A new location of Holocene dolomite formation, Lake Hayward, Western Australia

Holocene dolomite forms in the sediment of Lake Hayward, a small permanent hypersaline lake in the Clifton-Preston Lakeland System, Western Australia. The geomorphological setting of dolomite formation in Lake Hayward is similar to the Coorong region in South Australia. Unlike in the Coorong region, dolomite in Lake Hayward does not form as a direct precipitate from the lake water, but is of diagenetic origin. This can be deduced from the following features: (1) the dolomite occurs only below 60–70 cm from the sediment-water interface, (2) dolomite occurs as luminescing cement, and (3) dolomite has pristine well-formed rhomb-shaped crystals. The source of magnesium for dolomitization is probably from the concentration on inflowing groundwater by evaporation and the selective removal of calcium by chemical and biological aragonite/calcite precipitation.     

Systematic palaeontology and biostratigraphy of two Early Cretaceous condensed sections from the Barents Sea

Bivalve, brachiopod and cirripede faunas from the latest Jurassic and Early Cretaceous Barents Sea boreholes 7320/3-U-l and 7425/9-U-l are systematically described and illustrated. Microfossils have also been studied and the cores arc dated on the basis of the fossil recovery. The bivalve Buchia whose zonal sequence has been used for correlation of boreal marine sections is the most important biostratigraphic marker group in the condensed Boreal Berriasian-Hauterivian intervals of these cores. A new species of cirripede Zeugmatolepas? borealis Collins sp. nov. and dinoflagellate cyst Muderongia aequicornus Århus sp. nov. are described.
The Late Jurassic fine-grained elastics of core 7320/3-U-l are overlain by about 3 m of grey dolomitic limestone of Valanginian and Hauterivian age. The lowermost part of 7425/9-U-l is represented by a latest Volgian-earliest Berriasian fossiliferous greyish green marl. It is followed by a reddish brown fossilifcrous claystone of Berriasian and perhaps partly Valanginian age. Core 7425/9-U-l also contains a mainly Valanginian greyish green marly limestone which changes into a dark grey to black limestone of Early Barremian age in its upper part. The sedimentological change from condensation to dark grey clay deposition took place in the middle Barremian H. rude-fissicostatum ammonite Zone in 7425/9-U-l and probably slightly earlier in 7320/3-U-l. This was commenced at about the same time as deposition of the inaccurately and only indirectly dated fluvio-deltaic Festningen Sandstone Member on Spitsbergen. The dark claystone may thus be a distal equivalent to this sandstone unit.     

Sea level control of stacked late Quaternary coastal sequences, central Great Barrier Reef

Lithofacies analysis, pollen assemblages and radiocarbon age dates of 20 stratigraphic drill holes are used to develop an evolutionary history for late Quaternary sedimentation in two coastal embayments landward of the central Great Barrier Reef. Different physiographic settings of the embayments result in two contrasting styles of sedimentary sequence: (a) an exposed, moderate energy, beach barrier-lagoon system (Wyvuri Embayment) and (b) a protected, low energy, muddy inlet fill sequence (Mutchero Inlet). Despite sharp contrast in sequence style, similar depositional cycles occur in both embayments in response to late Quaternary sea level fluctuations including: (1) a last interglacial highstand (+2 m; c. 125 000 yr bp ) beach barrier (Wyvuri); (2) an early to mid-Holocene (8000–6100 yr bp ) transgressive beach barrier-lagoon (Wyvuri) and estuarine infill (Mutchero); and (3) mid-Holocene to present highstand beach barrier (Wyvuri) and estuarine (Mutchero) progradation. Preservation of such cycles in the stratigraphic record would produce a series of vertically stacked and offset linear barrier sands surrounded by lagoonal mud and fine grained shoreface sediment juxtaposed to muddy, estuarine infills. Sea level elevations are well recorded by the upward transition from Rhizophora-dominated intertidal mangrove mud to freshwater swamp (clearly identified by pollen analysis) and by the basal contacts of beach barrier sediments which sharply overlie the upper shoreface. Transgressive sedimentation is interrupted in both embayments by a constructional beach barrier (Wyvuri) and abbreviated progradation (Mutchero) corresponding to a — 5 m pause in relative sea level rise at c. 6800 yr bp . Sea level control of fine scale coastal sedimentation patterns is beginning to be widely recognized and provides an accurate analogue for stacked ancient sequences.     

