Tertiary stratigraphy of Western Australia     

Patrick G. Quilty 《Australian Journal of Earth Sciences》2013,60(3):301-318

This paper is a summary of the present knowledge of the Tertiary stratigraphy of Western Australia. Also included is new information on the Cainozoic of the Carnarvon Basin, a result of petroleum exploration in the area.

Tertiary rocks formed during more than one cycle of deposition in three basins (Eucla, Perth, and Carnarvon), and also as thin units deposited in a single transgression along the south coast. The Tertiary stratigraphy of the Bonaparte Gulf Basin is not well known.

Drilling in the Eucla Basin has encountered up to 400 m of Tertiary in the south central part, with uniform thinning towards the margins. The section begins with a middle‐upper Eocene carbonate unit which represents the dominant event in the Tertiary sedimentation in this basin. More carbonates were deposited in the late Oligocene‐early Miocene and middle Miocene.

Along the south coast, the so‐called Bremer Basin, the Plantagenet Group (up to 100 m) of siltstone, sandstone, spongolite, and minor limestone, was deposited during the late Eocene.

The Perth Basin contains up to 700 m of Tertiary sediment, formed during at least two phases of sedimentation. The upper Paleocene‐lower Eocene Kings Park Formation consists of marine shale, sandstone, and minor limestone, with a thickness of up to 450 m. The Stark Bay Formation (200 m) includes limestone, dolomite, and chert formed during the early and middle Miocene. Events after deposition of the Stark Bay Formation are not well known.

The northern Carnarvon Basin and Northwest Shelf contain by far the most voluminous Tertiary sediment known from Western Australia: 3500 m is known from BOCAL's Scott Reef No. 1. A more usual maximum thickness is 2500 m. Most sediments were laid down in four episodes, separated by unconformities: late Paleocene‐early Eocene; middle‐late Eocene; late Oligocene‐middle Miocene; and late Miocene to Recent.

The Paleocene‐early Eocene cycle consists of about 100–200 m (up to 450 m in the north) of carbonate, shale, and marl of the Cardabia Group containing rich faunas of planktonic foraminifera.

The middle‐late Eocene sediments include diverse rock types. Marine and nonmarine sandstone formed in the Merlinleigh Trough. At the same time, the Giralia Calcarenite (fauna dominated by the large foraminifer Discocyclina) and unnamed, deeper water shale, marl, and carbonate (with rich planktonic foraminiferal faunas) formed in the ocean outside the embayment. Thickness is usually of the order of 100–200 m.

The main cycle of sedimentation is the late Oligocene‐middle Miocene, during which time the Cape Range Group of carbonates formed. This contains dominantly large foraminiferal faunas, of a wide variety of shallow‐water microfacies, but recent oil exploration farther offshore has recovered outer continental shelf facies with abundant planktonic foraminifera. A minor disconformity representing N7 and perhaps parts of N6 and N8 is now thought to be widespread within the Cape Range Group. The last part of this cycle resulted in sedimentation mainly of coarse calcareous marine sandstone (unnamed), and, in the Cape Range area, of the sandstone and calcareous conglomerate of the Pilgramunna Formation. Maximum thickness encountered in WAPET wells is 900 m.

After an unconformity representing almost all the late Miocene, sedimentation began again, forming an upper Miocene‐Recent carbonate unit which includes some excellent planktonic faunas. Thickness is up to 1100 m.

Thin marine sediments of the White Mountain Formation outcrop in the Bonaparte Gulf Basin. They contain some foraminifera and a Miocene age has been suggested.  相似文献   

High-temperature infrared properties of forsterite   总被引：1，自引：0，他引：1  

Myriam Eckes  Benoit Gibert  Domingos De Sousa Meneses  Mohammed Malki  Patrick Echegut 《Physics and Chemistry of Minerals》2013,40(4):287-298

