Analysis of coprolites from the extinct mountain goat Myotragus balearicus     

Frido Welker  Elza Duijm  Kristiaan J. van der Gaag  Bas van Geel  Peter de Knijff  Jacqueline van Leeuwen  Dick Mol  Johannes van der Plicht  Niels Raes  Jelle Reumer  Barbara Gravendeel 《Quaternary Research》2014

Humans colonized the Balearic Islands 5–4 ka ago. They arrived in a uniquely adapted ecosystem with the Balearic mountain goat Myotragus balearicus (Bovidae, Antilopinae, Caprini) as the only large mammal. This mammal went extinct rapidly after human arrival. Several hypotheses have been proposed to explain the extinction of M. balearicus. For the present study ancient DNA analysis (Sanger sequencing, Roche-454, Ion Torrent), and pollen and macrofossil analyses were performed on preserved coprolites from M. balearicus, providing information on its diet and paleo-environment. The information retrieved shows that M. balearicus was heavily dependent on the Balearic box species Buxus balearica during at least part of the year, and that it was most probably a browser. Hindcast ecological niche modelling of B. balearica shows that local distribution of this plant species was affected by climate changes. This suggests that the extinction of M. balearicus can be related to the decline and regional extinction of a plant species that formed a major component of its diet. The vegetation change is thought to be caused by increased aridity occurring throughout the Mediterranean. Previous hypotheses relating the extinction of M. balearicus directly to the arrival of humans on the islands must therefore be adjusted.  相似文献   

Podiform chromitite formation in a low-Cr/high-Al system: An example from the Southwest Indian Ridge (SWIR)   总被引：1，自引：0，他引：1  

Betchaida D. Payot  Shoji Arai  Henry J. B. Dick  Natsue Abe  Yuji Ichiyama 《Mineralogy and Petrology》2014,108(4):533-549

Recent reassessment of abyssal peridotites obtained during the dredging of the oblique supersegment and the easternmost subsection of the Southwest Indian Ridge by the R/V Knorr Cruise 162 and the R/V Yokosuka YK98-07 revealed the occurrence of dunites containing podiform chromitites and dunites with variable chromite concentration closely associated with lherzolite and harzburgite. The size of the chromitite pods varies from a few mm to 2 cm in width. Chromites in the podifom chromitites have very low Cr# (=0.22–0.23) and low TiO₂ (<0.17 wt%). They are almost free of silicate inclusions except for a few euhedral sulfide grains which occur far from cracks and lamellae and are considered primary in origin. The lherzolite which possibly represents the wallrock hosting the dunites with podiform chromitites also show low spinel Cr#(=0.16) and low Cr# in the clinopyroxenes (=0.09–0.10) and orthopyroxenes (=0.07–0.09). The small size of the SWIR podiform chromitites is strongly controlled by the low Cr/Al available in the wallrock and the invading melt. The presence of sulfide inclusions and the absence of PGEs further attest to the low Cr/Al (i.e. low refractoriness) in the system involved in the genesis of the SWIR podiform chromitites. Lastly, the discovery of podiform chromitites in the SWIR implies that the formation of podiform chromitite at mid-oceanic ridges, regardless of its spreading rate, is highly possible.  相似文献   

A study of hybrid and chaotic long-range propagation in a doublesound channel environment     

Noel  C. Viala  C. Stephan  Y. 《Oceanic Engineering, IEEE Journal of》1999,24(4):447-457

This paper presents the results of the analysis of long range propagation (~200 km) in a range-dependent environment. The propagation medium is characterized by two deep sound channels. The range dependence enables energy transfer between the channels and leads to a mismatch between real data and ray predictions. To explain this mismatch, an analysis of hybrid ray propagation is presented. This analysis is completed by an interpretation in terms of chaos. This chaos is quantified in the particular case of the Bay of Biscay environment. This paper puts forward that mesoscale perturbations, such as the Mediterranean outflow in the North Atlantic, can affect long-range propagation. However, it shows that the ray theory remains reliable for a propagation range of several hundred kilometers  相似文献   

Response of precipitation over Greenland and the adjacent ocean to North Pacific warm spells during Dansgaard–Oeschger stadials     

Thorsten Kiefer  Stephan Lorenz  Michael Schulz  Gerrit Lohmann  Michael Sarnthein  Henry Elderfield 《地学学报》2002,14(4):295-300

ABSTRACT Palaeoceanographic reconstructions from the North Atlantic indicate massive ice breakouts from East Greenland near the onset of cold Dansgaard–Oeschger (D–O) stadials. In contrast to these coolings in the North Atlantic area, a new sea-surface temperature record reveals concomitant warm spells in the northern North Pacific. A sensitivity experiment with an atmospheric general circulation model is used to test the potential impact of sea-surface warmings by 3.5 °C in the North Pacific, on top of otherwise cold stadial climate conditions, on the precipitation regime over the Northern Hemisphere ice sheets. The model predicts a maximum response over East Greenland and the Greenland Sea, where a 40% increase in net annual snow accumulation occurs. This remote effect of North Pacific warm spells on the East Greenland snow-accumulation rate may play an important role in generating D–O cycles by rebuilding the ice lost during ice breakouts. In addition, the increased precipitation over the Greenland Sea may help to sustain the D–O stadial climate state.  相似文献   

The magma-to-mud cycle     

Dick Merriman 《Geology Today》2002,18(2):67-71

For more than 3700 million years of Earth history, the magma-to-mud cycle has steadily generated new crustal rock. Mud formed by rock weathering coats the Earth's surface and helps to sustain life. Reactive clay minerals are the key components of mud, and control the absorption and release of chemicals and fluids that are critical for the recycling of crustal rocks.  相似文献   

The geomorphology and sedimentology of the ‘Témpanos’ moraine at Laguna San Rafael,Chile     

Neil F. Glasser  Krister Jansson  Wishart A. Mitchell  Stephan Harrison 《第四纪科学杂志》2006,21(6):629-643

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Modeling of SMF tsunami hazard along the upper US East Coast: detailed impact around Ocean City,MD   总被引：1，自引：0，他引：1  

Stephan T. Grilli  Christopher O’Reilly  Jeffrey C. Harris  Tayebeh Tajalli Bakhsh  Babak Tehranirad  Saeideh Banihashemi  James T. Kirby  Christopher D. P. Baxter  Tamara Eggeling  Gangfeng Ma  Fengyan Shi 《Natural Hazards》2015,76(2):705-746

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The Southwest Indian Ridge: Remelting the Gondwanan Mantle     

JB Dick HENRY  Hole WOODS 《《地质学报》英文版》2015,89(Z2):27-27

<正>The Southwest Indian Ridge is an ultraslow spreading ridge(~14-mm/yr)that formed~150 Ma with the breakup of Gondwana.It extends 7700 km from the Bouvet to the Rodriguez Triple Junction,crossing over the flank of the large southern Geoid high centered over Marion and Crozet islands and the Conrad Rise.There is a  相似文献   

Getting Lost in Cities: Spatial Patterns of Phonetically Confusing Street Names          下载免费PDF全文

Keith Chan  Maria Vasardani  Stephan Winter 《Transactions in GIS》2015,19(4):535-562

A large street network is likely to contain duplicated or similar sounding street names. These conflicts can cause confusion in communication between people or in machine‐human interaction. Municipal authorities have begun to see the importance of uncovering these existing street name conflicts and mitigating future ones, for improved record keeping, emergency response, etc. However the commonly used Soundex phonetic algorithm is generally considered to produce poor similarity results in terms of uncovering street name conflicts. This study reports on a new fusion algorithm that combines phonetic methods and approximate string matching for street names, weighted by street type suffix (Avenue, Boulevard, Court, etc.), to quantitatively measure the collision/confusion potential presented by a pair of streets. This algorithm is then applied to the entire street network in Greater Melbourne, Australia, and the pattern of collisions at various spatial scales, and within municipalities, is mapped. The goal of this work is to produce better tools that can aid policy makers, administrators and industries dealing with location‐based services to make better decisions when assigning and disambiguating street names.  相似文献   

Urban green commons: Insights on urban common property systems   总被引：1，自引：0，他引：1  

Johan Colding  Stephan Barthel  Pim Bendt  Robbert Snep  Wim van der Knaap  Henrik Ernstson 《Global Environmental Change》2013,23(5):1039-1051

The aim of this paper is to shed new light on urban common property systems. We deal with urban commons in relation to urban green-space management, referring to them as urban green commons. Applying a property-rights analytic perspective, we synthesize information on urban green commons from three case-study regions in Sweden, Germany, and South Africa, and elaborate on their role for biodiversity conservation in urban settings, with a focus on business sites. Cases cover both formally established types of urban green commons and bottom-up emerged community-managed habitats. As our review demonstrates, the right to actively manage urban green space is a key characteristic of urban green commons whether ownership to land is in the private, public, the club realm domain, or constitutes a hybrid of these. We discuss the important linkages among urban common property systems, social–ecological learning, and management of ecosystem services and biodiversity. Several benefits can be associated with urban green commons, such as a reduction of costs for ecosystem management and as designs for reconnecting city-inhabitants to the biosphere. The emergence of urban green commons appears closely linked to dealing with societal crises and for reorganizing cities; hence, they play a key role in transforming cities toward more socially and ecologically benign environments. While a range of political questions circumscribe the feasibility of urban green commons, we discuss their usefulness in management of different types of urban habitats, their political justification and limitation, their potential for improved biodiversity conservation, and conditions for their emergence. We conclude by postulating some general policy advice.  相似文献