Flat-topped Mountains Research Articles

Mapping Ethiopia’s Ancient Spirituality and Amba Gishen: From Sacralisation to Desacralisation

Amba Gishen, a cross-shaped mountainous place in the Southern Wollo Zone of Ethiopia, has for centuries been the site of a royal medieval prison thanks to its geographical isolation on the top of an amba (flat-top mountain). The first African narrative source of the deposition of a relic at Amba Gishen is cited in one of the most sacred Christian manuscripts of Ethiopia, the Mäshafä Tefut (fifteenth century). The presence of a holy relic, the fragment of the True Cross brought here by emperor Zara Yacoq in 1446, changed the meaning of that space for the Ethiopian people. The shifting topographies, from Mountain of the Royal Family to Mount of Myrrh, metaphorically referring to the myrrh associated with the Passion of Christ, have given way to a devotional focus and function, making Amba Gishen one of the holiest places in the land. As a place and site of confinement, however, the space inspired distorted imagery of Abyssinia, as conveyed by Anglophone travel narratives. The scope of the present research is to illustrate the dynamics in determining the sacralisation of spaces by their topographical morphology. This is achieved through the (re-)appropriation of natural spaces from the Ethiopian Orthodox Tewahedo Church and through resisting the desacralisation featured in Western narratives.

Litho-structural control on rock slope failures at Garmaksla, Billefjorden coastline, Svalbard

The eastern slope of Garmaksla, a flat-topped mountain at the western margin of Billefjorden, Svalbard, is affected by mass movements of different types. Rotational rock slides, rock fall and a rock avalanche affecting the coastal cliff are shallow surface expressions covering a larger rock mass instability that is bordered to the west by the Balliolbreen Fault. This structural feature is part of the Billefjorden Fault Zone and accommodated multi-phase deformation since Devonian time. Based on a comprehensive morpho-structural analysis, the mapped surface features and rock slope failures are explained by a compound rock slide model that reveals a litho-structural control on the type and mechanism of slope instability. The Balliolbreen Fault serves as an inherited zone of weakness that is reactivated as the rear rupture surface of the rock slide. In addition, favourably oriented bedding planes and pre-existing fault zones serve as prime conditioning factors for the compound rock slide. A postglacial age of at least 6 ka is derived from 14 C dated sediments of Garmaksla Lake, a perennial sag pond along the main scarp. Although the current state of activity of the compound rock slide is unclear, an increase of shallow slope instabilities is expected owing to climate warming.

Peneplains and tectonics in North-East Greenland after opening of the North-East Atlantic

Elevated plateaus with deeply incised valleys characterise elevated, passive continental margins (EPCMs) in all climate zones. These features are, however, a topic of debate regarding when and how the large-scale landscapes formed. We have investigated and mapped the partly glaciated landscape of North-East Greenland (70–78°N). The area consists of crystalline basement and Palaeozoic–Mesozoic rift basins, capped by Palaeogene basalts that erupted during the northeast Atlantic break-up. Our stratigraphic landscape analysis reveals a typical EPCM dominated by two elevated erosion surfaces, extending 200 km east–west and 900 km north–south. The low-relief Upper Planation Surface (UPS; c. 2 km above sea level) cuts across basement and Palaeogene basalts, indicating that it was graded to base level defined by the Atlantic Ocean in post-basalt times and subsequently uplifted. The UPS formed prior to the deposition of mid-Miocene lavas that rest on it, south of the study area. In the interior basement terrains, the Lower Planation Surface (LPS) forms fluvial valley benches at c. 1 km above sea level, incised below the UPS. The LPS is thus younger than the UPS, which implies that it formed post mid-Miocene. Towards the coast, the valley benches merge to form a coherent surface that defines flat-topped mountains. This shows that the LPS was graded to near sea level and was subsequently uplifted. Hence, both the UPS and the LPS formed as peneplains – erosion surfaces graded to base level. The fluvial valley benches associated with the LPS further indicates that full glacial conditions were only established after the uplift of the LPS in the early Pliocene (c. 5 Ma). The uplift of the LPS led to re-exposure of a Mesozoic etch surface. We conclude that episodes of late Neogene tectonic uplift shaped the stepped landscape and elevated topography in North-East Greenland.

