Red Clastics Research Articles

Salt Deposits and Structure of the Maritime Provinces of Canada: ABSTRACT

Aeromagnetic, gravity, and seismic surveys in the Maritime Provinces of Canada have provided extensive new information bearing on (1) the geometry of the depositional basins, (2) the distribution and shape of the major salt masses, and (3) the sub-salt structure. The basins and uplifts exhibit a striking geometrical relationship of east- and northeast-trending elements that strongly suggest a shear pattern. This pattern was developed during the Acadian and possibly earlier orogenies. Large crustal blocks, bounded by faults, appear to have tilted and shifted, with rapid erosion and deposition during Mississippian and Pennsylvanian times creating large prisms of sediments which differ greatly in shape, size, and sedimentary facies. Widespread deposits of rock salt, gypsum, and anhydrite exist in the Windsor Group (Upper Mississippian) in all the Maritime basins. The saline facies is interbedded and interfingered with thin limestones, red and grey shale, and coarse red clastics, and in a few places lies directly on the basement rocks. In the anticlines, notably those of northern Nova Scotia, western Cape Breton, and southern New Brunswick, the rock salt thickened greatly in the axial region of the folds and in places pushed through the overlying rocks to the surface. This sequence of thickening of the salt within the folds followed by diapirism is similar to that of the salt anticlines of the Paradox Basin and South Persia. Little is known about the original depositional thicknesses of the saline facies, but grav ty data indicate wide differences in the amount of rock salt along the axes of the major anticlines. This may indicate the original pattern of salt deposition. A thick section of sandstone and shale, plentiful oil shows, a basin-wide seal afforded by the evaporite section, and the large structural traps provided by the major anticlines combine to make the sub-salt Horton Group (Lower Mississippian) rocks a prime target for oil and gas exploration in these largely untested basins. End_of_Article - Last_Page 358------------

Mesozoic Stratigraphy of Honduras: ABSTRACT

The Honduras basin is an intracontinental salient of a large marginal geosyncline that borders the southern side of the geanticline which divides northern Central America. During Mesozoic and Cenozoic time, 10,000-25,000 feet of sediments were deposited in the Honduras basin. No thick evaporite deposits have been found, suggesting the geosyncline was an open communication with the Pacific and Atlantic oceans. The Triassic and Jurassic periods are represented by 3,000 feet of deltaic, littoral clastics. The Lower Cretaceous is composed of 2,000 feet of black, shaly limestones containing oil seeps; 2,500 feet of red clastics; 2,000-6,000 feet of massive rudistid and miliolid limestones; and 2,000 feet of conglomerates and clastics derived from the lower formations. The Laramide orogeny divided the Honduras basin into the Ulua basin on the west and the Mosquitia embayment on the east. The main trough of the marginal geosyncline shifted south, and 35,000 feet of sediments were deposited in the area of Lake Nicaragua during Upper Cretaceous and Tertiary time. The Ulua basin received 2,000 feet of Upper Cretaceous and Eocene redbeds and limestones and then remained a positive area during the remainder of Cenozoic time. Compressive folding during the mid-Tertiary Antillean revolution, formed distinct east-west geanticlinal belts. Volcanism, beginning during this period and continuing until recent time, was responsible for the thick cover of flows and tuffs along the Pacific coast of Central America. The Mosquitia area of northeast Honduras and northern Nicaragua became a major embayment during Upper Cretaceous and Tertiary time. Thirteen hundred feet of Upper Cretaceous limestones and shales and 15,000 feet of Tertiary flood-plain and marine clastics underlie the broad Mosquitia continental shelf and extend eastward into the Caribbean Sea 150 miles. The Pliocene-Pleistocene Cascadian orogeny was responsible for the present-day topography of northern Central America. Wrench fault tectonics probably explain the complex structure of this region. End_of_Article - Last_Page 1774------------

Pennsylvanian Oil Possibilities of San Juan Basin, Four Corners Region

The San Juan basin is a post-Pennsylvanian tectonic subsidence area closely related in its early sedimentational history to the Paradox geosyncline. During early Pennsylvanian time, this region was subjected to widespread erosion, but received high-shelf Pinkerton Trail carbonates and fine gray clastics related to the Cordilleran geosyncline, followed by Cherokee subsidence to form a through-going seaway in whose deeper parts evaporites of the Paradox formation were deposited, succeeded by coarse arkosic clastic invasion from the strongly activated San Luis and Penasco positives on the east and fine-grained red clastics from the Zuni-Defiance positives on the west and southwest. Normal marine waters persisted during the deposition of the Honaker Trail-late Madera sediment , succeeded by filling of the seaway with red continental clastics across the Pennsylvanian-Permian temporal boundary everywhere except in the medial parts of the seaway where marine Wolfcamp carbonates were deposited. The southwest and west shelf of this seaway, with its sediment-controlling spurs and sags, appears to be a locale where commercial oil should be present in Pennsylvanian strata.

