Development of secondary porosity in the Fairholme carbonate complex (southwest Alberta, Canada)

Because of their economic importance as hydrocarbon reservoirs, the Upper Devonian dolomitized carbonate reefs in southwest Alberta have been the subject of several studies. Still, there is no consensus on the process of matrix dolomitization and furthermore, the process of vug development is not often addressed. The studied outcrops show features of an early diagenetic matrix-selective dolomitization by a Late Devonian seawater-derived fluid. Seepage reflux dolomitization combined with latent reflux is proposed, which best explains most chemical characteristics. The cements in the vugs are precipitated from warm saline, ⁸⁷Sr-enriched fluids and testify to thermogenic sulphate reduction based on the presence of sulphur, CO₂ and H₂S in inclusions, relatively high homogenization temperatures and depleted δ¹³C values, which sets constraints on the timing of vug formation. Secondary porosity may be created by the mixing of formation water with a tectonically and topographically driven fluid and by the dissolution of anhydrite nodules.     

Preliminary mariner 9 report on the geology of Mars

Mariner 9 pictures indicate that the surface of Mars has been shaped by impact, volcanic, tectonic, erosional and depositional activity. The moonlike cratered terrain, identified as the dominant surface unit from the Mariner 6 and 7 flyby data, has proven to be less typical of Mars than previously believed, although extensive in the mid- and high-latitude regions of the southern hemisphere. Martian craters are highly modified but their size-frequency distribution and morphology suggest that most were formed by impact. Circular basins encompassed by rugged terrain and filled with smooth plains material are recognized. These structures, like the craters, are more modified than corresponding features on the Moon and they exercise a less dominant influence on the regional geology. Smooth plains with few visible craters fill the large basins and the floors of larger craters; they also occupy large parts of the northern hemisphere where the plains lap against higher landforms. The middle northern latitudes of Mars from 90 to 150† longitude contain at least four large shield volcanoes each of which is about twice as massive as the largest on Earth. Steep-sided domes with summit craters and large, fresh-appearing volcanic craters with smooth rims are also present in this region. Multiple flow structures, ridges with lobate flanks, chain craters, and sinuous rilles occur in all regions, suggesting widespread volcanism. Evidence for tectonic activity postdating formation of the cratered terrain and some of the plains units is abundant in the equatorial area from 0 to 120° longitude.Some regions exhibit a complex semiradial array of graben that suggest doming and stretching of the surface. Others contain intensity faulted terrain with broader, deeper graben separated by a complex mosaic of flat-topped blocks. An east-west-trending canyon system about 100–200 km wide and about 2500 km long extends through the Coprates-Eos region. The canyons have gullied walls indicative of extensive headward erosion since their initial formation. Regionally depressed areas called chaotic terrain consist of intricately broken and jumbled blocks and appear to result from breaking up and slumping of older geologic units. Compressional features have not been identified in any of the pictures analyzed to data. Plumose light and dark surface markings can be explained by eolian transport. Mariner 9 has thus revealed that Mars is a complex planet with its own distinctive geologic history and that it is less primitive than the Moon.     

St. Magnus Bay,Shetland: A probable British meteorite crater of large size

The last two decades have witnessed a continually expanding programme of investigation concerned with the discovery of terrestrial impact craters or astroblemes as Dietz has called them. These are the wounds produced on the Earth's surface by the high speed collisions with giant meteorites which have taken place throughout geological time. With the exception of a few comparatively recent craters, most of the large scars originated tens or hundreds of millions of years ago and have been preserved as fossils in rocks which have since undergone considerable erosion and alteration.Although various workers have now gathered an impressive array of evidence appertaining to the topographical, petrological and mineralogical changes wrought by the sudden release of enormous quantities of energy when collisions occur, it still remains true that most discoveries of craters are made as a result of their quasi-circular appearance on maps or aerial photographs.A search of maps of the British Isles has revealed several possible impact sites, of which the most convincing is the feature known as St. Magnus Bay in the Shetland Islands. No explanation other than massive impact seems able to account for the peculiar shape of the bay and its resemblance to certain ancient Canadian impact crater residuals.In size it ranks among the dozen or so largest terrestrial impact features and is thus an important object for further study; in its own right and in the context of the currently enhanced speculation concerning the origin of craters on such bodies as the Moon and Mars.     

