Characterisation of the recreational fishery for southern rock lobster,Jasus edwardsii,in Tasmania,Australia: Implications for management

Southern rock lobster (Jasus edwardsii) support significant commercial and recreational fisheries in Tasmania, Australia. Since the mid 1990s the number of persons holding recreational lobster licences increased by over 80%, with c. 15 500 persons licensed in 2002/03. Assessment of the recreational fishery has been undertaken periodically since 1996 using a telephone‐diary survey method. The fishery was concentrated off the south‐east and east coasts of Tasmania and characterised by strong seasonality in catch and effort, which peaked markedly early in the fishing year (November‐January). Although pots were the most popular fishing method, daily catch rates by divers were more than double those for pots. Divers selectively harvested larger lobsters than those taken by pots and more frequently attained the daily bag limit of 5 lobsters. The estimated recreational harvest increased significantly since 1996/97 and in 2002/03 effectively reached a management trigger level of 10% of the total allowable commercial catch, flagging a review of recreational management arrangements.     

Crustal lineament control on magmatism and mineralization in northwestern Argentina: geological, geophysical, and remote sensing evidence

The relationship between long-lived deep crustal lineaments and the locations of magmatic centers and associated mineral deposits has been investigated in the Puna region of northwestern Argentina, through the analysis of regional aeromagnetic surveys, Landsat images, and geological information. The good exposure and excellent preservation of basement and supracrustal geology in this region makes it particularly suitable for such a study. At a regional scale, several contrasting magnetic domains are recognized, which correlate with crustal geology. Two basement domains are separated by a NNE-trending boundary, which is believed to correlate with a Paleozoic suture zone between the Pampia (to the southeast) and Arequipa–Antofalla terranes (to the northwest). Locally overlying these basement terranes is the Cenozoic magmatic domain, which is best developed in the N–S-trending volcanic arc at the western edge of the Puna (the Cordillera Occidental). In addition, four southeast-trending volcanic zones extend for several hundred kilometers across the Puna. Many important mineral deposits and areas of hydrothermal alteration are associated with these volcanic breakouts, and we have selected three such areas for more detailed study: Bajo de la Alumbrera (Argentina's largest porphyry copper deposit), Cerro Galán (the largest ignimbrite caldera in Argentina, with associated hydrothermal alteration zones), and El Queva (a historic polymetallic district located within a major volcanic range). A comparison of lineament maps generated from aeromagnetic and Landsat TM images reveals broad correlation between these different remote sensing techniques, which respectively highlight subsurface magnetic and surface geological features. In addition, the locations of magmatic and hydrothermal centers can be related to the interpreted structural framework, and are seen to occur near the intersections of major lineament zones. It is suggested that in three dimensions, such intersection zones form trans-lithospheric columns of low strength and high permeability during transpressional or transtensional tectonic strain, and may thereby serve as conduits for magma ascent to the shallow crust. Pooling of large volumes of deeply derived magma in shallow crustal magma chambers may then result in voluminous devolatilization and the formation of hydrothermal mineral deposits. It is important to note that in this model, structural intersections serve as facilitators for magma ascent and volatile exsolution, but do not in themselves cause this process—other factors such as magma supply rate and tectonic stress are essential primary ingredients, and local magmatic and volcanic processes affect the ultimate potential for ore formation. Nevertheless, we suggest that lineament analysis provides a valuable framework for guiding the early stages of mineral exploration; other regional and local geological considerations must then be applied to identify priority targets within this framework.     

