Volcanic facies architecture of an intra-arc strike-slip basin, Santa Rita Mountains, Southern Arizona     

Cathy J. Busby  Kari N. Bassett 《Bulletin of Volcanology》2007,70(1):85-103

The three-dimensional arrangement of volcanic deposits in strike-slip basins is not only the product of volcanic processes, but also of tectonic processes. We use a strike-slip basin within the Jurassic arc of southern Arizona (Santa Rita Glance Conglomerate) to construct a facies model for a strike-slip basin dominated by volcanism. This model is applicable to releasing-bend strike-slip basins, bounded on one side by a curved and dipping strike-slip fault, and on the other by curved normal faults. Numerous, very deep unconformities are formed during localized uplift in the basin as it passes through smaller restraining bends along the strike-slip fault. In our facies model, the basin fill thins and volcanism decreases markedly away from the master strike-slip fault (“deep” end), where subsidence is greatest, toward the basin-bounding normal faults (“shallow” end). Talus cone-alluvial fan deposits are largely restricted to the master fault-proximal (deep) end of the basin. Volcanic centers are sited along the master fault and along splays of it within the master fault-proximal (deep) end of the basin. To a lesser degree, volcanic centers also form along the curved faults that form structural highs between sub-basins and those that bound the distal ends of the basin. Abundant volcanism along the master fault and its splays kept the deep (master fault-proximal) end of the basin overfilled, so that it could not provide accommodation for reworked tuffs and extrabasinally-sourced ignimbrites that dominate the shallow (underfilled) end of the basin. This pattern of basin fill contrasts markedly with that of nonvolcanic strike-slip basins on transform margins, where clastic sedimentation commonly cannot keep pace with subsidence in the master fault-proximal end. Volcanic and subvolcanic rocks in the strike-slip basin largely record polygenetic (explosive and effusive) small-volume eruptions from many vents in the complexly faulted basin, referred to here as multi-vent complexes. Multi-vent complexes like these reflect proximity to a continuously active fault zone, where numerous strands of the fault frequently plumb small batches of magma to the surface. Releasing-bend extension promotes small, multivent styles of volcanism in preference to caldera collapse, which is more likely to form at releasing step-overs along a strike-slip fault. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

Diversity of murtoos and murtoo-related subglacial landforms in the Finnish area of the Fennoscandian Ice Sheet     

Antti E. K. Ojala  Joni Mäkinen  Elina Ahokangas  Kari Kajuutti  Markus Valkama  Aleksi Tuunainen  Jukka-Pekka Palmu 《Boreas: An International Journal of Quaternary Research》2021,50(4):1095-1115

Murtoos are recently discovered triangular-shaped subglacial landforms that form under warm-based ice and in association with significant subglacial meltwater flow. They appear in distinct fields and commonly occur in the area that was covered by the Fennoscandian Ice Sheet during glacial periods. Murtoos potentially represent a transition form from non-channelized to channelized subglacial drainage networks. In the present study, we analyse and classify murtoos and murtoo-related landforms in the Finnish area of the Fennoscandian Ice Sheet based on their characteristics and appearance in LiDAR-based digital elevations models. Combined with morphometric analyses, the observations suggest that five types of murtoos and murtoo-related landforms are common and widespread in Finland: (i) triangle-type murtoos (TTMs), (ii) chevron-type murtoos (CTMs), (iii) lobate-type murtoos (LTMs), (iv) murtoo-related ridges and escarpments (MREs), and (v) other murtoo-related polymorphous landforms (PMRs) that look like small mounds and ridges. The morphometric characteristics of the different types are described here in detail, and it is shown that they are spatially and geomorphologically related. In addition, we provide examples of murtoos other than the TTMs to demonstrate that different murtoo types and murtoo-related landforms are composed of similar sediments and architectural characteristics. The diversity of murtoo landforms and the transition between distinct murtoo types indicate rapid and complicated variations in the configuration of subglacial hydrology at different spatial and temporal scales. This study emphasizes the essential role of subglacial meltwater in the shaping of glacial landscapes and the redistribution of large volumes of sediments during the deglaciation of the Fennoscandian Ice Sheet.  相似文献   

Timescales of storage and recycling of crystal mush at Krafla Volcano,Iceland     

Kari M. Cooper  Kenneth W. W. Sims  John M. Eiler  Neil Banerjee 《Contributions to Mineralogy and Petrology》2016,171(6):54

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Gardening at the edge: Documenting the limits of tropical Polynesian kumara horticulture in southern New Zealand     

Kari N. Bassett  Hamish W. Gordon  David C. Nobes  Chris Jacomb 《Geoarchaeology》2004,19(3):185-218

