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Mark D. Bateman Tim C. Kinnaird Jon Hill Robert A. Ashurst Jenna Mohan Rebecca B. I. Bateman Ruth Robinson 《Boreas: An International Journal of Quaternary Research》2021,50(4):1059-1078
The Storegga tsunami, dated in Norway to 8150±30 cal. years BP, hit many countries bordering the North Sea. Run-ups of >30 m occurred and 1000s of kilometres of coast were impacted. Whilst recent modelling successfully generated a tsunami wave train, the wave heights and velocities, it under-estimated wave run-ups. Work presented here used luminescence to directly date the Storegga tsunami deposits at the type site of Maryton, Aberdeenshire in Scotland. It also undertook sedimentological characterization to establish provenance, and number and relative power of the tsunami waves. Tsunami model refinement used this to better understand coastal inundation. Luminescence ages successfully date Scottish Storegga tsunami deposits to 8100±250 years. Sedimentology showed that at Montrose, three tsunami waves came from the northeast or east, over-ran pre-existing marine sands and weathered igneous bedrock on the coastal plain. Incorporation of an inundation model predicts well a tsunami impacting on the Montrose Basin in terms of replicate direction and sediment size. However, under-estimation of run-up persisted requiring further consideration of palaeotopography and palaeo-near-shore bathymetry for it to agree with sedimentary evidence. Future model evolution incorporating this will be better able to inform on the hazard risk and potential impacts for future high-magnitude submarine generated tsunami events. 相似文献
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Ashworth Luisa Kinnaird Judith Ann Nex Paul Andrew Martin Erasmus Rudolph Marthinus Przybyłowicz Wojciech Józef 《Mineralogy and Petrology》2018,112(6):753-765
Mineralogy and Petrology - Mineralized NYF and LCT pegmatites occur throughout the northeast-trending Neoproterozoic Damara Belt, Namibia. Mineralization in the pegmatites varies geographically,... 相似文献
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Trace-element study and age dating of zircon from chromitites of the Bushveld Complex (South Africa)
Marina Yudovskaya Judith Kinnaird Anthony J. Naldrett Nickolay Rodionov Anton Antonov Sergey Simakin Dmitry Kuzmin 《Mineralogy and Petrology》2013,107(6):915-942
The layered Bushveld Complex hosts a number of chromitite layers, which were found to contain significant amounts of zircon grains compared with adjacent silicate rocks. Cathodoluminescent-dark, partially metamict cores and transparent rims of composite zircon grains were analyzed for trace elements with SIMS and LA-ICPMS techniques. The cores are enriched in REE, Y, Th and U and are characterized by distinctly flatter REE patterns in contrast to those of the rims and transparent homogenous crystals. Zircon from the different stratigraphic units has specific Th/U ratios, the highest of which (1.5–4) occurs in a Merensky Reef zircon core. The Ti content of Bushveld zircon ranges from 12 to 52 ppm correlating to a crystallization temperature range of 760–930 °C. The geochemical characteristics of the first zircon generation are consistent with its high-temperature crystallization as the first major U, Th and REE acceptor from a highly-evolved residue of the high-Mg basalt magma, whereas the rims and coreless crystals have crystallized from percolating intercumulus liquid of new influx of the same magma. U-Pb SHRIMP dating of zircon cores and rims does not reveal a distinguishable difference between their ages indicating the absence of inherited zircon. Concordia ages of 2,051?±?9 Ma (2σ, MSWD?=?0.1) and 2,056?±?5 Ma (2σ, MSWD?=?0.05) for zircons from the Merensky Reef and the Upper Platreef located equally near the top of the Critical Zone are in agreement with published ages for the Merensky Reef. Zircon from the deeper-seated Lower Group, Middle Group and Lower Platreef chromitites yields younger concordia ages that may reflect prolonged late-stage volatile activity. 相似文献
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Fluid inclusions in the Merensky Reef quartz and later pegmatite veins crosscutting the Platreef rocks of the Bushveld Complex are studied by a suite of advanced high-precision methods. Based on the conducted studies, we identify a few types of fluids, some having been separated during the crystallization of volatile matter-rich residual melt of original basic magma, while others are derivatives of later felsic (granite) melts that formed crosscutting veins in fully devitrified ultrabasic and basic rocks. The earliest fluid is captured by quartz in symplectitic intergrowths with intercumulus plagioclase from the Merensky Reef pyroxenite occurs as a homogenous dense dry reduced gas (CH4–N2 ± CO2) mixture separated from the aluminosilicate melt at 800–900°C and 3050 bar. The following heterophase highly concentrated fluids (60–80 wt % NaCl eq.) separated at over 550°C and below 3050 bar transport a large number of metals. Major saline components of such fluids included Na, K, Fe, Ca, and Mn chlorides, Ca and Na