排序方式： 共有4条查询结果，搜索用时 15 毫秒
1
1.
Mesoscale structures in Paleozoic rocks of the Ozark plateaus reveal four Pennsylvanian deformation episodes in midcontinent North America. The two earliest episodes can be assigned to progressive northwestward docking of the Ouachita terrane with North America. Early extensional structures (Event 1) indicate a northwest/southeast maximum horizontal stress (Hmax) during Early Pennsylvanian Ouachita terrane advance. Event 2 extensional and strike-slip structures indicate Hmax across the Ozark plateaus that varies systematically from north-northwest/south-southeast in the south to northeast/southwest in the north. This suggests development of a slip-line deformation field in response to minor northeastward lateral escape of lithospheric blocks away from the northwestward-moving Ouachita terrane's leading edge, which acted as an indenter in western Arkansas, southeastern Oklahoma, and Texas. Younger contractional and strike-slip structures of Event 3 indicate northeast/southwest Hmax across the entire Ozark plateaus, and deformation orientation and intensity are not readily assigned to Ouachita foreland deformation and may be related to Middle Pennsylvanian Ancestral Rockies contractional deformation. Finally, Event 4 contractional structures indicate northwest/southeast Hmax consistent with southern Appalachian late stage convergence.Deformation episodes are localized along basement fault zones, particularly at major bends, suggesting minor restraining-bend uplifts along strike-slip faults. Geometries of conjugate normal fault and hybrid shear joint arrays indicate localized areas of high differential stress consistent with basement block uplift at these bends. High-angle faults reactivated in a reverse sense and bedding-parallel veins suggest tensile minimum stresses and pore fluid pressures exceeding lithostatic stress, consistent with brine pulses driven into the midcontinent during Late Paleozoic orogeny (as proposed by other authors). 相似文献
2.
Removed overburden, burial, maturation, and petroleum generation analysis indicates that maturity in the Arkoma Basin and the Ouachita Foldbelt is explained effectively using simple burial models that account for the significant surface erosion that has occurred and assuming geothermal gradients similar to present-day gradients have been approximately constant through geologic time. Regional models, based on analysis at 115 well locations, indicate that from 5,000 to 15,000 ft (1.5–4.5 km) of section, differing with location from north to south and west to east, has been removed from the Arkoma Basin region, and as much as 25,000–40,000 ft (7.5–12 km) have been removed from areas of the Ouachita Foldbelt. Based on burial and thermal history reconstruction, increasing maturation from west to east across the basin is primarily the result of increasing overburden and subsequent surface erosion from west to east. The models predict most publicly available vitrinite reflectance data within a factor of 1.5 at two standard deviations. Comparison of model and measured reflectance-depth trends in six wells indicates that hydrothermal fluid movement should not have modified reflectance by more than approximately 20% in the center of the basin. Analysis indicates that most of the basin is overmature for oil production from intervals below the Spiro Sandstone, except to the north and northwest. Although thermal maturities are high, methane is stable throughout the basin. Except for the basal Arbuckle Group, all formations were thermally immature for oil generation prior to burial by the Mississippian and Morrowan in the Ouachita Foldbelt of Oklahoma and by the Atokan and Desmoinesian over most of the basin and study area. In the deeper part of the present basin, all strata entered and passed through the oil window during or within 10 My after Atokan time. Because no additional major quantities of hydrocarbons were generated after Atokan time, the hydrocarbons must have been emplaced and trapped during this brief time interval. 相似文献
3.
A. W. Walton K. M. Wojcik R. H. Goldstein C. E. Barker 《International Journal of Earth Sciences》1995,84(3):535-551
Diagenesis of Upper Carboniferous foreland shelf rocks in southeastern Kansas took place at temperatures as high as 100–150° C at a depth of less than 2 km. High temperatures are the result of the long distance (hundreds of kilometers) advection of groundwater related to collisional orogeny in the Ouachita tectonic belt to the south. Orogenic activity in the Ouachita area was broadly Late Carboniferous, equivalent to the Variscan activity of Europe. Mississippi Valley-type Pb-Zn deposits and oil and gas fields in the US midcontinent and elsewhere are commonly attributed to regional groundwater flow resulting from such collisional events. This paper describes the diagenesis and thermal effects in sandstone and limestone of Upper Carboniferous siliciclastic and limestone-shale cyclothems, the purported confining layer of a supposed regional aquifer. Diagenesis took place in early, intermediate, and late stages. Many intermediate and late stage events in the sandstones have equivalents in the limestones, suggesting that the causes were regional. The sandstone paragenesis includes siderite cement (early stage), quartz overgrowths (intermediate stage), dissolution of feldspar and carbonates, followed by minor Fe calcite, pore-filling kaolinite and sub-poikilotopic Ca ankerite (late stage). The limestone paragenesis includes calcite cement (early stage); megaquartz, chalcedony, and Fe calcite spar (intermediate stage); and dissolution, Ca-Fe dolomite and kaolinite (late stage). The R
m value of vitrinite shows a regional average of 0.6–0.7%; Rock-Eval T
maX suggests a comparable degree of organic maturity. The T
h of aqueous fluid inclusions in late stage Ca-Fe-Mg carbonates ranges from 90 to 160° and T
mice indicates very saline water (>200000 ppm NaCl equivalent); 18O suggests that the water is of basinal origin. Local warm spots have higher R
m, T
max, and T
h. The results constrain numerical models of regional fluid migration, which is widely viewed as an artesian flow from recharge areas in the Ouachita belt across the foreland basin onto the foreland shelf area. Such models must account for heating effects that extend at least 500 km from the orogenic front and affect both supposed aquifer beds and the overlying supposed confining layer. Warm spots indicate either more rapid or more prolonged flow locally. T
h and T
mice data show the highest temperatures coincided with high salinity fluids. 相似文献
4.
Rock fragment distributions and regolith evolution in the Ouachita Mountains,Arkansas, USA 总被引：2，自引：0，他引：2
Rock fragments in the regolith are a persistent property that reflects the combined influences of geologic controls, erosion, deposition, bioturbation, and weathering. The distribution of rock fragments in regoliths of the Ouachita Mountains, Arkansas, shows that sandstone fragments are common in all layers, even if sandstone is absent in parent material. Shale and sandstone fragments are produced at the bedrock weathering front, but the shale weathers rapidly and intact fragments are rare in the solum. Sandstone is weathered from ridgetop outcrops and transported downslope. Some of these fragments are moved downward, by faunalturbation and by transport into pits associated with rotting tree stumps. Upward movement by treethrow is common, resulting in a net concentration of rocks near the surface. However, the highest fragment concentrations are in the lower regolith, indicating active production at the weathering front. The regolith is a dynamic feature, reflecting the influences of vertical and horizontal processes, of active weathering at the bedrock interface, and of surficial sediment movements. The role of trees in redistributing rock fragments suggests that significant regolith mixing occurs over time scales associated with forest vegetation communities, and that forest soils have likely been extensively mixed within Holocene and historic time. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
1