Spatial and temporal patterns across an ecological boundary: Allochthonous effects of a young saltwater lake on a desert ecosystem

We documented changes in the abundance and composition of terrestrial flora and fauna with respect to distance from the sea edge and timing of large allochthonous inputs from the Salton Sea, California. We found significant effects that were most pronounced within 300 m of the shore, but extended 3 km inland via coyote scat deposition. The zone within 300 m of the sea had a higher density of vegetation with a distinctly different plant composition. The denser vegetation supported higher abundances of birds and reptiles. Coyotes exhibited spatial and temporal responses to marine subsidies of fish, while birds were likely subsidized by aquatic aerial insects. Top-down control, as well as dietary and habitat preferences, may have resulted in reduced number of ants, beetles, and small mammals near the sea. Species responses to the habitat edge appeared to be associated with life history, as the near shore habitat favored habitat generalists and shore specialists, while inland desert habitat favored many sand and open desert specialists. Ecosystem responses support current theories of allochthonous spatial subsidies and consumer-resource dynamics but were limited in scope, magnitude, and distance.     

The magmatic–hydrothermal transition—evidence from quartz phenocryst textures and endoskarn abundance in Cu–Zn skarns at the Empire Mine, Idaho, USA

Information about the magmatic to hydrothermal transition is preserved in late-stage features of quartz phenocrysts and endoskarn alteration in some Cu–Zn skarn deposits such as the Empire Mine in Idaho. Important features include: (1) quartz phenocrysts with strong resorption textures such as vermicular zones of igneous groundmass cutting primary quartz cathodoluminescence banding, (2) anomalous amounts of endoskarn (more than 50% of mineralized rock), (3) high F activities as evidenced by fluorite as an accessory mineral in igneous rocks, in alteration assemblages, and in fluid inclusions and by high F in hydroxyl sites in igneous biotite and amphibole, and (4) direct association of Zn, which normally is deposited distally at low temperature, with Cu in proximal locations and in endoskarn. These features are explained by the following model: (1) F lowers the solidus temperature of the magma, thus changing the timing, temperature, and duration of hydrothermal fluid exsolution. (2) Upon magmatic vapor saturation the F-rich hydrothermal fluids form bubbles that adhere to quartz phenocrysts and chemically corrode/tunnel into the quartz forming vermicular resorption textures. (3) F-rich hydrothermal fluids also promote the formation of endoskarn; silicic rocks are attacked by F-rich fluids in the same sense that carbonate wall rocks are dissolved by weakly to moderately acidic hydrothermal fluids. (4) Low fluid exsolution temperature facilitated by high F activity promotes high Zn/Cu ratios in proximal locations due to the solubility of Zn relative to Cu at lower temperatures. This model may be applicable at other localities such as the world-class Cu–Zn skarn Antamina mine, as well as some tin and rapakivi granites.     

The global warming potential of two healthy Nordic diets compared with the average Danish diet

The potential greenhouse gas (GHG) emissions from the production of food for three different diets are compared using consequential Life Cycle Assessment. Diet 1 is an Average Danish Diet (ADD); diet 2 is based on the Nordic Nutritional Recommendations (NNR), whilst diet 3 is a New Nordic Diet (NND) developed by the OPUS project. The NND contains locally produced Nordic foods where more than 75 % is organically produced. NNR and NND include less meat and more fruit and vegetables than the ADD. All diets were adjusted to contain a similar energy and protein content. The GHG emissions from the provision of NNR and NND were lower than for ADD, 8 % and 7 % respectively. If GHG emissions from transport (locally produced versus imported food) are also taken into account, the difference in GHG emissions between NND and ADD increases to 12 %. If the production method (organic versus conventional) is taken into account so that the ADD contains the actual ratio of organically produced food (6.6 %) and the NND contains 80 %, the GHG emissions for the NND are only 6 % less than for the ADD. When the NND was optimised to be more climate friendly, the global warming potential of the NND was 27 % lower than it was for the ADD. This was achieved by including less beef, and only including organic produce if the GHG emissions are lower than for the conventional version, or by substituting all meat with legumes, dairy products and eggs.     

