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1.
References     
Two well‐defined sequences of earthquakes in South Australia were recorded in January and October 1969, these being associated with main shocks of magnitude ML 4.4 and 4.1 respectively. The events occurred in a region of little previous seismic activity, near the boundary of the Adelaide Geosyncline and the Willyama Block.  相似文献   

2.
The stratigraphical problem of defining the lower boundary of the Adelaide System is discussed in relation to the geology of several critical areas in the Adelaide Geosyncline and adjacent shelf‐platform.

The Precambrian stratigraphical succession and geological history is outlined with the aid of Rb/Sr age‐determinations made by Dr W. Compston of the Australian National University.

It is concluded that the lower boundary of the Adelaide System is related to the collapse of older basement positive areas on which a regional erosional surface had developed. This surface is defined by the Callanna Beds, the oldest deposits of Willouran age. Willouran sedimentation began some time between 1,340 m.y. and 1,490 m.y. ago. Erosion of the basement rocks probably occupied a major early part of this time interval.  相似文献   

3.
Great Victoria Desert: Development and sand provenance   总被引：1，自引：0，他引：1  
Sands of the Great Victoria Desert, south‐central Australia, can be divided into three main groups on the basis of their physical and chemical characteristics (colour, grainsize parameters, mineralogy of heavy‐mineral suites, quartz oxygen isotopic composition, zircon U–Pb ages). The groups occupy the western, central and eastern Great Victoria Desert respectively, boundaries between them corresponding approximately to changes in the underlying rocks associated with the Yilgarn Craton to Officer Basin to Arckaringa Basin. Several lines of evidence suggest derivation of the sands mainly from local bedrock with very little subsequent aeolian transport. Ultimate protosources for the sands, each in order of importance, are: western Great Victoria Desert—Yilgarn Craton, Albany‐Fraser Orogen, Musgrave Complex; central Great Victoria Desert—Musgrave Complex; eastern Great Victoria Desert—Gawler and Curnamona Blocks, Adelaide Geosyncline, Musgrave Complex. Sediment from the Adelaide Geosyncline includes in addition an ‘exotic’ component from Palaeozoic sedimentary rocks probably derived mainly from Antarctica. Sediment transport of several hundred kilometres from these protosources to the sedimentary basins was dominantly by fluvial, not aeolian, means. Post‐Tertiary aeolian transport or reworking has been minimal, serving only to shape sand eroded from underlying sedimentary rocks or residual products of local basement weathering into the current dunes.  相似文献   

4.
A tectonic and sedimentary facies model is proposed to explain progressive evolution of the late Proterozoic to early Paleozoic Adelaide Rift (Geosyncline) of southern Australia. Tectonic and stratigraphic similarities are noted between the Adelaide Rift and many post Permian rifts and passive continental margins. Also the time span of the pre oceaniccrust accretion stage of the rifting process may be of the same order of magnitude, both in the Adelaide Rift and in post-Permian passive margins. These observations suggest that the underlying cause of the rifting process and the resultant crustal response have not changed significantly since late Precambrian times. More specifically the so-called “breakup unconformity”, observed in stratigraphic sequences beneath many present day passive continental margins, has been shown by various authors to correlate in time with earliest oceanic crust accretion, and it often separates underlying non-marine or paralic from fully marine shelf strata. In the Adelaide Rift, the unconformable Precambrian—Cambrian boundary is proposed as the analogue of this breakup unconformity, thereby explaining the apparently sudden influx of largely marine metazoans in Cambrian strata immediately above this unconformity.  相似文献   

5.
Books     
《Geology Today》1989,5(1):32-35
Book reviewed in this article:
Mathematics in Geology by John Ferguson.
A Practical Approach to Sedimentology by Roy Lindholm.
The Young Earth by E. G. Nisbet.
An Introduction to Geology by Brian Lee.
The Adelaide Geosyncline: Late Proterozoic Stratigraphy, Sedimentation, Palaeontology and Tectonics by W. V. Preiss.
Vertebrate Palaeontology and Evolution by Robert L. Carroll.
Drawing and Understanding Fossils: A Theoretical and Practical Guide for Beginners with Self-Assessment by E. W. Nield.
Volcanoes by C. Ollier.  相似文献   

