Non-marine Sequence Research Articles

Comparison of Pore-Filling Material in Some Pennsylvanian and Cretaceous Reservoir and Nonreservoir Sandstones: ABSTRACT

SEM and thin-section study of core samples from producing sandstones and associated fine-grained facies from several stratigraphic intervals of Pennsylvanian and Cretaceous age in the Rocky Mountain region show different processes of pore-size reduction relating to: (1) original pore-fluid composition; (2) grain size and texture; (3) depositional environment; (4) timing of diagenesis; and (5) depth of burial. The sandstones studied and depositional environments are: Tyler Sandstone, southwestern North Dakota, shoreline (barrier island); J sandstone, northeastern Colorado, distributary channel and channel margin; Frontier Sandstone, northeastern Wyoming, offshore marine bar; Almond Sandstone, southwestern Wyoming, shoreline (barrier island or tidal channel); Terry and Hygiene sandstones, northeastern Colorado, offshore marine bar; and Raton Formation, southeastern Colorado, fluvial channel and channel margin. All the reservoir sandstones were deposited by relatively high-energy transport processes in fluvial, brackish, or marine depositional environments, and represent initially clean sandstones with relatively good porosity and permeability. Pore space in five of the six reservoir sandstones has been initially reduced by precipitated kaolinite or chlorite. The Tyler Sandstone, a nearshore sandstone which underwent early near-surface diagenesis, exhibits reduced porosity related to precipitation of caliche. Associated fine-grained, nonreservoir facies show a pore-filling composition that differs from the reservoir facies in both the marine and nonmarine sequences. End_of_Article - Last_Page 550------------

Tectonic setting and syndepositional deformation of molasse and other nonmarine-paralic sedimentary basins

Molasse is a distinctive sedimentary facies consisting of alluvial and shallow marine deposits derived from source areas undergoing rapid uplift and erosion. The characteristic setting of molasse is within or adjacent to fold belts, and most molasse basins can be classified as foreland basin (external) or intermontane (internal) in type. Thick alluvial and shallow marine sequences in cratonic settings (e.g., taphrogenic troughs) have been classified as molasse by some workers, but this is not generally accepted.Most molasse is synorogenic, and the interdependence of sedimentation and tectonism results in structural and stratigraphic complexity. Intermontane basins generally are tensional in origin and are bounded by high angle (commonly normal) faults. Facies distributions adjacent to each fault depend on relative rates of differential movement, erosion, and sedimentation; accelerated source area uplift causes segmentation and progradation of alluvial fans and generates coarsening-upward sedimentary cycles. Complications are introduced if tectonism occurs in discrete pulses and if basins enlarge themselves along systems of stepped faults.Basins of compressional origin, such as those in a foreland setting, show a greater variety of internal complexity. Facies belts and trends of maximum thickness move progressively out from the core of the fold belt in response to a migration of the zone of active deformation. Conversely, broad structural warps may develop in response to a locally increased sedimentary load, such as a major delta. Folds or thrust faults growing within the basin cause local thinning or unconformable relationships, and may breach the surface so as to isolate parts of the alluvial plain as a synorogenic intermontane basin. Uplift of the fold belt may be discontinuous, causing the generation of stacked sedimentary megacycles. Basin margins commonly are characterized by intraformational angular unconformities and syndepositional folds.Rates of alluvial sedimentation and tectonic movement measured in modern environments are one to two orders of magnitude higher than rates deduced from ancient nonmarine sequences. This lends support to the idea that much sedimentation may be very episodic in nature, but it could also imply that alluvial sequences are deposited much more rapidly than current interpretations of the ancient record would imply, based as they are on relatively crude dating techniques. Only in some wrench-fault basins do calculated sedimentation rates compare with those measured in modern environments.