Morphology and post-Chaudian (Late Pleistocene) evolution of the submarine Danube fan complex

The Danube deep sea fan in the northwestem Black Sea has a lateral dimension of over 150 km and stretches from several hundred metres water depth down to the abyssal plain. Eight seismic sequences have been recognized in the fan complex. Each sequence consists of channel, levee and overbank deposits, as well as mass transport units. The Danube and the Ukrainian rivers have aggraded two surficial channel-levee systems which diverge and decrease in volume downfan. The channels of these systems have a low sinuosity, implying young age, steep gradients and/or limited sediment supply. Significant channel migration occurred in the course of fan development, which could be largely controlled by relative sea-level changes. The six youngest sequences mapped have been correlated to sea-level fluctuations from the post-Chaudian regression to the present day.     

Increase in late Neogene denudation of the European Alps confirmed by analysis of a fission-track thermochronology database

A sharp increase in deposited sediment volume since Pliocene times has been observed worldwide and in particular around the European Alps. This phenomenon has been linked to a rise in denudation rates controlled by an increase of either climatic or tectonic forcing. Observation of in-situ cooling histories for orogens is critical to assess the reality of the inferred increase in denudation rates, and to determine whether this phenomenon is widespread or localized at active tectonic structures. We exploit the unique density of fission-track ages in the Western European Alps to reconstruct cooling isoage surfaces and to estimate exhumation rates on the orogen scale between 13.5 and 2.5 Ma. Our novel technique is based on the association of isoage contours with age–elevation relationships. It uses map-view interpolation, enabling a spatio-temporal analysis of exhumation rates over the entire Western Alps. The resulting exhumation histories reconstructed for eight areas of the Western Alps display strong similarities in timing and rates with orogen-wide average denudation rates inferred from sediment volumes. This consistency validates the use of both techniques for the study of an orogen characterized by strong relief and high recent exhumation rates. We conclude that exhumation rates in the Western Alps have increased more than twofold since Late Miocene times. This increase may have been locally modulated by the distinct response of different tectonic units.     

伊利石结晶度Kbler,Weaver和Weber指数关系式常数的确定与应用

根据衍射峰具有的不同分布特点推导出了14个伊利石结晶度Kbler指数,Weaver指数和Weber指数关系式中常数项C1-C14的数值,提出了PearsonVII分布中形态参数μ与C5,C6,C11,C12的4个定量方程。由此,14个伊利石结晶度指数关系式可直接用于实际计算。根据阿尔卑斯复理石伊利石形态特征Sc=0.731,由这些关系式进行近变质带上下界线的转换得出与Kbler指数0.42～0.25。△2θ界线对应的Weaver指数和Weber指数的界线值分别为5.8～17.6和300～179。讨论了在自然干燥状态下直接进行伊蒙混层鉴定的基本原理。     

美国内华达Goldstrike矿区卡林型贝茨金矿同变形的富矿分带(续)

(接第 1期第 1 6页 )3　富矿分带与控制因素贝茨金矿中不同矿石矿物组合和蚀变类型的分布与构造背景、围岩岩石及在矿体中的位置有关。根据形态、矿物组成和地质背景可分出几种空间形式截然不同的矿石类型 ,彼此之间由废石或低含金量的岩石所分隔。富矿体的地球化学、矿物学、地质及冶金方面的分带在三维空间上是连续的。富矿体的形状和定位与 Peters向斜构造的特征 ,沉积岩的岩石组成以及闪长岩接触带的几何形态和厚度有关 (图 6 A,B)。根据对不同的矿石类型和围岩类型的研究结果 ,对不同的富矿体进行了分类和判别。 Pe-ters( 1 996 ,1 9…     

Multi‐phase late‐Neogene exhumation history of the Aar massif,Swiss central Alps

The late‐Neogene evolution of the European Alps was influenced by both tectonic and climatically driven erosion processes, which are difficult to disentangle. We use low‐temperature thermochronometry data from surface and borehole samples in the Aar massif–Rhône valley (Swiss central Alps) to constrain the exhumation history of the region. Multiple exhumation events are distinguished and linked to regional‐scale tectonic deformation (before 5 Ma), short‐lived climatically driven orogen contraction (between 4 and 3 Ma), and glacial valley carving since c. 1 Ma. Compared with previous studies, we clearly show the existence of two separate exhumation phases in the Late Miocene–Pliocene and better constrain the onset of glacial valley carving. The hydrothermal activity and geothermal anomalies currently observed in the borehole have been local and short‐lived, with only a minor influence on thermochronometric observations. We thus suggest that late‐stage glacial valley carving may have triggered topography‐driven fluid flow and transient hydrothermal circulation.