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贵州南部的泥盆系为一个大型的楔状体。从深水背景的广西南丹罗富剖面到古陆边缘的贵阳乌当剖面,泥盆系由13个层序变薄尖灭成5个层序,这是泥盆纪早期海侵尖灭与晚期海退尖灭的结果。研究区泥盆系由海侵碎屑岩岩系到清水台地碳酸盐岩岩系地层序列构成2个二级层序,又可进一步划分为13个三级层序。二级层序和三级层序均由其特殊的沉积相序列组成。研究区泥盆系层序地层划分和层序地层格架的建立提供了一个在年代地层与海平面变化框架内研究“相迁移”的良好实例。 相似文献
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M. A. H. Marsden 《Australian Journal of Earth Sciences》2013,60(1):125-162
Devonian rocks occur in northeastern Australia within the ‘Tasman Geosyncline’ in three major tectonic divisions—(a) a very broad mobile platform related to the last stages of stabilisation of the Lachlan Geosyncline, marginal to which is found, (b) the volcanic‐rich New England Geosyncline, and (c) a contrasting region in northern Queensland where complex marine to continental sedimentation occurred on cratonic blocks while non‐volcanic flysch‐like sedimentation occurred in the marginal Hodgkinson Basin. The tectonic setting was governed by differences in the nature of the continental margin, so that the New England Geosyncline and Hodgkinson Basin, which developed along the eastern margin of the continent from the earliest Devonian to the late Palaeozoic, show correspondingly different sedimentation and deformation histories. An integrated account of the Devonian geology of these regions is given, leading to.an interpretation of the environments of the Devonian in terms of plate‐tectonic movements, generally from the east. Postulated tectonic zones within the New England Geosyncline region include pre‐Devonian deep ocean deposits with mild high‐pressure low‐temperature meta‐morphism, and Devonian volcanic arc and marginal sea volcanic‐derived deposits. Within the mobile platform to the west, variable marine and continental deposits are associated with volcanicity in the zone transitional to the New England Geosyncline. In the northern region, rifting of the craton and development of an Atlantic‐type margin was followed by subduction with folding and metamorphism at the end of the Devonian. The Devonian rocks are strongly affected by intense late Palaeozoic tectonic and igneous activity in the eastern marginal regions, but only minor effects are seen to the west. 相似文献
4.
Ramues Gallois Alain Vadet Steve Etches 《Proceedings of the Geologists' Association. Geologists' Association》2019,130(2):187-195
Sediments of Kimmeridgian and Tithonian age are well exposed on the Boulonnais coast of northern France between Equihen and Cap Gris Nez and on the south coast of England at and adjacent to Kimmeridge Bay. Both successions were deposited on a marine shelf and lie within the Subboreal faunal province which enables detailed correlations to be made between them based on ammonite assemblages. They are, however, lithologically markedly different due to their environmental settings: close to a land area in the case of the Boulonnais and within a depositional basin in the case of Kimmeridge. The succession adjacent to the Kimmeridgian-Tithonian boundary exposed in the Boulonnais is highly condensed and laterally variable with more attenuated successions occurring close to the former Anglo-Brabant Massif land area. The boundary occurs at the end of a succession of up to six regressive-transgressive events that onlap the land area. This is in contrast to that at outcrop at Kimmeridge, where the Kimmeridgian-Tithonian boundary is marked by a correlative conformity in an unbroken basinal succession. The cliff and foreshore exposures in the Kimmeridge area provide the only unbroken succession in the Subboreal faunal province of the beds adjacent to the Kimmeridgian-Tithonian boundary. 相似文献
5.
