Southern Hemisphere strong polar mesoscale cyclones in high-resolution datasets     

Alexandre Pezza  Katherine Sadler  Petteri Uotila  Timo Vihma  Michel D. S. Mesquita  Phil Reid 《Climate Dynamics》2016,46(5-6):1647-1664

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Normal fault growth influenced by basement fabrics: The importance of preferential nucleation from pre‐existing structures     

Luca Collanega  Katherine Siuda  Christopher A.‐L. Jackson  Rebecca E. Bell  Alexander J. Coleman  Antje Lenhart  Craig Magee  Anna Breda 《Basin Research》2019,31(4):659-687

Reactivation of pre‐existing intra‐basement structures can influence the evolution of rift basins, yet the detailed kinematic relationship between these structures and overlying rift‐related faults remains poorly understood. Understanding the kinematic as well as geometric relationship between intra‐basement structures and rift‐related fault networks is important, with the extension direction in many rifted provinces typically thought to lie normal to fault strike. We here investigate this problem using a borehole‐constrained, 3D seismic reflection dataset from the Taranaki Basin, offshore New Zealand. Excellent imaging of intra‐basement structures and a relatively weakly deformed, stratigraphically simple sedimentary cover allow us to: (a) identify a range of interaction styles between intra‐basement structures and overlying, Plio‐Pleistocene rift‐related normal faults; and (b) examine the cover fault kinematics associated with each interaction style. Some of the normal faults parallel and are physically connected to intra‐basement reflections, which are interpreted as mylonitic reverse faults formed during Mesozoic subduction and basement terrane accretion. These geometric relationships indicate pre‐existing intra‐basement structures locally controlled the position and attitude of Plio‐Pleistocene rift‐related normal faults. However, through detailed 3D kinematic analysis of selected normal faults, we show that: (a) normal faults only nucleated above intra‐basement structures that experienced late Miocene compressional reactivation, (b) despite playing an important role during subsequent rifting, intra‐basement structures have not been significantly extensionally reactivated, and (c) preferential nucleation and propagation of normal faults within late Miocene reverse faults and folds appears to be the key genetic relationship between contractionally reactivated intra‐basement structures and rift‐related normal faults. Our analysis shows that km‐scale, intra‐basement structures can control the nucleation and development of newly formed, rift‐related normal faults, most likely due to a local perturbation of the regional stress field. Because of this, simply inverting fault strike for causal extension direction may be incorrect, especially in provinces where pre‐existing, intra‐basement structures occur. We also show that a detailed kinematic analysis is key to deciphering the temporal as well as simply the spatial or geometric relationship between structures developed at multiple structural levels.  相似文献   

Biotic consequences of a shift in invertebrate ecosystem engineers: Invasion of New Zealand rocky shores by a zone‐forming ascidian          下载免费PDF全文

Andrew R. Davis  Katherine Walls  Andrew Jeffs 《Marine Ecology》2018,39(3)

The pervasive effects of invasive ecosystem engineers, that is those species that modify their environment, are well documented, but rarely have the broader impacts of one foundation invertebrate species being replaced by another been examined. In New Zealand, green‐lipped mussels, Perna canaliculus, commonly dominate wave‐exposed rocky shores. The recent appearance of an invasive ecosystem engineer, the ascidian Pyura doppelgangera, at the very northern tip of New Zealand now threatens to exclude these bivalves from this habitat. Here, we report major shifts in assemblages associated with the invader and chronicle its continued spread. We examined epibiota associated with clumps of mussels and clumps of Pyura from two rocky shore habitats—pools and emergent substrata at two locations. We detected some differences in species richness in biota associated with the two foundation species, but faunal abundance only differed between the locations. These minor changes were dwarfed by the shift in species composition within clumps of each foundation species. Molluscs, particularly gastropods, and crustaceans dominated the assemblage within mussels. In contrast, tubicolous polychaetes dominated the fauna associated with the ascidian. Sessile epifauna, notably barnacles and calcareous tube‐dwelling polychaetes, were common on mussels, but never encountered on the ascidian. Multivariate analysis revealed marked dissimilarity (>80%) between the characteristic mussel and ascidian faunas with virtually no overlap. This biotic shift overshadowed any differences between habitats and locations. The broader implications of these faunal shifts for local and regional patterns of biodiversity, as well as ecosystem function, remain unclear, but deserve further attention.  相似文献   

Mineralogy and petrogenesis of lunar magnesian granulitic meteorite Northwest Africa 5744          下载免费PDF全文

Jeremy J. Kent  Alan D. Brandon  Katherine H. Joy  Anne H. Peslier  Thomas J. Lapen  Anthony J. Irving  Daniel M. Coleff 《Meteoritics & planetary science》2017,52(9):1916-1940

Lunar meteorite Northwest Africa (NWA) 5744 is a granulitic breccia with an anorthositic troctolite composition that may represent a distinct crustal lithology not previously described. This meteorite is the namesake and first‐discovered stone of its pairing group. Bulk rock major element abundances show the greatest affinity to Mg‐suite rocks, yet trace element abundances are more consistent with those of ferroan anorthosites. The relatively low abundances of incompatible trace elements (including K, P, Th, U, and rare earth elements) in NWA 5744 could indicate derivation from a highlands crustal lithology or mixture of lithologies that are distinct from the Procellarum KREEP terrane on the lunar nearside. Impact‐related thermal and shock metamorphism of NWA 5744 was intense enough to recrystallize mafic minerals in the matrix, but not intense enough to chemically equilibrate the constituent minerals. Thus, we infer that NWA 5744 was likely metamorphosed near the lunar surface, either as a lithic component within an impact melt sheet or from impact‐induced shock.  相似文献   

