Northern Uplift Research Articles

The differential collapse–filling evolution process of the paleo-underground river in the Northern Uplift of the Tarim Basin

The characteristics and stages of collapse–filling in paleo-underground rivers vary in recharge–runoff–discharge zones, constraining the associated fracture-caved reservoirs in carbonate strata. This paper comprehensively uses core, fluid inclusion, and carbon–oxygen isotope to probe the evolution process and migration of collapse–filling in paleo-underground rivers in the Northern Uplift of the Tarim Basin. The results show that 1) more than three stages of collapse–filling were identified in recharge–runoff–discharge zones, and a four-stage differential collapse–filling process was proposed to summarize the evolution of paleo-underground rivers. 2) The collapse–filling process varies spatiotemporally in the recharge, runoff, and discharge zones. Hydrodynamic strength and filling capacity migrate gradually from the recharge zone to the discharge zone. 3) Collapse–filling mechanisms, including gravity, suffusion, and suction–erosion mechanisms, also vary along with the collapse–filling evolution process of paleo-underground rivers. The research provided a new insight to recognize and interpret the differential planar distribution and vertical filling of the paleo-underground river system, which can be further applied to investigate the fracture-caved karst reservoirs.

Evolution and Controlling Factors of the Reef and Carbonate Platform in Wan’an Basin, South China Sea

In this study, high-resolution seismic profiles and well data provided a good opportunity for better understanding the reefs and carbonate platforms in the Wan’an Basin, southwest of the South China Sea, and also provided valuable information for the oil–gas exploration in the reef reservoirs. Four evolutional phases, including the initial phase, the prosperous phase, the recession phase and the submerged phase, of the reefs and carbonate platforms are proposed according to our data. In the Early Miocene, a few small, isolated carbonate platforms initiated in the center of the basin. In the Middle Miocene, they flourished and mainly formed around the Northern Uplift and Central Uplift, with two belts of carbonate platforms in the western area and eastern area that were mainly platform-edge reefs, massive reefs and a few point reefs. In the Late Miocene, the carbonate platforms began to retreat towards the high topographic position because of the rising of sea level. Meanwhile, the numbers and styles of reefs increased to include platform-edge reefs, massive reefs, atoll reefs and point reefs. Since the Pliocene, most of the carbonate platforms have been covered by detrital materials from terrestrial sources. Crustal tectonic activity provides favorable topography for reef growth and the distribution of platforms, and eustasy controlled the vertical growth and lateral migration of reefs. Since the Late Miocene, the rapidly crustal tectonic subsidence and the rising of relative sea level may lead to the drowning of the carbonate platform.

Ultra-Deep Dolomite Reservoir Quality Classification and its Effect on Acid-Fracturing Based on Natural Fracture Activity Analysis: A Case Study of the Cambrian Subsalt Reservoir in Northern Uplift of Tarim Basin

Taking the >8,000 m buried Cambrian subsalt dolomite reservoir in the northern uplift of the Tarim Basin as an example, this study used imaging logging, cores, outcrops, and other data to identify natural fractures and obtain parameters of natural fractures, including strike, azimuth, width, length, and apparent porosity, and clarified the characteristics of natural fractures in the well section. Based on the logging data, wellbore rock mechanics, in situ stress, and elastic parameters were established. The analysis of the mechanical characteristics of natural fractures was carried out to find out the shear stress, normal stress, and their ratio of each natural fracture in the reservoir section. Combined with the stress value of each fracture, the quantitative characterization parameter Fractures Geomechanical Activity Index of the mechanical characteristics of natural fractures is established. Combined with the petrophysical parameters of natural fractures, the evaluation model of the quality index of the reservoir containing the natural fractures is established. According to the classification of reservoir quality, combined with the petrophysical properties of the reservoir section, the optimization of the acid-fracturing scheme and injection pressure can be carried out in order to increase the production after acid-fracturing. In this study, the quality of the reservoir with natural fractures is divided into three categories: the QRCF of a Class I reservoir is 0.6∼1, of Class II reservoir is 0.3∼0.6, and of Class III reservoir is less than 0.3. The application of Well L1 and other wells shows that there are great differences in the development of natural fractures at different depths of the Cambrian subsalt dolomite reservoir so as to QRCF. The Class I reservoir is easy for acid-fracturing to achieve high performance. The Class II reservoir needs large-scale acid-fracturing, and the Class III reservoir cannot be acid-fractured under the current methods. The research results provide a reference for the classification of the fracture mechanical activity of an ultra-deep Cambrian subsalt dolomite reservoir and the optimization of acid-fracturing treatment parameters of similar reservoirs.