云南景洪东南地区出露一套泥盆系,前人将其以粗粒碎屑岩为特征的部分命名为怕当组,根据腕足类化石鉴定其地质时代为中泥盆世;以碎屑岩、凝灰岩为特征的部分被命名为南光组,根据植物化石斜方薄皮木（Lepotophloeum rhombicum）划归晚泥盆世。对其沉积环境尚存在陆相和海陆交互相、浅海陆架相、半深海-深海相沉积环境的不同认识。本研究发现,粗粒碎屑岩层序中也发现有晚泥盆世标准植物化石斜方薄皮木（Lepotophloeum rhombicum）,并且粗粒碎屑岩层序位于剖面上部,南光组位于剖面下部,说明两者的地质时代均为晚泥盆世。故建议废除怕当组,将两者合并为上泥盆统南光组。南光组具有典型的鲍马序列特征,含有放射虫等海洋环境生物化石,属于深海浊流沉积层序。 相似文献
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《Australian Journal of Earth Sciences》2013,60(5):645-664
Laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) analysis of zircons confirm a Late Devonian to Early Carboniferous age (ca 360–350 Ma) for silicic volcanic rocks of the Campwyn Volcanics and Yarrol terrane of the northern New England Fold Belt (Queensland). These rocks are coeval with silicic volcanism recorded elsewhere in the fold belt at this time (Connors Arch, Drummond Basin). The new U–Pb zircon ages, in combination with those from previous studies, show that silicic magmatism was both widespread across the northern New England Fold Belt (>250 000 km2 and ≥500 km inboard of plate margin) and protracted, occurring over a period of ～15 million years. Zircon inheritance is commonplace in the Late Devonian — Early Carboniferous volcanics, reflecting anatectic melting and considerable reworking of continental crust. Inherited zircon components range from ca 370 to ca 2050 Ma, with Middle Devonian (385–370 Ma) zircons being common to almost all dated units. Precambrian zircon components record either Precambrian crystalline crust or sedimentary accumulations that were present above or within the zone of magma formation. This contrasts with a lack of significant zircon inheritance in younger Permo‐Carboniferous igneous rocks intruded through, and emplaced on top of, the Devonian‐Carboniferous successions. The inheritance data and location of these volcanic rocks at the eastern margins of the northern New England Fold Belt, coupled with Sr–Nd, Pb isotopic data and depleted mantle model ages for Late Palaeozoic and Mesozoic magmatism, imply that Precambrian mafic and felsic crustal materials (potentially as old as 2050 Ma), or at the very least Lower Palaeozoic rocks derived from the reworking of Precambrian rocks, comprise basement to the eastern parts of the fold belt. This crustal basement architecture may be a relict from the Late Proterozoic breakup of the Rodinian supercontinent. 相似文献
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L. P. Black J. L. Everard M. P. McClenaghan C. R. Calver A. M. Fioretti 《Australian Journal of Earth Sciences》2013,60(7):933-968
Devonian–Carboniferous granites are widespread in Tasmania. In eastern Tasmania, Devonian granites intrude Ordovician–Early Devonian quartz-rich turbidites of the Mathinna Supergroup. The earliest (～400 Ma) I-type granodiorites may be arc-related. Following the Tabberabberan Orogeny (～389 Ma), more felsic and, finally, strongly fractionated I- and S-type granites were emplaced until ～373 Ma. In contrast, western Tasmania granites intrude a more diverse terrane of predominantly marine shelf successions, with depositional ages as old as Late Mesoproterozoic. They are mostly felsic and fractionated I- and S-types emplaced from ～374–351 Ma, possibly in response to post-collisional crustal extension following juxtaposition of the eastern and western Tasmanian terranes. Granites from the two terranes are readily distinguishable by the age spectra of their inherited zircon, which are noticeably similar to those of the detrital zircon from sedimentary successions in their respective terranes. Furthermore, within each terrane, both I and S-types yield similar inheritance patterns. This suggests a pivotal role for the sedimentary successions in the petrogenesis of both types. Western Tasmanian granites are also enriched in ～1600 Ma zircon, which is essentially unrepresented in the exposed supracrustal succession. Subtle differences between the inheritance and detrital age spectra in eastern Tasmania probably relate to unrepresentative sampling of the supracrustal rocks. Nd, Sr and Pb isotopic characteristics of the granites are consistent with their derivation by mixing of magmas derived from the mantle, possibly the lower crust, and from supracrustal rocks. Systematic isotopic trends in some eastern Tasmanian I-types, particularly in the Scottsdale Batholith, correlate well with major and trace element geochemistry and age. The isotopes are inconsistent with simple restite unmixing or crystal fractionation in a closed magma chamber, and indicate progressive contamination by the Mathinna Supergroup, or similar rocks. The isotopic characteristics of late, strongly fractionated granites, although sometimes obscured by hydrothermal alteration, are also consistent with concurrent assimilation-fractional crystallisation processes. Together with the close association of some strongly fractionated I- and S-types, this suggests that such granites were generated directly in the lower crust, and were not derived from unfractionated parental granite magmas. 相似文献
8.
