Economic and Other Factors Affecting Petroleum Exploration: ABSTRACT Association Round Table 1897 shore winds is moved into clay dune complexes and eventually carried downwind to develop loess sheets. This extensive up- wind deflation of the system is accompanied by windward accreting clay-sand ridges with nuclei composed of either beach-ridge remnants of a Pleistocene barrier-strandplain sys- tem or remnants of inter-blowout areas developed during early phases of the deflation of the coastward margin of the system. Principal source of sand and loess is, therefore, local, repre- senting reworking of underlying, older sands. A sand source resulting from longshore convergence and inland transport from Padre Island accounts for only the minor, local infllling of Laguna Madre in the land-cut area, and is not the principal source of eoUan sand throughout the system. Facies fabric within Pleistocene depositional systems provides principal con- trol of environments, sedimentary processes, and resulting fa- cies within the subsequent eolian system. BRUCE, C. H., Mobil Oil Corp., Corpus Christi, Tex. PRESSURED SHALE AND RELATED SEDIMENT DEFORMATION—MECHA- NISM FOR DEVELOPMENT OF REGIONAL CONTEMPORANEOUS FAULTS Regional contemporaneous faults of the Texas coastal area are formed on the seaward flanks of deeply buried Unear shale masses characterized by low bulk density and high fluid pres- sure. From seismic data these masses have been observed to range in size up to 25 mi wide and 10,000 ft vertically. These features, aligned subparallel with the coast are en echelon or branching in pattern, and represent residual masses of under- compacted sediment between sand-shale depoaxes in which greater compaction has occurred. Most regional contemporane- ous fault systems in the Texas coastal area were formed during times of shoreline regression when the duration of fault devel- opment extended over short periods of geologic time, and where comparatively simple down-to-the-basin fault patterns were developed. In cross-sectional view, faults in these systems flatten and converge at depth to planes related to fluid pressure, and form the seaward flanks of underlying shale masses. Data indicate that faults formed during time of shoreline regression were developed primarily through differential compaction of adjacent sedimentary masses. These faults die out at depth near the depoaxis of the sand-shale section. In areas where subsidence exceeded the rate of deposition, gravitational faults developed where basinward sea-floor incli- nation was estabUshed in the immediate area of deposition. Some of these faults became bedding plane type when the incUnation of basinward-dipping beds equaled the critical slope angle for gravitational slide. Fault patterns developed in this manner are comparatively complex and consist of numerous antithetic faults and related rotational blocks. Nondepositional (structural) faults are common on the land- ward flanks of deeply buried shale masses. Many of these faults dip seaward and intersect the underlying low-density shale at relatively steep angles. Conclusions derived from these observations support the concept of regional contemporaneous fault development through sedimentary processes where thick masses of shale are present and where deep-seated tectonic effects are minimal. BUTLER, E. A., and H. W. SIMPSON, Atlantic Richfield Co., Dallas, Tex. DlVERSnT-EqUITABILITY ANALYSIS AS P A L E O E C O L O O I C T O O L Diversity-equitability analysis of microfaunal data as used by Beerbower and Jordan shows promise of being a rapid and useful technique for mapping paleoenvironmental gradients. It may even provide a more satisfactory definition of environmen- tal boundaries than biofacies analysis based on taxonomic com- position. Faunal diversity is calculated as Shannon's information the- ory average uncertainty measure. Using this diversity measure, a few equally common taxa can yield as high a diversity index as many unequally common taxa. Lloyd and Ghelardi's equita- bility index may be used to separate these two diversity compo- nents and refine seemingly homogeneous data. Recent microfaunal data from Barnstable Harbor, Massa- chusetts, and the northern Gulf of Mexico have been subjected to diversity-equitabihty analysis. From Barnstiible Harbor, con- tours based on the equitability index can be related rather clearly to tidal action within the harbor. A diversity-equitability plot of published Holocene Gulf of Mexico data reveals that some environments may be characterized by a unique D / E range. Although these results must be considered preliminary, an analysis of parts of the lower Miocene sequence in Block 24 field, High Island area, oflshore Texas, shows that the techni- que merits further consideration and is potentially a very useful tool for both identifying and mapping ancient environments. CLARK, H. C , Dept. Geology, Rice Univ., Houston, Tex. PALEOMAGNETISM OF LATE PLEISTOCENE-HOLOCENE SEDIMENTS, GULF OF M E X I C O Detailed paleomagnetic studies have been made on 15 sedi- ment cores selected along north-south lines in the eastern and western Gulf of Mexico. The piston cores were sampled at 20- cm intervals immediately upon extrusion and measurements of natural remanent magnetization (NRM) were made using a 5hZ spinner magnetometer. Excursions of the geomagnetic field are recorded at 2 levels in many cores. Extrapolation of the ZY boundary in the western Gulf indicates that the younger feature is between 13.5 and 17.5 X 10' years BP, and is consistent with the age determination of the Laschamp event. Dates are not available for the eastern Gulf cores, but the depth of the paleo- magnetic feature correlates with the expected sedimentation rates. The older feature is less distinct and further extrapolation of the ZY boundary places it between 20.0 and 24.0 X \(fi years BP. This age is within the range of a geomagnetic feature that is not the Laschamp. These re ".ults show that with extreme care, paleomagnetic measureme its may be used as a stratigraphic tool in the Gulf of Mexico. Several points should bi considered. First, because of the high sedimentation rates, the 2 yotmg features described herein are the only ones expected in piston cores from this region. Second, direction scatter is quite pronounced in the upper 1/2 m and lower few centimeters of several cores. Corre- lations at these levels are difficult. Finally, as measurement of the geomagnetic features described lasted for only a short time and did not traverse a full 180°, dense sampling is recom- mended to assure their definition. CRANDALL, K. H., Consulting Geologist, Piedmont, CaUf ECONOMIC AND OTHER FACTORS AFFECTING PETROLEUM EXPLORATION There is today almost universal agreement that we are facing a potential energy crisis, both imminently in the U.S. and possibly worldwide after the turn of the century. All studies of energy supply and demand indicate such tremendous growth in demand tiiat conventional sources will be hard pressed to sup- ply it. The short-range aimual growth rate in domestic and free- world demand for petroleum is estimated at 5% and 7 1/2% respectively, resulting in 19 million and 57 million bbl/day total demand in 1975. By 1980 U.S. demand will be nearly 25 million bbl and free foreign need nearly 90 miUion bbl/day. The areas which will supply this demand, especially for fhe U.S., ark quite imcertain because of the bewildering variety of poUtical, legal, and environmental factors—as contrasted with purely economic ones—which will be of critical influence. Therefore, it is difficult to forecast the areas and the amounts and costs of exploration and development, as well as prices and earnings. One thing is certain, however, there will be a growing short- age of domestic crude and an increasing dependence on foreign suppUes. Both the cost and dependabiUty of the latter are questionable in view of political considerations and the policies and actions of OPEC. 1898 Association Round Table Any interruption of our foreign energy supplies would have a dramatic effect on our economy and security and would show the dangerous results of the lack of a coherent and positive energy policy. There are very few discovered but undeveloped oil reserves in the U.S. except on the North Slope, and those probably cannot be made available before 1976. Though the recent NPC-AAPG study indicates almost 200 bilhon bbl of undiscovered but expectable recoverable U.S. reserves, any large increase in ex- ploratory effort to find them cannot have any great effect on our crude deficit before 1978 because of the necessary lead times. It is obvious, however, that certain steps can and should be taken immediately to encourage or to cause such an increase so that the period of danger to our economy and security will be as brief as possible. FITZGERALD, D. M., and A. H. BOUMA, Dept. Oceanogra- phy, Texas A&M Univ., College Station, Tex. CONSOLIDATION STUDIES OF DELTAIC SEDIMENTS The Texas Colorado River delta, which built across Mata- gorda Bay between 1929 and 1941, was selected for consolida- tion research. The objectives were to observe structural changes which occur wjien deltaic sediments undergo primary consoli- dation, and to correlate these consohdated sedimentary struc- tures with those reported from ancient deltaic environments. Double cores were collected along a traverse parallel with the main river channel in the southeast lobe of the delta. One core was spUt lengthwise, described, and radiographed. An analo- gous undisturbed section of the second core was then selected for consohdation. Consolidation, through vertically compressing the sediments, partly creates new structures or makes poorly visible structures more discernible. It was noted in some cases that convolute laminations and recumbent folding formed after sections con- taining parallel laminations were consolidated. It was also ob- served that apparent homogeneous sections, after compaction, changed structurally to reveal parallel laminations. Consequently, it should be realized that consolidation will aiTect unconsolidated sediments and that these changes should be considered when comparing recent and ancient environ- ments. FLOYD, B. L., Independent, Portland, Tex. DRILLING FUNDS AND THE ENERGY CRISIS (No abstract submitted) GALLOWAY, W. E., Continental Oil Co., Exploration Re- search Div., Ponca City, Okla. SlCNIHCANCE OF R E S E R V O I R D I A G E N E T I C ALTERATION FOR PETROLEUM EXPLORATION, GULF OF ALASKA TERTIARY BASIN The Tertiary clastic section of the Gulf of Alaska sedimen- tary basin is considered an