The middle Cretaceous (110–94 Ma) evolution of Tangza Basin in the western Tibetan Plateau and implications for initial topographic growth of northern Lhasa

AbstractReconstruction of Cretaceous geological evolution of Tibetan Plateau growth is critical for assessing the effect of India-Asia collision on the formation of its high elevation. However, Cretaceous topographic evolution and geodynamic mechanism in northern Lhasa remain ambiguous. Here we present results from sedimentology, zircon U-Pb ages, and detrital Cr-spinel composition of the Tangza Formation in the western part of northern Lhasa. Sedimentary lithofacies document that orbitolinid foraminifera–limestone beds were deposited in a shallow-marine setting, while clastic rocks accumulated in an alluvial fan during the middle Cretaceous. Zircon U-Pb ages of interbedded volcanic rocks place a robust constraint on the initiation of clastic rock deposition at ca. 106 Ma. Sandstones are enriched lithic fragments with abundant volcanic grains. U-Pb ages of detrital zircon display a prominent age population at 101–130 Ma with a 120 Ma peak. These data indicate that the clastic rocks were mainly derived from northern Lhasa, including an Early Cretaceous magmatic arc. Sedimentary and provenance characteristics are most consistent with deposition in a local foreland basin. The activation of south-vergent local thrusting may be responsible for loading of the Tangza foreland basin. This thrust faulting may be associated with crustal shortening induced by the continuous convergence of Lhasa and Qiangtang since collision initiated during the Early Cretaceous. The initial uplift of western and central parts of northern Lhasa and eastern Gangdese arc occurred at ca. 106 Ma, while the widespread uplift of northern and central Lhasa probably initiated at ca. 92 Ma. The mid–Late Cretaceous uplift in Lhasa was significantly earlier than the early Cenozoic India-Asia collision.

The early Palaeogene transition from thin-skinned to thick-skinned shortening in the Potosí uplift, Sierra Madre Oriental, northeastern Mexico

ABSTRACT The central Sierra Madre Oriental in Mexico developed primarily in the Late Cretaceous to early Palaeogene as a thin-skinned fold belt above a décollement hosted in Jurassic evaporite. In some regions shortening transitioned to sub-décollement structural levels, resulting in thick-skinned uplifts such as the Potosí uplift in Nuevo León. Thick-skinned deformation in the Potosí uplift involved folding of sub-décollement strata into an NNW-trending anticlinorium, cleavage development, thrust and conjugate strike-slip faulting, and extension fractures associated with barite mineralization. These structures consistently record subhorizontal shortening, directed ~52–65° in the southern uplift, ~69–72° in the northern uplift. Palaeocene to mid-Eocene zircon (U-Th)/He cooling dates record the timing of exhumation associated with thick-skinned uplift and suggest a continuation of shortening rather than a separate tectonic event. Zircon (U-Th)/He dates across the southern Potosí uplift and the Aramberri uplift, ~50 km to the south, range from ~66–53 Ma, whereas dates in the northern part of the Potosí uplift range from ~49–44 Ma. We attribute the transition to thick-skinned shortening to the mechanical strengthening of a planar décollement as rheologically weak evaporite was evacuated beneath synclinal keels of detachment folds. Along-strike differences in timing of exhumation and shortening directions may relate to differences in mechanical stratigraphy. Thicker intervals of evaporite in the northern uplift allowed thin-skinned shortening to continue while the southern uplift transitioned to thick-skinned shortening as the evaporite décollement was exhausted. As a result, stress-strain trajectories in the northern uplift refracted clockwise during continued deformation. Our findings provide new insight into the structural evolution of the Potosí uplift and may provide a framework for studying other thick-skinned uplifts in the orogen, and more generally orogenic belts that record a transition in deformation styles during progressive shortening.

Microfacies characteristics and depositional evolution of typical wave-dominated littoral deposits – A case of Carboniferous ‘Donghe sandstones’ in Hudson Oilfield, Tarim basin, NW China

Hudson Oilfield, which located in the northern Uplift of Tarim Basin, is considered to be the largest whole-shaped oilfield in China, and the extensive Carboniferous ‘Donghe sandstones’, one of the most important marine sandstones units for oil and gas exploration in Tabei Uplift, constitutes the main reservoir. However, not all this sandstones are with good physical properties, and hence, the sedimentary characteristics and depositional evolution is believed to be critical to prediction of reservoir. It is determined that wave-dominated clastic littoral deposits with no barrier are the main depositional environment based on the modern sedimentary theory and related data analysis including ancient landform characteristics. And transitional zone, shoreface, foreshore, backshore and dune are considered as the five subenvironments. Through data of high resolution dipmeter logging and imaging logging, different sedimentary structures and other facies marks observed from cores of research regions are demarcated, and thirteen microfacies are further identified. Based on the detailed microfacies types, the evolution process of Carboniferous ‘Donghe sandstones’ can be divided to four main periods, in which, early highstand systems tract (HST) deposits in Period 1-2, and late HST deposits in Period 3-4.

Mitogenomic Phylogeny, Diversification, and Biogeography of South American Spiny Rats.

Echimyidae is one of the most speciose and ecologically diverse rodent families in the world, occupying a wide range of habitats in the Neotropics. However, a resolved phylogeny at the genus-level is still lacking for these 22 genera of South American spiny rats, including the coypu (Myocastorinae), and 5 genera of West Indian hutias (Capromyidae) relatives. Here, we used Illumina shotgun sequencing to assemble 38 new complete mitogenomes, establishing Echimyidae, and Capromyidae as the first major rodent families to be completely sequenced at the genus-level for their mitochondrial DNA. Combining mitogenomes and nuclear exons, we inferred a robust phylogenetic framework that reveals several newly supported nodes as well as the tempo of the higher level diversification of these rodents. Incorporating the full generic diversity of extant echimyids leads us to propose a new higher level classification of two subfamilies: Euryzygomatomyinae and Echimyinae. Of note, the enigmatic Carterodon displays fast-evolving mitochondrial and nuclear sequences, with a long branch that destabilizes the deepest divergences of the echimyid tree, thereby challenging the sister-group relationship between Capromyidae and Euryzygomatomyinae. Biogeographical analyses involving higher level taxa show that several vicariant and dispersal events impacted the evolutionary history of echimyids. The diversification history of Echimyidae seems to have been influenced by two major historical factors, namely (1) recurrent connections between Atlantic and Amazonian Forests and (2) the Northern uplift of the Andes.

Structural differences between the western and eastern Qiongdongnan Basin: evidence of Indochina block extrusion and South China Sea seafloor spreading

Located at the intersection between a NW-trending slip system and NE-trending rift system in the northern South China Sea, the Qiongdongnan Basin provides key clues for us to understand the proposed extrusion of the Indochina Block along with Red River Fault Zone and extensional margins. In this paper we for the first time systematically reveal the striking structural differences between the western and eastern sector of the Qiongdongnan Basin. Influenced by the NW-trending slip faults, the western Qiongdongnan Basin developed E–W-trending faults, and was subsequently inverted at 30–21 Ma. The eastern sector was dominated by faults with NE orientation before 30 Ma, and thereafter with various orientations from NE, to EW and NW during the period 30–21 Ma; rifting display composite symmetric graben instead of the composite half graben or asymmetric graben in the west. The deep and thermal structures in turn are invoked to account for such deformation differences. The lithosphere of the eastern Qiongdongnan Basin is very hot and thinned because of mantle upwelling and heating, composite symmetric grabens formed and the faults varied with the basal plate boundary. However, the Southern and Northern Uplift area and middle of the central depression is located on normal lithosphere and formed half grabens or simple grabens. The lithosphere in the western sector is transitional from very hot to normal. Eventually, the Paleogene tectonic development of the Qiongdongnan Basin may be summarized into three stages with dominating influences, the retreat of the West Pacific subduction zone (44–36 Ma), slow Indochina block extrusion together with slab-pull of the Proto-South China Sea (36–30 Ma), rapid Indochina block extrusion together with the South China Sea seafloor spreading (30–21 Ma).

