The geologic history of the passive margin off new england and the canadian maritime provinces     

Elazar Uchupi  James Albert Austin Jr.   《Tectonophysics》1979,59(1-4)

The geologic history of the passive continental margin off the east coast of North America from New England to Newfoundland is described using all available geological and geophysical information. “Rift” and “drift” phases of the margin's evolution are recognized, with rifting initiated in Late Triassic and completed by Early Jurassic. The plate decoupling process created a complex block-faulted terrain as a result of uplift and tensional fracturing. The approximate plane of continental separation is marked by a “hinge zone” characterized by a pronounced steepening of basement gradients. Since the Early Jurassic, the margin has undergone continual subsidence in response to cooling and sediment loading. This “drift” sequence attains its maximum thickness in the vicinity of the continental slope and thins both landward and seaward. On the shelf, this unit consists of Mesozoic evaporites, carbonates, and deltaic deposits. Overlying these sediments is a prograding wedge of Cenozoic elastics. On the rise, the Mesozoic sediments are evaporites, hemipelagic limestones and shales and carbonaceous clays. The Cenozoic is dominantly terrigenous material. Separating these two sedimentary provinces is the continental slope, a site of major facies changes and a Mesozoic reef complex.  相似文献   

Shasta ground sloth (Nothrotheriops shastense hoffstetter) at Shelter Cave, New Mexico: Environment, diet, and extinction     

Robert S. Thompson  Thomas R. Van Devender  Paul S. Martin  Theresa Foppe  Austin Long 《Quaternary Research》1980,14(3):360-376

Seven coprolites of the extinct Shasta ground sloth (Nothrotheriops shastense) were recently discovered in the Los Angeles County Museum collection from Shelter Cave, New Mexico. Three dung balls provided radiocarbon ages of 11,330, 12,330 and 12,430 yr B.P. Packrat (Neotoma) middens disclose a xeric juniper woodland at Shelter Cave during the sloth's occupation. Plant cuticles from the dung indicate that the ground sloth had a diet dominated by mormon tea (Ephedra) and other xerophytic shrubs. Pollen spectra from the coprolites have high representations of anemophilous plants and low representations of the dietary items shown in the cuticle analysis.Fifteen radiocarbon dates of sloth dung obtained since 1974 strengthen the hypothesis that sloth extinction occurred about 11,000 yr B.P. Paleoenvironmental studies indicate that ground sloths lived in juniper woodlands and montane conifer communities. Nothrotheriops commonly dined on shrubs that are still present in these habitats. It is difficult to explain the demise of the Shasta ground sloth by climatic change or dietary stress. Human predation remains as a possible explanation; ground sloth extinction appears to coincide with the time of Clovis mammoth hunters.  相似文献   

Field meeting at Sevenoaks,Kent: 10th July, 1948     

G. Austin Browne  F.G.S. 《Proceedings of the Geologists' Association. Geologists' Association》1949,60(4):274

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A high-resolution diatom-inferred palaeoconductivity and lake level record of the Aral Sea for the last 1600 yr   总被引：1，自引：0，他引：1  

Patrick Austin  Anson Mackay  Olga Palagushkina  Melanie Leng   《Quaternary Research》2007,67(3):383-393

Formerly the world's fourth largest lake by area, the Aral Sea is presently undergoing extreme desiccation due to large-scale irrigation strategies implemented in the Soviet era. As part of the INTAS-funded CLIMAN project into Holocene climatic variability and the evolution of human settlement in the Aral Sea basin, fossil diatom assemblages contained within a sediment core obtained from the Aral Sea have been applied to a diatom-based inference model of conductivity (r² = 0.767, RMSEP = 0.469 log₁₀ μS cm^− 1). This has provided a high-resolution record of conductivity and lake level change over the last ca. 1600 yr. Three severe episodes of lake level regression are indicated at ca. AD 400, AD 1195–1355 and ca. AD 1780 to the present day. The first two regressions may be linked to the natural diversion of the Amu Darya away from the Aral Sea and the failure of cyclones formed in the Mediterranean to penetrate more continental regions. Human activity, however, and in particular the destruction of irrigation facilities are synchronous with these early regressions and contributed to the severity of the observed low stands.  相似文献   

The determination of hourly values of total solar radiation from daily summations     

Austin Whillier 《Theoretical and Applied Climatology》1956,7(2):197-204

Summary Curves, based on measured total (direct plus sky) solar radiation data for several stations in the Union of South Africa, are presented which enable the hourly distribution of total solar radiation on a horizontal surface to be determined for any locality, and any time of year on a long-term basis. In addition a graph is given showing the fraction of the daily total radiation which is received between stated hours, together with curves for four stations for estimating the difference between morning and afternoon total radiation for hour-pairs symmetrical about noon.Although based on South African solar radiation data, the curves are presented in a form convenient for use, as a first approximation, for localities anywhere in the world, and for any time of year. They are applicable for long-term averages as well as for cloudless days.