RegCM3对东亚环流和中国气候模拟能力的检验

使用RegCM3区域气候模式,嵌套ERA40再分析资料,对东亚地区进行了15年（1987～2001年）时间长度的数值积分试验,分析了模式对东亚平均环流及中国地区气温和降水的模拟。结果表明,模式对东亚平均环流的特征和中国地区降水、地面气温的年、季地理分布和季节变化特征均具有一定的模拟能力,对气温和降水年际变率的模拟也较好。此外模式模拟在测站稀少地区,可以提供局地如降水分布更可靠的信息。模式对气温的模拟存在1-3℃的系统性冷偏差;对中国地区降水地理分布的模拟也存在一定偏差,如对年平均降水的模拟中,降水最大值位置与观测有一定差距,特别是对冬季降水中心的模拟存在较大偏差。模式模拟的夏季降水,在中国北方地区总体偏大100-200 mm,南方总体偏小100-200 mm。模式对地面气温的模拟效果好于降水。     

Deep mantle roots and continental emergence: implications for whole-Earth elemental cycling,long-term climate,and the Cambrian explosion

Elevations on Earth are dominantly controlled by crustal buoyancy, primarily through variations in crustal thickness: continents ride higher than ocean basins because they are underlain by thicker crust. Mountain building, where crust is magmatically or tectonically thickened, is thus key to making continents. However, most of the continents have long passed their mountain building origins, having since subsided back to near sea level. The elevations of the old, stable continents are lower than that expected for their crustal thicknesses, requiring a subcrustal component of negative buoyancy that develops after mountain building. While initial subsidence is driven by crustal erosion, thermal relaxation through growth of a cold thermal boundary layer provides the negative buoyancy that causes continents to subside further. The maximum thickness of this thermal boundary layer is controlled by the thickness of a chemically and rheologically distinct continental mantle root, formed during large-scale mantle melting billions of years ago. The final resting elevation of a stabilized continent is controlled by the thickness of this thermal boundary layer and the temperature of the Earth’s mantle, such that continents ride higher in a cooler mantle and lower in a hot mantle. Constrained by the thermal history of the Earth, continents are predicted to have been mostly below sea level for most of Earth’s history, with areas of land being confined to narrow strips of active mountain building. Large-scale emergence of stable continents occurred late in Earth’s history (Neoproterozoic) over a 100–300 million year transition, irreversibly altering the surface of the Earth in terms of weathering, climate, biogeochemical cycling and the evolution of life. Climate during the transition would be expected to be unstable, swinging back and forth between icehouse and greenhouse states as higher order fluctuations in mantle dynamics would cause the Earth to fluctuate rapidly between water and terrestrial worlds.     

Morphology and distribution of dolines on ultramafic rocks from airborne LiDAR data: the case of southern Grande Terre in New Caledonia (SW Pacific)

Dolines are closed geomorphological depressions which are surface manifestations of karstic systems. Usually developed on limestones, they also typify the morphology of the New Caledonian landscape, particularly on the southern massif of the main island (known as Massif du Sud). The specificity of dolines here lies in their development on ultramafic rocks. They are evidences of subsidence, suffosion and collapse phenomena resulting from dissolution weathering of peridotites. However, extensive underground drainage systems are still not yet recognized. Semi‐automatic mapping of dolines is carried out on a 148 km² area of the Massif du Sud from a high accuracy LiDAR digital elevation model. In this area 8601 dolines ranging from 1 m² to 2 km² are identified and morphologically characterized with precision. Most are small, shallow and round‐shaped, yet more complex shapes are locally observed. Size distribution analysis allows the setting of a threshold of 20 000 m² above which surface processes rather than chemical weathering control doline evolution. Doline density analysis reveals high concentrations on flat areas where ferricrete overlies the complete weathering profile, especially in the case of elevated rainy watersheds. Dolines are aligned and elongated along a north 135° ± 5° major fracture direction, which is inherited from the obduction of the Pacific Plate upper mantle in the Late Eocene. Finally, we propose a pioneering morphometric typology of dolines that provides important clues as to pseudokarstic activity. We define collapse, bowl‐shaped and flat bottom dolines. Collapse and bowl‐shaped dolines are assumed to denote active pseudokarst. They may widen and deepen, or eventually be filled by sediments. They are distinguished from flat bottom dolines that are partially to completely filled, which suggests that they are associated with paleo‐pseudokarsts. However the groundwater flow paths associated with the genesis and evolution of dolines must be clarified, thus collapse and bowl‐shaped dolines should be hydrologically monitored. Copyright © 2016 John Wiley & Sons, Ltd.