6.
In the Desert Syncline of the southern Georgina Basin there is an Early and Middle Cambrian sequence unconformably overlying late Proterozoic sediments. Stratigraphic drilling and subsequent palaeontological studies have allowed the documentation of the sequence across the Proterozoic‐Cambrian unconformity. Earliest Cambrian green shales are bioturbated and contain distinctive acritarchs. These are overlain, probably unconformably, by sandstone with Diplocraterion burrows, in turn succeeded by archaeocyathan dolostone. Ordian and Templetonian (Middle Cambrian) shales and carbonates unconformably overlie the Early Cambrian sequence. The stratigraphic sequence is very similar to that in the Amadeus Basin and the Adelaide Geosyncline.  相似文献   

7.
A detailed sedimentological and chronostratigraphic analysis of the Umberatana Group in the northern Adelaide Geosyncline has uncovered a depositional history involving the rapid progradation (at least 20 km) of a giant reef complex (up to 1.1 km relief) during mid-Cryogenian interglacial times. The reef complex, which occurs in the Balcanoona Formation, displays facies similar to Phanerozoic reefs. These include a basal forereef (slope) facies, overlain by a reef-margin facies (consisting of both stromatolitic and non-stromatolitic frameworks), and an upper backreef (platform) facies consisting of shallow-water peloidal and oolitic carbonate. The thickening of the reef complex in a basinward direction, and the distribution of the key facies are consistent with the progradation of the platform into deep water. Progradation was contemporaneous with deposition of the upper Tapley Hill Formation and had largely ceased after a major margin failure event. Following this event, reef growth continued for a short time before becoming extinct, possibly as a result of global climatic cooling and/or eustatic sea-level fall.  相似文献   

8.
Heavy mineral studies on Pleistocene tills from North America, Upper Palaeozoic tillites of South Africa and Australia, and late Precambrian tillites of South Australia show that the heavy mineral suites of the Pleistocene tills are dominated by amphiboles, the Upper Palaeozoic tillites by garnet, and the late Precambrian tillites by zircon and tourmaline. About half of the garnets in the Upper Palaeozoic tillites show evidence of having been rounded, and retain delicate surface chattermark trails, which indicates that these garnets have not undergone chemical attack since deposition. Although the remainder of the garnets show, by way of etching, that intrastratal solutions were active in the sediments, it is suggested that amphiboles, pyroxenes and epidote, which must have been present in the original Upper Palaeozoic heavy mineral suites, were lost primarily by the action of sorting and mechanical abrasion in beach environments prior to, and during interglacial periods. The absence of garnet and the etching of tourmaline and zircon in the late Precambrian tillites is attributed to the action of alkaline intrastratal solutions over the long time interval during which the tillites were buried in the Adelaide Geosyncline.  相似文献   

9.
ABSTRACT Usually well preserved fluidization pillars and sand filled fluidization pipes occur within submarine channel sands of the basal Uratanna Formation (Lower Cambrian) in the Adelaide Geosyncline of South Australia. The morphology of these structures reflects complex lateral and vertical movement of fluids during liquefaction and dewatering. Fluidization pipes acted as conduits for highly concentrated, upward directed fluid flow. The formation and maintenance of these pipes was dependent upon the development of a pipe wall composed of clay plugged fine sand. Formed during initial fluidization, this lining acted as a permeability barrier, confining and concentrating fluidized flow within the pipe. Each of the pipes is surrounded by a cylindrical fluidization halo in which leakage through the pipe lining produced partial fluidization of the surrounding sediment. Fine scale structures within these haloes indicate that fluids flowed radially and upward out of the fluidization pipes at an acute angle. These fluids merged with and influenced the orientation and size of adjacent fluidization pillars. The fluidization pipes of the Uratanna Formation may represent unusual preservation of the unstable fluid flow conditions that occur during incipient fluidization of sand beds.  相似文献   

10.
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   

11.
Isolated quartzose pebbles, clusters of quartz granules, orthogonal aggregates of poorly sorted quartzose coarse sand, and ovoid pellets (≤2 mm long) of quartz silt occur in hemipelagic marine mudstone of the mid-Ediacaran Bunyeroo Formation exposed in the Adelaide Geosyncline (Adelaide Rift Complex), and ovoid pellets of quartz silt in cores of the correlative marine Dey Dey Mudstone from deep drillholes in the Officer Basin, South Australia. This detritus is interpreted respectively as dropstones, dumps, and frozen aggregates dispersed by sea ice possibly of seasonal origin, and till pellets transported by glacial ice. The ice-rafted material in the Bunyeroo Formation only has been found <10 m stratigraphically below and above a horizon of dacitic ejecta related to the 90 km diameter Acraman impact structure in the Mesoproterozoic Gawler Range Volcanics 300 km to the west. Furthermore, till pellets have been identified 4.4 to 68 m below distal Acraman ejecta in the Dey Dey Mudstone >500 km northwest of the impact site. The Acraman impact took place at a low paleolatitude (～12.5°) and would have adversely affected the global environment. The stratigraphic observations imply, however, that the impact occurred during, but did not trigger, a cold interval marked by sea ice and glacial ice, although the temporal relationship with Ediacaran glaciations elsewhere in Australia and on other continents is unclear. Release from the combined environmental stresses of a frigid, glacial climate near sea-level and a major impact in low latitudes may have been a factor influencing subsequent Ediacaran biotic evolution.  相似文献   

12.
The dispersed carbonaceous matter (kerogen), illite, and magnetic response of the Tindelpina Shale Member in the lower part of the thick, extensive Tapley Hill Formation provide three complementary methods for zoning the incipient metamorphic character of rocks comprising the late Precambrian Adelaide System where they crop out between Adelaide, Olary, and Marree in the Adelaide Geosyncline. The methods are based on the following parameters: kerogen structure (as determined by X-ray diffraction) and composition (percentage carbon, hydrogen to carbon atomic ratio, δ 13CPDB); illite crystallinity; and amplitude and type of aeromagnetic anomalies.Kerogen is the most definitive indicator of metamorphic change in the Tindelpina Shale. It has been used to delineate a western subgraphitic zone (85–91%C, H/C > 0.10) which is separated from an eastern graphitic zone (91–98%C, H/C < 0.10) by a north-trending line through Adelaide, Mintaro, Orroroo, and Baratta. A similar two-fold zonation appears to exist in the Mouth Painter—Copley—Marree area. Metamorphic adjustment of the stable carbon isotopic composition of the kerogen is also evident. Kerogen rank correlates well with illite crystallinity. Illites in the western zone have Weaver indices of less than six. Crystallinity increases to the east where 2M illite becomes the dominant illite polymorph. The eastern graphitic zone largely coincides in location and extent with a zone of linear aeromagnetic anomalies of amplitude exceeding 100 gammas. In the lower Tapley Hill Formation the anomaly is attributed to remanent magnetism, probably associted with metamorphic growth of magnetite.All three indicators suggest an increase in metamorphic grade from west to east across the geosyncline, in agreement with published observations based on conventional petrographic analysis of pelitic (and to a lesser extent, carbonate) rocks. Illite and chlorite, characteristic of the anchizone of burial diagenesis, are the dominant sheet silicates in the shales studied, although incipient metamorphic alteration of chlorite to biotite has occurred in some specimens from the graphitic zone. The subgraphitic and graphitic facies of the Tindelpina Shale correspond with the chlorite and biotite (and higher) zones, respectively, of low-pressure intermediate-type metamorphism previously established for the Mount Lofty and Flinders Ranges.Greater depth of burial of the lower Tapley Hill Formation in the eastern half of the geosyncline would account for the metamorphic trend observed in its organic matter and clay mineral content. Differential burial does not, however, adequately explain the magnetics, nor the absence of biotite-grade rocks in the central Flinders Ranges. Other magnetically anomalous beds are found throughout the Adelaide System and in overlying Cambrian strata. For the magnetism in these different stratigraphic intervals to be of metamorphic derivation, a regional thermal event, perhaps related to the Cambro-Ordovician Delamerian Orogeny, must be postulated.  相似文献   