New evidence on the Neogene uplift of South Tianshan: constraints from the (U–Th)/He and AFT ages of borehole samples of the Tarim basin and implications for hydrocarbon generation

We identified a Neogene rapid uplift-denudation event of the South Tianshan based on apatite (U–Th)/He and apatite fission track (AFT) ages in Tertiary rocks of the Tarim basin, using borehole samples. The (U–Th)/He thermochronology can be used to reveal the tectono-thermal events with lower temperature than that of AFT thermochronology and has not been used previously to study the uplift of the Tianshan Mountain. Using these data, we show the relationship between the uplift of the South Tianshan and the subsidence/deposition of the northern Tarim basin during the Neogene. The apatite helium ages reveal the migration of uplift, erosion and deposition in the northern Tarim basin. A rapid uplift of the South Tianshan during the Miocene and a corresponding rapid subsidence in the northern Tarim basin occurred. However, in the Pliocene, the Kuqa Depression and South Tianshan uplifted and eroded at the same time and in turn provided the detrital source rocks for the Northern Uplift of the Tarim basin. In contrast to earlier studies, we arrive at the conclusion that the South Tianshan experienced rapid uplift in the Miocene based on (U–Th)/He data of apatite obtained from borehole samples collected in the Tarim basin itself, and not from the bordering mountain chain. Combined apatite (U–Th)/He and fission track thermochronometry enables reconstruction of thermal histories of sedimentary rocks between 40 and 120°C, and this has implications for the generation of liquid hydrocarbon in the 65–120°C range in the basin. Thermal and burial histories of typical samples were also modelled to show the rapid uplift in our study. Our works not only provide a new evidence for the South Tianshan uplift but also indicate that there is a coupling between uplift and subsidence in the South Tianshan and adjacent northern part of the Tarim basin, which controlled hydrocarbon accumulation in the Kuqa Depression and Northern Uplift of the Tarim basin.

Isotope geochemistry of ore fluids for the Dongsheng sandstone-type uranium deposit, China

The Dongsheng sandstone-type uranium deposit is one of the large-sized sandstone-type uranium deposits discovered in the northern part of the Ordos Basin of China in recent years. Geochemical characteristics of the Dongsheng uranium deposit are significantly different from those of the typical interlayered oxidized sandstone-type uranium ore deposits in the region of Middle Asia. Fluid inclusion studies of the uranium deposit showed that the uranium ore-forming temperatures are within the range of 150–160°C. Their 3He/4He ratios are within the range of 0.02–1.00 R/Ra, about 5–40 times those of the crust. Their 40Ar/36Ar ratios vary from 584 to 1243, much higher than the values of atmospheric argon. The δ18OH2O and δD values of fluid inclusions from the uranium deposit are −3.0‰–−8.75‰ and −55.8‰–−71.3‰, respectively, reflecting the characteristics of of meteoric water and magmatic water. The δ18OH2O and δD values of kaolinite layer at the bottom of the uranium ore deposit are 6.1‰ and −77‰, respectively, showing the characteristics of magmatic water. The δ13CV-PDB and δ18OH2O values of calcite veins in uranium ores are −8.0‰ and 5.76‰, respectively, showing the characteristics of mantle source. Geochemical characteristics of fluid inclusions indicated that the ore-formation fluid for the Dongsheng uranium deposit was a mixed fluid of meteoric water and deep-source fluid from the crust. It was proposed that the Jurassic-Cretaceous U-rich metamorphic rocks and granites widespread in the northern uplift area of the Ordos Basin had been weathered and denudated and the ore-forming elements, mainly uranium, were transported by meteoric waters to the Dongsheng region, where uranium ores were formed. Tectonothermal events and magmatic activities in the Ordos Basin during the Mesozoic made fluids in the deep interior and oil/gas at shallow levels upwarp along the fault zone and activated fractures, filling into U-bearing clastic sandstones, thus providing necessary energy for the formation of uranium ores.