Geological framework of the Brazilian continental margin

Based on distinctive stratigraphic and/or structural characteristics, the Brazilian continental margin can be divided into two main provinces: (1) The southeastern-eastern province, extending from the Pelotas to the Recife-Joao Pessoa Basin, presents a tensional tectonic style of Late Jurassic-Early Cretaceous age, paralleling the structural alignements of the Precambrian basement, except in the north-eastern segment where the Mesozoic faults of the Recife-Joao Pessoa Basin cut across the east-west basement directions. The basin-fill, Upper Jurassic through Recent, consists, where complete, of three stratigraphic sequences, each of a distinct depositional environment: (a) a lower clastic non-marine sequence; (b) a middle evaporitic sequence, and (c) an upper clastic paralic and open marine sequence. (2) The northern province, extending from the Potiguar Basin to the Amazon Submarine Basin, displays both tensional and compressional tectonic styles of Upper Jurassic (?) to Upper Cretaceous age either paralleling or cutting transversally the basement alignments. The stratigraphic column differs from the southeastern-eastern province in lacking the Lower Cretaceous evaporitic rocks.

Cretaceous Stratigraphy of the Glacier National Park Area, Northwestern Montana

ABSTRACT A sequence of Cretaceous formations as much as 7,000 ft (2,134 m) thick crops out in the eastern and southeastern parts of Glacier National Park and in the adjoining area to the east. Recognition of the many persistent lithologic units in this Cretaceous sequence should be of value in interpreting the complex structure of the region. The oldest rocks, the Kootenai Formation of Early Cretaceous age, consist chiefly of variegated mudstone, siltstone and sandstone of nonmarine origin. In the Park area the thickness of the Kootenai is probably greater than 1,000 ft (305 m). A conspicuous black chert conglomerate, the Cut Bank Sandstone Member, forms the base of the formation and rests unconformably on Upper Jurassic rocks. The Blackleaf Formation, also of Early Cretaceous age, conformably overlies the Kootenai and is about 750 to 800 ft (229-244 m) thick. A marine unit consisting of dark-gray fissile shale and quartzose sandstone forms the basal part of the Blackleaf. Most of the formation is alternating beds of light-coloured, nonmarine clastics. The marine Marias River Shale of Late Cretaceous age unconformably overlies the Blackleaf and is about 1,200 to 1,300 ft (366-396 m) thick. Most of the Marias River is dark-gray shale that contains calcareous and ferruginous concretions and is locally sandy and calcareous. Conformably overlying the Marias River Shale is a marine transitional unit consisting of interbedded shale and sandstone, herein referred to as the Telegraph Creek Formation. The formation ranges in thickness from 120 to 170 ft (36-52 m) on the Kevin-Sunburst dome east of Glacier National Park. The Virgelle Sandstone, which averages 160 ft (49 m) thick, is a massive light-brown sandstone conformably overlying the Telegraph Creek Formation. Resting conformably on the Virgelle Sandstone is the Two Medicine Formation, a nonmarine unit that consists mostly of mudstone with minor lenticular sandstone. The formation is about 2,000 ft (610 m) thick in the Park area. A dark-gray marine formation, the Bearpaw Shale, conformably overlies the Two Medicine Formation. The Bearpaw is nearly 400 ft (122 m) thick east of the Park, but thins to only 235 ft (72 m) south of the Park. The Bearpaw grades upward into a unit of alternating sandstone, siltstone and shale that is as much as 400 ft (122 m) thick. The Horsethief Sandstone, about 90 ft (27 m) thick, is a massive cliff-forming sandstone that was deposited in a regressive marine environment above the Bearpaw. Conformably overlying the Horsethief Sandstone is the St. Mary River Formation, a nonmarine sequence. The St. Mary River Formation is about 1,000 ft (305 m) thick near the eastern margin of the Disturbed belt. Another nonmarine unit, the Willow Creek Formation, overlies the St. Mary River Formation. The Willow Creek consists of about 800 ft (244 m) of variegated clayey rocks and sandstone. The top of the Cretaceous is somewhere within this formation.

