Piedmont Belt Research Articles

Provenance of cretaceous sediments in the West Kunlun piedmont belt and implications for tectonic evolutionary events

The West Kunlun orogenic belt located in the northwestern margin of the Qinghai-Tibet Plateau is an important record of the formation and northward extension of the plateau, but the current research mainly focuses on the tectonic activities of the Cenozoic era, and there is still considerable controversy regarding the formation and evolutionary history of pre-Cenozoic orogenic belts. This study focuses on Cretaceous sandstone samples from the Kedong region in the piedmont belt of the West Kunlun orogenic belt. U-Pb geochronological analysis was performed on 200 detrital zircon grains from the core samples. Combined with stratigraphic data and previous research, the main provenance direction was investigated to constrain the tectonic evolutionary history of the orogenic belt’s peripheral regions. The results show that the detrital zircons are aged from 290 to 208 Ma, 520–310 Ma, 810–580 Ma, 1,400–880 Ma and 2,548–1,730 Ma, reflecting the complexity of provenance in this area. Based on a comprehensive analysis of the characteristics of igneous rocks, zircon age composition and stratigraphic conditions in potential source areas, it is concluded that the primary source regions include the East Kunlun orogenic belt and the North and South Kunlun terranes, with a low likelihood of contributions from within the Tarim Basin. The evolution of the West Kunlun orogenic belt can generally be divided into two opening and two closing phases. The detrital zircon ages predominantly exhibit two peak values at 259 Ma and 459 Ma, respectively representing the ages of transition from oceanic crust subduction to continent-continent collision for the Paleo-Tethys Ocean and the Proto-Tethys Ocean. Additionally, there is a temporal gap between the evolution of the Proto-Tethys Ocean and the Paleo-Tethys Ocean. The Triassic period marks a transitional phase in tectonic evolution, shifting into an intracontinental evolutionary stage. This study provides new geochronological evidence for the early developmental history of the West Kunlun orogenic belt.

Sedimentary evolution and sequence stratigraphic model of Neogene–Quaternary terrestrial foreland basin in Southwest Tarim

Based on the research results of stratigraphic sedimentary facies, plane maps of sedimentary facies for four periods of the Neogene terrestrial foreland basin in Southwest Tarim were compiled. Research results conclude that the Neogene Miocene developed alluvial fan facies, fan delta facies, and lacustrine facies successively from the piedmont belt to the Maigaiti Slope. During the sedimentation of the Miocene Anju’an Formation, the lake range expanded to its maximum. According to the new division scheme for five-order sequences in prototype sedimentary basin, the stratigraphic sequence of a terrestrial foreland basin was divided and compared, and a sequence development and evolution model was established. Research results show that: (1) the Neogene–Quaternary is a typical type I sedimentary sequence with huge thickness; (2) the Neogene is a period of tectonic compression and flexural subsidence sedimentation in the foreland basin; with the maximum lake flooding surface at the top of the Miocene Anju’an Formation as the boundary, the lower part is a second-order super-sequence of the lacustrine transgression system tracts (TST), the upper part is a second-order super-sequence of the highstand system tracts (HST), and the Quaternary is a second-order super-sequence of the lowstand system tracts (LST) in forced lacustrine regression caused by the Late Himalayan tectonic movement; (3) the classic sequence stratigraphy made an error in establishing the theoretical model of marine type I sequences, as it placed the LST in the wrong position. The corrected type I sequences are in the order of TST, HST, and LST. (4) Finally, two examples were applied to demonstrate the development position of the LST, indicating that whether it is a marine or terrestrial prototype sedimentary basin, the LST was developed during the late stage of tectonic compression and uplift in a basin, and is the sedimentary sequence at the top of the prototype sedimentary basin.

Characteristics of orderly hydrocarbon accumulation of deep reservoirs in Kuqa Depression and its exploration implications