Polarized emittance measurements were acquired for synthetic forsterite, the pure magnesium end member of the olivines group, on the whole infrared spectral range and up to the melting point by using CO₂ laser heating. The experimental data, fitted with a semi-quantum dielectric function model, allowed the retrieval of the temperature dependence of the absorption coefficient of forsterite both in the opaque and semi-transparent regions. The analysis of the phonon parameters indicates that the lattice dynamics evolve drastically with increasing temperature. The normal modes involving motions of the magnesium cations located in site 1 are the more impacted, and some of them vanish around 1,200 K. The results confirm that the enhancement of the lattice anharmonicity and the increasing mobility of the magnesium cations are closely linked and are at the origin of the anomalies observed in the evolution of the thermophysical properties. This complete set of spectroscopic data may be a step toward a more precise evaluation of the impact of thermal radiation heat transfer inside systems involving forsterite and quantification of their heat budget.  相似文献   

Geology and metamorphism of the Ladakh Terrane and Shyok Suture Zone in the Chogo Lungma – Turmik area (northern Pakistan)     

Franco Rolfo  Bruno Lombardo  Roberto Compagnoni  Patrick Le Fort  Yves Lemennicier  Arnaud Pêcher 《Geodinamica Acta》2013,26(5):251-270

Abstract

Metamorphism of the Askore Amphibolite, metabasaltic and metasedimentary medium-grade hornblendebearing schists at the northernmost portion of the Ladakh Terrane and of the Shyok Suture Zone, mainly a low-grade volcano-sedimentary series, has been studied in the area between the Chogo Lungma glacier and the Indus river halfway between Skardu and Rondu.

In the Askore Amphibolite the peak assemblage in the amphibolite facies defines the regional metamorphic foliation, and is overprinted by a later static recrystallization at comparable P-T conditions. In spite of similar peak temperatures (630–650°C), geobarometry based on amphibole composition reveals a marked difference between garnet – epidote – andesine amphibolites exposed just above the Main Mantle Thrust at the head of Turmik valley, which equilibrated at high pressures (about 10 kbar) in late Miocene (Tortonian), and biotite – epidote – oligoclase amphibolites outcropping at the mouth of Turmik valley, which equilibrated at pressures of c. 6 kbar before late Eocene (Priabonian).

The Dasu Ultramafite and other smaller lens-shaped bodies of low- to medium-grade metaperidotite separate the Ladakh Terrane from the Shyok Suture Zone. They are antigorite serpentinites, often with talc and magnesite, in which relict cumulitic structures are locally recognisable. The ultramafites may represent remnants of oceanic lithosphere separating the Ladakh-Kohistan island arc from the Asian plate, or they may be deep crustal rocks stripped from the basement of the arc.

The mostly greenschist-facies Shyok Suture Zone shows the lithology of a calc-alkaline volcano-sedimentary series. It is supposed to be a remnant of a back arc basin of early Cretaceous age, separating the arc from the southern margin of Asia. Chloritoid, kyanite and biotite have been found in individual thrust sheets occurring at different structural levels and totally subordinate in volume to very low- and low-grade rocks. Such sharp differences in mineral paragenesis, together with field evidence of local shear, suggest a complex internal structure for the Shyok Suture Zone. From the head of Chogo Lungma glacier to the Basha valley, close to the contact with the Karakorum Metamorphic Complex, the rocks of the Shyok Suture Zone record a late Miocene metamorphic event at medium pressures and temperatures. Thermobarometric and geochronological evidence suggests that this event can be related to the exhumation and thrusting of the Karakorum metamorphic core over the Shyok Suture Zone.  相似文献   

The motion of magnetic fronts in spiral galaxies     

D. Moss  A. Petrov  D. Sokoloff 《地球物理与天体物理流体动力学》2013,107(1-2):129-149

Abstract

We study the nonlinear asymptotic thin disc approximation to the mean field dynamo equations, as applicable to spiral galaxies. The circumstances in which sharp magnetic field structures (fronts) can propagate radially are investigated, and an expression for the speed of propagation derived. We find that the speed of an interior front is proportional to η//R _? (where η is the diffusivity and R_t the galactic radius), whereas an exterior front moves with speed of order , where γ is the local growth rate of the dynamo. Numerical simulations are presented, that agree well with our asymptotic results. Further, we perform numerical experiments using the 'no-z' approximation for thin disc dynamos, and show that the propagation of magnetic fronts in this approximation can also be understood in terms of our asymptotic results.  相似文献   

Nonlinear galactic dynamos     

David Moss  Ilkka Tuominen 《地球物理与天体物理流体动力学》2013,107(1-3):113-120

Abstract

We present trial calculations for a simple nonlinear ‘‘thick disk'’ galaxy dynamo. The nonlinearity is a simple α-quenching. Our strictly axisymmetric solution demonstrates the possibility of a nonlinear interaction between modes of opposite parity. We suggest that a three dimensional model might exhibit a similar persistent interaction between axisymmetric and non-axisymmetric modes.  相似文献   

Persistent organic pollutants in marine biota of São Pedro and São Paulo Archipelago,Brazil     

Patrick S. Dias  Caio V.Z. Cipro  Satie Taniguchi  Rosalinda C. Montone 《Marine pollution bulletin》2013

Remote islands, such as the São Pedro and São Paulo Archipelago (SPSPA), Brazil, are pristine areas. However, these locations are not exempt from the arrival of anthropogenic agents, such as persistent organic pollutants (POPs). The present study aimed to determine the occurrence and distribution of POPs in the marine biota of the SPSPA. Sample extractions were performed using a microwave-assisted method. The predominant compounds were PCBs and DDTs, which respectively had mean wet weight concentrations of 62.23 and 9.23 ng g⁻¹ in the tropical two-wing flying fish (Exocoetus volitans), 78.66 and 6.81 ng g⁻¹ in the brown booby (Sula leucogaster) and 43.40 and 3.03 ng g⁻¹ in the red rock crab (Grapsus grapsus). Low levels of contaminants suggest a relative degree of isolation. Occurrence and distribution profiles of PCBs support long-range atmospheric transport as the main source of contamination and demonstrate the ubiquity of these pollutants in the marine environment.  相似文献   

Changes in ecosystem structure,function and hydrological connectivity control water,soil and carbon losses in semi‐arid grass to woody vegetation transitions     

Alan Puttock  Christopher J.A. Macleod  Roland Bol  Patrick Sessford  Jennifer Dungait  Richard E. Brazier 《地球表面变化过程与地形》2013,38(13):1602-1611

Connectivity has recently emerged as a key concept for understanding hydrological response to vegetation change in semi‐arid environments, providing an explanatory link between abiotic and biotic, structure and function. Reduced vegetation cover following woody encroachment, generally promotes longer, more connected overland flow pathways, which has the potential to result in an accentuated rainfall‐runoff response and fluxes of both soil erosion and carbon. This paper investigates changing hydrological connectivity as an emergent property of changing ecosystem structure over two contrasting semi‐arid grass to woody vegetation transitions in New Mexico, USA. Vegetation structure is quantified to evaluate if it can be used to explain observed variations in water, sediment and carbon fluxes. Hydrological connectivity is quantified using a flow length metric, combining topographic and vegetation cover data. Results demonstrate that the two woody‐dominated sites have significantly longer mean flowpath lengths (4 · 3 m), than the grass‐dominated sites (2 · 4 m). Mean flowpath lengths illustrate a significant positive relationship with the functional response. The woody‐dominated sites lost more water, soil and carbon than their grassland counterparts. Woody sites erode more, with mean event‐based sediment yields of 1203 g, compared to 295 g from grasslands. In addition, the woody sites lost more organic carbon, with mean event yields of 39 g compared to 5 g from grassland sites. Finally, hydrological connectivity (expressed as mean flowpath length) is discussed as a meaningful measure of the interaction between structure and function and how this manifests under the extreme rainfall that occurs in semi‐arid deserts. In combination with rainfall characteristics, connectivity emerges as a useful tool to explain the impact of vegetation change on water, soil and carbon losses across semi‐arid environments. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Submerged macrophytes avoiding a negative feedback in reaction to hydrodynamic stress     

