The Stratigraphy,Sedimentology, and Fossils of the Haughton Formation: A Post-Impact Crater-Fill,Devon Island,N.W.T., Canada     

Leo J. Hickey  Kirk R. Johnson  Mary R. Dawson 《Meteoritics & planetary science》1988,23(3):221-231

Abstract— After the impact that formed Haughton crater, 22.4 ± 1.4 Ma ago (early Miocene), the cavity filled with water and began to accumulate lacustrine sediments. These preserve detailed evidence of pre-impact stratigraphy and post-impact morphology and development of the crater, as well as of the climatic and biotic regime in which it lay. In this report we formally designate these sediments as the Haughton Formation, of which only a 48 m thick remnant covering approximately 7 km² still exists. Dolomite-rich, poorly-sorted silt, fine sand, and mud are the principal lithologies. The formation unconformably overlies a blanket of allochthonous impact breccia forming the floor of the original crater. Presence of a debris-flow deposit in the base of the sequence indicates that lacustine deposition began very shortly after crater formation. The Haughton Formation contains a moderately diverse and highly endemic vertebrate fauna as well as palynomorphs and plant macrofossils that indicate a cool-temperate climatic regime. A small percentage of reworked Late Cretaceous and early Tertiary palynomorphs point to the former existence of the Eureka Sound Formation in the drainage area of the crater. In addition, the distribution of the lake beds indicates the absence of an inner ring on the west side of the crater, and the 3° to 3.5° inward dip of Haughton strata implies that the central mass has subsided approximately 300 to 350 m since deposition began.  相似文献   

Photographic monitoring of soiling and decay of roadside walls in central Oxford, England     

Mary J. Thornbush  Heather A. Viles 《Environmental Geology》2008,56(3-4):777-787

As part of the Environmental Monitoring of Integrated Transport Strategies (EMITS) project, which examined the impact of the Oxford Transport Strategy (OTS) on the soiling and decay of buildings and structures in central Oxford, England, a simple photographic survey of a sample of roadside walls was carried out in 1997, with re-surveys in 1999 and 2003. Thirty photographs were taken each time, covering an area of stonework approximately 30 × 30 cm in dimensions at 1–1.3 m above pavement level. The resulting images have been used to investigate, both qualitatively as well as quantitatively, the progression of soiling and decay. Comparison of images by eye reveals a number of minor changes in soiling and decay patterns, but generally indicates stability except at one site where dramatic, superficial damage occurred over 2 years. Quantitative analysis of decay features (concavities resulting from surface blistering, flaking, and scaling), using simple techniques in Adobe Photoshop, shows variable pixel-based size proportions of concavities across 6 years of survey. Colour images (in Lab Color) generally have a reduced proportion of pixels, representing decay features in comparison to black and white (Grayscale) images. The study conveys that colour images provide more information both for general observations of soiling and decay patterns and for segmentation of decay-produced concavities. The study indicates that simple repeat photography can reveal useful information about changing patterns of both soiling and decay, although unavoidable variation in external lighting conditions between re-surveys is a factor limiting the accuracy of change detection.  相似文献   

Fumarole distribution,morphology, and encrustation mineralogy associated with the 1986 eruptive deposits of mount St. Augustine,Alaska     

