West Dome Research Articles

Timing and mechanisms controlling evaporite diapirism on Ellef Ringnes Island, Canadian Arctic Archipelago

ABSTRACTThe Permo‐Carboniferous to Eocene Sverdrup Basin in Canada's Arctic Archipelago is strongly influenced by evaporite diapirism. However, salt structures within the basin have not been extensively investigated recently due to their remote location. This study includes the interpretation of legacy seismic reflection and borehole data to characterize the geometry of selected evaporite domes, and 1D backstripping of wells to investigate tectonic and sedimentary influences on diapirism. Extensional rift‐structures appear to have played a significant role in the formation of evaporite domes by triggering and directing salt movement. Diapirism was initiated by at least the Middle Triassic and continued to develop during the Mesozoic. Differential loading of salt on opposing east–west dome margins led to their present day asymmetric geometries. Diapir growth rates in the Mesozoic were closely linked to the rate of sedimentation and influenced by regional tectonism.

Teaching Astronomy at the UCM Observatory

There is a long tradition on teaching Astronomy at the UCM University. Since 1972 it is possible to study Astrophysics at the Faculty of Physics of the UCM. The facilities of the UCM Observatory are improving continuously every year. Nowadays two domes (4 m) are available. The west dome is mainly used for doing solar observations while the east dome is generally used to do night observations. The available instruments allow us to make a small-scaled reproduction of how people work in a large observatory. At the UCM Observatory students of the Astrophysics career do many different kinds of exercises based on the current techniques used by professional astronomers. In addition, during the last years of the career they also have the opportunity of doing a research work under the supervision of a professor.

Stratigraphy of the lower Maitai group at west dome, southland, New Zealand

Five formations (Upukerora Formation, Wooded Peak Limestone, Tramway Formation, Little Ben Sandstone, and Greville Formation) representing the lower to middle Maitai Group are mapped on the southern flanks of West Dome, northern Southland. The rocks are dominantly redeposited volcaniclastic sediments and include breccia, conglomerate, sandstone, mudstone, and tuff, as well as redeposited atomodesmatinid (bivalve) limestone. Felsic tuffs are unusually abundant in the Tramway Formation and Wooded Peak Limestone at West Dome. A new unit, the Waitaramea Member, is introduced for distinctive strata in the upper part of the Wooded Peak Limestone characterised by devitrified felsic tuff, red mudstone, and reddish green sandstone. The biostratigraphic age of the lower Maitai Group on West Dome remains poorly constrained but bryozoan genera described from fossiliferous conglomerate lenses in the Wooded Peak Limestone confirm a late Early Permian to Late Permian age. These incude Dyscritella, Paralio‐clema, Fenestella, Maychella, Shulgapora, and others. Trace fossils are locally abundant in the Wooded Peak Limestone and Tramway Formation, and include Scalarituba, Pla‐nolites, and Lophoctenium. Lower Maitai strata at West Dome are overturned, dipping steeply to the north. They are weakly metamorphosed and contain abundant fine‐grained authigenic minerals including both lawsonite and laumontite.

Microbial biomass, respiration and diversity in ultramafic soils of West Dome, New Zealand

Ultramafic soils are colonised by plant communities adapted to naturally elevated heavy metal content but it is not known whether soil microbial communities are similarly adapted to heavy metals. We measured microbial properties of six ultramafic soils that ranged in heavy metal content to test whether microbial diversity would decrease and respiratory quotient (microbial respiration:biomass) increase due to the stress imposed by increasing metal content. Soil samples were collected from beneath Nothofagus solandri var. cliffortioides tall forest, tall Leptospermum scoparium shrubland, open Leptospermum scoparium shrubland, an open Leptospermum scoparium shrubland with the rare ultramafic endemic Celmisia spedenii, a mixed divaricate shrubland, and a red tussock (Chionochloa rubra) grassland on the Dun Mountain Ophiolite belt, New Zealand. Samples were analysed for catabolic evenness using the catabolic response profile technique, microbial biomass, microbial respiration, and soil properties (pH, total carbon, total nitrogen, magnesium and total or extractable chromium and nickel). The sites differed in base saturation, pH and concentrations of metals, particularly magnesium, chromium and nickel, properties that are a major determinant of the plant communities that develop. Microbial biomass and respiration, catabolic evenness (range of 19.1 to 22.7) and the respiratory quotient were not correlated to any of the measured soil chemical properties. Factor analysis of the respiratory responses showed that the microbial communities under each vegetation type were distinct. The second factor extracted was correlated to total carbon (r2=0.62, P<0.01), basal respiration (r2=0.55, P<0.01) and microbial biomass (r2=0.65, P<0.01). Increasing metals concentrations had no direct impact on microbial diversity, biomass, respiration or community energetics. However, we suggest that metal concentrations may have exerted an indirect effect on the structure of the microbial communities through control of the vegetation community and litter inputs of carbon to the soil.