Piper Oil Field, North Sea: Fault-Block Structure with Upper Jurassic Beach/Bar Reservoir Sands

Piper field discovery well, 15/17-1a, drilled through 192 ft (52 m) of oil-bearing Upper Jurassic sandstone on December 22, 1972. Subsequent appraisal wells delineated approximately 8,600 productive acres with an estimated 1.55 billion bbl of 36° API gravity low-sulfur oil in place and 650-900 million bbl recoverable. Reservoir sandstones are Oxfordian and early Kimmeridgian in age, of marine origin, and unconformably overlie a nonmarine Middle Jurassic sedimentary sequence. The gross-reservoir thickness averages 250 ft (76 m) in the field area and is comprised of several individual sandstone bodies 40-70 ft (12-21 m) thick. Within individual sandstone bodies the grain size grades either upward or downward from very fine sandstone or siltstone to coarse-grained sandstone. The sandstones generally are well sorted, highly bioturbated, friable, and have excellent porosity and permeability. Individual sandstone bodies record local regressions or transgressions. Regressive sands, accreting seaward as foreset beds, were generally thicker than transgressive sands. Isopachs of Triassic through Cretaceous units suggest that the Piper structure grew intermittently before, during, and after deposition of the reservoir sands. Post-Albian-pre-Toronian/Coniacian faulting and erosion and rejuvenated faulting during pre-Maestrichtian Late Cretaceous time formed a series of eroded and tilted fault blocks. The domal structure mapped at the base of the Tertiary is not evident in the younger horizons because of the masking effect of middle Tertiary deltaic deposits. Regional subsidence continued throughout the Tertiary and formed the present North Sea basin.

Early Sinking History of Ninetyeast Ridge, Northeastern Indian Ocean

Three sites were drilled on Ninetyeast Ridge. They penetrated a sequence of pelagic calcareous oozes underlain by a shallow-water sequence whose ages are Paleocene at Site 214, late Maastrichtian at 216, and late Campanian at 217. At Site 214, the southernmost drilled, a nonmarine sequence that consists of volcaniclastic sediments and thin lignite beds of Paleocene age was penetrated above the basement rocks. At Site 216, volcaniclastic material in the basal sediments is mostly reworked. Both Sites 214 and 216 bottomed in probable subaerial lava flows. Site 217, the northernmost drilled, bottomed in a strongly dolomitized sequence interpreted as a lagoonal reef facies that was subjected periodically to hypersaline conditions and, sometimes, actual emergence. There is excellent correlation between volcanic, sedimentary, and paleontological data: all evidence indicates rapid sinking. The diachronous facies change (older and deeper to the north) is consistent with the notion of rapid northward movement during sinking, and there is some biogeographic evidence to support this.

GEOLOGIC HISTORY OF THE BASS BASIN

The Bass Basin is located offshore between the southern coast of Victoria and the northern coast of Tasmania. It is bounded on the west by King Island and on the east by Flinders Island and the Bassian Rise. Water depths throughout the basin rarely exceed 270 feet (82 metres) and the area has been actively explored for hydrocarbons since 1963.The oldest sedimentary rocks encountered whilst drilling are Early Cretaceous, but the greatest volume of sediment was deposited during the Tertiary. Lithologies vary from continental sandstone, siltstone, shale, and coal in the older, non-marine Cretaceous to Middle Eocene section to limestone, marl, mudstone, and shale in the younger, marine Late Eocene to Recent section. Drilling and seismic data indicate that there was a considerable amount of volcanic activity in the Bass Basin throughout its history.Three distinctively different structural provinces can be recognised in the basin. These provinces are referred to as- a) southeastern area, b) central area, and c) northwestern area.The southeastern area exhibits the earliest structural growth (Early Cretaceous) whereas the structural growth in the central and northwestern areas occurred in Early and Late Tertiary respectively. Structural style also varies from tilted fault blocks with thousands of feet of vertical displacement in the southeastern area, to low relief, small anticlinal folds and minor faults in the northwestern area. Most of the prominent structural trends are oriented in a northwest-southeast direction which is parallel or sub-parallel to the present basin axis.Seismic and E-log correlations within the non-marine Cretaceous and Lower Tertiary section are extremely difficult and palynology is used to differentiate time-rock units. Five separate zones are identifiable within the Eocene and Paleocene, and the Cretaceous has been sub-divided into ten zones which can be related to the time-rock units in the adjacent Otway and Gippsland Basins.Non-commercial accumulations of hydrocarbons have been found in three different structural features: Pelican, Cormorant and Bass −3. These accumulations are from within the Lower Tertiary non-marine sequence known as the Eastern View Group.