THE EXPLORATION POTENTIAL STUDY OF DEEP SEATED GAS IN TARIM BASIN

With the shallow natural gas exploration becoming difficult at present ,deep-seated natural gas exploration has become the hot issue. Tarim basin, which is situated in the western part of China, is the biggest sedimentary basin in China. The study result show that Tarim basin has three major better hydrocarbon source rocks, which are the Cambrian-Ordovician, Carboniferous-lower Permian and Triassic-Tertiary source rocks, and high efficiency gas reservoirs and seal rocks, forming five sets of regional associations of gas reservoir and capping bed. Therefore, the basin has better physical condition for deep-seated gas generation, storage and conservation. Based on the present condition of gas exploration, the authors point out that Kuche depression, Northern uplift, Central uplift, Bachu uplift and South-western depression in Tarim basin has wider exploration prospect for deep seated gas.

Structure, Isotopes, and 40Ar/39Ar Dating of the Pengjiakuang Gold Deposit, Mesozoic Jiaolai Basin, Eastern China

The Pengjiakuang gold deposit, located on the northeastern margin of the Mesozoic Jiaolai basin, eastern Shandong Province, China, is controlled by a low-angle detachment fault. Three economic ore bodies and more than 10 mineralized bodies have been proved in recent years. The main ore bodies are made up of gold-bearing breccia, cataclastic rocks, and sulfide-quartz veins in lenses and veins. Gold ores are typically brecciated, veinlet, and disseminated. Lamprophyre dikes are spatially and temporally associated with the gold ore bodies. The isotopic analysis indicates that the δ34S range (6.5-12.89‰) of sulfides in the Pengjiakuang gold deposit is consistent approximately with that of metamorphic rocks, Mesozoic granites, and the Jiaojia and Linglong gold deposits in eastern Shandong. However, there are wide ranges of compositions of δ34S and lead isotopes in the Pengjiakuang ore except for lower 206Pb/204Pb ratios. Analyses of sulfur and lead isotopic compositions suggest that the ores have a multiple origin. Unlike the Jiaojia and Linglong deposits, the oxygen and hydrogen isotopic compositions of fluid inclusions in the Pengjiakuang deposit show a mixed source: dominant meteoric water, and subordinate magmatic water. The Ar-Ar method was adopted to date the Au-bearing quartz. Brecciated ore yields a 40Ar/39Ar age of 118.42 ± 0.25 Ma and an isochron age of about 117.03 ± 0.13 Ma. Veinlet ore yields a 40Ar/39Ar age of 118.70 ± 1.40 Ma and an isochron age of 117.33 ± 0.15 Ma. The results indicate that the Pengjiakuang gold deposit was formed at ∼117.3-118.4 Ma. Biotite from a lamprophyre dike gives an age of 117.49 ± 0.25 Ma and an isochron age of 116.83 ± 0.36 Ma. Clearly, the formation of both lamprophyre dikes and gold mineralization are coeval products of tectonic-magmatic activity. The consistency in metallogenic age between the Pengjiakuang gold deposit, located on the margin of a Mesozoic pull-apart basin, and gold deposits of the northern uplift area in eastern Shandong suggests that both can be ascribed to the same the metallogenic event.

40Ar/39Ar and Rb-Sr isochron dating of the gold deposits on northern margin of the Jiaolai Basin, Shandong, China

The Pengjiakuang, Dazhuangzi and Fayunkuang gold deposits, located on the northern margin of the Mesozoic Jiaolai Basin, east of Shandong Province, are controlled by a low-angle normal fault. Gold ores are typically brecciated, veinlet and disseminated. The Ar-Ar and Rb-Sr isochron dating methods were adopted to date ores and lamprophyre dike. The results indicate that the age of the Pengjiakuang gold deposit is 117.33—118.42 Ma, that of the Dazhuangzi gold deposit is 117.39 Ma, and that of the Fayunkuang gold deposit is (128.49±7.2) Ma. The consistency in metallogenic age between the gold deposits on the margin of the Jiaolai Basin and the gold deposits (115—126 Ma) of the northern uplift area suggests that both were formed in the same metallogenic period. That is to say, the large-scale metallogeny of the Jiaodong region took place in late-Yanshannian ((120±10) Ma).

