On the use of geochronology of detrital grains in determining the time of deposition of clastic sedimentary strata     

Peter Copeland 《Basin Research》2020,32(6):1532-1546

Placing geologic events in a temporal framework is essential to telling the story of Earth history. However, clastic sedimentary rocks can be difficult to date in an absolute reference because they are made up of grains that are older than the rock in which they are now found, and some clastic rocks do not contain fossils that allow precise reference to the Geologic Timescale. For such rocks, the isotopic dating of detrital minerals can be used to estimate the time of deposition; the clastic rock must be younger than the youngest grain analysed. However, many researchers eschew this simple and straightforward approach in favour of schemes that estimate the maximum allowable depositional age as the weighted mean of the age of several grains, chosen by a variety of selection criteria. This is a mistake; in the absence of a geochemical resemblance apart from the similarity of their age, detrital grains should not be assumed to have originated in the same system and therefore any averaging or other manipulation of such data is statistically invalid and produces results without geologic significance. In the absence of interbedded volcanic rocks or index fossils, dating of detrital minerals can be an important aid in understanding the time of deposition of clastic rocks, but the best estimate will come from taking note of the youngest single grain and not by inappropriately averaging data.  相似文献   

Tectono-sedimentary evolution of Jurassic–Cretaceous diapiric structures: Miravete anticline,Maestrat Basin,Spain     

Jaume Vergés  Yohann Poprawski  Ylènia Almar  Peter A. Drzewiecki  Mar Moragas  Telm Bover-Arnal  Chiara Macchiavelli  Wayne Wright  Grégoire Messager  Jean-Christophe Embry  David Hunt 《Basin Research》2020,32(6):1653-1684

Integration of extensive fieldwork, remote sensing mapping and 3D models from high-quality drone photographs relates tectonics and sedimentation to define the Jurassic–early Albian diapiric evolution of the N–S Miravete anticline, the NW-SE Castel de Cabra anticline and the NW-SE Cañada Vellida ridge in the Maestrat Basin (Iberian Ranges, Spain). The pre shortening diapiric structures are defined by well-exposed and unambiguous halokinetic geometries such as hooks and flaps, salt walls and collapse normal faults. These were developed on Triassic salt-bearing deposits, previously misinterpreted because they were hidden and overprinted by the Alpine shortening. The Miravete anticline grew during the Jurassic and Early Cretaceous and was rejuvenated during Cenozoic shortening. Its evolution is separated into four halokinetic stages, including the latest Alpine compression. Regionally, the well-exposed Castel de Cabra salt anticline and Cañada Vellida salt wall confirm the widespread Jurassic and Early Cretaceous diapiric evolution of the Maestrat Basin. The NE flank of the Cañada Vellida salt wall is characterized by hook patterns and by a 500-m-long thin Upper Jurassic carbonates defining an upturned flap, inferred as the roof of the salt wall before NE-directed salt extrusion. A regional E-W cross section through the Ababuj, Miravete and Cañada-Benatanduz anticlines shows typical geometries of salt-related rift basins, partly decoupled from basement faults. These structures could form a broader diapiric region still to be investigated. In this section, the Camarillas and Fortanete minibasins displayed well-developed bowl geometries at the onset of shortening. The most active period of diapiric growth in the Maestrat Basin occurred during the Early Cretaceous, which is also recorded in the Eastern Betics, Asturias and Basque-Cantabrian basins. This period coincides with the peak of eastward drift of the Iberian microplate, with speeds of 20 mm/year. The transtensional regime is interpreted to have played a role in diapiric development.  相似文献   

Proactive Management of Ecosystem Services in Oil Sands Pre-mining Phase     

Omotehinse  A. O.  De Tomi  G.  Baninla  Yvette 《Natural Resources Research》2020,29(2):949-965

Natural Resources Research - Ecosystems and their services are essential to human well-being, but mining activities often cause adverse impacts on these services. Although impact of mining...  相似文献   

Evaluation of Interactions Between Oilfield Chemicals and Reservoir Rocks     

Wuyep  E. O.  Oluyemi  G. F.  Yates  K.  Akisanya  A. R. 《Natural Resources Research》2020,29(2):1239-1258

Natural Resources Research - Sand failure and production occurs when the formation stress exceeds the strength of the formation, which is derived majorly from the natural material that cements the...  相似文献   

