摘要:

The Ordovician sedimentary rocks of the southeastern Lachlan Fold Belt in the Mystery Bay area are folded into two approximately coaxial and subhorizontally plunging fold series: F1and F2. Regional domains with internally consistent F1and F2trends are juxtaposed along strike‐slip faults. Locally developed kink bands commonly have a close spatial relationship with the domain boundaries.

ISSN:0812-0099    

DOI:10.1080/08120098908729505

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Zinc mineralization in Devonian carbonates of the Lennard Shelf, northern Canning Basin is similar in many respects to that of the Mississippi Valley‐type including estimated minimum temperatures of sulphide precipitation between 70 and 110°C. Apparent apatite fission track ages for Precambrian granitic basement and for detrital apatites in Devonian carbonates in and near Pb‐Zn mineralization generally range between 260 and 340 Ma, with Precambrian samples tending to have slightly older apatite fission track ages than the Devonian carbonates. These apparent ages are younger than the stratigraphic age of the material analysed, indicating that appreciable annealing of fission tracks in apatite has occurred in post‐Devonian times. Mean horizontal confined track lengths are 12–13 μm for most samples and preclude attaching any ‘event’ significance to the fission track ages. Studies of well sequences (Grevillea 1 and Kennedia 1) indicate a period of rapid uplift in the area during the Late Triassic/Early Jurassic. Assuming a constant geothermal gradient of 30°C/km, approximately 1.5 km of uplift and erosion is estimated. Immediate thermal effects related to Miocene lamproite intrusion into Precambrian basement appear to be restricted to within 200 m of the contact zone.

ISSN:0812-0099    

DOI:10.1080/08120098908729506

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Apatite fission track analysis of 44 surface and borehole samples indicates that the Papuan Fold Belt was uplifted, eroded and cooled from the earliest Pliocene (5 Ma) to the present day. Uplift and cooling of basement in the Kubor and Muller Anticlines, 250 km apart, took place at 4.0±0.5 Ma, but thrusting of the large anticlines at the mountain front was probably within the last 1 Ma. This timing casts doubt on tectonic models requiring ongoing compression in the Miocene and favours a model with Late Miocene collision of New Guinea with an island arc to the north. The Mesozoic section in the western fold belt was heated to ≫100°C in the Pliocene, so is only prospective for gas and condensate, but the eastern fold belt had maximum palaeotemperatures at least 20°C lower, hence it is prospective for oil. A northeast‐southwest structural lineament is inferred to separate the western and eastern provinces. Mountain front anticlines, such as Iehi, underwent considerable heating in the Late Cretaceous, prior to Palaeocene uplift and erosion associated with opening of the Coral Sea. Pliocene heating was negligible in comparison. Any oil generation in the frontal anticlines would have been in the Late Cretaceous. This is likely to be true throughout the Fly Platform to the southwest, but in the fold belt hydrocarbons were generated during deep burial in the Pliocene. Thermal modelling of the Iehi 1 well indicates ∼ 800 m of Late Cretaceous eroded in the Palaeocene. Modelling of other fission track data suggests the presence of Late Jurassic and Early Cretaceous volcanogenic sediments in the fold belt.

ISSN:0812-0099    

DOI:10.1080/08120098908729507

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The Mordor Complex, a series of highly differentiated potassic rocks (phlogopite lherzolite, phlogopite wehrlite to syenite) which intrudes Precambrian gneiss and amphibolite of the Arunta Block, central Australia, is a rare example of highly potassic magmatism of pre‐Phanerozoic age. Sm‐Nd and U‐Pb whole‐rock isochrons confirm a previously published Rb‐Sr emplacement age of ∼ 1150 Ma. The magmas of the complex possessed a range of initial isotopic compositions, with initial87Sr/86Sr ˜ 0.71 (from Langworthy & Black 1978),ϵNd from ‐9.5 to ‐11.6, initial 206Pb/204Pb from 16.33 to 16.85 and initial207Pb/204Pb from 15.46 to 15.56, and were derived from isotopically evolved, ‘enriched mantle’ sources, in common with many Phanerozoic examples of potassic magmatism. Evolution of the highly negative initialϵNd values requires that Sm/Nd fractionation occurred in the magma sources at least ∼ 830 Ma prior to emplacement of the complex, suggesting that the Mordor sources were generated either prior to or shortly after formation of Arunta Block crust at ∼ 2000 Ma. The processes generating enriched mantle sources, such as those from which many Phanerozoic examples of potassic magmatism are derived, have therefore operated since at least the mid‐Proterozoic.

ISSN:0812-0099    

DOI:10.1080/08120098908729508

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The Perth Basin is a narrow, elongate structure with an onshore area of some 45 000 km2, extending approximately 1000 km along the Western Australian coastline and bounded in the east by the Darling Range. Sedimentary fill ranges in age from Silurian to Modern, with Quaternary sediments attaining a maximum thickness of some 150 m. Amino acid racemization reactions are applied in assessments of the relative ages of several Quaternary marginal marine lithostratigraphic units within the Perth region. These sequences were deposited in response to four temporally distinct marine transgressions during the early, middle and late Pleistocene and the Holocene. Amino acid data indicate that Pleistocene and Holocene sequences may only be delineated using this method within increments of approximately 20 000 and 3000 years, respectively, with an effective time span serving approximately the last 600 000 years for regions presently characterized by temperate climates in Australia (MAT 18°C). The range of the technique may be significantly less for tropical settings that experience higher mean annual temperatures and as a corollary have higher ‘Effective Quaternary Temperature’ histories. The extent of racemization evident in Last Interglacial and Penultimate Interglacial molluscan fossils from the Perth region compare favourably with the same species from coastal deposits of equivalent age in South Australia and highlights the possibility of chronocorrelation of deposits from widely separated sites.

ISSN:0812-0099    

DOI:10.1080/08120098908729509

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Shallow marine sediments of the Broughton Formation are dominated by immature volcanic debris of intermediate to basic composition, generated in an adjacent subaerial environment by volcanism responsible for the nine shoshonite units intercalated within sediments of the Kiama region. Sediment was supplied to the offshore environment via periodic storm‐generated, expanded high density turbidity currents. Initial deposition, represented by the Westley Park Sandstone Member, was below storm wave base, during which time the depositional surface was subjected to post‐depositional tractional reworking by northerly directed, tidally influenced bottom currents. The resulting positive‐relief sand bodies on the seafloor contain tractional sedimentary structures (the ‘tractional facies association'). Areas of the substrate between these sand bodies retained their turbidite bedding structure (the ‘rhythmically bedded facies association') but were extensively bioturbated by a diverse deposit‐feeding biomass.

ISSN:0812-0099    

DOI:10.1080/08120098908729510

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

ISSN:0812-0099    

DOI:10.1080/08120098908729511

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

ISSN:0812-0099    

DOI:10.1080/08120098908729512

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

ISSN:0812-0099    

DOI:10.1080/08120098908729513

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

ISSN:0812-0099    

DOI:10.1080/08120098908729514

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor