Rb-Sr systematics of Permian volcanites in the Schwarzwald (SW-Germany)     

Helmut Schleicher  Hans Joachim Lippolt  Ingrid Raczek 《Contributions to Mineralogy and Petrology》1983,84(2-3):272-280

Rb-Sr mineral ages and Sr isotopic ratios were determined for several Permian rhyolites of the Schwarzwald, mainly by using mica-apatite pairs. Extrusion ages between_307+5 and 286+7 Ma were found ( _Rb=1.42· 10^–11 a^–1, 2). The initial Sr isotopic ratios range from 0,710 to 0.7125, with one exception (St. Märgen: 0.706). The Rb-Sr age of the granite porphyry Schweighof in the Southern Schwarzwald is 323+4 Ma.Thus the subsequent volcanic activity of the Hercynian orogeny lasted nearly 20–30 Ma, starting in the Late Carboniferous and culminating in the Early Permian. The volcanic activity moved in time from South to North. In the Southern as well as the Northern Schwarzwald a hiatus of about 20 Ma exists between late orogenic plutonism and subsequent volcanism. The initial ratios lie on the crustal evolution line of Schwarzwald basement and favour, with the St. Märgen porphyry as exception, a crustal provenance of the volcanic magmas.  相似文献   

Zu Wärmehaushalt und Hydroklima der nordamerikanischen Deserts     

Prof. Dr. Ingrid Henning  Dr. D. Henning 《Theoretical and Applied Climatology》1984,34(4):341-352

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A New Model for Coastal Resource Productivity and Sea‐Level Change: The Role of Physical Sedimentary Processes in Assessing the Archaeological Potential of Submerged Landscapes from the Northwest Australian Continental Shelf     

Ingrid Ward  Piers Larcombe  Peter Veth 《Geoarchaeology》2015,30(1):19-31

Existing models of coastal occupation, in one form or another, embrace the assumption that changes in mean sea level were the prime driver for shifts in coastal resource productivity of consequence to coastal foragers. Focusing on the North West Shelf of Australia, this paper considers the role of physical sedimentary processes in understanding both past coastal resource productivity and the archaeology of drowned coastal landscapes. From a review of up‐to‐date literature on sea‐level related coastal formation process related to the North West Shelf, we describe the complex interplay of sea‐level change and sedimentary processes in determining (i) coastal resource availability, and (ii) archaeological site preservation potential through time. We argue that human behavioral models that have been linked solely to changes in sea level change from ca. 45 ka onward along the Australia continental shelf have inadequately accounted for local sedimentary regimes. It is not past sea‐level per se, which is of relevance to coastal productivity and human behavioral ecology models but changes in tidal regimes, coastal configurations and sedimentation. We conclude that our understanding of maritime adaptations for Sahul (Greater Australia) remain incomplete without investigating former coastlines and archaeological information that now lies submerged offshore.  相似文献   

Multipurpose agroforestry as a climate change resiliency option for farmers: an example of local adaptation in Vietnam     

Quan Nguyen  Minh Ha Hoang  Ingrid Öborn  Meine van Noordwijk 《Climatic change》2013,117(1-2):241-257

Increasing frequency, intensity and duration of severe weather events are posing major challenges to global food security and livelihoods of rural people. Agriculture has evolved through adaptation to local circumstances for thousands of years. Local experience in responding to severe weather conditions, accumulated over generations and centuries, is valuable for developing adaptation options to current climate change. This study aimed to: (i) identify tree species that reduce vulnerability of cropping systems under climate variability; and (ii) develop a method for rapidly assessing vulnerability and exploring strategies of smallholder farmers in rural areas exposed to climate variability. Participatory Rural Appraisal methods in combination with Geographical Information Systems tools and statistical analysis of meteorological data were used to evaluate local vulnerability to climate change and to investigate local adaptation measures in two selected villages in Vietnam, one of the countries most vulnerable to climate change. The low predictability of severe weather events makes food crops, especially grain production, insecure. This study shows that while rice and rain-fed crops suffered over 40 % yield losses in years of extreme drought or flood, tree-based systems and cattle were less affected. 13 tree species performed well under the harsh local climate conditions in home and forest gardens to provide income, food, feed and other environmental benefits. Thus, this research suggests that maintenance and enhancement of locally evolved agroforestry systems, with high resilience and multiple benefits, can contribute to climate change adaptation.  相似文献   

Metasomatism of ferroan granites in the northern Aravalli orogen,NW India: geochemical and isotopic constraints,and its metallogenic significance   总被引：1，自引：0，他引：1  

Parampreet Kaur  Naveen Chaudhri  Albrecht W. Hofmann  Ingrid Raczek  Martin Okrusch  Susanne Skora  Jürgen Koepke 《International Journal of Earth Sciences》2014,103(4):1083-1112