Late Pleistocene Vertebrates and Other Fossils from Epiguruk, Northwestern Alaska     

Thomas D. Hamilton  Gall M. Ashley  Katherine M. Reed  Charles E. Schweger 《Quaternary Research》1993,39(3)

Sediments exposed at Epiguruk, a large cutbank on the Kobuk River about 170 km inland from Kotzebue Sound, record multiple episodes of glacial-age alluviation followed by interstadial downcutting and formation of paleosols. Vertebrate remains from Epiguruk include mammoth, bison, caribou, an equid, a canid, arctic ground squirrel, lemmings, and voles. Radiocarbon ages of bone validated by concordant ages of peat and wood span the interval between about 37,000 and 14,000 yr B.P. The late Pleistocene pollen record is dominated by Cyperaceae, with Artemisia, Salix, Betula, and Gramineae also generally abundant. The fossil record from Epiguruk indicates that the Kobuk River valley supported tundra vegetation with abundant riparian willows during middle and late Wisconsin time. Large herbivores were present during the height of late Wisconsin glaciation as well as during its waning stage and the preceding interstadial interval. The Kobuk River valley would have been a favorable refugium for plants, animals, and possibly humans throughout the last glaciation.  相似文献   

Reply to Carcaillet and Vernet     

Katherine J. Willis  Edina Rudner  Pl Sümegi 《Quaternary Research》2001,55(3):388

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Calcification, photosynthesis and growth of the bloom-forming coccolithophore, Emiliania huxleyi     

William M. Balch  Patrick M. Holligan  Katherine A. Kilpatrick 《Continental Shelf Research》1992,12(12)

Measurements were made of photosynthesis and calcification in a bloom of coccolithophores in the Gulf of Maine as well as in laboratory batch cultures of the Emiliania huxleyi strain 88E. The¹⁴C technique for measuring calcification was evaluated with calcifying and noncalcifying coccolithophore strains. Shipboard bloom observations showed physiological evidence of stratification between surface and deep populations within the surface mixed layer. Photosynthesis and calcification rates were enhanced within hours of addition of KNO₃ or nitrate-rich deep water (to the same final concentration). Such rates were strongly temperature dependent in laboratory cultures, decreasing over a factor of two from 15 to 20°C. Calcification was considerably less light-dependent than photosynthesis and consistently had a measurable dark rate. In culture, maximum calcification rates and degree of cell plating were limited to logarithmic growth phase. This was followed by rapid increase in the coccolith shedding rate 1 day prior to the onset of stationary phase which continued several days after cell division stopped. The regional significance of these features to total organic and inorganic carbon production as well as calcite burial is discussed.  相似文献   

Seventh Annual Georgia-Florida Conference     

Wendy Shaw  Katherine Schipke 《The Professional geographer》1992,44(4):473-474

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Bitumens associated with lead,zinc and flnorite ore minerals in North Derbyshire,England     

Katherine L. Pering 《Geochimica et cosmochimica acta》1973,37(3):401-417

A bitumen deposit in north Derbyshire, England, is described and studied using the techniques of gas chromatography, infra-red spectrophotometry and elemental analysis. The bitumens are associated with lead-zinc-fluorite ore minerals concentrated along an unconformable contact between the Carboniferous Limestone and the overlying shales. Three varieties of bitumen are distinguished and are compared with the dispersed bitumens in both the Carboniferous Limestone and the Edale Shales, with crude oils believed to be derived from these shales, and with inclusions in the hydrothermal mineral fiuorite, associated with the limestone-shale contact. One of the varieties recognized, a brittle brown solid, contains aliphatic hydrocarbons very similar to those of the shales and to those of the crude oils likely derived from these shales. The other two are a viscous oil and a brittle, black solid, which geologic evidence suggests were originally derived from the limestone. They contain a very complex mixture of aliphatic hydrocarbons quite different from those in the limestone, however. Aliphatic hydrocarbons isolated from fluorite, which is hydrothermally formed, in nearby massive deposits are almost identical to those of the limestone and shale. This observation indicates that alteration of the aliphatic hydrocarbons in the sediment by hydrothermal fluids is an unlikely explanation for the origin of the complex mixtures of hydrocarbons in the viscous oil and brittle, black solid. On the basis of indirect evidence of high nitrogen content, presence of unsaturated hydrocarbons, and suitability of the environment for bacterial growth, it is suggested that selective bacterial alteration of the aliphatic hydrocarbons is the main process responsible for their present composition. A geologic history for the deposit is postulated that involves a two-phase introduction of bitumens. Each phase is suggested to have begun as a pulse of warm saline fluids migrating along the shale-limestone unconformity passed through the topographic high at Windy Knoll. Microbial oxidation of the bitumens may have taken place during the deposition process or, more likely, as a recent secondary oxidation process.  相似文献   

Political Economy and International Labour Migration: The Case of Polynesians in New Zealand     

Katherine D. Gibson 《New Zealand geographer》1983,39(1):29-42

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