important potential future petro- leum province. Considerable work in the onshore area has been carriesl out by industry preparatory to a projected sale of fed- eral leases on the continental shelf. Examination of numerous samples collected from measured sections in Oligocene to Pleis- tocene strata has shown that the sandstones are mineralogically immature and unstable. Diagenetic alteration of these potential reservoir sands at shallow to intermediate depths of burial has resulted in the ubiquitous formation of authigenie clay rims and coats around detrital grains and of poie-filling zeolite cements. These diagenetic alterations adversely affect both porosity and permeability and will provide a major limitation on the thick- ness of the sedimentary section than can be considered pros- pective. A compaction versus depth gradient, which is related to the sandstone porosity gradient, can be determined in off- shore areas by combination of seismically derived interval, velocity depth profiles, with a velocity-density calibration based on well data from the Hecate Strait (a geologically similar Pacific Margin basin lying off British Columbia). The resultant density configuration can be cross checked by gravity modeling along the same seismic line. Work on a line off Cape Yakataga shows that the prospective section is characterized by a high velocity and density gradient, indicating rapid loss of reservoir porosity with increasing depth of burial, as predicted by the onshore diagenetic model. Semiquantitative evaluation of the compaction profile using the onshore reservoir data suggests that even in the youngest sections porosity decreases to less than 20% at depths of 5,000 to 8,000 ft. GUEVARA, E. H., and R. GARCIA, Bur. Econ. Geology, Univ. of Texas at Austin, Austin, Tex. DEPOSITIONAL SYSTEMS AND OIL-GAS RESERVOIRS IN QUEEN CITY FORMATION (EOCENE), TEXAS Regional surface and subsurface studies indicate that thick deltaic (Queen City Formation) and thin shelf (Reklaw and Weches Formations) sequences compose the stratigraphic inter- val between the top of the Wilcox Group and the base of the Sparta Formation. In East Texas, the Queen City Formation accumulated as part of a high-constructive, lobate delta system; and in South Texas, as part of a high-destructive, wave-domi- nated delta system. In South Texas, principal facies are mean- der-belt sand, lagoonal mud, stacked coastal barriers, and pro- delta-shelf mud facies; in East Texas, delta plain, delta front, and prodelta facies are dominant; and in Central Texas, the principal facies are strandplain sands originated by southwest- ward longshore drift of sediments from the high-constructive delta system. Facies distribution, composition, and size of the deltas in East Texas are similar to lobes of the Holocene high-construc- tive Mississippi delta system and to ancient deltas in the lower part of the Wilcox and in the Jackson Groups of the Gulf Coast basin. Fluvial-deltaic sediments of South Texas are comparable to Pleistocene high-destructive wave-dominated facies on the Surinam coast, to the Holocene Rhone delta system, and to ancient deltas in the upper part of the Wilcox Group. Queen City deltas prograded gulfward over shelf muds and glauconites of the Reklaw Formation; they are overlain by comparable shelf facies of the Weches Formation. In East Texas, deltaic facies wedge out eastward; terrigenous elastics of the high-destructive deltas extend southward into Mexico. Hydrocarbons are produced from thin strike-oriented sands downdip from the belt of maximum sand thickness of the high- destructive deltas in South Texas; only a minor amount of oil and gas has been obtained from delta front and distributary channel sands of the high-constructive deltas in East Texas. HAAS, M. W., Vice-President for Exploration, Humble Oil & Refining Co., Houston, Tex. PETROLEUM EXPLORATION AND ENVIRONMENTAL CONSERVATION U. S. faces energy crisis.—V. S. energy demands will nearly double by 1985. All our principal sources of fuel will be needed to meet the demand; if domestic supplies cannot keep pace, we face increasing reliance on foreign oil. Energy and public iands.—Much of U. S. energy potential, including offshore oil and gas reserves, is on publicly owned lands. Potentially productive acreage in the federal and state domain should be made available to industry in a manner designed to maximize timely development. Environmental delays.—A principal factor in delaying explo- ration of frontier areas is environmental concern. Many envi- ronmental objections are founded on the argument that oil and gas development is incompatible with other uses of the same land or water area. Compatible use.—If exploration is to proceed at a pace con- sistent with national needs in the future, the concept of compat- ible multiple use of lands must be established as national pol- icy. Industry must demonstrate from available examples that this concept is sound and results in maximum benefits to public and private interests. Geologisls must contribute.—Petroleum geologists should bring their knowledge to bear on public environmental issues and work for reasoned solutions based on scientific fact. Much exploration today awaits public consent; geologists must aid in showing pubUc that energy-environmental problems can be