Lawrence Kodosky  Mary Keskinen 《Bulletin of Volcanology》1990,52(3):175-185

Numerous rootless fumaroles were developed on pyroclastic flows and a lava flow generated during the March 1986 eruptive cycle of Mount St. Augustine. Gases issued from fumarole vents with four different shapes: fissure, phreatic explosion crater, single/multiple ovoid opening, and diffuse, multiple opening. Fumarole distribution and morphology were controlled by preeruption drainage and topography, as well as by the thickness, compaction, and settling of the flow deposits. Fumarole temperatures measured in June and July 1986 ranged from 75°–394°C. Varying amounts of colorful and often roughly zoned encrustations are associated with all fumarole vent shapes. Only six types of crystalline phases were detected by X-ray diffraction, with gypsum the most abundant mineral, followed by anhydrite, sulfur, tridymite, halite, and soda alum. Scanning electron microscopy and energy dispersive X-ray analysis revealed a number of amorphous phases, mainly halogen-rich, as well as other minor crystalline phases. The mineral assemblages in the encrustations suggest formation conditions for these deposits within a general range of 25°–250°C in an oxidizing environment. Many of the amorphous phases are metastable and upon cooling of the fumarole lose nonstructural water and crystallize to more stable forms. The high halogen contents of the fumarole condensates and the mineralogy, chemistry, and morphology of the encrustations support leaching of the andesitic ash and lava flow by condensed acid vapors as the primary source for the chemical components contained in the encrustations. Comparison of traceelement (Sr, Ba, V, Co, Ni, and Cr) contents in unaltered and altered ash suggests that trace-element distribution follows a pattern of isomorphic substitution in the encrustation phases.  相似文献   

Miscellaneous information     

James R. Rice  Mary Hubbard  Andrea Borgia  G?ran Ekstr?m  S. J. Gibowicz  et al. 《Bulletin of Volcanology》1990,52(Z1):81-91

Miscellaneous information  相似文献   

Spatial Distribution–Abundance Relationships in Juvenile (Age 0) Red Drum (<Emphasis Type="Italic">Sciaenops ocellatus</Emphasis>) and Spotted Seatrout (<Emphasis Type="Italic">Cynoscion nebulosus</Emphasis>). I: Influence of Freshwater Inflow     

Shannon D. Whaley  Mary. C. Christman  James J. BurdJr. 《Estuaries and Coasts》2016,39(3):742-751

We examined relationships between freshwater inflow and population abundance and distribution of two size classes (15–50 mm Standard Length and 51–100 mm SL) of spotted seatrout (Cynoscion nebulosus) and red drum (Sciaenops ocellatus) over our 13-year study covering shallow waters of Tampa Bay and several adjacent rivers. Juveniles of seatrout were relatively abundant most years and broadly distributed primarily in the bay. Freshwater inflow was positively related to spatial distribution and abundance of smaller juveniles of seatrout, yet it was unrelated to the larger size class. Red drum juveniles were less abundant and narrowly distributed primarily within the rivers. Lower portions of the Alafia, Little Manatee, and Manatee Rivers—a combined area comprising only 2 % of the study area—contained 40–96 % of the annual population. Freshwater inflow was positively related to population distribution and abundance of larger red drum suggesting that reductions in inflow can reduce both habitat area and populations. Inflow was related to abundance but not distribution of the smaller red drum suggesting that inflow may increase habitat quality but perhaps not quantity at this earlier growth stage. Comparing spatial and population dynamics of multiple species can help prioritize them for conservation and management issues, such as freshwater inflow regulation. Reductions in inflow reduce populations and spatial distribution of at least one juvenile life stage of these two fishery species. Due to their narrow spatial distribution in the rivers, juveniles of red drum appear to be particularly vulnerable to modification of the riverine environment.  相似文献   

Relay zone evolution: a history of repeated fault propagation and linkage,central Corinth rift,Greece          下载免费PDF全文

