ABSTRACT

The history of economic micropaleontology in the Texas and Louisiana Gulf Coast area is presented with emphasis on application of micropaleontology to the solution of geological problems. Records indicate that Hilgard and Hopkins were the first Americans to study oil well samples in this country, between 1878 and 1884. Pioneers such as Joseph A. Cushman, J. A. Udden, Esther R. Applin, Alva C. Ellisor and Hedwig T. Kniker are known for their achievements in the development of taxonomic and economic micropaleontology. Additional work done by J. B. Garrett and A. D. Ellis, in the early 1930's, was important in establishment of foraminiferal zones of the Gulf Coast Cenozoic.

Cushman and Ellisor are credited with the erection of the first middle and lower Miocene foram zones in conjunction with electric log correlations in Louisiana. Much of the early work on biostratigraphic zonations was done on the Eocene, Oligocene and Miocene sections of Louisiana and Texas.

Well-site micropaleontology became increasingly popular in the late 1930's and 1940's when it became evident that foraminiferal markers could be utilized to great advantage for correlation purposes and for the prevention of drilling into high pressure sections and sections known to stick drill pipe such as in the heaving shales of the Hackberry, Abbeville and Harang of south Louisiana's Miocene and Oligocene salt dome trend.

Major paleontological advancements occurred in the 1950's and 1960's. Attention was focused on ecology and paleoecology of microfossils, notably the foraminifera. Significant contributions were made by several leading researchers in the field of planktonic foraminifera and ostracodes. Calcareous nannofossils became increasingly popular and began to achieve status given previously to planktonic foraminifera in their utility as intercontinental markers. Palynology also gained popularity in the early 1960's and was used mostly in the older sections of the Mesozoic and Paleozoic of the Gulf Coast where the bulk of sediments were deposited in marginal marine and non-marine environments. Development of the offshore further increased the needs for applied micropaleontology, biostratigraphy and paleoecology.

EARLY ACADEMIC HISTORY

Croneis (1941) reported in a presidential address delivered before a joint meeting of A.A.P.G.-S.E.P.M.-S.E.G. that as early as 1877, foraminifera from well cuttings were used by Felix Karrer to determine the age of Miocene strata penetrated in an Austrian water well drilled near Vienna. Several other instances were cited where foraminifera from well cuttings aided in determining the age of the strata drilled.

In a symposium on micropaleontology, Howe (1959) stated "As far as I know, the first micropaleontological work done on well samples in this country was that of Hilgard & Hopkins (1878, 1884). The work was actually done by Hopkins under Hilgard's direction. The first paper was a well illustrated report on the microscopic fossils encountered in a well at New Orleans; the second on borings across the Mississippi Valley between Memphis and Vicksburg". Unfortunately for geologists and paleontologists, these were published by the, U. S. Engineers in the War Department.

It was reported by Katherine Van Winkle Palmer (1953) that a decade later, Gilbert D. Harris (1895) made a preliminary report on the organic remains encountered in a deep well at Galveston and determined the age of the various formations encountered. Dr. E. T. Dumble, in charge of the State Geological Survey of Texas, pointed out the significance of the material acquired stating, "It will make a most important chapter in our knowledge of the history of the Gulf Coast and furnish a section for reference and comparison which could have been so obtained in no other way".

For the next twenty years, the work in the Gulf Coast on the foraminifera was conducted by academicians. Dr. Joseph A. Cushman (Todd, 1950), who became an international authority on the Order Foraminifera, began a study in the first decade of this century on the living forms. In 1912, Dr. Cushman became associated with the United States Geological Survey and was involved with surface mapping, However, he did some work on well samples and his first published work bearing on the economic use of foraminifera appeared as a brief report in United States Geological Survey, Professional Paper 90-H, December, 1914 by L. W. Stephenson on the deep water well at Charleston, South Carolina. It gave impetus to the detailed study of foraminiferal faunas in well sections in commercial work in the petroleum industry. Formations were identified and the ecology was discussed (Croneis, 1941, op. cit., p. 1224).

Contemporaneous with the work of Cushman was that of Dr. J. A. Udden who made microscopic examinations from 1908 to 1911 of cuttings from wells drilled for oil or water in Illinois. A few years later, Udden came to Texas and continued his study of micropaleontology. He sold the idea of its importance to petroleum geologists (Croneis, 1941, op. cit., p. 1221). Mr. Wallace Bostic who was then employed by the Rio Bravo Oil Co. in Houston, Texas, trained in Udden's laboratory in Austin. Later, Bostic expanded the work in the Rio Bravo office. Dr. E. T. Dumble, formerly with the Texas State Geological Survey, but now in charge of geological work at the Rio Bravo Oil Co., recognized the value of biostratigraphy and employed Esther Richards (Mrs. Paul Applin) as a micro-paleontologist in 1920. A short time later, Alva C. Ellisor joined the geology department of the Humble Oil and Refining Co. (Exxon). In 1921, the Texas Co. employed

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Hedwig T. Kniker. Within the next year, Grace Newman, Laura Lee Lane, and Emma Jane Coffman (Mrs. John Miller) became affiliated with various oil companies in Houston (Ellisor, 1947). Economic paleontology was then launched in Houston.