13.
The Olary Block comprises a set of Palaeoproterozoic to Mesoproterozoic basement inliers that were deformed together with the Neoproterozoic sedimentary cover of the Adelaide Geosyncline during the ca 500 Ma Cambro‐Ordovician Delamerian Orogeny. Balanced and restored structural sections across this region show shortening of less than 20%. These basement inliers represent the interface between a region of thick‐skinned deformation bordering the Curnamona Craton to the north and a region of thin‐skinned deformation to the south and west in the Nackara Arc. The basement inliers represent upthrust segments of the subsided basin margin with the sedimentary package thickening to the south and to the west. Earlier formed extensional faults provided the major strain guides during Delamerian shortening. An early phase of east‐west shortening is interpreted to be synchronous with dextral strike‐slip deformation along basement‐relay structures (e.g. Darling River lineament). During progressive shortening the tectonic transport direction rotated into a northwest to north direction, coeval with the onset of the main phase of thin‐skinned fold deformation in the adjacent Nackara Arc.  相似文献   

14.
The sedimentary history and biostratigraphy of China during the Cambrian Period are broadly discussed within the framework of major tectonic divisions of the country. Five platform domains (North China Platform, southwest China Platform, Chiangnan Belt, Tarim Platform, and Tsaidem Platform) and five eugeosynclinal belts (South Tibet‐western Yunnan Belt, Tienshan‐Altai‐Great Khingan Geosyncline, Chilian Geosyncline, Kunlun‐Tibet‐western Yunnan Geosyncline and Southeast China Geosyncline) are recognised and discussed individually. A zonal scheme for Chinese Cambrian biostratigraphy is provided and the problems of the Precambrian to Cambrian, Cambrian to Ordovician and also the series boundaries are discussed. International correlation of the Cambrian of China, especially with Australia, is outlined in some detail.  相似文献   

15.
华北地台与秦岭地槽构造关系初探   总被引：1，自引：1，他引：1  
边界问题或构造关系问题,一直是地质学家最为关心的问题之一。华北地台与秦岭地槽构造关系的实质是洋壳与陆壳的矛盾统一和相互转化。中晚元古代时,秦岭地槽为洋壳演化区,华北地台为陆壳区,幸岭洋壳板块俯冲至华北陆壳板块之下:黑沟—铁炉子断裂相当俯冲带,其北洛南—栾川断隆是陆壳被改造而具陆缘弧性质;陆缘弧发展晚期在其南缘发育有弧前坳陷;陆缘弧之北的熊耳断坳则为弧后裂陷盆地;陆缘弧与弧后裂陷盆地之间的马超营—石门断裂为前陆断裂带。因此,秦岭地槽与华北地台的具体界线应以中晚元古代时大洋与大陆的分界线——黑沟—铁炉子断裂为准,而马超营—石门断裂仅为陆壳改造区内次级单位的分界.  相似文献   

16.