Fault blocks and inliers of uppermost Silurian to Middle Devonian strata in the Yarrol Province of central coastal Queensland have been interpreted either as island-arc deposits or as a continental-margin sequence. They can be grouped into four assemblages with different age ranges, stratigraphic successions, geophysical signatures, basalt geochemistry, and coral faunas. Basalt compositions from the Middle Devonian Capella Creek Group at Mt Morgan are remarkably similar to analyses from the modern Kermadec Arc, and are most consistent with an intra-oceanic arc associated with a backarc basin. They cannot be matched with basalts from any modern continental arc, including those with a thin crust (Southern Volcanic Zone of the Andes) or those built on recently accreted juvenile oceanic terranes (Eastern Volcanic Front of Kamchatka). Analyses from the other assemblages also suggest island-arc settings, although some backarc basin basalt compositions could be present. Arguments for a continental-margin setting based on structure, provenance, and palaeogeography are not conclusive, and none excludes an oceanic setting for the uppermost Silurian to Middle Devonian rocks. The Mt Morgan gold–copper orebody is associated with a felsic volcanic centre like those of the modern Izu–Bonin Arc, and may have formed within a submarine caldera. The data are most consistent with formation of the Capella Creek Group as an intra-oceanic arc related to an east-dipping subduction zone, with outboard assemblages to the east representing remnant arc or backarc basin sequences. Collision of these exotic terranes with the continent probably coincided with the Middle–Upper Devonian unconformity at Mt Morgan. An Upper Devonian overlap sequence indicates that all four assemblages had reached essentially their present relative positions early in Late Devonian time. Apart from a small number of samples with compositions typical of spreading backarc basins, Upper Devonian basalts and basaltic andesites of the Lochenbar and Mt Hoopbound Formations and the Three Moon Conglomerate are most like tholeiitic or transitional suites from evolved oceanic arcs such as the Lesser Antilles, Marianas, Vanuatu, and the Aleutians. However, they also match some samples from the Eastern Volcanic Front of Kamchatka. Their rare-earth and high field strength element patterns are also remarkably similar to Upper Devonian island arc tholeiites in the ophiolitic Marlborough terrane, supporting a subduction-related origin and a lack of involvement of continental crust in their genesis. Modern basalts from rifted backarc basins do not match the Yarrol Province rocks as well as those from evolved oceanic arcs, and commonly have consistently higher MgO contents at equivalent levels of rare-earth and high field strength elements. One of the most significant points for any tectonic model is that the Upper Devonian basalts become more arc-like from east to west, with all samples that can be matched most readily with backarc basin basalts located along the eastern edge of the outcrop belt. It is difficult to account for all geochemical variations in the Upper Devonian basalts of the Yarrol Province by any simplistic tectonic model using either a west-dipping or an east-dipping subduction zone. On a regional scale, the Upper Devonian rocks represent a transitional phase in the change from an intra-oceanic setting, epitomised by the Middle Devonian Capella Creek Group, to a continental margin setting in the northern New England Orogen in the Carboniferous, but the tectonic evolution must have been more complex than any of the models published to date. Certainly there are many similarities to the southern New England Orogen, where basalt geochemistry indicates rifting of an intra-oceanic arc in Middle to Late Devonian time. 相似文献
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A. Alabushev 《International Journal of Earth Sciences》1995,84(2):237-244
The marine sedimentary formations of the Middle Albian to Maastrichtian in the Cretaceous Sakhalin Basin (CSB) were investigated. These successions of strata consist of interbedded sandy, clayey and calcareous rocks which are underlain by heterogeneous metamorphosed (up to greenschist facies) Paleozoic to Mesozoic (pre-Aptian) rocks. The studied sections display several different facies reflecting geological settings ranging from an inner shelf to a continental slope. Three depositional complexes bound by regional subaerial unconformities are recognized within the marine successions. Since the Albian, the CSB has been a rapidly subsiding marginal part of the Okhotsk Sea plate. The Naiba Valley succession, corresponding to a sublittoral zone, shows extremely high sedimentation rates up to 190 m/Ma. The stratigraphic distribution of lithofacies indicates that the CSB became shallower from the Middle Albian to the Maastrichtian. 相似文献
10.