The Kuqa depression is an important oil and gas production area in western China, and there are abundant natural gas resources in the deep and ultra‐deep tight reservoirs. In this study, the accumulation law of deep oil and gas in the Kuqa depression has been systematically discussed based on the analysis of geochemical parameters, reservoir fluid inclusions and the recovery of burial‐thermal evolution history in different structural zones. The results show that the lacustrine mudstones of the Triassic Huangshanjie and Upper Jurassic Qiakemake formations in the Kuqa depression are the main oil‐generating source rocks, and the coal‐measure source rocks of the Middle and Lower Jurassic are the main gas‐generating source rocks. The oil and gas in the northern tectonic belt originated from the Huangshanjie and Yangxia formations have the characteristics of ‘lower‐source and upper‐reservoir’ and ‘self‐generation and self‐storage’. The source rocks in the central tectonic belt are of high maturity and mainly generate natural gas, and a small amount of crude oil is derived from mudstones of the Jurassic Qiakemake Formation. The oil and gas in the southern slope belt are mainly derived from the source rocks of the Huangshanjie Formation, followed by the Jurassic source rocks. The ordered accumulation of oil and gas in the Kuqa depression is controlled by the effective spatiotemporal matching of multi‐stage tectonic evolution and hydrocarbon generation evolution of multi‐source rocks. Three spatiotemporal ordered hydrocarbon accumulation series have been proposed: early near‐source accumulation, late far and near‐source accumulation, and late upper‐near source accumulation. The piedmont belt is dominated by the near‐source continuous accumulation mode, the thrust belt is dominated by the ultra‐late upper source accumulation mode, and the slope belt is dominated by the late far‐source accumulation mode. Therefore, future exploration will focus on the tight lithologic reservoirs in the northern piedmont belt, the structural reservoirs in the central structural belt, and the unconformity hidden reservoirs in the southern slope belt.

Recognition of Petroleum Origin in the Northern Piedmont Belt of Turpan-Hami Basin and Its Significance

The Turpan-Hami Basin has been considered as the most typical coal-derived-oil basin in China for a long time. However, with the deepening exploration, this theory has caused increasing controversy and some scholars doubt that Permian or Jurassic dark mudstone may be the main source rocks. The origin uncertainty even restricts deciding the exploration direction. Taking the reservoirs of the northern piedmont belt as an example, this paper analyzed oil sources by the geochemical characteristic comparison of inclusions, crude oil, and source rocks. Combined with the previous studies, the hydrocarbon accumulation model is established. The results show that the geochemical characteristics of the inclusions and oil in most areas are obviously different. Most reservoirs are mixed-source reservoirs. The oil sources varied in different regions. In the area near Bogeda, C19+20TT and C28 sterane content in oil are high, indicating that coal and Permian lacustrine mudstone are main contributors. Far away from Bogeda, bounded by the thick coal seam of Xishanyao Formation, oil sources are quite different. Above it, C19+20TT is high and gammacerane and pregnane are low, C29>>C28>C27sterane, indicating that coal and carbonaceous mudstone are main sources. Under that, C21TT and C23TT content in the inclusions are high, C29≥C27>C28sterane, while C19+20TT and pregnane content in the oil are also high, indicating that it is a mixed oil system mainly derived from Jurassic lacustrine mudstone and coal. Lacustrine mudstone has higher contribution. This phenomenon is mainly related to different fault styles in different zones. Near Bogeda, strong stress caused vertical large faults developed, which connected Jurassic reservoirs and Permian source rocks. Far from Bogeda, the faults sliped along the thick coal seam, It is difficult for deep hydrocarbon to enter the shallow layer. In the future, it should be considered to look for the traps with relatively high-quality reservoir-cap combinations for exploration in the hydrocarbon supply window of effected hydrocarbon kitchens.

Three-dimensional electromagnetic method in shallow surface exploration in complex piedmont belt

In the complex piedmont area, the quality of seismic data is generally poor, and it is difficult to build the shallow velocity model, which leads to the inaccurate determination of the stratigraphic and structural positions. The combination of seismic and non-seismic exploration is an effective way for oil and gas exploration in complex piedmont belt. In the northwest of Sichuan Province, the joint exploration of three-dimensional audio-magnetotelluric (AMT) and transient electromagnetic (TEM) is carried out. The transient electromagnetic data is used as static correction for audio-magnetotelluric data, and the AMT data is used to detect the shallow surface structure within 1.5km buried depth. The three-dimensional geoelectric model of the study area is obtained by using AMT three-dimensional inversion, and the geological structure interpretation is carried out by combining well logging with the statistical data of rock physical properties, which provides a basis for seismic building the shallow surface model.