Jonas Schoelynck  Dieter Meire  Kris Bal  Kerst Buis  Peter Troch  Tjeerd Bouma  Patrick Meire  Stijn Temmerman 《Limnologica》2013,43(5):371-380

In most aquatic ecosystems, hydrodynamic conditions are a key abiotic factor determining species distribution and aquatic plant abundance. Recently, local differences in hydrodynamic conditions have been shown to be an explanatory mechanism for the patchy pattern of Callitriche platycarpa Kütz. vegetation in lowland rivers. These local conditions consists of specific areas of increased shear zones, resulting in additional plant stress and erosion of the sediment on the one hand and local decreased shear zones resulting in zones favourable to plant growth and sedimentation of bed material on the other hand. In this study, the process of this spatial plant-flow-sedimentation interaction has been illustrated quantitatively by in situ flume measurements. By disturbing the incoming discharge on a single patch in such flume, we have quantified the behaviour and influence of a C. platycarpa patch under normal field conditions (base flow). Additionally, the behaviour of a C. platycarpa patch under different conditions of hydrodynamic stress has been examined in a laboratory flume. Indeed, flexible, submerged macrophytes are capable to adapt patch dimensions with changing stream velocities. At times of modest hydrodynamic stress, the species takes a position near the water surface and optimises its leaf stand, thereby maximising its photosynthetic capacity. At times of peak discharge, the patch will bend down towards the river bed and become more confined and streamlined, as such averting the stream velocity and diminishing the risk of breaking or being uprooted.In this paper, the processes of local hydrodynamic conditions on the patch and the patch’ intriguing life strategy of avoiding negative feedback was shown.  相似文献   

Evaluation of a Finite-Element Sea-Ice Ocean Model (FESOM) set-up to study the interannual to decadal variability in the deep-water formation rates     

Patrick Scholz  Gerrit Lohmann  Qiang Wang  Sergey Danilov 《Ocean Dynamics》2013,63(4):347-370

The characteristics of a global set-up of the Finite-Element Sea-Ice Ocean Model under forcing of the period 1958–2004 are presented. The model set-up is designed to study the variability in the deep-water mass formation areas and was therefore regionally better resolved in the deep-water formation areas in the Labrador Sea, Greenland Sea, Weddell Sea and Ross Sea. The sea-ice model reproduces realistic sea-ice distributions and variabilities in the sea-ice extent of both hemispheres as well as sea-ice transport that compares well with observational data. Based on a comparison between model and ocean weather ship data in the North Atlantic, we observe that the vertical structure is well captured in areas with a high resolution. In our model set-up, we are able to simulate decadal ocean variability including several salinity anomaly events and corresponding fingerprint in the vertical hydrography. The ocean state of the model set-up features pronounced variability in the Atlantic Meridional Overturning Circulation as well as the associated mixed layer depth pattern in the North Atlantic deep-water formation areas.  相似文献   

Finding a “Disappearing” Nontimber Forest Resource: Using Grounded Visualization to Explore Urbanization Impacts on Sweetgrass Basketmaking in Greater Mt. Pleasant,South Carolina∗     

Patrick T. Hurley  Angela C. Halfacre  Norm S. Levine  Marianne K. Burke 《The Professional geographer》2013,65(4):556-578

Despite growing interest in urbanization and its social and ecological impacts on formerly rural areas, empirical research remains limited. Extant studies largely focus either on issues of social exclusion and enclosure or ecological change. This article uses the case of sweetgrass basketmaking in Mt. Pleasant, South Carolina, to explore the implications of urbanization, including gentrification, for the distribution and accessibility of sweetgrass, an economically important nontimber forest product (NTFP) for historically African American communities, in this rapidly growing area. We explore the usefulness of grounded visualization for research efforts that are examining the existence of “fringe ecologies” associated with NTFP. Our findings highlight the importance of integrated qualitative and quantitative analyses for revealing the complex social and ecological changes that accompany both urbanization and rural gentrification.  相似文献