An obliquity-controlled Early Pleistocene river terrace record from Western Turkey?

Investigation of the Pleistocene sequence of the Gediz River, Western Turkey, has revealed a record of Early Pleistocene river terraces. Eleven terraces spanning the interval from 1.67 to 1.245 million years ago (MIS 59–37) are preserved beneath basaltic lava flows. The high number of terraces over this short time period reflects high-frequency sedimentation/incision cycles preserved due to the fortuitous combination of relatively high uplift rates (0.16 mm yr⁻¹) and progressive southwards valley migration. Comparison of this record with ODP967 from the Eastern Mediterranean Basin suggests a link between the production of terraces and obliquity-driven 41,000 year climate cycles in the Early Pleistocene.     

Research, Extension and Industry – Working Together Can Achieve Results

Over recent decades, research has been directed to assessing the impacts of land uses on valuable natural assets, such as the Great Barrier Reef. Land managers in adjacent areas are expected to adopt practices to minimize any adverse affects on downstream environments. Conversely, researchers are being pressed to provide answers to the problems. In response, researchers and environmental managers are bombarding land managers with information regarding the potential environmental implications of their practices. Is this an effective mode to achieve on-ground change?

Collaboration between all groups – research, industry and extension – may be more effective in developing and implementing practical solutions to these more complex issues. A change from the research and extension models currently used may be needed to achieve positive resource management outcomes.

Research, development and extension initiatives underway in the Australian sugar industry to improve farm practice and reduce the potential for adverse impacts on downstream environments are discussed. Case studies provide some insights into how science and extension skills work best together and how an industry group can respond to a community concern.     

Propagation history and passive rotation of mesoscale normal faults: implications for synrift stratigraphic development

Field data from onshore exposures of the Oligo-Miocene Gulf of Suez Rift in the Sinai document the passive rotation of early formed mesoscale synthetic and antithetic faults and associated half-graben due to long-lived activity on large displacement (2–5 km) block-bounding faults. Early formed small-displacement (<350 m) mesoscale antithetic faults and half-graben within regional-scale fault blocks underwent progressive steepening due to footwall uplift, rotational faulting and footwall flexing on large-displacement, block-bounding faults. In contrast, mesoscale synthetic faults were progressively rotated to shallower angles. Analysis of palaeohorizontal surfaces within synrift sediments deposited in half-graben adjacent to the mesoscale faults indicate passive rotations of up to 25° about horizontal axes since deposition. Passive burial and in-filling of early formed mesoscale faults and half-graben by synrift sediments is consistent with extension being transferred from numerous mesoscale faults to few block-bounding macroscale faults as extension preceded. Furthermore, this transfer of extension appears to be associated with a marked change in basin configuration, synrift sediment dispersal patterns and facies development. Identification of early formed, passively rotated normal faults and half-graben is important for correctly reconstructing the early stages of basin palaeogeography and sediment dispersal, and for addressing models of rift basin evolution.     

The competing impacts of geology and groundwater on electrical resistivity around Wrightsville Beach,NC

Measurements of electrical resistivity have long been used to find freshwater resources below the earth's surface. Recently, offshore resistivity and electromagnetic techniques have been used to map occurrences of submarine groundwater originating from the offshore extension of terrestrial aquifers. In many cases, observations of a high resistivity (low conductivity) anomaly in the seafloor are sufficient to suggest the presence of fresh (and less conductive) pore waters. Data from offshore Wrightsville Beach, NC show highly variable resistivity structure, with moderately high resistivity at depths of ～20 m subsurface that is at least in part caused by lithologic complexity in an underlying limestone unit, the Castle Hayne. These offshore results suggest caution in the interpretation of resistivity anomalies simply in terms of groundwater volumes. In contrast, low onshore resistivities show evidence for intrusion of saltwater into the subsurface beneath the beach, adjacent to areas of pumping for water supply.