The late Palaeoproterozoic (1.72–1.70 Ga) ferroan granites of the Khetri complex, northern Aravalli orogen, NW India, were extensively metasomatised ~900 Ma after their emplacement, at around 850–830 Ma by low-temperature (ca. 400 °C) meteoric fluids that attained metamorphic character after exchanging oxygen with the surrounding metamorphic rocks. Albitisation is the dominant metasomatic process that was accompanied by Mg and Ca metasomatism. A two-stage metasomatic model is applicable to all the altered ferroan intrusives. The stage I is represented by a metasomatic reaction interface that developed as a result of transformation of the original microcline–oligoclase (An_12–14) granite to microcline–albite (An_1–3) granite, and this stage is rarely preserved. In contrast, the stage II metasomatic reaction front, where the microcline-bearing albite granite has been transformed to microcline-free albite granite, is readily recognisable in the field and present in most of the intrusives. Some of them lack an obvious reaction interface due to the presence of stage II albite granites only. When studied in isolation, these intrusives were incorrectly classified and their tectonic setting was misinterpreted. Furthermore, our results show that the mafic mineralogy of metasomatised granites has a significant impact on the characterisation of such rocks in the magmatic classification and discrimination diagrams. Nevertheless, the stage I metasomatised granites can be appropriately characterised in these diagrams, whereas the characterisation of the stage II granites will lead to erroneous interpretations. The close spatial association of these high heat producing ferroan granites with iron oxide–copper–gold (IOCG), U and REE mineralisation in the region indicates a genetic link between the metasomatism and the mineralisation. World-class IOCG, U and REE deposits are associated with metasomatised ferroan granites, suggesting that such a relationship may act as a critical first-order exploration target for undiscovered mineral deposits.  相似文献   

Mapping the archaeological soil archive of sand and gravel mineral reserves in Britain     

Ingrid Ward  Barry Smith  Russell Lawley 《Geoarchaeology》2009,24(1):1-21

Primary sand and gravel deposits in Britain play an important role in preserving our cultural heritage and are also a valuable aggregate resource. While an understanding of the extrinsic properties of the soil archive (such as pH, redox, groundwater) can provide a firstorder assessment of the potential risk to any archaeologically sensitive deposits, we have very poor definition of spatial variations in the extrinsic properties of soil that influence archaeological preservation at a regional and national scale. Developments in digital geological mapping, remote sensing, and geochemical survey data undertaken by the British Geological Survey (BGS) have, however, significantly extended capabilities in this respect and can potentially be used to provide a primary assessment of the sensitivity of the present soil archive and the potential risk from changes to the soil process on cultural material in areas earmarked for aggregate extraction. Two of the major factors affecting archaeological preservation—soil acidification and groundwater—can be mapped or predicted at scales of better than 1:50,000 across increasingly large parts of the country using a combination of regional hydrogeological, geophysical, and geochemical data. Additional data from site investigations may further refine preservation potential as a function of changes in redox potential and acidity. These data, maps and models can be used to (1) better establish a baseline for archaeological preservation at a regional and national scale and (2) improve our understanding of how the physical and chemical properties of the near surface environment can be managed to sustainably preserve archaeological materials in areas impacted by sand and gravel extraction. © 2009 Wiley Periodicals, Inc.  相似文献   

Paleoenvironmental dynamics in central-eastern Brazil during the last 23 000 years: tropical peatland record in the Cerrado biome     

Camila Rodrigues Costa  Cynthia Fernandes Pinto da Luz  Ingrid Horák-Terra  Plínio Barbosa de Camargo  Uidemar Morais Barral  Carlos Victor Mendonça-Filho  Thamyres Sabrina Gonçalves  Alexandre Christófaro Silva 《第四纪科学杂志》2023,38(1):61-75

The Cerrado biome is the second largest in Brazil, but the evolution of the Cerrado during the late Quaternary is not yet fully known. This study identifies paleoenvironmental changes during the last 23 000 years, based on a tropical mountain peatland record, in the Serra do Espinhaço Meridional in central-eastern Brazil. A multi-proxy approach was used that involved palynological analysis, stable isotopes (δ¹³C, δ¹⁵N), geochemistry, radiocarbon dating and multivariate statistics derived from a peatland core from Rio Preto (Minas Gerais state). The study reveals a very humid and cold climate during the late Pleistocene, with an increase in temperature and decrease in humidity at the Pleistocene–Holocene transition. During this period there was strong instability in the landscape (episodes of erosion). At the beginning of the Holocene there was a reduction in humidity with greater landscape stability. The current sub-humid climatic conditions seem to have been established in the mid-/late Holocene, with periods of landscape instability. Our findings agree with other Cerrado records that contradict previously established hypotheses, such as the Amazonian Refuge and the Pleistocene Arc.  相似文献