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Zusammenfassung Es werden Kurven der Globalstrahlung von Sonne und Himmel abgeleitet, die auf langjährigen Meßwerten für gewisse Stationen in der Südafrikanischen Union beruhen und gestatten, die stündliche Verteilung der Globalstrahlung auf Horizontalfläche für einen beliebigen Ort und für jede Jahreszeit zu bestimmen. In einem Diagramm wird gezeigt, welcher Anteil der täglichen Strahlungssumme zwischen bestimmten Stunden einfällt, außerdem werden Kurven für vier Stationen aufgestellt, um den Unterschied zwischen Vormittags- und Nachmittags-Globalstrahlung für zum wahren Mittag symmetrisch gelegene Stundenpaare zu untersuchen. Obgleich diese Kurven auf südafrikanischen Strahlungsmessungen basieren, ermöglicht ihre Form in erster Annäherung auch die Anwendung auf beliebige Orte der Erde und auf alle Jahreszeiten; sie können sowohl auf langjährige Mittelwerte wie auch auf wolkenlose Tage Anwendung finden.

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Résumé A partir des moyennes de mesures portant sur un certain nombre d'années de plusieurs stations de l'Union Sud-Africaine, l'auteur déduit des courbes qui permettent de déterminer la répartition horaire du rayonnement global du soleil et du ciel sur une surface horizontale pour un lieu donné et pour chaque saison. Un diagramme indique quelle est la proportion de la somme diurne du rayonnement entre des heures déterminées. D'autre part il construit des courbes pour quatre stations afin d'examiner la différence entre la rayonnement global du matin et de l'après-midi et cela pour des couples d'heures situées symétriquement par rapport au midi vrai. Bien que ces courbes aient été faites à partir de mesures du rayonnement en Afrique du Sud, à première approximation leur forme permet de les employer également dans d'autres régions de la Terre et pour toutes les saisons. Elles peuvent être utilisées aussi bien pour des moyennes portant sur de nombreuses années que pour les jours sans nuages.

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With 3 Figures  相似文献   

Assessing the significance of along-strike variations of middle to late Miocene prograding clinoformal sequence geometries beneath the New Jersey continental shelf     

Craig S. Fulthorpe  James A. Austin Jr 《Basin Research》2008,20(2):269-283

Seismic mapping of high-resolution multichannel seismic profiles along the New Jersey margin illustrates how characteristics of middle–late Miocene clinoformal sequence boundaries (SBs) change markedly along strike in presumed response to local depositional and erosional processes. Most SBs converge from SW to NE, in part as a result of the influence of underlying basin morphology on accommodation space, but also in response to differential subsidence and presumed along-strike variations in sediment supply from the adjacent margin. The curvature of clinoform breaks, historically viewed as marking palaeo-shelf edges, is variable and such breaks are rarely sharp. Gently curved palaeo-shelf/slope transitions cannot be assigned precise palaeobathymetric significance and probably instead reflect post-depositional sediment reworking. The amount of erosional truncation landward of clinoform breaks varies significantly. Documented along-strike variability in SB morphology occurs, even though middle–late Miocene palaeo-shelf edges are nearly linear in plan view. Therefore, such linearity cannot be a product of uniform sedimentary processes and/or accumulation along strike, but instead reflects elongation of depocentres of originally variable cross-sectional geometry, possibly with the assistance of along-strike currents. The observed lateral geometric heterogeneity of Neogene sequences can exert profound and unwanted influences on the outcome of scientific drilling intended to calibrate seismic stratigraphic interpretations in the absence of sufficient three-dimensional (3D) seismic control.  相似文献   

Temporal observations of rip current circulation on a macro-tidal beach   总被引：2，自引：0，他引：2  

Martin Austin  Tim Scott  Jeff Brown  Jenna Brown  Jamie MacMahan  Gerd Masselink  Paul Russell 《Continental Shelf Research》2010

A field experiment was conducted on a high energy macro-tidal beach (Perranporth, UK) to examine rip current dynamics over a low-tide transverse bar/rip system in response to changing tide and wave conditions. Hydrodynamic data were collected using an array of in situ acoustic doppler current meters and pressure transducers, as well as 12 GPS-tracked Lagrangian surf zone drifters. Inter-tidal and sub-tidal morphology were measured through RTK-GPS and echo-sounder surveys. Data were collected for eight consecutive days (15 tides) over a spring-neap tidal cycle with tidal ranges of 4–6.5 m and offshore significant wave heights of 1–2 m and peak periods of 5–12 s.  相似文献   