Sedimentary characteristics of humid alluvial fan and its control on hydrocarbon accumulation: A case study on the northern margin of the Junggar Basin, west China

Alluvial fans in humid regions are different from arid alluvial fans for the special sedimentary characteristics and distribution pattern. In this paper, we systematically studied the sedimentary facies of Jurassic Badaowan Formation in the northern margin piedmont belt of Junggar Basin based on the comprehensive analysis of geological and geophysical data acquired. The results show that under the comprehensive influences of tectonic setting, paleo-provenance and paleo-climate, large-scaled humid alluvial fans are developed in the piedmont belt of Hala'alt mountain. The fluvial activity of alluvial fan is stronger and more stable in the humid type than that in the arid type. Three subfacies are identified in the humid alluvial fan, i.e. the upper fan, middle fan and lower fan. The middle fan can be further divided into braided river channel and the peat bog. Then we build the sedimentary facies model based on the microfacies types and distributions. This model is significantly different from arid alluvial fan in lithologic features, sedimentary sequences, distribution scales and microfacies match patterns. The reservoir distribution is mainly controlled by the favorable microfacies, lithofacies and depositional fabric. We suggest that the braided river channel glutenite lithofacies and grit lithofacies in the middle fan subfacies are the most favorable reservoir facies belt for hydrocarbon accumulation.

Crop wild relatives of Kazakhstani Tien Shan: Flora, vegetation, resources

This paper presents the results of the field study on species composition, geographical distribution, phytocoenotic diversity and resources of crop wild relatives (CWR) in Kazakhstan's ranges of the Tien Shan Mountains. Taxa of not only cultivated genera of crops are taken into account, but also a wider range of species of high socio-economic importance, including medicinal, fodder, essential oil and other species. List of CWR includes 289 species belonging to 39 families and 145 genera. Among them, 9 species listed in the Red Data book of Kazakhstan: Pistacia vera, Rheum wittrockii, Armeniaca vulgaris, Malus sieversii, Allium pskemense, Allochrusa gypsophilloides, Sorbus sibirica, Vitis vinifera and Artemisia cina. The highest plant diversity is recorded in intermountain plains and river valleys where meadow vegetation forms a high abundance of forage and resource plants. The diversity of wild fruit plants is concentrated in gallery forests. CWR of cereals are confined to dry steppe slopes in low piedmont belt. The populations of almond, pistachio, plum and cherry were recorded at dry slopes of low mountain belt. The estimation of the raw material base for 13 resource plants is given. Only Rumex tianschanicus, Berberis sphaerocarpa are recommended for industrial harvesting; for local pharmacy chain – Mentha longifolia, Origanum vulgare, O. vulgare subsp. gracile, Ziziphora clinopodioides, Hypericum scabrum, Hypericum perforatum, and five Rosa species.

珲春盆地地下水补径排条件及其影响因素

本次研究对珲春盆地地下水位进行了测量，利用测量数据分析了珲春盆地地下水的补给、径流和排泄特征及其影响因素。总体上，珲春盆地地下水位东部高、西部低，由山前地带向珲春河河谷地带、从东北向西南方向径流。在北部山前地区，地下水由北向南径流；东部山前地区地下水由东向西径流；南部山前地区地下水由东南向西北方向径流。水力坡度由山前向平原逐渐减小。除接受大气降水补给外，研究区在七户洞村、和平村、新华村、红星村、支边村等地接受基岩山区侧向径流补给；中华村、春景村、东岗村、南秦孟村等地是地下水径流区；研究区地下水在八家子村、沙坨子村、西崴子村等向图们江排泄。 The groundwater level of Hunchun Basin was measured, and the recharge, runoff and discharge characteristics of groundwater in Hunchun Basin and the influencing factors are analyzed by using the measured data. Generally, the groundwater level in the Hunchun Basin is high in the east and low in the west. It flows from the piedmont belt to the Hunchun River valley which is from northeast to southwest. The groundwater flows from north to south in the northern piedmont area; the groundwater in the eastern piedmont area flows from east to west; the groundwater in the southern piedmont area flows from southeast to northwest. The hydraulic gradient gradually decreases from the piedmont to the plain. The groundwater is recharged from the bedrock area in Qihudong village, Heping village, Xinhua village, Hongxing village, Zhibian village etc. The Zhonghua village, Chunjing village, Donggang village, Nanqinmeng village are groundwater runoff areas. The groundwater is discharged to Tumen River in Bajiazi village, Shatuozi village, Xiwaizi village etc.