A reinterpretation of the role of granitoids in the genesis of Neoproterozoic gold mineralization in the Telfer Dome, Western Australia

The Telfer gold mine, in the Paterson province of Western Australia, is one of Australia's largest gold deposits with more than 4 million oz (M oz; or 125 t) of gold produced since mining commenced in 1977. Hosted by low-grade, dominantly marine, metasedimentary sequences of the upper Yeneena Group ( approximately 1,000-750 Ma), the Neoproterozoic mineralization (700-600 Ma) is localized within the northwest-trending Telfer dome, which consists of two en echelon, asymmetric, doubly plunging anticlines called the Main and the West dome. Within these two domes, gold and minor copper occur as a series of vertically stacked, strata-bound to stratiform, gold-copper sulfide quartz reefs (up to several meters in thickness) linked by zones of intense stockwork and sheeted veins. Carbon, oxygen, boron, lead, and sulfur isotope data (including SHRIMP microanalysis) from ore sulfides and alteration minerals (carbonates and tourmalines), in conjunction with tourmaline and pyrite compositional data, indicate that the ore fluid solutes were derived chiefly from sedimentary host rocks and not Neoproterozoic granitoids. A model for Telfer mineralization is proposed, such that granitoids act primarily as sources of heat that drive thermal convection cells in which heated saline formational-contact metamorphic fluids scavenge gold, copper, and sulfur from the surrounding sedimentary wall rocks at depth. This style of ore fluid generation shares some similarities with a convective porphyry copper (gold) model, although the lack of hornfelses, proximal granitoids, and types of alteration characteristic of porphyry copper deposits implies that the Telfer dome deposits did not form in the near-porphyry environment. These data do suggest, however, highly channelized fluid flow to the domal sites of mineralization after an initial period of extensive deep fluid circulation and leaching of sulfur and metals from the sedimentary wall rocks adjacent to the pluton(s). A regional-scale deep structure capable of focusing these deeper fluids to higher stratigraphic levels is the north-northwest-trending Telfer lineament upon which the Telfer dome is situated. Periodic reactivation of this structure, during the the Paterson orogeny, would allow for episodes of widespread fluid advection at depth under essentially lithostatic fluid pressures, followed by rapid ingress of fluids into the structure, triggered by a decrease in fluid pressure during reactivation.

Soil-vegetation relationships on the Dun Mountain Ophiolite Belt at West Dome, Southland, New Zealand

Abstract Six plant communities growing on soils associated with the Dun Mountain Ophiolite Belt on the western flanks of West Dome, Southland arc described. The most widespread communities within the study area are Nothofagus solandri var. cliffortioides forest, tall Leptospermum scoparium scruland, and an open Leptospermum scoparium shrubland and an open Leptospermum scoparium shrubland variant with the rare ultramafic endemic Celmisia spedenii G. Simpson. Less extensive are mixed divaricate shrubland and Chionochloa rubra (red tussock) grassland. Soil properties for each community were compared. Surface horizons under Nothofagus forest were the most acid and had the highest CEC and lowest base saturation of all the soils studied. In contrast surface horizon under open Leptospermum with Celmisia spedenii and divaricate shrubland had very high base saturation and were slightly acid. The former community, however, had soils formed mostly in in situ serpentinite in which the exchange complex was dominated b...