Devonian reef complexes were well developed in Western Australia and South China, but no detailed direct comparison has been made between reef building in the two regions. The regions differ in several respects, including tectonic, stratigraphic and palaeoceanographic–palaeogeographic settings, and the reef building styles reflect minor differences in reef builders and reef facies. Similarities and differences between the two reef complexes provide insights into the characteristics of platform margins, reef facies and microbial carbonates of both regions. Here we present a comparison of platform margin types from different stratigraphic positions in the Late Devonian reef complex of the Canning Basin, Western Australia and Middle and Late Devonian margin to marginal slope successions in Guilin, South China. Comparisons are integrated into a review of the reefal stratigraphy of both regions. Reef facies, reef complex architecture, temporal reef builder associations, 2nd order stratigraphy and platform cyclicity in the two regions were generally similar where the successions overlap temporally. However, carbonate deposition began earlier in South China. Carbonate complexes were also more widespread in South China and represent a thicker succession overall. Platforms in the Canning Basin grew directly on Precambrian crystalline basement or early Palaeozoic sedimentary rocks, but in South China, carbonate complexes developed conformably on older Devonian siliciclastic strata. Pre-Frasnian reef facies in South China had more abundant skeletal frameworks than in Canning Basin reefs of equivalent age, and Famennian shoaling margins containing various microbial reefs may have been more common and probably more diverse in South China. However, Late Devonian platform margin types have been documented more completely in the Canning Basin. Deep intra-platform troughs (deep depressions containing non-carbonate pelagic sediments — Nandan-type successions) that developed along syndepositional faults characterize Devonian carbonate platforms in South China, but have no equivalent on the Lennard Shelf, Canning Basin where inter-reef areas were more shallow. The South China platform-to-depression pattern was generally continuous from the Lower to Upper Devonian, indicating that many pre-Devonian tectonic features continued to exercise considerable effect through deposition. Localized, fault-controlled subsidence was an important factor in both regions, but similarities in 2nd order aggradation–progradation cycles suggest that eustasy was also an important control on the larger scale stratigraphic development of both regions. 相似文献
11.
This palaeomagnetic study has investigated intrusive and extrusive calc-alkaline igneous rocks comprising the pre-Ordovician basement of central England and the Welsh Borderlands and dated ca. 560–530 Ma. Demagnetization studies resolve a range of magnetic components in both the older volcanic successions comprising the eastern Uriconian volcanics, and in the younger intrusive episodes comprising the Charnwood and South Leicestershire outcrops. Post-Ordovician overprinting is largely absent and the remanence record dates from ca. 560–420 Ma. Within this time interval field tests are inadequate to confirm a primary origin and some components may be overprints acquired in immediate post-Uriconian (Cadomian) or during late Ordovician (early Caledonian) thermotectonic events. A first order continuity is recognized on a palaeomagnetic scale between the data from the Midlands-Welsh Borderlands and the terranes exposed in Anglesey and Southwest Wales. The British terranes moved through low latitudes during the interval represented by the Uriconian episode; they crossed the palaeoequator during the folding of these rocks and prior to emplacement of the later intrusive suite. Collectively they had rotated through ca. 170° and moved into intermediate latitudes by mid-Lower Cambrian times. Post-Lower Cambrian movements on the Malvernian lineament are a possible explanation for second order differences between the palaeomagnetic records of the English Midlands and the Welsh Borderlands; the largest possible regional rotation here is a ca. 90° movement of the Charnwood block with respect to the other outcrops. Correlation with the Gondwana APW path places the Anglo-Welsh basement in the vicinity of a comparable calc-alkaline volcanic province linked to a subducting plate margin in the Afro-Arabian area. Subsequent continental breakup led to termination of this volcanic activity and establishment of a passive marine shelf environment later in Lower Cambrian times. 相似文献
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13.