As this was a new field, the first several years were spent examining well samples to become acquainted with the foraminiferal faunas and to determine stratigraphic relationships to the sections penetrated by the drill. There was skepticism among the geologists at this time as to the relative value of this work.

ECONOMIC HISTORY

"Credit for the revolution which took place in the use of foraminifera properly goes to three ladies, Esther Richards Applin, Alva C. Ellisor and Hedwig T. Kniker. Their paper on the subsurface stratigraphy of the coastal plain of Texas and Louisiana (1925) had been presented before the Annual Meeting of the American Association of Petroleum Geologists in Shreveport, Louisiana and the discussion which followed opened the eyes of oil company executives" (Howe, op. cit., p. 511).

This paper described some subsurface shale beds and termed.them middle Oligocene formation. They were divided into three paleontological zones, the uppermost designated as the Discorbis zone, the middle as the Heterostegina zone and the lowest as the Marginulina zone. The origin of the term middle Oligocene is due to the Heterostegina being identified by Cushman as H. antillea, a species characteristic of the Antigua formation which must, in my opinion, be the type of the American middle Oligocene. The age of these zones was disputed for years.

Prior to the paleontological zonation of these beds, geologists had been correlating with drillers logs. This was rather difficult in the coastal area where the lithology consists of sands, clays, calcareous mudstones and occasional limestones. The updip limit of the "Middle Oligocene" beds is roughly a short distance west of Corpus Christi, extending northeastward to north of Houston and eastward to a short distance north of Beaumont, into Louisiana north of Lafayette, and east to Baton Rouge.

The Eocene section beyond the updip limits of the "Middle Oligocene" was being drilled. Sand pinch-outs on the Reynosa Escarpment in southwest Texas were being explored as well as domes at Humble, Sour Lake, Hull, Hockley, etc. The identification of the shales was unknown. The shale on salt domes was intruded into the overlying beds by the salt and was compressed, fractured, dehydrated and heaved when penetrated by the drill. A study of the foraminifera in both well cuttings and surface samples made by Cushman and Applin (1926) proved conclusively they were Jackson. The beds underlying the Jackson were studied by Weinzierl and Applin (1929) and were shown to be Yegua (uppermost Claiborne). Continued drilling in this trend prompted Ellisor (1933) to publish a report which brought the Jackson fauna up to date and also included a study of the foraminifera if the subsurface Vicksburg (Oligocene) which greatly increased our knowledge of the section.

Drilling proceeded in the "Middle Oligocene" trend with little paleontological information added other than the Discorbis zone being divided into the small and large Discorbis and the Marginulina zone being split into "Round Marg." and "Flat Marg.". The sands immediately below the Marginulina zone were called "Marg. sands". Deeper drilling revealed a lower thick sand to which the term Frio was applied. There was considerable controversy over the name.

The Shreveport Geological Society (1934) sponsored a field trip in central Mississippi based on field work by B. W. Blanpied and Roy Hazzard. One of the localities studied is near Waynesboro, Wayne County. A portion of the section exposed here is called upper and lower Chickasawhay, which is underlain by the Bucatunna clay which separates it from the Byram marl (Vicksburg, Oligocene). The age assignment of these beds became a heated controversy. The profession was divided into two groups. One group assigned the Chickasawhay beds to the Miocene while the other referred to them as Oligocene. The controversy lasted for five years.

Ellis (1939) described four species of foraminifera from the previously mentioned Chickasawhay beds. The stratigraphic significance of these foraminifera aided greatly in correlation of the Frio. The mudstone bed below the Marginulina sands contains Cibicides hazzardi. The underlying sand is generally accepted as being the top of the Frio.

Nonion struma occurs near the middle portion of the section. Nodosaria blanpiedi, found only in the lower Chickasawhay on the surface, serves as a marker for the top of the basal section. The impact of this information was not realized for some years. The section of less than a hundred feet, exposed at Waynesboro, thickens to the southwest in Louisiana and Texas and becomes several thousands of feet in thickness. If the Miocene (Cushman and Ellisor, 1939) overlies the "Middle Oligocene" and Chickasawhay underlies "Middle Oligocene", it becomes apparent that the Chickasawhay cannot be Miocene in age.

