with the very similar build of European mountain chains. These mountains are not merely the edge of an ancient Llanoria, but a great range of world-wide importance.

Crinerville Oil Field, Carter County, Oklahoma

The Crinerville oil field, near Brock, Carter County, Oklahoma, occurs on a surface anticline in Pennsylvanian strata on the west side of, and faulted against, the Criner Hills. The reverse dip of 15° on the northeast side of the anticline disappears under a large part of the anticline in shales within 900 feet of the surface. Production comes from Pennsylvanian oil sands which overlap a truncated portion of the original Criner Hills of Ordovician limestone, now buried at a depth of more than 1,000 feet. The oil originated in the Pennsylvanian shales, and a small quantity migrated laterally into the Ordovician. The field was opened in January, 1922, and has produced between 1,000 and 1,500 barrels a day ever since. The total production to June 30, 1927, was slightly ore than 2,300,000 barrels.