Fossils from the Cambrian to Devonian rocks of southern Thailand, the Langkawi Islands, mainland Kedah, Perlis, north Perak and central West Peninsular Malaysia are listed and reviewed, and their stratigraphy and correlation reassessed. The hitherto anomalous record of the trilobite Dalmanitina from Malaysia is reviewed and found to be of latest Ordovician (Hirnantian) age, rather than Lower Silurian age as previously reported, and is considered a probable synonym of the widespread Mucronaspis mucronata. A new stratigraphical nomenclature is erected for part of the Langkawi, mainland Kedah and Perlis area successions, in which the term Setul Limestone (which stretched from the Ordovician to the Devonian) is abandoned and replaced by the Middle Ordovician Kaki Bukit Limestone, the late Ordovician and early Silurian Tanjong Dendang Formation, the Silurian Mempelam Limestone, and the early Devonian Timah Tasoh Formation, all underlying the paraconformity with the late Devonian Langgun Red Beds. There was a single depositional basin in the generally shallow-water and cratonic areas of southern Thailand, Langkawi, and mainland Kedah and Perlis, in contrast to the deeper-water basin of north Perak. Only Silurian rocks are dated with certainty within another basin in central West Malaysia, near Kuala Lumpur, which were also cratonic and shallow-water, although to the east in west Pahang there are basal Devonian deeper-water sediments with graptolites. The area is reviewed in its position within the Sibumasu Terrane, which, in the Palaeozoic, also included central and northern Thailand, Burma (Myanmar) and southwest China (part of Yunnan Province). 相似文献
14.
Aram BAYET-GOLL Paul M. MYROW Guillermo F. ACE?OLAZA Reza MOUSSAVI-HARAMI Asadollah MAHBOUBI 《《地质学报》英文版》2016,90(5):1572-1597
The Lower Ordovician Shirgesht Formation in central Iran is composed of siliciclastic and carbonate rocks deposited in diverse coastal and marine shelfal environments (tidal flat, lagoon, shoreface, offshore-shelf and carbonate ramp). Five facies associations contain diverse ichnofossil assemblages that show distinct proximal to distal trends formed in a wide range of physical-chemical conditions. The ethological groups of trace fossils in the Shirgesht Formation reflect a gradient of depositional stress conditions across a wave-influenced shoreline and shelf. Deposits of wave-influenced environments make up a significant component of the geological record of shallow marine settings, and the ability to determine paleoenvironments in detail in such successions is critical for reconstruction of depositional histories and sequence-stratigraphic interpretation.The Cruziana ichnofacies of the study shows highly diverse suites that record the establishment of a benthic community under stable conditions and a long-term colonization window. The Skolithos ichnofacies recognized is a low diversity opportunistic ichnocommunity suite that resulted from colonization after tempestite deposition in a stressed environment. The strata record an onshore to offshore replacement of the Cruziana ichnofacies (with abundant feeding traces of deposit-feeders) by the Skolithos ichnofacies (dominated by suspension-feeders and predators). A transitional zone between the two ichnofacies coincides with the offshore-transition/distal lower-surface deposits. The distribution of ichnofacies, the diversity and range of ethological characteristics reflected by the ichnogenera, and the wide range of wave-dominated coastal facies demonstrate the potential to use individual trace fossils and ichnofacies for significantly refined palaeoenvironmental analysis of wave-dominated coastal settings, particularly in Ordovician successions. 相似文献
15.