An Ion and Electron Microprobe Study of the Mineralogy of Enclaves and Host Syenites of the Red Hill Complex, New Hampshire, USA

The Red Hill complex of New Hampshire is unusual for the WhiteMountain Magma Series of northern New England because it consistsof both silica-undersaturated and -saturated to -oversaturatedsyenites. Amphibole, pyroxene, and apatite in two of the saturatedunits, the Outer Coarse Syenite (OCS) and the Garland Peak Syenite(GPS), and in the undersaturated Nepheline Sodalite Syenite(NSS), were analyzed to determine the relationship between coexistingunder-saturated and saturated magmas. Mafic enclaves in theNSS and the GPS were also studied to elucidate their relationshipswith the host syenites. In addition to mafic enclaves, the NSS contains later emplacedcamptonitic dikes and associated pipe-like benmoreites. Thebenmoreites contain amphibole that is compositionally continuouswith amphibole in the NSS. However, REE and other trace elementabundances in apatite from the benmoreites and the NSS are notcompatible with a genetic relationship between the two. Maficenclaves within the NSS contain amphibole and pyroxene thatare compositionally continuous with the NSS. Bulk-rock compositionsof the enclaves plot along trends defined by the NSS. Furthermore,chondrite-normalized REE patterns for apatite in both the enclavesand the NSS are parallel, and REE abundances increase systematicallyfrom the enclaves to the NSS. We therefore suggest that theenclaves represent magmas similar to the NSS parent that intrudedup into its daughter products. These magmas appear to have beentephritic to phonotephritic in composition. Abundances of REE in apatite in the Nepheline Sodalite Syenite(NSS) are distinct from those in apatite in the silica-saturatedOCS. OCS apatites have LREE abundances up to 26 000 times chondritesand La/Yb ratios of 16–27. NSS apatites have comparableLREE concentrations, but HREE abundances are considerably lowerthan those of the OCS; La/Yb ratios range from 68 to 104. Theseobserved differences in both the REE and other trace elementabundances between apatite in the two rocks present difficultieswith a common parental magma hypothesis for the NSS and OCS.Hence it is suggested that, although the OCS and NSS are contemporaneousin time and space, they are probably not consanguineous. The silica-saturated GPS is a fine-grained syenite containingstrongly zoned amphiboles with kaersutite to hastingsite coresrimmed by hastingsitic hornblende and ferro-hornblende. Discretegrains of hastingsitic hornblende and ferro-hornblende occurin a feldspar-quartz groundmass. Coarser-grained, quartz-richpatches, containing feldspars and ferro-hornblende and ferroedenite,are also found in the GPS. The kaersutite cores are identicalto the amphibole in the GPS enclaves and the NSS suite. TheseGPS enclaves are silica undersaturated; the kaersutite coresin the GPS host rocks are probably xenocrysts derived from disaggregatedundersaturated magmas similar to that represented by the enclaves.     

“THE END OF MODERN HISTORY”?*

ABSTRACT. The first half of the twentieth century marked both an end to confidence in human control of the earth and a prelude to the contemporary era of intense environmental concern after 1950. This conspectus of the environmental history/historical geography of the transitional years between 1900 and 1950 focuses on rising concerns over resource supplies and exploitation, particularly land settlement, timber supplies, soil erosion, and river-basin control. Conservation and the pervasiveness of ecological thinking and analogy form a strong underlying theme.     

The Effects of Fe3? and Mn3? on Aluminum Silicate Phase Relations in North-Central New Mexico, U.S.A.