蒙古国西部早–中侏罗世含煤盆地的演化和后期改造—以希奈金斯盆地为例<br> Evolution and Later Reformation of Early-Middle Jurassic Coal-Bearing Basins in Western Mongolia—A Case Study from the Shinejinst Basin

因基底构造、同造山应力场和区域演化的不同，蒙古东、西两部早–中侏罗世含煤盆地有不同的几何学和运动学特征。控制中带磨拉石盆地西段发育的是两条近北西向的压扭性断裂带，与蒙古–鄂霍次克缝合线西段的走向一致。近北西向断裂由北西西–近东西向的斜冲段和北西向的斜冲–走滑段组成，前者的前锋断层控制了下盘的含煤盆地发育。这些控盆断裂向北(东)斜冲，成盆动力来自中国西部特提斯洋早侏罗世末闭合和嗣后的碰撞产生的向北推挤。希奈金斯盆地演化可分为三个阶段，后期经历了四期改造。西部寻找下–中侏罗统大煤田的方向是希奈金斯盆地南次盆类型的构造盆地；其主要特征，一是成煤期盆地发育受北西西–近东西向斜冲断层及近北东向左行剪切断层控制，二是早白垩世的拉张事件中处于正断层的上盘，三是新生代隆升时位于山前或山麓地区。 Owing to variation of the basement structures, syn-orogenic stress fields and regional tectonic evolution, the Early-Middle Jurassic coal-bearing basins in western Mongoliashow different geometric and kinematic features from the simultaneous molasse basins in easternMongolia. The west segment of the Mongolia-Okhotsk suture is a NW- striking transfer zone, which constraints two transpressional fracture belts developing in western Mongolia. The tran- spressional fracture consists of the oblique thrust with NWW- to nearly E-W-striking, and the NW-orientated oblique thrust-strike slipping fault. The front fault of the oblique thrust controls a coal-forming basin in its lower plate. The ba- sin-controlling fault thrusts north(east)wards, with the basin dynamics resulting from a northward push-compression caused by closure of Tethyan ocean in the end of Early Jurassic in western China and followed continent-continent col- lision. The evolution of the Shinejinst Basin can be divided into three stages, which experiences four episodes of refor- mation after its reversion. The coal-search direction for the Lower-Middle Jurassic large coal fields in western Mongo- lia should be a kind of the South Sub-Basin of Shinejinst Basin, which could be indicated by three characters: 1) the basin-controlling faults being NWW- to nearly E-W-striking oblique thrust as well as NE-striking sinistral shearing fault, 2) to be situated at upper side of normal fault in Early Cretaceous extension, and 3) to be located along the piedmont belt of thrust or foothill of range in the Cenozoic uplifting.

Research of Drilling Complexities in Dabei Belt of Tarim Basin

Kuche depression of Tarim Basin went through tectogenesis many times, due to the southward thrust compressional stress from Tianshan fold uplift, the geology condition of this area is extraordinarily complex, there are problems such as depth difference in geological horizons, abnormal pressure formations and irregular distribution of special lithologies, etc. All of these problems have brought even more difficulties in engineering design and construction. Accidents such as well leakage, drilling sticking and complex situations happened frequently. All of those have influenced the engineering progress seriously and lowered the actual effect of drilling. In order to resolve the problems and complex situations above, we did detailed researches on accidents in the Kuche piedmont belt of Tarim Basin and studied reasons for complex situations, and then we proposed engineering resolutions and evaluated them.

Structural styles and hydrocarbon accumulation of the northern piedmont belt in the Taibei Sag, Turpan-Hami Basin

Abstract The northern piedmont belt of the Taibei Sag is one of the oil rich structural belts in the Turpan-Hami Basin. Based on the interpretation of seismic cross sections and the analyses of discovered hydrocarbon accumulations, the geologic structure can be divided into six structural styles, thrust-imbricate structure, imbricate fan structure, thrust-opposite structure, pop-up structure, forward thrust structure and duplex structure. According to the study of the distribution regularity of the structural styles, the fold thrust belt controlled by three levels tectonic transform zones is characterized by zonation from the south to the north and segmentation from the west to the east, and it can be classified into thrust-nappe belt, breaking belt and frontal belt by mechanism of tectonic deformation. The leading edge with two accumulation forming models which are the leading edge pop-up model and the leading edge imbricate fan model is the most favorable hydrocarbon enriched belt in the northern margin of the Taibei Sag. The thrust-opposite structures in the rear edge of the deformable zone have good preservation, potential source kitchen on the footwall, higher fault dip, and good communication of sandbodies. They are the next favorable exploration structures.