Sedimentary Facies and Correlations of Gallup Sandstone and Associated Formations, Northwestern New Mexico: ABSTRACT

The Gallup Sandstone of Late Cretaceous age is a regressive clastic wedge that prograded about halfway across the San Juan basin from a probable source in southwestern Arizona. Numerous closely spaced detailed surface sections, measured along the outcrop belt on the west and south sides of the San Juan basin and extending about 70 mi south of Gallup, New Mexico, into the Zuni basin, have facilitated detailed correlations of the complex of marine, coastal-barrier sandstones and associated nonmarine paludal mudstones and fluvial channel sandstones that comprise the formation. South of Gallup the Pescado Tongue of the Mancos Shale separates the Gallup into two parts; a lower part called the Atarque Member of early Carlile to early-late Carlile age, and an upper part of lates Carlile to possibly earliest Niobrara (?) age. Only the upper part is present in the San Juan basin. Physical tracing of some of the units indicates discrepancies of former correlations. The Horsehead Tongue of the Mancos was found to be the same unit as the Pescado Tongue, and hence the term should be abandoned. The widely distributed Juana Lopez (Sanostee) Member of the Mancos Shale was traced southeast of Gallup where it grades into a nonmarine sequence below the Pescado Tongue. Hence, the Pescado Tongue is younger than formerly considered, and undoubtedly is equivalent to the lower half of the D-Cross Tongue in the southeast. The upper pink fluvial sandstone of the type area near Gallup has been traced to the north where it merges with the coastal-barrier sequence north of Sanostee. The name Torrivio Sandstone Member of the Gallup is proposed for this unit. On the east, along the outcrop belt, it pinches out into nonmarine paludal mudstones of the Dilco Coal Member of the Crevasse Canyon Formation. The basal transgressive upper Mancos Shale of early Niobrara age, which extends to a few miles northeast of Gallup, overlies the Gallup and associated nonmarine deposits of the Dilco. In the northwest corner of New Mexico and the southwest corner of Colorado, this transgression truncates as deep as the Juana Lopez interval. A belt 15-20 mi wide, in which the rate of truncation is greatest, coincides with the location of the so-called Gallup oil fields or pools which produce from lenticular marine sandstone bodies associated with Niobrara transgression. On the south side of the San Juan basin, another type of transgressive sand, which has been informally referred to as the Stray sandstone, is an offlap sequence associated with the Niobrara transgression. All these sands are genetical y unrelated to the type Gallup Sandstone. A northwesterly trending shoreline prevails for most of the units of the Gallup and associated formations. End_of_Article - Last_Page 959------------

