A late Pleistocene steppe bison (Bison priscus) partial carcass from Tsiigehtchic, Northwest Territories, Canada     

Grant D. Zazula  Glen MacKay  Thomas D. Andrews  Beth Shapiro  Brandon Letts  Fiona Brock 《Quaternary Science Reviews》2009,28(25-26):2734-2742

A partial steppe bison (Bison priscus) carcass was recovered at Tsiigehtchic, near the confluence of the Arctic Red and Mackenzie Rivers, Northwest Territories, Canada in September of 2007. The carcass includes a complete cranium with horn cores and sheaths, several complete post-cranial elements (many of which have some mummified soft tissue), intestines and a large piece of hide. A piece of metacarpal bone was subsampled and yielded an AMS radiocarbon age of 11,830 ± 45 ¹⁴C yr BP (OxA-18549). Mitochondrial DNA sequenced from a hair sample confirms that Tsiigehtchic steppe bison (Bison priscus) did not belong to the lineage that eventually gave rise to modern bison (Bison bison). This is the first radiocarbon dated Bison priscus in the Mackenzie River valley, and to our knowledge, the first reported Pleistocene mammal soft tissue remains from the glaciated regions of northern Canada. Investigation of the recovery site indicates that the steppe bison was released from the permafrost during a landslide within unconsolidated glacial outwash gravel. These data indicate that the lower Mackenzie River valley was ice free and inhabited by steppe bison by 11,800 ¹⁴C years ago. This date is important for the deglacial chronology of the Laurentide Ice Sheet and the opening of the northern portal to the Ice Free Corridor. The presence of steppe bison raises further potential for the discovery of more late Pleistocene fauna, and possibly archaeological evidence, in the region.  相似文献   

The Quaternary in Britain: edited by John Neale and John Flenley,Pergamon Press, 1981, ISBN 0-08-026254-6, 267 pp. $35.00     

J.T. Andrews 《Quaternary Science Reviews》1982,1(2):iv-v

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Ground water flow in a desert basin: challenges of simulating transport of dissolved chromium     

Andrews CB  Neville CJ 《Ground water》2003,41(2):219-226

A large chromium plume that evolved from chromium releases in a valley near the Mojave River was studied to understand the processes controlling fate and migration of chromium in ground water and used as a tracer to study the dynamics of a basin and range ground water system. The valley that was studied is naturally arid with high evapotranspiration such that essentially no precipitation infiltrates to the water table. The dominant natural hydrogeologic processes are recharge to the ground water system from the Mojave River during the infrequent episodes when there is flow in the river, and ground water flow toward a playa lake where the ground water evaporates. Agricultural pumping in the valley from the mid-1930s to the 1970s significantly altered ground water flow conditions by decreasing water levels in the valley by more than 20 m. This pumping declined significantly as a result of dewatering of the aquifer, and water levels have since recovered modestly. The ground water system was modeled using MODFLOW, and chromium transport was simulated using MT3D. Several innovative modifications were made to these modeling programs to simulate important processes in this ground water system. Modifications to MODFLOW include developing a new well package that estimates pumping rates from irrigation wells at each time step based on available drawdown. MT3D was modified to account for mass trapped above the water table when the water table declines beneath nonirrigated areas and to redistribute mass to the system when water levels rise.  相似文献   

Analysis of Ground-Water Remedial Alternatives at a Superfund Site   总被引：3，自引：0，他引：3  

C. Zheng  G. D. Bennett  C. B. Andrews 《Ground water》1991,29(6):838-848

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Impact of a Power Plant on the Ground-Water System of a Wetland     

Charles B. Andrews  Mary P. Anderson 《Ground water》1978,16(2):105-111

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The Impact of the Use of Heat Pumps on Ground-Water Temperatures   总被引：1，自引：0，他引：1  

Charles B. Andrews 《Ground water》1978,16(6):437-443

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Saponite and celadonite in layer 2 basalts,DSDP Leg 37   总被引：1，自引：0，他引：1  

Anthony J. Andrews 《Contributions to Mineralogy and Petrology》1980,73(4):323-340

Detailed examination of igneous core recovered during Leg 37 of the DSDP, has revealed that basalt diagenesis, an alteration effect resulting from low temperature interaction with seawater, is pervasive to depths of greater than 600 meters in layer 2. Phyllosilicates are among the main components of this low grade alteration effect and occur exclusively as saponite, celadonite and interlayered mixtures of these two phases. Saponites fall into two chemical groups as (a) Mg rich-Fe poor types characteristic of oxidative diagenesis and (b) Fe rich-Mg poor types characteristic of non-oxidative diagenesis. Celadonite is entirely restricted in occurrence to the oxidative diagenetic environment (oxidation halos) and rarely, if ever, occurs as a pure phase. In this respect, X-ray and electron microprobe analyses suggest the presence of interlayered smectite in some cases and iron-oxide contamination in others.Phyllosilicates generated during oxidative diagenesis of basalt occur in discrete mineralogical zones, typically arranged in the sequence Fe³⁺-oxide, celadonite, saponite proceeding outwards from a vein. The generation of these zones are modelled in terms of an infiltration dominated metasomatic process and their occurrence reflects a gradual extraction of oxygen from inflowing seawater during progressive reaction with the massive crystalline basalt.Mass balance calculations applied to the oxidative diagenetic process suggest that a source external to the immediate environment of the massive crystalline rock is required for Si, Fe, K, Mg, Ca, and Al, in order to account for the observed secondary minerals. While Mg, K, and Ca are indigenous to seawater, Si, Fe, and Al were probably enriched in the fluid during wall rock reactions in the fracture system.It is suggested that diagenesis of layer 2 basalts results in the extraction of Mg and K from seawater, in enough quantity to contribute significantly to the chemical mass balance of the oceans.  相似文献   