Tracing ground water input to base flow using sulfate (S, O) isotopes     

Gu A  Gray F  Eastoe CJ  Norman LM  Duarte O  Long A 《Ground water》2008,46(3):502-509

Sulfate (S and O) isotopes used in conjunction with sulfate concentration provide a tracer for ground water contributions to base flow. They are particularly useful in areas where rock sources of contrasting S isotope character are juxtaposed, where water chemistry or H and O isotopes fail to distinguish water sources, and in arid areas where rain water contributions to base flow are minimal. Sonoita Creek basin in southern Arizona, where evaporite and igneous sources of sulfur are commonly juxtaposed, serves as an example. Base flow in Sonoita Creek is a mixture of three ground water sources: A, basin ground water with sulfate resembling that from Permian evaporite; B, ground water from the Patagonia Mountains; and C, ground water associated with Temporal Gulch. B and C contain sulfate like that of acid rock drainage in the region but differ in sulfate content. Source A contributes 50% to 70%, with the remainder equally divided between B and C during the base flow seasons. The proportion of B generally increases downstream. The proportion of A is greatest under drought conditions.  相似文献   

Ocean urea fertilization for carbon credits poses high ecological risks     

Glibert PM  Azanza R  Burford M  Furuya K  Abal E  Al-Azri A  Al-Yamani F  Andersen P  Anderson DM  Beardall J  Berg GM  Brand L  Bronk D  Brookes J  Burkholder JM  Cembella A  Cochlan WP  Collier JL  Collos Y  Diaz R  Doblin M  Drennen T  Dyhrman S  Fukuyo Y  Furnas M  Galloway J  Granéli E  Ha DV  Hallegraeff G  Harrison J  Harrison PJ  Heil CA  Heimann K  Howarth R  Jauzein C  Kana AA  Kana TM  Kim H  Kudela R  Legrand C  Mallin M  Mulholland M  Murray S  O'Neil J  Pitcher G  Qi Y  Rabalais N  Raine R  Seitzinger S  Salomon PS  Solomon C 《Marine pollution bulletin》2008,56(6):1049-1056

The proposed plan for enrichment of the Sulu Sea, Philippines, a region of rich marine biodiversity, with thousands of tonnes of urea in order to stimulate algal blooms and sequester carbon is flawed for multiple reasons. Urea is preferentially used as a nitrogen source by some cyanobacteria and dinoflagellates, many of which are neutrally or positively buoyant. Biological pumps to the deep sea are classically leaky, and the inefficient burial of new biomass makes the estimation of a net loss of carbon from the atmosphere questionable at best. The potential for growth of toxic dinoflagellates is also high, as many grow well on urea and some even increase their toxicity when grown on urea. Many toxic dinoflagellates form cysts which can settle to the sediment and germinate in subsequent years, forming new blooms even without further fertilization. If large-scale blooms do occur, it is likely that they will contribute to hypoxia in the bottom waters upon decomposition. Lastly, urea production requires fossil fuel usage, further limiting the potential for net carbon sequestration. The environmental and economic impacts are potentially great and need to be rigorously assessed.  相似文献   

Characterisation and Simulation of the Multiscaling Properties of the Energy-Containing Scales of Horizontal Surface-Layer Winds   总被引：1，自引：1，他引：0  

Michael K. Lauren  Merab Menabde  Alan W. Seed  Geoffrey L. Austin 《Boundary-Layer Meteorology》1999,90(1):21-46

The multiscaling statistics of atmospheric surface-layer winds at low wavenumbers above farmland and in the lee of a mountain range were examined using a hot-wire and lightweight cup anemometer. It was found that the horizontal velocity spectra could be broken into high and low-wavenumber regimes according to the parameters given by this analysis. The low-wavenumber end of the spectrum possessed a spectral slope parameter that varied between values of 0.8 and 1.35 at the farmland site during the period of the experiment, and the high-wavenumber end – corresponding to the inertial range – possessed a spectral slope slightly greater than -5/3. The larger values for this parameter for the low-wavenumber end appeared to coincide with unstable conditions. In the lee of the mountain range, the low-wavenumber spectral slope parameter was larger still, at 1.45. The low-wavenumber signals over farmland were much less intermittent than inertial-range signals, but in the lee of the mountain range the intermittency increased. From this analysis, it was shown that the statistical properties of the recorded wind signal could be reproduced using a bounded random multiplicative cascade. The model was successfully used to simulate the wind velocity field directly, rather than simulating the energy dissipation field. Since the spectral slope parameter for low wavenumbers appeared to be a function of atmospheric stability, the method presented is a simple way of generating wind signals characteristic of a variety of atmospheric conditions.  相似文献