Congruence between morphological variation and altitudinal gradient across a hybrid zone between carrion and hooded crows

Geographic variation of morphology and plumage colour was studied across a hybrid zone between allopatric populations of the carrion crow (Corvus corone corone) and the hooded crow (Corvus corone comix) in northwestern Italy. Principal component analysis on plumage colour scores and canonical variate analysis on 37 morphometric variables indicated that a clinal geographic variation in plumage colour and morphology existed across the hybrid zone. Morphology and colour showed congruent (P < 0.005) variation. Plumage colour variation was strictly correlated with altitude (P < 0.001) and the same held true for morphology (P < 0.01). Parental allopatric populations of the carrion crow and the hooded crow inhabit different habitats in northern Italy. The hybrid zone corresponds to a piedmont belt, through which a steep ecological gradient exists. Present evidence could suggest that carrion and hooded crows have parap‐atrically diverged under the effects of ecological selective gradients. However, congruence in variation of different character systems argues in favour of a ‘phylogenetic’ origin of this hybrid zone.

Fault‐generated mountain fronts in the central apennines (Central Italy): Geomorphological features and seismotectonic implications

AbstractThe morphotectonic framework of the Central Apennines is given by faulted blocks bounded by normal faults, mostly trending NW–SE, NNW–SSE and NE–SW, which cut previous compressive structures. Such a structural setting is consistent with the focal mechanisms of the earthquakes which often occur in this area.In this paper, three lithologically different normal fault‐generated mountain fronts are analysed in order to assess the relations between their geomorphic features and active tectonics. They border the Norcia depression (Sibillini Mts, Umbria), the Amatrice–Campotosto plateau (Laga Mts, Lazio) and the Fucino basin (Marsica Mts, Abruzzi).The Norcia depression is bounded by a N20°W trending normal fault to the east and by a parallel antithetic fault to the west. The main fault has a 1000 m throw and gives rise to a wide fault escarpment, characterized by: (1) sharp slope breaks due to low angle gravity faults; (2) important paleolandslides; and (3) several fault scarplets on the piedmont belt affecting Quaternary deposits.The Amatrice–Campotosto plateau is delimited by the western slope of Mt Gorzano which runs along a N20°W trending normal fault having a 1500m throw. Minor parallel faults dislocate Quaternary landforms. Large‐scale massmovements also occur here.The Fucino basin was struck by the 1915 Avezzano earthquake (I=XI MCS) which produced extensive surface faulting along two parallel NW trending normal fault escarpments on the eastern border of the basin. There is paleoseismic evidence including buried gravity graben in Late Glacial gravels and tectonic dip‐slip striations on Holocene calcitic crusts covering bedrock normal fault planes.These data suggest that active extensional tectonics plays a major role in the slope morphogenesis of the Central Apennines and they indicate the importance of geomorphic analysis in seismic zonation of this area.

Rodingites from the southern Appalachian Piedmont, South Carolina, USA

Rodingites composed predominantly of grossular-andradite and epidote-group minerals have been identified at one locality in the ophiolitic (?) Hammett Grove Meta-igneous Suite in the southern Appalachian Piedmont, South Carolina. The rodingites occur at or near the contact between altered (steatitized) ultramafic rocks and gneissic country rocks of the Inner Piedmont belt. The rodingites formed contemporaneously with antigorite in the host rock as the last of several cooling assemblages following the middle or early Paleozoic metamorphic thermal peak at middle- or upper-amphibolite facies conditions. Petrographic and geochemical evidence suggests that the rodingites formed by calcium metasomatism of gabbroic and immature graywacke protoliths, and that static conditions prevailed during metasomatism. Fluid inclusion work indicates that the serpentinizing fluid was relatively saline; it contained 5.3 ± 1.0 equiv. wt.% NaCl and the crystallization temperature is estimated to have been between 350-500°C

Isotopic evidence for a tectonic boundary between the Kings Mountain and Inner Piedmont belts, southern Appalachians

Concordant U-Pb zircon ages of ∼320 Ma for the deformed High Shoals Granite of the Kings Mountain belt (KMB) extend the range of known Alleghanian (late Paleozoic) deformation and metamorphism in the southern Appalachian Piedmont. Isotope systematics in KMB rocks suggest an affinity with terranes to the southeast rather than with the Inner Piedmont belt to the northwest. Lead-isotope systematics in meta-igneous rocks of the KMB suggest direct or indirect mantle derivation with little or no crustal contamination.