Updated Characterization of Dorowa Phosphate Rock Mined in Zimbabwe     

Tumbure  Akinson  Bretherton  Mike R.  Bishop  Peter  Hedley  Mike J. 《Natural Resources Research》2020,29(3):1561-1570

Natural Resources Research - The physical and chemical characteristics of mined phosphate rock will vary temporally as the location and nature of the ore body changes and as the type of equipment...  相似文献   

The aqueous photochemical transformation of acrylic acid   总被引：3，自引：0，他引：3  

O. Bajt  B. ket  J. Faganeli 《Marine Chemistry》1997,58(3-4)

Acrylic acid in sea water is thought to occur mostly as the product of microbial cleavage of dimethylsulphoniopropionate (DMSP), but could also be a pollutant introduced by waste waters of the organic chemical industry. Solutions of acrylic acid in natural and artificial sea water, and distilled and riverine water were photolyzed using a photochemical reactor and exposure to sunlight. The transformation of acrylic acid comprises the decarboxylation of the carboxylic group and subsequent polymerization to a polyethylene type molecule. Kinetic studies showed the lowest reaction rate in distilled water and somewhat higher and very similar rates in other aqueous media. The approximately similar reaction rates in all natural waters studied suggest that inorganic ions, especially Na⁺, Mg²⁺ and halides, and dissolved organic matter (probably humics) enhance the reaction rates. On studying the influence of different concentration ranges on the reaction kinetics, an exponential increase of rates with decreasing concentration was found. The reaction rate in the sea water solution in field conditions is rather slow. In thirty days exposure about 15% of the reactant was transformed. This reaction seems to be important in the marine environment in specific conditions, especially in phycospheres and macroaggregates where higher concentrations of acrylic acid inhibit the bacterial metabolism.  相似文献   

Seasonal Study of Methane and Nitrous Oxide in the Coastal Waters of the Southern Baltic Sea   总被引：2，自引：0，他引：2  

H.W. Bange  S. Dahlke  R. Ramesh  L.-A. Meyer-Reil  S. Rapsomanikis  M.O. Andreae 《Estuarine, Coastal and Shelf Science》1998,47(6):807-817

Atmospheric and dissolved methane (CH₄) and nitrous oxide (N₂O) were measured in the unique coastal ecosystem of theBoddenwaters, including the western Oder estuary, (southern Baltic Sea) during five campaigns between 1994 and 1997. The CH₄saturations, ranging from 105–15 500%, showed great spatial and temporal variability with maximum values in September and minimum values in December. The N₂O saturations were in the range of 91–312% with a maximum in March. Enhanced concentrations of both gases were observed only in the western Oder estuary near the mouth of the Peene River. Thus, we conclude that the distributions of CH₄and N₂O in the investigatedBoddenwaters are, directly or indirectly, linked to the Peene River runoff and not to the Oder River. Our estimate of the annual CH₄emissions from theBoddenwaters to the atmosphere indicates a significant contribution (c. 17%) to the overall CH₄emissions from the Baltic Sea. In contrast, theBoddenwaters represent only a small source for atmospheric N₂O.CH₄production rates estimated from sediment slurry experiments revealed a significant spatial variability and indicated that methanogenic activity was related to acetate consumption in the surface sediment layer. Sedimentary CH₄production might depend on different amounts of accumulation of organic material.  相似文献   

WWATCH模式模拟南海海浪场的结果分析   总被引：25，自引：3，他引：25       下载免费PDF全文

齐义泉  朱伯承  施平  毛庆文  范辰五 《海洋学报》2003,25(4):1-9

利用美国NOAA/NCEP环境模拟中心海洋模拟小组近年新开发的一个准业务化的海浪数值模式WAVEWATCH Ⅲ(以下简称WWATCH),以每天4次的NOAA/NCEP再分析风场资料为输入,模拟了1996年的南海海域的海面风浪场,通过分析TOPEX/Poseidon(以下简称T/P)高度计的上升和下降轨道在南海海域的交叉点位置处的风、浪观测资料与NCEP风场和WWATCH模式模拟的有效波高大小,可以看出,NCEP风场基本与T/P高度计的风速观测结果一致,相应的模式模拟的有效波高也基本与卫星高度计的有效波高观测结果相一致,但从空间上看,在计算区域中心附近海域的结果一致性较好,靠近计算边界附近海域的结果相对较差,但这种因边界而影响模拟结果的范围很有限;从时间上看,冬季风期间的结果一致性较好,而夏季风期间的结果偏小的趋势明显,并且这种偏小主要出现在夏季风期间的极小风速值附近。  相似文献   