江苏境内华北与扬子岩石地层区界线划分 总被引：1，自引：0，他引：1
以构造演化的活动论、地质发展历史的阶段论、岩石生成的时空联系论的观点 ,采用“层层剥皮”分析方法 ,根据江苏境内岩石地层序列、岩性特征、空间分布、沉积环境、含矿性、生物组合等情况按时间和空间 (华北和扬子岩石地层区 )对江苏境内岩石地层综合分区界线划分进行讨论 ,并就华北与扬子岩石地层区在江苏境内的界线 ,提出自北东向南西以海泗断裂—郯庐东侧断裂作为两者改造后的界线 ,其北西侧为华北岩石地层区 ,南东侧为扬子岩石地层区。依据江苏岩石地层时空分布实际情况 ,提出了江苏岩石地层综合分区的 7个原则 :1)岩石地层层序发育程度及其建造序列宏观岩性组合特征 ;2 )岩石生成环境 (古气候、古地理、古构造 )及其时空变化 ;3)生物群 (组合 )特征和生物分区 ;4 )区域变质岩生成时期及其特征 ;5 )区域岩浆岩生成时期及其特征 ;6 )区域地球物理场特征 ;7)区域大地构造属性。 相似文献
16.
Extrusive and high level intrusive Early Devonian keratophyres are the oldest in situ igneous rocks in the Tamworth Block of the New England Fold Belt of eastern Australia. They show extensive evidence of degradation, including the destruction of magmatic phases, the growth of low grade metamorphic minerals, and changes in composition involving the dilution of elemental abundances in response to silica addition. Relations between the less mobile minor and trace elements, and limited data on clinopyroxene compositions, lead to the conclusion that these Early Devonian volcanic rocks are mostly calc‐alkaline volcanic arc andesites with minor dacite. These rocks unconformably overlie a sequence of Early Palaeozoic forearc basin deposits, indicating that the Early Devonian marks a period of readjustment of tectonic elements within the New England Fold Belt, associated with a marked east‐directed stepping out of the magmatic arc. Generation of the keratophyres in a subduction zone environment limits the position of the trench to 100 km east of the Peel Fault System. 相似文献
17.
The tectonic setting of the Devonian rocks in the New England Orogen has been the subject of considerable debate and controversy for many years. Our studies reveal that they have formed in intra-oceanic island arc and back arc basin (BAB) settings based on Th/Yb, Nb/Yb, Ba/La and Zr/Y ratios. Further, many of the samples that formed in a BAB have a mixture of MORB and arc-like characteristics, a few are almost entirely MORB-like. The arc-like features are believed to be due to the presence of a subduction component in the basaltic magma, the amount of which is controlled by the distance from the arc. Those samples with MORB-like compositions are thought to have originated at spreading centres. The compositions of Late Devonian basalts become more arc-like to the west suggesting a west facing polarity. Based on the tectonic setting and spatial relationship of Late Devonian sequences, we propose that two subduction zones existed during the Late Devonian, one dipping west beneath the Lachlan Orogen, the other dipping east beneath a rifted intra oceanic arc. Obduction of this intra oceanic arc over the continental margin of the Lachlan Orogen in the latest Devonian at approximately 375 Ma led to the development of a new west dipping subduction zone oceanward and commencement of continental, arc magmatism. 相似文献
18.
B.E. Leveridge R.K. Shail 《Proceedings of the Geologists' Association. Geologists' Association》2011,122(4):568-615
Deep marine deposits of the Gramscatho Basin of south Cornwall reflect two tectonic regimes; Early to Middle Devonian rifting of continental lithosphere with formation of oceanic lithosphere to the south, and Middle Devonian to earliest Carboniferous convergence along its southern margin. Sediments on thinned continental crust to the north and oceanic lithosphere to the south were juxtaposed in the Late Devonian when nappes of deep water flysch and olistostrome were thrust up on to the northern continental margin of the basin. Basin closure was accommodated by forward propagating thrust nappes, accompanied by penecontemporaneous sedimentation. The stratigraphical sequences of major nappes illustrate the progradation of flysch with climactic sedimentation of olistostrome in late Mid- to Late Devonian times. The Lizard Complex, including the Lizard ophiolite, within that nappe stack, constitutes part of one of the GCR sites which are largely in the allochthonous rocks. Many of those sites feature the olistostrome, Roseland Breccia Formation, with its great variety of sedimentary, igneous and metamorphic clasts (up to 1.5 km), and the association of ocean floor basalt and penecontemporaneous acidic volcanics indicative of the coming together of oceanic and continental plates. A site at the top of the parautochthonous continental margin succession displays the erosion products of the youngest nappe as it emerged and advanced across the sediment surface, marking closure of the oceanised Gramscatho Basin and continental collision. 相似文献
19.