Mafic rocks of the Southern Appalachians; a review

Subaerially erupted metabasalts of tholeiitic affinity, which occur as conformable units in late Precambrian stratified sequences. Intrusive equivalents. Late Precambrian volcanism related to a divergent plate tectonic setting. Devonian Hillabee Greenstone complex (Talladega Belt) at the southwestern fringe of the Blue Ridge Belt shows tholeiitic and calc-alkaline affinities suggestive of a volcanic arc or actively developing continental margin environment. Metabasalts of tholeiitic affinity and probable late Precambrian age are also abundant in the Inner Piedmont Belt. Some of these (for example, the Dadeville Complex) are associated with younger but pre-metamorphic mafic intrusives. Mafic rocks of the Kings Mountain, Charlotte, and Carolina slate belts include metamorphosed late Precambrian to Cambrian basaltic flows and tuffs deposited in submarine environments and a large number of gabbroic complexes.--Modified journal abstract.

Rb-Sr ages of granitic gneisses of the Inner Piedmont belt of northwestern North Carolina and southwestern South Carolina

Granitic gneisses from the Inner Piedmont belt of northwest North Carolina have Rb-Sr whole-rock ages of 427 ± 9 m.y., 460 ± 9 m.y. and possibly 534 m.y. Initial 87 Sr/ 86 Sr ratios for these rocks are approximately 0.704. Rb-Sr data for granitic gneisses from the Inner Piedmont belt of southwestern South Carolina and adjacent Georgia suggest a whole-rock age of approximately 423 m.y. and an initial 87 Sr/ 86 Sr ratio of 0.7069. These ages are tentatively interpreted as times of igneous crystallization. Together with previously published results, these data suggest that 460 to 420 m.y. ago was a time of significant igneous activity in the Inner Piedmont of North and South Carolina; igneous activity also occurred 545 to 525 and 350 to 335 m.y. ago.

Detailed analysis of tectonic levels in the Appalachian Piedmont

Recent mapping has provided a close look at detail relationships contrasting a major infrastructural zone with an adjacent suprastructural area in the southern U.S. Piedmont. The Inner Piedmont belt infrastructural flow folds terminate against a northeast trending polydeformational cataclastic zone as one traverses toward the southeast along the South Carolina — Georgia border. The broad axial part of the infrastructural Inner Piedmont is represented by a complex of sillimanite-bearing mica gneiss and schist. Interlayered amphibolite permits recognition of major nappe-like antiforms and synforms. The southeastern edge of the Inner Piedmont is devided from the axial core by a tectonic slide, and is a separate and distinct nappe. Granitoid gneiss and amphibolite dominate in it.

Analysis of the Piedmont in Northwest South Carolina

Two major autochthonous nappes and a deep synformal structure occur in the Piedmont of northwest South Carolina. The cataclastic Brevard zone, which borders the Blue Ridge geologic belt on the southeast, is associated with the synformal belt of partially cataclastic and retrograded rocks at low amphibolite facies grade. This Non-migmatitic belt contains tight cylindroidal isoclines and tectonic slides with a northwest vergence. Refolded isoclines in the Non-migmatitic belt occur near the Brevard zone as a result of recurring displacements there. Immediately southeast lies the Walhalla nappe, which contains kyanite-grade rocks complexly folded into a northeast-plunging conical system. The migmatite front lies within this nappe and in places is coincident with the major slide boundary between the Walhalla nappe and the underlying synformal Non-migmatitic belt. The major slide that separates the overlying Six Mile nappe from the Walhalla nappe is subhorizontal; however, in the broad root zone of both nappes in the southeast part of the area, northwest dips and steep dips represent the attitudes of s-surfaces in many locations. The autochthonous nappe complex probably formed in a continental rise assemblage subjected to intense thermal effects in the early Paleozoic. Sedimentary and (or) volcanic-volcaniclastic assemblages sited along the continental margin were squeezed as a detachment zone between the northwest-driving Piedmont nappes and the activated craton margin. These assemblages became tectonically related to a detachment zone overlying the rising infrastructural nappes, which is now eroded away with the overlying supra-structure. Annealed textures indicate that metamorphism outlasted penetrative deformation, except along the Brevard zone, which continued as a zone of dislocation while thermal metamorphism waned. Late Paleozoic Alleghanian movements may be recorded as microbreccia zones within the Brevard zone and Inner Piedmont belt. This event was not penetrative; instead, it was one of vertical en bloc uplift primarily centered in the Inner Piedmont, and perhaps it accompanied a weak retrogressive metamorphism.

Inner Piedmont Belt of the Southern Crystalline Appalachians: Reply

Inner Piedmont Belt of the Southern Crystalline Appalachians: Reply