Molas and Associated Formations in San Juan Basin-Needle Mountains Area, Southwestern Colorado

A review of some of the literature dealing with the Molas formation and its equivalents in the Four Corners area reveals differences of opinion about its age and historical significance. The writers studied and sampled exposures along the northern rim of the San Juan basin and in the Needle Mountains, southwestern Colorado, and made petrographic, insoluble-residue, heavy-mineral, and clay-mineral (x-ray diffractometer) analyses of the samples. Units examined include the Upper Devonian Ouray limestone, Lower Mississippian Leadville limestone, and Mississippian-Pennsylvanian Molas formation. Insoluble residues from the Ouray and Leadville are distinctive; boulders from each were identified in the basal Coalbank Hill member (named herein) of the Molas formation. The boulders are packed in a red clay and silt matrix which overlies the limestones and has sifted down into joints, pits, and caverns in them. Overlying the Coalbank Hill is the Middle member of the Molas, a poorly stratified unit of stream-deposited red clastics. The upper Molas member is made up of well stratified clastics, largely red, and contains marine fossils in its upper part. The upper Molas grades into the overlying green and gray clastics and interbedded li estones of the Pinkerton Trail or Hermosa formation. Illite is the chief clay mineral in residues from the Ouray, the Leadville, limestone boulders in the Coalbank Hill member, and in the Upper member of the Molas. Kaolinite is the chief clay mineral in the matrix of the Coalbank Hill and Middle member of the Molas. The interpretation presented is that a residual deposit accumulated in southwestern Colorado as solution of Mississippian and Devonian limestones took place during post-Osage, pre-Pennsylvanian erosion. The upper part of the old regolith was eroded and deposited elsewhere by streams; some of it was finally deposited in and reworked by the advancing early Pennsylvanian sea. In some areas, deposition of the Molas red clastics continued into early Des Moines time.

Stratigraphy of the Upper and Middle Permian of West Texas and Southeast New Mexico: ABSTRACT

The stratigraphic phenomena of the Permian basin are related directly to gradation which may be classified as follows: (1) gradual gradation of clastics into marine beds basinward and (2) abrupt gradation of clastics and evaporites into reef limestone. Surface studies and subsurface work with stereograms and paleogeographic maps reveal that, as a result of this gradation, many of the various facies are time equivalents. A significant example of type (2) gradation is found in the Glass Mountains approximately five miles north of Iron Mountain. The clastics of the Word formation may be traced on the surface into the Vidrio limestone. Over a considerable area northeast of the Glass Mountains variable thicknesses of Vidrio limestone and underlying thick sandstones both grade nto San Andres limestone over structurally high areas. The appearance, subsequent movements and disappearance of a number of the structural features are placed in the Permian time scale. Recognized as major structures are the Val Verde basin, the Cerf basin and the Blackstone arch. The latter extends northward from southeastern Pecos County across the Sheffield channel and the Fort Stockton arch into the Sand Hills arch. The Central Basin platform was built over this feature. A perspective of the Permian basin in its entirety indicates that the Anadarko basin is an integral part of the larger basin on the south. During San Andres time sands moved into the Midland basin by way of the Sheffield channel which connected with the Delaware and Cerf basins. It appears that the sands moving into the Delaware basin came from the west through Salt Flat, which is just west of the Delaware Mountains. Throughout all Permian time red clastics, which were derived from the northwest, northeast, and east, were deposited in the northern part of the basin, the dark sediments of southern origin forming in the south portion. End_Page 1710------------------------------ The presence of facies in the South Plains syncline and the Midland basin similar to those of Oklahoma led to the adoption of Oklahoma nomenclature in West Texas. It is used in part in this paper. The El Reno group with its basal sandstone, the San Angelo, is the red clastic time equivalent of the San Andres and its basal sandstone, the Glorieta. By subsurface correlations the Whitehorse group is traced to its surface outcrop, west of Carlsbad, and is tied into Lang's Chalk Bluff formation. To the south it is traced to the Glass Mountains, where it appears to be equivalent to the Gilliam formation. Sediments of volcanic origin are present in the Leonard, San Andres and their time equivalents, gradually disappearing to the north. They are also present in the Whitehorse in its southern evelopment. Unconformities are recognized as the best time markers because of the changing facies. By this means the base of the Permian is found near the middle of the Cisco, as described by Plummer and Moore, and at the base of the Wolfcamp and Abo. The unconformity at the base of the Leonard of the Glass Mountains is represented on the east rim of the basin by a change in sedimentation. A conglomerate, 300 feet below the base of the Word, appears to be equivalent to the base of the El Reno group, the San Andres and the Delaware Mountain formation. An unconformity exists at the base of the Whitehorse along the entire length of the east rim of the basin. In the Glass Mountains it appears to be represented by a hiatus at the base of the Gilliam. Eleven hundred feet below the top of the Delaware M untain formation a break in deposition has been reported which may represent this unconformity. While the lower Castile was being deposited in the southwestern portion of the basin, a hiatus occurred in the remaining areas. An unconformity at the base of the upper Castile and the Quartermaster is indicated in several areas on the east rim of the basin by a conglomerate at the base of the latter. End_of_Article - Last_Page 1711------------