The seismicity of South Australia over the period 1980–92 is presented as a follow‐up to earlier studies. The South Australian seismic network has undergone a significant expansion in the last decade, and with it an increase in the number and precision of located earthquakes. The distribution of recent seismic activity is similar to the historical pattern of earthquakes and the previous instrumental seismicity maps, all of which show the three main areas as being the Flinders‐Mt Lofty Ranges, Eyre Peninsula, and the southeast. The one notable exception in the recent study is the presence of earthquake activity in the Musgrave Block, a previously aseismic region. Intensity characteristics are reported for earthquakes that were sufficiently widely felt. Fault plane solutions for three Flinders Ranges earthquakes (previously unpublished) are also presented; the focal mechanisms are consistent with predominant northeast‐southwest compression. The seismic moment method was used to estimate the seismic risk for the major population centres in terms of probability of exceedance of seismic intensity within a given period. These estimates are based on the recurrence parameters and intensity attenuation function for the region. The results place Adelaide close to the AS2121 ‐ 1979 Earthquake Code Zone I/Zone 2 boundary.  相似文献   

17.
A significant aspect of Late Proterozoic sedimentation in the Adelaide Geosyncline, South Australia, is the presence of kilometre-deep erosional incisions which have been termed canyons. These structures were formerly described to be of submarine origin, cut and filled in an inferred basin-slope setting by subaqueous processes. Subsequent detailed research, particularly on a specific incision known as Patsy Springs Canyon, indicates that sedimentary structures within some of the canyon-filling sediments are indicative of deposition above fair weather wave base. In addition, an unusual carbonate unit, which is observed to veneer upper portions of canyon shoulders and to contribute to carbonate breccias interbedded with canyon-fill, has a stable isotope signature which may imply a non-marine origin. The presence of the carbonate veneer, where it is in situ, suggests that at least upper portions of the canyons could have been emergent during the canyon-filling phase. Considering these observations, and combining them with regional stratigraphical relationships, an alternative model for canyon genesis is proposed involving subaerial erosion and subsequent filling by coastal onlap. Such a model requires base-level changes of the order of 1 km, in order to account for observed canyon cutting and filling. Vertical movements associated with halokinesis, or thermally-induced uplift of the order of 1 km, could have resulted in the observed erosional events. Alternatively, a Messinian-style evaporitic lowering of base-level is currently receiving serious attention. With present knowledge this mechanism most satisfactorily explains all observations.  相似文献   

18.
Stratigraphic and sedimentological investigation of the interglacial succession within the Cryogenian-aged Umberatana Group of the Northern and Central Flinders Ranges reveals a complex array of sedimentary successions lying between the Sturtian and Marinoan glacial deposits. The Sturtian–Marinoan Series boundary was first defined from the Adelaide area at the uppermost contact of the Brighton Limestone. In the Northern Flinders Ranges the Sturtian–Marinoan Series boundary has been positioned at the uppermost contact of the Balcanoona Formation, which is thought to correlate with the Brighton Limestone. In the Northern Flinders Ranges a major unconformity separates the Sturtian and Marinoan-aged sedimentary successions (Nepouie–Upalinna Subgroups). In moderately deep marine depositional settings, this submarine unconformity is located at the base of the Yankaninna Formation where erosion has deeply incised (up to 300 m) into the underlying Tapley Hill Formation. In shallower marine settings the unconformity is found at the base of the Weetootla Dolomite. In very deep water depositional settings this unconformity is not recognised, and the Yankaninna Formation appears to conformably overlie the Tapley Hill Formation suggesting that this erosional feature is restricted to shallow and moderately deep depositional settings. This unconformity presents a regionally persistent chronostratigraphic marker horizon, which reliably marks the Sturtian–Marinoan Series boundary at the base of the Yankaninna Formation from shallow shelfal to deep-water basinal settings throughout the Northern Flinders Ranges. In the Central Flinders Ranges the post-Sturtian glacial stratigraphy records a very similar depositional record to that observed in the Northern Flinders Ranges. In the Central regions the Tapley Hill Formation is overlain by deep-marine carbonates and calcareous shales of the Wockerawirra Dolomite and Sunderland Formations, respectively. The base of the Wockerawirra Dolomite is found to be in erosional contact with the underlying Tapley Hill Formation. This stratigraphic relationship, together with lithological similarities, indicates the Wockerawirra Dolomite and Sunderland Formation of the Central Flinders Ranges are lateral correlatives of the Yankaninna Formation of the Northern Flinders Ranges. The regional nature of the Sturtian–Marinoan unconformity in the Adelaide Geosyncline suggest the possible existence of a glacio-eustatic event that may correlate with glacials/glaciation elsewhere on the Earth during the Cryogenian.  相似文献   