The topography of the Okavango Delta, Botswana, and its tectonic and sedimentological implications

A topographic map of the Okavango Delta and environs has been constructed using a combination of elevation data including trigonometric beacons and spot heights from the government of Botswana, surveys of the navigable channels, U. S. Department of Defense data and measurements made during a geophysical survey of the region. The topography provides insight into the local tectonic and sedimentary history. Local tectonics are dominated by uplift and horst formation associated with the Ghanzi Ridge, and an arch to the north of the Panhandle, which appear to represent the tips of incipient rifts which are propagating from the northeast. The Delta has formed in the resulting depression between these arches. The Panhandle has developed along a fault, and may be largely an erosional feature incised into the northern uplift zone. The Delta itself is an alluvial fan of remarkably uniform gradient. There is no evidence of regional tilting of the fan surface. Local highs and lows are developed on the fan, but channel location is relatively insensitive to this local topography. Moreover, marked elevation differences exist between adjacent channels, creating hydrologically unstable conditions. These unusual features of the local hydrology arise because of the confining effect of channel-flanking vegetation. Sedimentation in the Delta appears to be causing crustal sagging of the central Delta, which has: tilted the major palaeo-shoreline of the Mababe Depression to the west; formed a local depression within the Ghanzi Ridge facing the Delta; and detached a sliver of the ridge along the Thamalakane fault. It is suggested that local seismicity also results mainly from sediment loading. The Selinda spillway occupies a marked local depression, which is a graben between the Gumare fault and an extension of the Linyanti fault. It is probable that southwesterly propagation of the uplift zone associated with the incipient rift will ultimately deflect the Okavango River into the Chobe-Zambezi river system via this graben.

Quantification of Cenozoic vertical movements of Scandinavia by correlation of morphological surfaces with offshore data

Correlation between offshore geology and onshore morphological elements suggests that the enveloping summit level of Scandinavia originated as a peneplain in the Jurassic. Deep weathering profiles locally encountered in the mountainous areas are interpreted as relics of Mesozoic denudation. Late Cretaceous and Early Tertiary uplift of northern and western Fennoscandia caused deep erosion, and an erosional surface which marks a lower level of elevation was formed in the east. In northern Fennoscandia, this erosional surface was transgressed in the Eocene, and its present elevation is a result of uplift in the Neogene. The recognition of the Mesozoic peneplain and the Tertiary erosional surface has allowed a quantification of the two major phases of Cenozoic uplift. The Paleogene uplift phase had a maximum of almost 1500 m in northern Scandinavia, while the Neogene phase had its uplift centra in South Norway and Lofoten which were uplifted approximately 1000 m. The corresponding Neogene erosion of the coastal areas is estimated to have reached a maximum of 800–1000 m along the coast of southern Norway and slightly more to the north.

Tectonic Evolution and Petroleum Potential of Tarim Basin in the Northwestern China: ABSTRACT

The Mesozoic-Cenozoic Tarim basin is 560,000 km{sup 2} in area and overlaps the Precambrian Tarim craton. The sharp unconformity on top of the basement marks the Tarim movement through which the Tarim craton was converted into a stable area. There are numerous oil-generating rocks in Tarim basin. Based on comprehensive studies, it is concluded that the oil of Shacan 2 well in the Northern uplift is derived from marine algae and lower aquatic precursors and is a highly matured, migrated, and biodegraded petroleum. The oil was sourced from Ordovician and Cambrian source rocks, which are the main sources of petroleum in Tarim and are widely distributed. The Carboniferous-Lower Permian carbonaceous mudstone and carbonate of marine facies in the western Tarim are also source rocks, but of secondary importance compared with those of the lower Paleozoic. Dark mudstone and coal seams in Upper Triassic and Jurassic lacustrine-swamp facies are also important source rocks in Tarim basin. They are widely distributed in Baicheng, the Southwestern and the Central depressions and are proved to be oil sources in Yiqikelike and Kekeya oil fields and in the oil seeps of the Kashi area. Upper Cretaceous-Paleogene carbonate, clastic, and salt-gypsum assemblages could be source rocksmore » in the Southwestern depression, but need to be studied. Miocene dark mudstones of lacustrine facies are probably source rocks in Kashi, Kuqa, Awati and Yiecheng areas. The petroleum reserves of Tarim basin are hard to estimate because large-scale exploration has been going on for just a few years. The Chinese explorationists believe that the reserve of petroleum in the whole Tarim basin is in the range of 70 to 130 billion barrels. After recent testing of the Tazhong 1 well in the Central depression, some Chinese experts have even more optimistic estimates.« less