E. C. Leitch C. L. Fergusson R. A. Henderson V. J. Morand 《Australian Journal of Earth Sciences》2013,60(4):301-310
Devonian and Carboniferous (Yarrol terrane) rocks, Early Permian strata, and Permian‐(?)Triassic plutons outcrop in the Stanage Bay region of the northern New England Fold Belt. The Early‐(?)Middle Devonian Mt Holly Formation consists mainly of coarse volcaniclastic rocks of intermediate‐silicic provenance, and mafic, intermediate and silicic volcanics. Limestone is abundant in the Duke Island, along with a significant component of quartz sandstone on Hunter Island. Most Carboniferous rocks can be placed in two units, the late Tournaisian‐Namurian Campwyn Volcanics, composed of coarse volcaniclastic sedimentary rocks, silicic ash flow tuff and widespread oolitic limestone, and the conformably overlying Neerkol Formation dominated by volcaniclastic sandstone and siltstone with uncommon pebble conglomerate and scattered silicic ash fall tuff. Strata of uncertain stratigraphic affinity are mapped as ‘undifferentiated Carboniferous’. The Early Permian Youlambie Conglomerate unconformably overlies Carboniferous rocks. It consists of mudstone, sandstone and conglomerate, the last containing clasts of Carboniferous sedimentary rocks, diverse volcanics and rare granitic rocks. Intrusive bodies include the altered and variably strained Tynemouth Diorite of possible Devonian age, and a quartz monzonite mass of likely Late Permian or Triassic age. The rocks of the Yarrol terrane accumulated in shallow (Mt Holly, Campwyn) and deeper (Neerkol) marine conditions proximal to an active magmatic arc which was probably of continental margin type. The Youlambie Conglomerate was deposited unconformably above the Yarrol terrane in a rift basin. Late Permian regional deformation, which involved east‐west horizontal shortening achieved by folding, cleavage formation and east‐over‐west thrusting, increases in intensity towards the east. 相似文献
20.
R. J. Coventry 《Australian Journal of Earth Sciences》2013,60(4):579-583
The Drummond Basin represents a major, backarc extensional system located at the inboard margin of the northern New England Orogen. Its synrift (cycle 1) infill is distinctively volcanic and volcani‐clastic in character and displays complex facies relationships and considerable variations in thickness controlled by the history and fabric of extensional faulting and the distribution of coeval volcanic centres. Subtle inheritance signatures in the age spectra obtained by SHRIMP (II) Pb‐U dating of zircons from volcanic units have impeded age assignment. New geochronologic data indicate that basinal subsidence was initiated in the north in latest Devonian (Famennian) time but was delayed until the Early Carboniferous (Tournaisian) in the south. Northern successions are dominated by volcaniclastic strata that accumulated distal to the loci of contemporary volcanism, whereas southern successions are dominated by silicic flows and ash‐flow tuffs and associated hypabyssal intrusive suites proximal to, or coincident with, volcanic loci. The Burdekin, Clarke River and Bundock Creek Basins located north of the Drummond Basin are broadly coeval features with comparable Infill. They likewise represent backarc basins developed inboard of the northern New England Orogen which trends offshore at latitude 20°S and appears to be represented in basement cores recovered from the Coral Sea. Calc‐alkaline magmatism of Late Devonian‐Early Carboniferous age extended at least 400 km inboard of the Gondwanan plate margin now represented in Queensland and related to an acute angle of subduction along the active margin at that time. 相似文献