Trace metal composition of colloidal organic material in marine environments   总被引：2，自引：0，他引：2  

Laodong Guo  Peter H. Santschi  Kent W. Warnken 《Marine Chemistry》2000,70(4)

Marine colloidal material (1 kDa–0.2 μm) was isolated by cross-flow ultrafiltration followed by diafiltration and freeze-drying from surface waters of the Gulf of Mexico and the Middle Atlantic Bight (MAB), as well as from estuarine waters of Galveston Bay. Elemental characterization of isolated colloidal material included organic carbon (OC) and selected trace metal (Cu, Pb, Zn, Cd, Co, Ni, Cr, Be, Fe, Al, Mn, V, Ba, and Ti) determinations. It was found that levels of these metals in marine colloids ranged from <0.1 to 50 μg/g colloidal matter, except for Fe which generally had a concentration >120 μg/g. Most metals (Cu, Pb, Zn, Ni, Al, Mn, V, and Ti) had an average concentration >1 μg/g while concentrations of Cd, Co and Be were usually <1 μg/g. Metal concentrations (μg/g) in isolated colloids were, in general, higher in Galveston Bay than in the Gulf of Mexico, suggesting either high abundance of trace metals in estuarine waters or differences in organic matter composition. Higher colloidal metal concentrations in the MAB than in the Gulf of Mexico might be due to higher terrestrial inputs in the MAB. Colloidal metal concentrations (μg/g) were generally lower than those in average soils, continental crust and suspended particles. However, metal/aluminum ratios (Me/Al) in isolated marine colloids were significantly higher than those for average soils and continental crust. Most importantly, colloids had a metal composition and metal/OC ratio (Me/C) similar to humic substances and marine plankton, suggesting that marine colloids largely originate from planktonic sources and are composed of predominately organic components. The Me/C ratios of Galveston Bay colloids followed the sequence of Cu>Ni, Cr, Zn>Mn>Co>Pb, Cd, which is similar to the Irving–Williams order except for Mn, suggesting that the interaction of metals with marine colloids is determined by the affinity of metals for specific organic ligands.  相似文献   

Thermal fronts and cross-frontal heat flux in the southern Huanghai Sea and the East China Sea   总被引：1，自引：0，他引：1  

PARK Sunghye  CHU Peter C 《海洋学报(英文版)》2008,27(5):1-20

Synoptic features in/around thermal fronts and cross-frontal heat fluxes in the southern Huanghai./Yellow Sea and East China Sea （HES） were examined using the data collected from four airborne expendable bathythermograph surveys with horizontal approxmately 35 km and vertical 1 m（from the surface to 400 m deep） spacings. Since the fronts are strongly affected by HES current system, the synoptic thermal features in/around them represent the interaction of currents with surrounding water masses. These features can not be obtained from climatological data. The identified thermal features are listed as follows ： （ 1 ） multiple boundaries of cold water, asymmetric thermocline intrusion, locally-split front by homogeneous water of approxmately 18 ℃, and mergence of the front by the Taiwan Warm Current in/around summertime southern Cheju - Changjiang/Yangtze front and Tsushima front; （2） springtime frontal eddy-like feature around Tsushima front; （3） year-round cyclonic meandering and summertime temperature-inversion at the bottom of the surface mixed layer in Cheju - Tsushima front; and （4） multistructure of Kuroshio front. In the Kuroshio front the mean variance of vertical temperature gradient is an order of degree smaller than that in other HES fronts. The southern Cheju- Changjiang front and Cheju -Tsushima front are connected with each other in the summer with comparable cross-frontal temperature gradient. However, cross-frontal heat flux and lateral eddy diffusivity are stronger in the southern Cheju - Changjiang front. The cross-frontal heat exchange is the largest in the mixing zone between the modified Huanghai Sea bottom cold water and the Tsushima Warm Current, which is attributable to enhanced thermocline intrusions.  相似文献