An Erratum has been published for this article in Geoarchaeology 19(6) 2004, 613. Kumara (Ipomoea batatus), a major food source for Maori, was brought to New Zealand from tropical Eastern Polynesia ∼700 years ago. Maori successfully adapted their cultivation techniques to grow kumara in New Zealand's cooler, seasonal climate, although most kumara cultivation was limited to the warmer North Island, with cultivation becoming more marginal southward. Banks Peninsula area is considered to be the southernmost limit for kumara gardening. The Okuora Farm archeological site on the southern side of Banks Peninsula has five pits that appear to be of the raised‐rim type used for over winter storage of kumara tubers. We conducted a preliminary investigation into the nature of the pits and surrounding 1 km² area using nondestructive techniques in accordance with Maori designation of food storage sites as tapu. Ground penetrating radar (GPR) investigation of two of the pits revealed subsurface disturbances consistent with postholes and drains, typical of raised rim kumara storage pits. Soil modification typical of kumara gardening was identified on a 1 ha area on a warm north‐northwest facing hillside. Several large borrow pits were identified as the likely source of the gravel added to the modified soil, possibly to retain heat and moisture. A plant phytolith study of soil samples identified several that appear to be from kumara. The combination of results strongly suggests this site was one of the southernmost Maori kumara gardening sites yet identified in New Zealand. © 2004 Wiley Periodicals, Inc.  相似文献   

PASSEQ 2006–2008: Passive seismic experiment in Trans-European Suture Zone     

M. Wilde-Piórko  W. H. Geissler  J. Plomerová  M. Grad  V. Babuška  E. Brückl  J. Cyziene  W. Czuba  R. England  E. Gaczyński  R. Gazdova  S. Gregersen  A. Guterch  W. Hanka  E. Hegedűs  B. Heuer  P. Jedlička  J. Lazauskiene  G. Randy Keller  R. Kind  K. Klinge  P. Kolinsky  K. Komminaho  E. Kozlovskaya  F. Krüger  T. Larsen  M. Majdański  J. Málek  G. Motuza  O. Novotný  R. Pietrasiak  Th. Plenefisch  B. Růžek  S. Sliaupa  P. Środa  M. Świeczak  T. Tiira  P. Voss  P. Wiejacz 《Studia Geophysica et Geodaetica》2008,52(3):439-448

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Crustal and upper mantle velocity model along the DOBRE-4 profile from North Dobruja to the central region of the Ukrainian Shield: 2. geotectonic interpretation     

V. I. Starostenko  T. Janik  O. B. Gintov  D. V. Lysynchuk  P. Środa  W. Czuba  E. V. Kolomiyets  P. Aleksandrowski  V. D. Omelchenko  K. Komminaho  A. Guterch  T. Tiira  D. N. Gryn  O. V. Legostaeva  G. Thybo  A. V. Tolkunov 《Izvestiya Physics of the Solid Earth》2017,53(2):205-213

This part of the paper addresses the geotectonic interpretation of the velocity model obtained from the results of seismic studies under the DOBRE-4 project in Ukraine. The velocity field does not show distinct lateral changes from the Precambrian platform towards the younger tectonic structures in the southwest. Hence, based on the seismic data alone, it is not possible to recognize the tectonic units that are known on the surface. The Moho has an undulating pattern over an interval with a length of ~150 km. The amplitude of the undulations reaches 8 to 17 km. The similar wavelike behavior, although on a shorter spatial scale and lower amplitude, is also typical of the upper crust and upper mantle. The presence of several separate horizons in the folded crust revealed by the velocity model is consistent with the presence of the folded systems which have different extensions on the different depth levels in the Earth’s crust. This situation is believed to be typical of folding on the lithospheric scale and to reflect the rheological stratification of the crust. The DOBRE-4 velocity section of the crust and adjacent part of the mantle promotes a clearer view of the geodynamical model describing the formation of the southwestern part of East European Platform in the Early Precambrian from the plate’s tectonic standpoint.  相似文献   

Geografi i videregående skole i Fagfornyelsen: Forslag til et rammeverk for feltarbeid som fremmer dybdelæring     

Kari Beate Remmen 《Norsk geografisk tidsskrift. Norwegian journal of geography》2020,74(2):105-110

ABSTRAKT

Feltarbeid har en lang tradisjon i geografiundervisningen, men er fremdeles utfordrende å gjennomføre i skolefaget geografi. Denne artikkelen tar utgangspunkt i et kompetansemål i den nye læreplanen i geografi for videregående skole, utviklet gjennom Fagfornyelsen 2020. I kompetansemålet heter det at elevene skal kunne «gjennomføre eit feltarbeid for å undersøkje og presentere geografiske forhold». Dybdelæring er et viktig begrep i Fagfornyelsen, som blant annet innebærer å utvikle forståelse av begreper og sammenhenger i faget. Dette er ambisiøst for elever som får undervisning i geografi to timer per uke i ett år i videregående skole. I artikkelen undersøkes elementer som kan være viktige å ta hensyn til i undervisning av det overnevnte kompetansemålet. Gjennom drøfting av teori og empiriske eksempler identifiseres elementer som kan fremme dybdelæring: gi et oppdrag om å løse en arealsak og åpne for at elevene kan trekke inn egne etno-geografiske erfaringer, forbered elevene på feltarbeidet gjennom å øve på ferdigheter, gjennomfør feltarbeidet i nærmiljøet, diskuter data i lys av teori og etno-geografiske erfaringer, og reflekter over egne beslutninger i arealsaken. Disse elementene kan til sammen fungere som et rammeverk for lærere og forskere som skal designe feltarbeid i geografiundervisning som fremmer dybdelæring.  相似文献   