sulphates and carbonates. According to LA ICP-MS analysis data, inclusions of these fluids contain high concentrations of Fe, Cr, K, and Na at the level of a few wt % and also significant contents of Cu, Sn, Sb, Mo, Au, Ag, Bi, and Ni in a concentration range from a few to thousands of ppm. Relatively lower-temperature (much higher than 450°C) fluids accompanying the crystallization of crosscutting quartz–feldspar pegmatite veins at the Platreef are also highly concentrated (from 70–80% to 40–14 wt % NaCl eq.), oxidized and metal-bearing. High concentrations of metals such as Na, K, Ca, Mn, Fe, and Pb at the level of wt % and also Ni, Co, Cu, As, Mo, Sn, Sb, and Bi (1–500 ppm) in inclusions in quartz of later pegmatite veins suggest the possible participation of magmatogene fluids related to later felsic intrusions in the redistribution of primary magmatic concentrations of metals. The oxidation of reduced heterophase fluids may be the most important geochemical barrier invoking the crystallization of solid mineral phases from heterophase fluids. 相似文献
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Judith A. Kinnaird D. Hutchinson L. Schurmann P. A. M. Nex Renee de Lange 《Mineralium Deposita》2005,40(5):576-597
The Platreef, the putative local analogue of the Merensky Reef, forms the floor to the mafic succession in the northern limb
of the Bushveld Complex. We define the Platreef as ‘the lithologically variable unit, dominated by pyroxenite, which is irregularly
mineralised with PGE, Cu and Ni, between the Transvaal metasedimentary footwall or Archaean basement and the overlying Main
Zone gabbronorite’. We define the mineralisation around calcsilicate xenoliths within the Main Zone in the far north of the
limb as a ‘Platreef-style‘ mineralisation. The Platreef (ss) has a strike extent of ∼30 km, whereas Platreef-style mineralisation
occurs over a strike length of 110 km. The Platreef varies from 400 m thick in the S to <50 m in the N. The overall strike
is NW or N, with dips 40–45°W at surface, shallowing down dip, The overall geometry of the southern Platreef appears to have
been controlled by irregular floor topography. The maximum thickness of the southern Platreef occurs in two sub-basins on
the farms Macalacaskop and Turfspuit. Lithologically, the southern Platreef is heterogeneous and more variable than sectors
further north and, although predominantly pyroxenitic, includes dunites, peridotites and norite cycles with anorthosite in
the mid to upper portion. Zones of intense serpentinisation may occur throughout the package. Faults offset the strike of
the Platreef: a N–S, steeply dipping set is predominant with secondary ENE and ESE sets dipping 50–70°S. The fault architecture
was pre-Bushveld and also locally controlled thickening and thinning of the succession. Country rock xenoliths, <1500 m long,
are common. On Macalacaskop, these are typically quartzites and hornfelsed banded ironstones, shales, mudstones and siltstones
whereas on Turfspruit dolomitic or calcsilicate xenoliths also occur. Sulphides may reach >30 modal% in some intersections.
These are dominated by pyrrhotite, with lesser pentlandite and chalcopyrite, minor pyrite and traces of a wide compositional
range of sulphides. In the southern sector, mineralised zones have Cu grades of 0.1–0.25% and Ni 0.15–0.36%. Massive sulphides
are localised, commonly, but not exclusively towards the contact with footwall metasedimentary rocks. Magmatic sulphides are
disseminated or net-textured ranging from a few microns to 2 cm grains of pyrrhotite and pentlandite with chalcopyrite and
minor pyrite. Much of the sulphide is associated with intergranular plagioclase, or quartz-feldspar symplectites, along the
margins of rounded cumulus orthopyroxenes. The PGEs in the southern sector occur as tellurides, bismuthides, arsenides, antimonides,
bismuthoantimonides and complex bismuthotellurides. PGM are rarely included in the sulphides but occur as micron-sized satellite
grains around interstitial sulphides and within alteration assemblages in serpentinised zones. The Pt:Pd ratio ∼1 and PGE
grade may be decoupled from S and base metal abundance. 相似文献
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Using three different approaches of OSL for the study of young fluvial sediments at the coastal plain of the Usumacinta–Grijalva River Basin,southern Mexico 
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下载免费PDF全文 Esperanza Muñoz‐Salinas Miguel Castillo David Sanderson Tim Kinnaird Epifanio Cruz‐Zaragoza 《地球表面变化过程与地形》2016,41(6):823-834