19.
Tasman Geosyncline greenstones and ophiolites   总被引：1，自引：1，他引：0  
Palaeozoic greenstones lying at the base of stratigraphic sequences or in fault blocks in the Tasman Geosyncline are compared with the Penrose Conference definnition of an ophiolite by using tabulated petrological, structural, and metallogenic data. Of 45 occurrences, only 9 are recognizably ophiolites: 4 are in rift zones adjoining Precambrian continental crust at the ends of the geosyncline; and away from the margins, in that part of the geosyncline most typically of West Pacific‐type, only 5 of the 33 greenstone occurrences are recognizably ophiolites. Ophiolites are rare in the Tasman Geosyncline, in contrast to several Atlantic‐type geosynclines. This may be a characteristic of West Pacific‐type geosynclines in general.

Alpine‐type serpentinites are rather common in the Tasman Geosyncline. The metallogeny of some shows affinities with ophiolites, suggesting a common origin as oceanic crust. Their relative abundance suggests that West Pacific‐type geosynclines, such as the Tasman Geosyncline, may have developed on oceanic crust of unusual composition. Alternatively, it may reflect differences of deformation style between Atlantic‐ and West Pacific‐type geosynclines.

The term ophiolite has been used uncritically in plate tectonic analyses of the Tasman Geosyncline, calling in question the objectivity of these analyses. If objectivity is to be maintained, some indication should be given of the quality of the data used in plate tectonic analyses.  相似文献   

20.
The late Proterozoic Adelaide Geosyncline, along with overlying Cambrian strata, comprises a thick sequence of sediments and sparse volcanics which accumulated in a major rift and passive margin setting. During late syn-rift or early post-rift phases, large volumes of terrigenous and carbonate sediments of the late Proterozoic Umberatana and Wilpena Groups and Cambrian Hawker Group filled the rift. Submarine canyon development was related to at least four of these depositional cycles, the most notable of which resulted in incision and subsequent filling of the major (several kilometres in width and up to 1.5 km deep) submarine canyons by the Wonoka Formation. The Wonoka Formation canyons are not obviously fault controlled. They are interpreted to have been eroded by turbidity currents during a relative low-stand of sea-level. They were subsequently filled by a fining-upwards suite of sediments which reflects subsequent relative rise of sea-level and carbonate platform development. Ultimately the canyon complex was buried by north-westerly progradation of overlying fluvial and slope sequences (Billy Springs Beds and possibly correlative upper Pound Subgroup). It is considered likely that more distal elements of this prograding clastic wedge provided the necessary material for canyon erosion, prior to canyon filling and ultimate burial by what may have been elements of the same depositional cycle. It is considered possible that the series of isolated outcrops of canyon cross-sections within the Wonoka Formation are sections of a single canyon thalweg developed within a considerably broader zone of slope degradation. If this interpretation is correct, then the gorge-like Patsy Springs Canyon lies in more proximal regions of the basin-slope, whereas 40 km to the north-east the lower slope is cut by the Fortress Hill Canyon Complex. Palaeocurrent analyses of channel-fill turbidites within the canyons imply that the Fortress Hill Complex is in fact the outcropping western edge of a sinuous, incised canyon thalweg. The Wonoka Formation canyons, containing basal sedimentary breccias but only minor conglomerates, are considered typical of passive margin canyon development. They are contrasted with the generally highly conglomeratic channel-fills observed in outcropping Tertiary and Cretaceous examples of active margin canyons and upper fan valleys.  相似文献   

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