Biomarker responses as indication of contaminant effects in blue mussel (Mytilus edulis) and female eelpout (Zoarces viviparus) from the southwestern Baltic Sea   总被引：1，自引：0，他引：1  

Schiedek D  Broeg K  Barsiene J  Lehtonen KK  Gercken J  Pfeifer S  Vuontisjärvi H  Vuorinen PJ  Dedonyte V  Koehler A  Balk L  Schneider R 《Marine pollution bulletin》2006,53(8-9):387-405

During a field study performed in spring and autumn 2001 and 2002, blue mussels (Mytilus edulis) and female eelpout (Zoarces viviparus) were collected at three locations in the Wismar Bay (Baltic Sea), and several biomarkers of contaminant effects were analysed. Besides seasonal and inter-annual variations, biomarker signals were most pronounced at the location closest to Wismar Harbour (Wendorf) in both species. Lysosomal membrane stability (LMS) was lowest and acetylcholinesterase activity (AChE) was significantly reduced. Frequency of micronuclei (MN) was significantly higher (in blue mussels), indicating mutagenic effects. In eelpout elevated levels of DNA adducts, EROD induction and PAH-metabolites were measured. Metallothionein (MT), biomarker for trace metal exposure, showed a gradient only in spring. Organochlorine contaminant analyses (PCBs, DDTs) corresponded to the observed biomarker levels. The results obtained clearly demonstrate pollution effects in the southwestern Baltic Sea. Moreover, they show that a multibiomarker approach is also applicable in a brackish water environment.  相似文献   

Lithostratigraphy and Optically Stimulated Luminescence age determinations of pre‐Late Weichselian deposits in the Suupohja area,western Finland     

Reijo Pitkäranta  Juha‐Pekka Lunkka  Kari O. Eskola 《Boreas: An International Journal of Quaternary Research》2014,43(1):193-207

The lithostratigraphy of pre‐Late Weichselian sediments and OSL‐dating results from four localities in the Suupohja area of western Finland, adjacent to the centre of the former Scandinavian glaciations, are presented. The studied sections expose glacifluvial, quiet‐water, littoral and aeolian deposits overlain by Middle and/or Late Weichselian tills. Litho‐ and biostratigraphical results together with seven OSL age determinations on buried glacifluvial sediment at Rävåsen (94±15 ka) and on till‐covered littoral and aeolian sediments at Risåsen, Rävåsen, Jätinmäki and Kiviharju (79±10 to 54±8 ka), accompanied by previous datings and interpretations, suggest that the glacifluvial sediments at Risåsen were deposited at the end of the Saalian Stage (MIS 6) and those at Risåsen were deposited possibly in the Early Weichselian Substage (MIS 5d?). Palaeosol horizons and ice‐wedge casts together with the dated littoral and aeolian sediments between the Harrinkangas Formation (Saalian) and the overlying till(s) indicate that western Finland was ice‐free during most of the Weichselian time. Littoral deposits, dated to the Middle Weichselian (MIS 4–3), occur at altitudes of 50–90 m a.s.l., which indicates significant glacio‐isostatic depression. The depression resulted from expansion of the ice sheet in the west of Finland at that time.  相似文献   

Evaluation of snow products over the Tibetan Plateau          下载免费PDF全文

Juntao Yang  Lingmei Jiang  Cécile B. Ménard  Kari Luojus  Juha Lemmetyinen  Jouni Pulliainen 《水文研究》2015,29(15):3247-3260

Four satellite‐based snow products are evaluated over the Tibetan Plateau for the 2007–2010 snow seasons. The Moderate Resolution Imaging Spectroradiometer (MODIS) Terra and Aqua snow cover daily L3 Global 500‐m grid products (MOD10A1 and MYD10A1), the National Oceanic and Atmospheric Administration Interactive Multisensor Snow and Ice Mapping System (IMS) daily Northern Hemisphere snow cover product and the Advanced Microwave Scanning Radiometer – Earth Observing System Daily Snow Water Equivalent were validated against Thematic Mapper (TM) snow cover maps of Landsat‐5 and meteorological station snow depth observations. The overall accuracy of MOD10A1, MYD10A1 and IMS is higher than 91% against stations observations and than 79% against Landsat TM images. In general, the daily MODIS snow cover products show better performance than the multisensor IMS product. However, the IMS snow cover product is suitable for larger scale (~4km) analysis and applications, with the advantage over MODIS to allow for mitigation for cloud cover. The accuracy of the three products decreases with decreasing snow depth. Overestimation errors are most common over forested regions; the IMS and Advanced Microwave Scanning Radiometer – Earth Observing System Snow Water Equivalent products also show poorer performance that the MODIS products over grassland. By identifying weaknesses in the satellite products, this study provides a focus for the improvement of snow products over the Tibetan plateau. The quantitative evaluation of the products proposed here can also be used to assess their relative weight in data assimilation, against other data sources, such as modelling and in situ measurement networks. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献