Radioelements,radiogenic helium and age relationships for groundwaters from the granites at Stripa,Sweden   总被引：1，自引：0，他引：1  

J.N Andrews  I.S Giles  R.L.F Kay  D.J Lee  J.K Osmond  J.B Cowart  P Fritz  J.F Barker  J Gale 《Geochimica et cosmochimica acta》1982,46(9):1533-1543

The solution of radioelements and radiogenic ⁴He by groundwaters in fractured rocks is dependent upon the radioelement distribution in the rock matrix and the extent of the rock-water interface. The ${}^{234}\text{U}{}^{238}\text{U}$ activity ratio and the dissolved U, Rn and He contents of such groundwaters respond to changes in the flow regime with time. Although ${}^{234}\text{U}{}^{238}\text{U}$ activity ratios change with groundwater residence time as a consequence of ²³⁴Th-recoil induced solution of ²³⁴U, the activity ratio is strongly influenced by the U distribution within fractures, by the extent of the rock-water interface and by the amount of ²³⁸U in solution. A model for the quantitative evaluation of these effects is presented.Groundwaters from depths up to 880 m in the Stripa granite have variable dissolved uranium contents and ${}^{234}\text{U}{}^{238}\text{U}$ activity ratios. The uranium geochemistry is primarily determined by variations in flow path rather than by groundwater age.Dissolved radiogenic ⁴He in the groundwaters increases with their depth of origin, and is dependent upon the U content of the granite and upon its fracture porosity. It increases with groundwater residence time but movement of ⁴He by diffusion and transport processes make the actual groundwater age indeterminate.  相似文献   

On the effect of low-temperature seawater-basalt interaction on the distribution of sulfur in oceanic crust,layer 2     

Anthony J. Andrews 《Earth and Planetary Science Letters》1979,46(1):68-80

A detailed geochemical-petrological examination of layer 2 basalts recovered during Leg 37 of the DSDP has revealed that the original distribution, form and abundance of igneous sulfide have been profoundly altered during low-grade oxidative diagenesis. The net result appears to have been a rather pervasive remobilization of igneous sulfide to form secondary pyrite accompanied by a bulk loss of sulfur equivalent to about 50–60% of the original igneous value, assuming initial saturation. It is suggested that during infiltration of seawater into the massive crystal-line rock, igneous sulfide has experienced pervasive oxidation, under conditions of limited oxidation potential, to form a series of unstable, soluble sulfur species, primarily in the form of SO₃^2? and S₂O₃^2?. Spontaneous decomposition of these intermediate compounds through disproportionation has resulted in partial reconstitution of the sulfur as secondary pyrite and the generation of SO₄^2? ion, which, due to its kinetic stability, has been lost from the basalt system and ultimately transferred to the ocean. This model not only satisfies the geochemical and petrological observations but also provides a suitable explanation for the highly variable δ³⁴S values which characterize secondary sulfides in deep ocean floor basalts.  相似文献   

Rapid ice-sheet growth and initiation of the last glaciation     

R.G. Johnson  J.T. Andrews 《Quaternary Research》1979,12(1):119-134

Calculations based on temperature-corrected oxygen-isotope ratios from deep-sea cores yield a glacioeustatic sea-level fall in excess of 50 m during the first 10,000 yr of the last glaciation, and generally support the local regression of about 70 m inferred from tectonically rising New Guinea beaches. We propose that this rapid glacial buildup depended on high-latitude cooling, and large increases of high-latitude regional winter precipitation in the Laurentide and the Fennoscandian-Barents Sea areas, and that these factors were caused by a critical alteration of North Atlantic Drift currents and their associated subpolar atmospheric circulation. In support of this, faunal data from northeast North Atlantic deep-sea cores show that the glacial buildup was accompanied by a sudden loss of most of the North Atlantic Drift from the Greenland-Norwegian Sea, a factor favoring reduced heat input into the higher latitudes. Subpolar mollusk and foraminifera fauna from elevated marine deposits on the Baffin Island coast, and northwest North Atlantic core data suggest a continuation or an associated restoration of subpolar water west of Greenland as far north as Baffin Bay, a factor favoring precipitation in the northeast Canadian region. Heat transport and atmospheric circulation considerations suggest that the loss of the northeast North Atlantic Drift was itself a major instrument of high-latitude climate change, and probably marked the initiation of major new ice-sheet growth.  相似文献