Electrical Accessory Curves--New Tool for Subsurface Correlation: ABSTRACT

Electrical accessory curves facilitate recognition of subsurface formations from electrical logs and more accurate physical correlation of rock units. Two types of electrical accessory curves, which show the variation in percentage of thickness of sandstone (SP), and low resistivity mudstone as a function of depth, have been used to examine Laramide deformation in the Powder River basin of Wyoming during deposition of the thick (8,000 ft), nonmarine Late Cretaceous and Tertiary deposits which filled the basin. The Laramide orogeny did not start in this part of Wyoming in late Maestrichtian, during deposition of the Lance Formation, and was only weakly active in early Paleocene time, during deposition of the Tullock Formation. Strong deformation started in middle Paleocene with subsidence along the axis of the basin and deposition of fine-grained Lebo mudstones. Other Laramide structures associated with basin deformation probably were started at this time. Strong subsidence continued into late Paleocene when coarse clastics of the Tongue River Formation first were deposited, indicating uplift and erosion of the adjacent mountains. Deformation continued through part of the Eocene, but ceased before Oligocene time. Cross sections using electrical accessory curves illustrate their use in other thick nonmarine rock sequences and for detailed studies of subtle marine shale correlations. Electrical accessory curves are a new tool to help solve difficult subsurface rock correlation problems and they should be helpful in many other areas. End_of_Article - Last_Page 612------------

Surat Basin, Australia--Subsurface Stratigraphy, History, and Petroleum

The Surat basin, in southeastern Queensland and northeastern New South Wales, is a segment of the Great Artesian basin. Deposition of fluvial quartzose sands began late in Triassic time in areas east of the Surat basin and transgressed westward to the central and northern parts of the basin. They covered folded and block-faulted Triassic and older rocks which had been nearly base-leveled. The quartzose sands were succeeded by a largely nonmarine sand and mud sequence which reached a maximum thickness of about 7,500 ft. The basin expanded south and west, but expansion was interrupted by uplift and erosion about the middle of Jurassic time. Sedimentation continued into the Cretaceous and conditions became marine. The basin contracted southward and westward in medial Cretace us time in response to the deformation which affected the area north and east of the basin. Thirty million bbl of oil and 135 billion cu ft of gas have been proved in small Jurassic fields on both sides of the Surat basin. The source of the oil and gas was probably in nonmarine Jurassic rocks, but the marine rocks of the Permian may have contributed. In all likelihood the amount of petroleum generated was relatively small. Possible original accumulations were destroyed by middle Jurassic and post-middle Cretaceous erosion. Many structural traps, which are mostly compacted drapes on contemporaneous highs, reached their present amplification too late to receive migrating petroleum. Alternatively, tilting and flushing have emptied some traps which received petroleum. Drilling has proved that most structures (seismic closures) which do not have a stratigraphic component of closu e are barren. Some areas of primary stratigraphic trapping probably remain, undisturbed by erosion and flushing, and closed against regional, post-accumulation tilting.

Geology of Western Canadian Continental Shelf: ABSTRACT

This paper deals primarily with the stratigraphy of the Tertiary sediments in the Tofino and Queen Charlotte basins of Canada's Pacific shelf. Information is included from Mesozoic and Tertiary outcrops along the shoreline margins of the basins; End_Page 1908------------------------------ from the six Richfield Oil Corporation wildcats on the Queen Charlotte Islands; from Shell Canada's aeromagnetic, reflection, and refraction seismic surveys; and from 14 offshore wildcats drilled between May 1967 and May 1969. The pre-Tertiary framework of the shelf consists of a thick and complex sequence of Mesozoic sedimentary, metamorphic, and intrusive and extrusive igneous rocks. Little is known about the early Tertiary history, but data from the Tofino basin suggest widespread early-middle Eocene submarine volcanic activity, initial uplift followed by subsidence in late Eocene time, distinct transgressions of Oligocene-early Miocene seas, followed by a middle Miocene period of crustal deformation, uplift, and regression. There was a major transgression in late Miocene and a lesser one in early Pliocene time, followed by a regressive phase in late Pliocene-Pleistocene time. The early Tertiary volcanism in the Tofino basin spread northward and continued, at least sporadically, in the Queen Charlotte basin into the Miocene. Tertiary sedimentation in the Queen Charlotte basin did not begin until the Miocene and, although interrupted by perhaps two periods of uplift and erosion, continued through the Pliocene into the Pleistocene. The maximum thickness of Tertiary sediments is more than 15,000 ft. Depositional environments range from deep-water, open-marine sequences of shales, siltstones, and sandstones in the Tofino basin, through both deep- and shallow-water marine sediments in the Queen Charlotte basin, to a thick nonmarine sequence of sandstone, shale, siltstone, and coal in Hecate Strait and the Queen Charlotte Islands. The sands in both basins are composed primarily of feldspars and quartz, and those of the Queen Charlotte basin are characterized by high porosity and low permeability. There is a wide variety of structural styles including areas of numerous large anticlines with multiple unconformities and complex growth and fault histories; areas of small, gentle, low-relief anticlines; and areas where the Tertiary sediments onlap older volcanics with little or no folding of the sediments. There are insufficient deep seismic reflections to interpret and understand properly the structural style of the Tofino basin, but at least two basic mechanisms must be considered: (1) simple compressional folding with detachment from the basement, and (2) flowage of the overpressured shales into the cores of the anticlines. At various times in different places in the basin, each of these mechanisms might have been dominant. Both oil and gas shows have been encountered, but no commercial accumulations have yet been found. End_of_Article - Last_Page 1909------------