Aluminum silicate triple-point occurrences are common in metamorphicrocks of northern New Mexico. The three polymorphs show extensivesolid solution, with Fe and Mn substituting for Al. Mineraltextures, the spatial distribution of phases, and the systematicpartitioning of Fe and Mn indicate that the kyanite-andalusite-sillimaniteassemblages crystallized in equilibrium. The compositions ofminerals in the three-phase assemblage vary across the studyarea, recording regional variations in the pressures and temperaturesof metamorphism. The highest-pressure rocks, exposed at RioMora, contain kyanite at higher elevations and sillimanite atlower elevations. A sub-horizontal isograd separates the twominerals. Kyanite and sillimanite have nearly identical Fe contentwhich varies systematically with X_Fe2O3 in hematite or ilmenite.Andalusite occurs only along a single manganiferous layer, incrystals rich in MnAlSiO₅ and saturated in FeAlSiO₅. Triple-pointassemblages can be found wherever the folded manganiferous layercrosses the unfolded kyanite-sillimanite isograd. The TruchasRange, preserving slightly lower pressures of metamorphism,shows kyanite-andalusite-sillimanite in rocks with titaniferoushematite. Andalusite is enriched in Fe relative to kyanite andsillimanite, but no polymorphs contain Mn. Rocks with lowerX_Fe2O3 in hematite have kyanite and sillimanite without andalusite,whereas rocks with pure hematite contain only andalusite. Theshallowest erosional levels are preserved in the western PicurisRange where the three polymorphs occur as pure minerals in ilmenite-bearingrocks. Hematitic samples contain only andalusite which showsextensive solid solution of both Fe and Mn. The assemblage kyanite-andalusite-sillimanite is not invariant.Iron and manganese both add degrees of freedom. These transitionmetals have stabilized the three-phase assemblage, in apparentchemical equilibrium, across a P-T interval of 500-540 ?C, 3?8-4?6kb in rocks from New Mexico. The saturation level of FeAlSiO5in andalusite does not vary with Mn content but does vary withpressure and temperature. Calculations indicate that a 2-3 kbdecrease in pressure or a 25-50 ?C increase in temperature resultsin a 1 mole per cent increase in X_FeAlSiO5 in iron-saturatedandalusite.     

CELEBRATING CENTRIFUGAL FORCES IN AMERICAN GEOGRAPHY

GEOGRAPHY IN AMERICA AT THE DAWN OF THE 21^ST CENTURY. Edited by GARY L. GAILE and CORT J. WILLMOTT.     

Indian Ocean tsunamis: environmental and socio-economic impacts in Langkawi, Malaysia

We report the results of a study of the physical characteristics and socio-economic impacts of the Indian Ocean Tsunami of 26 December 2004 on the tourist island of Langkawi, Malaysia. In comparison with many other locations struck by the tsunami, the immediate physical and socio-economic impacts in Langkawi were relatively minor. A detailed survey of the watermark and ground elevations was undertaken in the worst affected area between Sungei Kuala Teriang and Sungei Kuala Melaka. Here, the tsunami reached a maximum elevation of 4.29 m as it crossed the coast, with a maximum flow depth of 2.0 m and a very consistent run-up elevation relative to mean sea level of 300 ± 10 cm. The tsunami inundated inshore areas for 300 m and penetrated inland along creeks for 500–1000 m. Structural damage to buildings was confined to within 50–150 m of the shoreline where about 10% of the houses were completely destroyed and 60–70% suffered significant structural damage. Damage was particularly severe in areas where there was no engineered coastal protection, but while coastal revetments did provide enhanced protection for houses at the waterfront, the coastline in the study area appeared to be more heavily impacted than elsewhere in Langkawi because wave energy was focused on the area by offshore breakwaters built to protect the Langkawi port and airport. Emergency response after the tsunami was rapid and efficient but would have been improved if the local police station had not been rendered inoperative by the first wave, and if a mechanism had been in place to ensure that informal advance warnings transmitted between Phuket (Thailand), Langkawi and Penang (Malaysia) by tourist operators could have been more widely disseminated.     

Object-oriented data modelling for spatial databases

Data modelling is a critical stage of database design. Recent research has focused upon object-oriented data models, which appear more appropriate for certain applications than either the traditional relational model or the entity-relationship approach. The object-oriented approach has proved to be especially fruitful in application areas, such as the design of geographical information systems which have a richly structured knowledge domain and are associated with multimedia databases. This article discusses the key concepts in object-oriented modelling and demonstrates the applicability of an object-oriented design methodology to the design of geographical information systems. In order to show more clearly how this methodology may be applied, the paper considers the specific object-oriented data model IFO. Standard cartographic primitives are represented using IFO, which are then used in the modelling of some standard administrative units in the United Kingdom. The paper concludes by discussing current research issues and directions in this area.