The Schlumberger Co. introduced the electric log in the Gulf Coast area in the early nineteen thirties. The efficiency of this tool led some workers to predict no further need for paleontologists. Correlation with the electric log is not difficult if the wells are along strike, but correlation problems often occur in deeper drilling of down-dip sands separated by deep-water shale wedges. Identification of these wedges is not possible in faulted sections unless great numbers of electric logs are available. Shale wedges are identified by means of foraminifera and this demonstrates the need for paleontology.

Garrett and Ellis (1937) described and figured the most common and distinctive Marginulinas which occurred in Oligocene beds. Those which eventually were used as zone markers are Marginulina idiomorpha, Marginulina vaginata and Marginulina howei. There are sands below each of the fossil zones.

Drilling continued in the Frio trend and six or seven paleontological laboratories were operating in south Texas and south Louisiana. The section was being zoned by placing letters and numbers beside generic names. Garrett (1939) described some of the fauna from the "Middle Oligocene" beds of Jefferson County, Texas. Specific

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names were placed on a large number of the foraminifera and the Discorbis zone was divided from younger to older into Discorbis nomada and Discorbis gravelli.

Drilling in Louisiana shifted to the younger marine Miocene beds. Cushman and Ellisor (1939) described the foraminifera from these strata from the southeastern and southwestern part of the state and with the use of electric logs and forams, Ellisor (1940) zoned an area of complex deposition. Of particular importance is Bigenerina humblei, Uvigerina lirettensis, Siphonina davisi and Cibicides opima.

Garrett (1942) described some Miocene foraminifera from the subsurface strata of coastal Texas which supplemented previous work on the Miocene. Several species such as Planulina palmerana, Lenticulina hanseni and Discorbis bolivarensis extend over into southwest Louisiana, adding more correlation points to those set up by Ellisor (1940 op. cit.).

In the early nineteen forties, drilling continued in the Frio and as the wells were located nearer the present coast-line the section continued to expand. Newer zones were set up such as Textularia seligi, Anomalina bilateralis, Cibicides mississippiensis and the Vicksburg of early Oligocene.

"MIDDLE OLIGOCENE" NAMED

The so-called "Middle Oligocene" beds were called "Middle Marine" and various other names by geologists working in this area. The Houston Geological Society, realizing that a description and type locality was needed for this portion of the section appointed a committee for this purpose. The name Anahuac was chosen. Ellisor (1944) wrote a complete report citing the history and fauna of the formation.

HEAVING SHALES

Drilling problems arose in Southwest Louisiana, principally at Hackberry field in Cameron Parish. A shale or mudstone occurring several hundred feet below the top and pushed vertically by the salt to a level on the dome considerably above its normal position posed a problem. When encountered by the drill and drilling mud, it expanded, exfoliated and caused the drill pipe to stick. Its true stratigraphic position was unknown and was referred to by some as Alazan (now Huasteca) and Mexican Vicksburg. Garrett (1938) completed a study of the strata, described the fauna, and termed it Hackberry Assemblage, not a formation. Where the heaving shale with this assemblage is known to be intruded on a dome, most companies have a paleontologist at the well site to prevent drilling into this hazardous section.

A well was drilled in 1936 to a depth greater than 11,000 feet in the Abbeville field, Vermilion Parish, Louisiana. Strata similar to those of Hackberry were encountered. Foraminifera were used to show that these strata were Miocene in age. For company use, J. B. Garrett (Goheen, 1959) applied the name Abbeville to these beds. The faunal assemblage was never described but the name was adopted for general use. Under certain conditions, these shales react similarly to those containing the Hackberry Assemblage.

As early as 1933, several wells were drilled by the Barnsdall Oil Co. at what is now called Valentine field, Lafourche Parish, Louisiana. The Harang No. 1 well encountered an unusual fauna which was observed by Lloyd M. Pyeatt who was doing paleontological work at the well site. Few wells had been drilled in this part of the state at that time and the tremendous thickening of the Miocene was unknown. It was speculated that the fauna might be downdip Vicksburg.

J. B. Garrett examined samples from the Harang well in 1937 and thought at first the fauna was correlatable with a fauna at the Hackberry field. Several years later, he correlated the fauna of the Harang well with that of some wells drilled in the Bayou des Allemands field, St. Charles Parish and concluded that it was upper Miocene in age. The term Harang just grew as "Topsy". The first published report on the Harang fauna is that of Pope and Smith (1948). The Harang shale possesses the same characteristics as those of the Hackberry and Abbeville shales which heave when encountered in a displaced position on domes (Pope, 1955) and (Stuckey, 1964).