Petrography Of The Upper Cenozoic Non-marine Sediments In The San Pedro Valley, Arizona

ABSTRACT An Upper Cenozoic (Late Pliocene-middle Pleistocene) non-marine sedimentary sequence--the St. David Formation--crops out in badland topography on both sides of the San Pedro River near St. David, Arizona. It consists chiefly of fluvial floodplain silts and clays with smaller amounts of sand, gravels, fresh-water limestones, pyroclastic units, and paleosols. An immature mineral suite and angularity of the mineral grains suggest that source areas for sediments in the St. David Formation were nearby. X-ray analyses show that the clay suite is dominated by illite in the lower part, and by montmorillonite in the middle and upper parts; the change was probably initiated in part by volcanic activity. Red beds, which are common in the lower part of the formation, may have been formed in part diagenetically. Very fine crystalline limestones and green clays contain fresh-water algae, ostracods, and molluscs suggesting deposition in lakes, ponds, and swamps. Results of the sedimentologic and petrographic studies indicate that the St. David Formation was deposited by a large, slow-moving, through-flowing stream system which spread fine-grained sediments on an aggrading floodplain, and at times in lakes and ponds.As indicated by the vertebrate fossils, savannas and open-grasslands probably prevailed in areas away from the streams.

New Observations on the Wilcox Group: ABSTRACT

For reasons of regional relationships, the base of the Wilcox group is best placed at the base of the Seguin formation as redefined by Beckman and Turner, 1943. This formation is a transgressive shallow-marine sequence of glauconitic sands topped by the Caldwell Knob oyster bed. The latter is a biostrome, 0-23 feet thick. The Seguin formation is 92 feet thick in central Texas. The Seguin formation is overlain by the Hooper formation (newly proposed), about 325 feet thick in central Texas. The Hooper is a regressive partly marine, partly non-marine sequence of glauconitic sands and lignitic clays. An erosional disconformity separates the Hooper from the overlying Simsboro sand, a non-marine kaolinitic very coarse sand, about 75 feet thick in central Texas. The Simsboro san is succeeded by a great mass of non-marine sediment composed of shales, clays, silts, sands, old soils, lignites, channel sandstones, and clay-ironstone lenses. The Butler clay, previously regarded as occupying the stratigraphic position of the Hooper, rests on the Simsboro sand at the Butler clay type locality. Hence the Butler clay is merely the basal part of the Calvert Bluff formation from which it can not be separated on lithologic grounds. The top of the Wilcox group is placed at the base of the Carrizo sand, a fluviatile sand, which rests with a regional erosional disconformity on the Wilcox. A hilly buried topography exists at this break and is recognizable in the Tyler basin, central Texas, and possibly other marginal updip areas. The data presented are the work of Ralph Giannone, William W. Sharp, Jr., and H. B. Stenzel. End_of_Article - Last_Page 2625------------