Stratigraphic and structural relations of the southern Dun Mountain Ophiolite Belt and enclosing strata, northwestern Southland, New Zealand

Abstract Three lithostratigraphic groupings are recognised to the northwest and southeast of the Five Rivers Plain in northwestern Southland: the lower Maitai Group consisting of the Greville, Little Ben, Tramway, and Upukerora Formations; the conformably underlying Dun Mountain Ophiolite Belt; and the Caples Group which lies to the east of the ophiolite and is separated from it by the Livingstone-Macpherson Fault System. On the northern side of the plain, the Maitai Group and ophiolite belt are deformed into a series of sinistral-verging steeply plunging folds which become extensively disrupted by left-lateral strike-slip faults in the east. The deformational pattern has resulted in acrossstrike repetition of these units and accounts for their apparent offset between West Dome and Lintley and the apparent thickening of the ophiolite belt between West Dome and Black Ridge. Sandstones of the Greville and Little Ben Formations are quartz poor and were derived from an undissected basic-intermediate volcanic ...

Celmisia spedeniiG. Simpson, an ultramafic endemic, andCelmisia markii, sp. nov., from southern New Zealand

Abstract The taxonomic status of Celmisia spedenii G. Simpson is examined. Plants from the type locality at West Dome in Southland are morphologically and ecologically distinct from plants in Fiordland and north-west Otago and are here recognised as two species, contra Given (1975). Celmisia spedenii G. Simpson occurs only on ultramafic soils in northern Southland, and is currently the sole taxon endemic to ultramafic outcrops in the southern half of the South Island. Celmisia markii is described as a new species. It is confined to areas above treeline in western Fiordland and northwest Otago, between Haast River and Caswell Sound.

Post-Laramide Tectonic History of the Eastern Uinta Mountains, Utah, Colorado, And Wyoming

Recent restudy of the Bishop Conglomerate, the subjacent Gilbert Peak erosion surface, and the Browns Park Formation helps clarify the post-Laramide history of the eastern Uinta Mountains, Utah, Colorado, and Wyoming. The Uinta Mountains are formed from a large, east-trending compound anticline that consists of two elongate domes aligned on a single east-west axis. The east dome, which rose higher than the west dome but is now lower and more deeply dissected, began to tilt and subside in late Oligocene time after Laramide compression had given way to middle Tertiary ex­ tension. The geometry of deformation is expressed in the attitude of the deformed Gilbert Peak erosion surface. Much of the deformation preceded deposition of the Browns Park Formation, but deformation was still in progress during and after deposition. The whole east dome was tilted eastward, lowering the Bishop Conglomerate below present drainage in a sag between the east end of the range and the town of Maybell, Colorado - an area that then became the locus of deposition for the Browns Park Formation. In addition, the north flank of the eastern Uinta Mountains was lowered and tilted southward and the south flank was tilted northward by a rotational movement that lowered the crest of the range about 1,570 m. Deformation drastically altered the drainage regime, reversing some streams and giving rise to others. Post-Browns Park movements continued locally into the Quaternary, generally coinciding with earlier-formed structures.

Celmisia spedeniG. Simpson andCelmisia thomsoniCheeseman - Two Rediscovered Species

Abstract Two species of Celmisia, C. spedeni G. Simpson and C. thomsoni Cheeseman, from the southern part of South Island, New Zealand have been rediscovered. Recently collected specimens and field-notes are used to provide detailed descriptions of morphology, geographic range, and habitat. The taxonomic position of each species is clarified. Celmisia spedeni (Fig. 1) has long been a source of confusion, almost all specimens so labelled in herbaria bear little resemblance to the type specimen, and most are referable to members of the Celmisia gracilenta complex. The only locality given by Simpson (1945) was West Dome, Garvie Mountains. Allan (1961) described the range as about latitude 42° to 45°30'S, and commented, “As understood here a rather polymorphic and plastic species with leaves usually much more rigid than those of C. gracilenta. It does not appear to occur within the wetter areas”. Allan, in his synopsis, linked it with C. gracilenta, C. insignis, C. alpina, and C. graminifolia. However, recent...

SOME OBSERVATIONS ON THE ALPINE VEGETATION OF MOUNT BIOTA (PAPUA)

The alpine vegetation of the West Dome (Mt Biota) of the Albert Edward Range is a combination of secondary and primary aspects which alternate mosaiclike and often form distinct seral vegetations. Towards the original shrubberies seral communities are growing with treeferns increasing in number towards the shrubberies' edges. A true alpine vegetation is found only towards the summit and consists of a wide open vegetation with few scattered plants.