OSTRACODA

Some of the earliest work on this group of fossils is that of Israelsky (1929) who described some Cretaceous ostracodes from Arkansas. The University of Texas published a voluminous report by Alexander (1929) on Ostracoda of the Cretaceous of North Texas. Additional papers by Alexander were written on Eocene ostracodes. Dr. H. V. Howe, Louisiana State University, became interested in Tertiary ostracodes in 1930. Howe and Garrett (1934) were the authors of a pioneer paper using ostracodes for Tertiary correlation. M. B. Stephenson followed with papers on Tertiary ostracodes from Eocene to Miocene. Howe and others described the ostracodes of the Jackson, Vicksburg and Choctawhatchee. The ostracodes are shallow water forms and most of them disappear in the sub-surface where the water was deeper than their normal habitat. There are several formations in the Tertiary section where the ostracodes are important markers, namely Wilcox and Reklaw.

NEW METHODS

Ecology

One of the earliest papers on ecology in the Gulf Coast was that of Phleger and Parker (1951). This paper described and recorded the distribution of recent foraminifera in the Gulf of Mexico. Later, Crouch (1955) demonstrated the use of paleontology to determine the area where favorable sands are developed. Crouch (1959) by means of foraminifera showed the tremendous thickening of the section in the offshore. Ecologic studies continued to the extent that three quarters of the G.C.A.G.S. Transactions, Volume 16 (1966) was devoted to ecology.

Planktonics

Work was being done in the early nineteen fifties on planktonic foraminifera in the Caribbean area. Akers (1954) brought this to the attention of paleontologists in Texas and Louisiana. He pointed out their value in the sediments deposited in deep water. A monumental academic

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work by Loeblich and collaborators (1957) on planktonic foraminifera served as a stimulus for their use in the Gulf Coast area.

The author considers the introduction of the use of planktonics as a milestone. This work is contemporary and some of the current workers, John H. Beard, James L. Lamb, Hans Bolli, and Emile Pessagno, Jr. are recognized.

Nannoplankton

Calcareous nannofossils have been known for a hundred years but it was the advent of the electron microscope as an aid in identification that prompted their use in exploration for petroleum. The paper which gave impetus to their use in economic work was that of Hay, et al, (1967).

By 1969, several papers appeared in the G.C.A.G.S. Transactions dealing with planktonic foraminifera and nannoplankton. A number of companies have adopted their use for correlation, especially in the offshore area. Calcareous nannofossils are extremely useful in correlation of deep-water sediments and are regarded as equal to or better than planktonic forams in intercontinental correlations.

Palynology

Studies were made of spores and pollen many years ago. Their use was in conjunction with coal beds. Woods (1955a) pointed out a sudden surge of interest in palynology once their economic value was known. Woods (1955b) stated, "Certain of these windblown fossils offer a distinct advantage in permitting correlation of strata deposited under ecologic conditions unfavorable for the distribution of marine or fresh water animals". In the last twenty years, considerable progress has been made in the use of palynology in the oil industry. One unique application was the determination of the age of salt from our domes by Jux (1961). Palynology is presently being used by a number of oil companies and is particularly valuable in correlation of rocks of Cretaceous and Paleozoic ages.

Offshore

The writer feels that offshore exploration is a milestone in the use of micropaleontology. The area is far removed from any surface outcrops and can be compared to the land only by the fauna previously encountered in the wells located near the present shoreline. All of the experience and knowledge gained in the past fifty years is being used to solve the problems which might arise. Some operators chose not to use paleontology in their offshore program. Some used only geophysical information and depended upon pre-geology blind luck as old time wildcatters did. Some were successful, but one cannot help but think how much more efficient their operations might have been with the use of paleontology.

SUMMARY

In view of the past events discussed in this paper, it is obvious that micropaleontology is invaluable in both surface and subsurface correlations. It is used to detect faults before the log is run. It can demonstrate thickening on the downthrown side of faults which in some fields is tremendous. The ecology of a region can be worked out. Well-site paleontology reduces cost in saving drilling time because heavy mud need not be used until the paleontologists pick the danger points above high-pressure sands and heaving shales.

The origin of the mud lumps of the Mississippi River was debated for two centuries. The mystery was not solved until the paleontological investigation of Andersen (1961). The results of his study suggest that the weight of recent sediments is forcing older unconsolidated sediments upward into the bed of the river.

Micropaleontology appears to be an imporant tool for the exploration of oil and gas. Though the work is rewarding, the author is of the opinion that the economic remuneration is the lowest of all disciplines of geoscience.