Romain Hemelsdaël  Mary Ford 《Basin Research》2016,28(1):34-56

Established models indicate that, before being breached, relay zones along rift borders can evolve either by lengthening and rotating during progressive overlap of growing fault segments (isolated fault model), or, by simply rotating without lengthening before breaching (coherent fault model). The spatio‐temporal distribution of vertical motions in a relay zone can thus be used to distinguish fault growth mechanisms. Depositional relay zones that develop at sea level and accommodate both deposition on the ramp itself as well as transfer of sediments from the uplifting footwall into the hangingwall depocentres and provide the most complete record of vertical motions. We examine the development of a depositional relay ramp on the border of the active Corinth rift, Greece to reconstruct fault interaction in time and space using both onshore and offshore (2D seismic lines) data. The Akrata relay zone developed over a period of ca. 0.5 Myr since the Middle Pleistocene between the newly forming East Helike Fault (EHF) that propagated towards the older, more established Derveni Fault (DF). The relay zone captured the Krathis River, which deposited prograding Gilbert‐type deltas on the sub‐horizontal ramp. Successive oblique faults record progressive linkage and basinward migration of accommodation along the ramp axis, whereas marine terraces record diachronous uplift in their footwalls. Although early linkage of the relay zone occurs, continuous propagation and linkage of the EHF onto the static DF is recorded before final beaching. Rotation on forced folds above the upward and laterally propagating normal faults at the borders of the relay zone represents the ramp hinges. The Akrata relay zone cannot be compared directly to a simple fault growth model because (1) the relay zone connects two fault segments of different generations; (2) multiple linkages during propagation was facilitated by the presence of pre‐existing crustal structures, inherited from the Hellenide fold and thrust belt. The linkage of the EHF to the DF contributed to the westward and northward propagation of the southern rift border.  相似文献   

Environmental controls on food web regimes: A fluvial perspective     

Mary E. Power 《Progress in Oceanography》2006,68(2-4):125

Because food web regimes control the biomass of primary producers (e.g., plants or algae), intermediate consumers (e.g., invertebrates), and large top predators (tuna, killer whales), they are of societal as well as academic interest. Some controls over food web regimes may be internal, but many are mediated by conditions or fluxes over large spatial scales. To understand locally observed changes in food webs, we must learn more about how environmental gradients and boundaries affect the fluxes of energy, materials, or organisms through landscapes or seascapes that influence local species interactions. Marine biologists and oceanographers have overcome formidable challenges of fieldwork on the high seas to make remarkable progress towards this goal. In river drainage networks, we have opportunities to address similar questions at smaller spatial scales, in ecosystems with clear physical structure and organization. Despite these advantages, we still have much to learn about linkages between fluxes from watershed landscapes and local food webs in river networks. Longitudinal (downstream) gradients in productivity, disturbance regimes, and habitat structure exert strong effects on the organisms and energy sources of river food webs, but their effects on species interactions are just beginning to be explored. In fluid ecosystems with less obvious physical structure, like the open ocean, discerning features that control the movement of organisms and affect food web dynamics is even more challenging. In both habitats, new sensing, tracing and mapping technologies have revealed how landscape or seascape features (e.g., watershed divides, ocean fronts or circulation cells) channel, contain or concentrate organisms, energy and materials. Field experiments and direct in situ observations of basic natural history, however, remain as vital as ever in interpreting the responses of biota to these features. We need field data that quantify the many spatial and temporal scales of functional relationships that link environments, fluxes and food web interactions to understand how they will respond to intensifying anthropogenic forcing over the coming decades.  相似文献   

Isabella Bird and Japan: A Reassessment. By Kiyonori Kanasaka. Translated by Nicholas Pertwee. xxxiii and 277 pp.; maps,diagrs., illus., bibliog., index. Folkestone,U.K.: Renaissance, 2017. $45.00 (cloth), isbn 9781898823513.          下载免费PDF全文

Mary G. McDonald 《Geographical review》2018,108(4):637-639

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Spatial distribution of chaetognaths off the northern Bicol Shelf, Philippines (Pacific coast)     

Noblezada  Mary Mar P.; Campos  Wilfredo L. 《ICES Journal of Marine Science》2008,65(3):484-494

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The USDA-Agricultural Research Service's long term agro-ecosystems Walnut Gulch Experimental Watershed,Arizona, USA     

David C. Goodrich  Philip Heilman  Mark Nearing  Mary Nichols  Russ L. Scott  C. Jason Williams  Joel Biederman 《水文研究》2021,35(9):e14349

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