We use three different approaches of optically stimulated luminescence (OSL) to study young fluvial sediments located at the main channels of one of the largest fluvial systems of North America: the Usumacinta–Grijalva. We use the pulsed photo‐stimulated luminescence (PPSL) system also known as portable OSL reader, full OSL dating and profiling OSL dating in samples extracted from vertical sediment profiles (n = 9) of riverbanks to detect changes in depositional rates of sediments and to obtain the age of the deposits. The results of the PPSL system show that the luminescence signals of vertical sediment profiles highly scattered from the top to the bottom contrast with the luminescence pattern observed on well‐reset sequences of fluvial deposits where luminescence increase from the top to the bottom of the profile. The profiling and full OSL ages yielded large uncertainty values on their ages. Based on the inconsistencies observed in both ages and luminescence patterns of profiles we suggest that these fluvial deposits were not fully reset during their transport. As an explanation, we propose that in the Usumacinta and Grijalva rivers the cyclonic storms during the wet season promote the entrainment of large volumes of sediments due to high‐erosional episodes around the basin resulting from hyper‐concentrated and turbid flows. We conclude that the PPSL, profiling and full OSL dating of sediments are useful tools to quantify and to assess the depositional patterns in fluvial settings during the Holocene. These techniques also can yield information about sites where increases in the sediment load of rivers may produce poorly resetting of grains affecting the results of OSL dating. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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Using OSL to assess hypotheses related to the impacts of land use change with the early nineteenth century arrival of Europeans in south‐eastern Australia: an exploratory case study from Grabben Gullen Creek,New South Wales 下载免费PDF全文
下载免费PDF全文 A common explanation for intense soil erosion and gullying in SE Australia is the introduction by Europeans of new land use practices following their arrival in Australia in the late 18th century. Eucalyptus woodlands were cleared to introduce farming, and valley bottoms, characterized by chains of ponds with organic‐rich swampy meadow (SM) soils, were subsequently buried by thick deposits of ‘post‐settlement alluvium’ (PSA) generated by erosion in the catchment. In this study, optically stimulated luminescence (OSL) is used to evaluate the source(s) of the PSA in Grabben Gullen Creek (GGC), Australia. We use a portable OSL reader to measure total photon counts on bulk polymineral and polygrain‐size samples from nine profiles along the Creek. We use these luminescence signals as geotracers of sediment source(s) and transport pathways. We obtained higher luminescence signals in the PSA than in the SM sediments, suggesting different sources and fluvial transport conditions for these two widespread sedimentary units. Portable OSL reader data from soils in the GGC catchment that are potential sources for the SM sediments and PSA show that the high luminescence signals recorded in the PSA are similar to those from subsoil samples in granite soils, suggesting that the PSA was derived by gullying of granite subsoils. In the SM sediments, luminescence signals decrease upwards from the base of the profile, as expected in well‐reset fluvial deposits, but with one or more changes in gradient in the profile of photon counts with depth, most likely indicating changes in sediment deposition rates. To calculate deposition rates in the SM sediments, several samples were dated using OSL. The OSL ages produced low scatter in the equivalent doses, confirming the well‐reset nature of the grains composing the SM and indicating a process of sediment transport in dilute flows, as is interpreted from the portable OSL signals. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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The development of functional portable optically stimulated luminescence (OSL) readers over the last decade has provided practitioners with the capability to acquire luminescence signals from geological materials relatively rapidly, which allows for expedient preliminary chronostratigraphic insight when working with complex depositional systems of late Quaternary age. Typically, when using the portable OSL reader, infrared (IR) or blue post-IR OSL signals are acquired from bulk unprocessed materials, in contrast to regular luminescence dating, which is usually based on measurements on pure quartz or feldspar mineral separates, or on select silt-sized polymineralic portions. To demonstrate the utility of portable OSL measurements, this paper outlines the basic features of portable OSL readers and their constraints. Subsequently, case studies in which the instrument has been used to elucidate cryptostratigraphic variations in sedimentary sequences for geomorphological applications are reviewed. The studies can generally be grouped into three main categories. The first includes studies where the variation of portable OSL reader luminescence signal intensities with depth are plotted to generate profiles that contextualize sediment stratigraphy. In the second group, portable OSL reader luminescence signal intensities are used to interpret sediment processes that shed light on depositional histories. In the last category, luminescence signals from the portable OSL reader are calibrated to approximate numerical burial ages of depositional units. The paper concludes with a discussion of possible future directions. © 2020 John Wiley & Sons, Ltd. 相似文献