The Pantepui in the Brazilian Amazon: Vascular Flora of Serra Do Aracá, a Cradle of Diversity, Richness and Endemism

Formed by tall flat-topped mountains known as tepuis, the Pantepui is an important center of vascular plant endemism and diversity in South America. In Brazil, the Pantepui is mostly on the border of Venezuela, and an isolated area, Serra do Araca, stands out as the tepui southernmost. In this paper we present a floristic survey of the vascular plants that occur on Serra do Araca, compare the richness to other tepuis, and commented on the conservation of Amazonian “campos rupestres”. Our dataset includes over 1600 records, either collected by us in three field expeditions, or by other botanists. A checklist with 436 species of vascular plants is provided. Our study also shows that among the 34 tepuis of the Pantepui, Serra do Araca ranks tenth in species richness and has 24 endemic species. Serra do Araca, like other tepuis, houses representatives of ancestral lineages of vascular plants of South America, showing how important tepuis are as cradles of lineages. Despite its importance for Amazonian biodiversity, Serra do Araca is one of the natural reserves in the Amazon with the highest number of requests for mining.

Plant communities and environmental factors in the Guayana Highlands: monitoring for conservation under future climate change

The Guayana Highlands (GH) constitute a highly diverse, but relatively poorly studied Neotropical biome, comprised of ∼50 flat-topped mountain summits (called tepuis). Previous studies based on warming forecasts for the region suggested that an upward displacement of environmental conditions of 500–700 m could occur by 2100, potentially resulting in the extinction of c. 50% of its endemic flora due to total habitat loss. To assess the ecological responses of the species to climate change, and select the appropriate conservation measures, long-term monitoring of the GH plant communities will be necessary. In this study, the baseline state for future comparisons was established for the best explored tepui in terms of its flora, Roraima-tepui (2810 m), through a floristic characterization of its different vegetation types. We also identified the environmental gradients underlying the major plant communities, and assessed the effects of human activities on the chemistry of soils and water at three field camps. Our results yielded five main community types: three meadows, one shrubland, and one forest, with their corresponding diagnostic species. The herbaceous communities were mainly influenced by the presence of flat sandy soils, with varying flooding capacity. Shrublands and forests were characterized by irregular organic soils with very low pH. Finally, pH values below 3 were measured on an organic soil of a field camp, although further studies will be necessary to attribute this deviation to human activities.

Identification of peneplains by multi‐parameter assessment of digital elevation models

ABSTRACTThe concept of peneplains has existed since the end of the nineteenth century. Typical peneplains are elevated geomorphological features with a low relief surface on top. They may be tilted due to tectonic activity or intersected by evolving erosion. Until now neither a standardized definition for peneplains, nor an established procedure to identify and quantify well preserved peneplains as prominent landforms existed. At present the global availability of homogeneous digital elevation models (DEMs) provides an accurate characterization of the morphology of the Earth surface. In this study a new, numerical, DEM‐based fuzzy‐logic approach is presented for the delineation of peneplains solely from a morphological perspective. The approach is based on a morphometric analysis of the 90‐arcsec Shuttle Radar Topography Mission (SRTM) DEM. Four critical parameters are employed which are implemented within a geographic information system (GIS). The parameters for the correct and unambiguous description of a ‘flat top mountain’ are: (i) slope, (ii) curvature, (iii) terrain ruggedness index, and (iv) relative height. The approach was developed using a test area in the central Tibetan Plateau, which is characterized by representative and well preserved peneplains and for which additional field data were collected. In order to verify the method, peneplains were delineated in different regions with various geological settings for which potential peneplains were already described in the literature. The results from the Appalachian Mountains, Andes, Massif Central, and New Zealand confirm the robustness of the proposed approach. Copyright © 2015 John Wiley & Sons, Ltd.

Establishing a baseline of plant diversity and endemism on a neotropical mountain summit for future comparative studies assessing upward migration: an approach from biogeography and nature conservation

Climate change is forcing many plant species to shift their range in search of adequate environmental conditions, being localized endemic species particularly at risk on mountain summits. The Pantepui biogeographic province, a set of flat-topped mountain summits (called tepuis) of northern South America, contains both high plant diversity and a high degree of endemism. Previous studies based on warming projections for the area suggested that half of the Pantepui endemic flora would disappear due to habitat loss by 2100. In this study, we selected one of the best-explored tepuis, Roraima-tepui, to establish the baseline of diversity and endemism for comparisons with historical data and future monitoring surveys, aimed at testing the hypothesis of upward migration of plants in response to global warming. We also analysed floristic and physiognomic features of the Eastern Tepui Chain (ETC, the mountain range where Roraima is located), and the phytogeographic patterns of both the ETC and Pantepui. The Roraima summit contains 227 species, including 44 new records, 13 exotic species (some of them with high invasive potential), and at least one species new to science. At the ETC level, Roraima is the tepui with highest species richness and degree of endemism, and shows a relatively high floristic similarity with Kukenán and Ilú. Herbaceous species dominate over shrubs on these tepuis, Tramen and Maringma, whereas on Yuruaní, Karaurín and Uei, they reach similar abundances. At the Pantepui level, endemic species have highly localized distribution patterns (17% local endemics). Conservation opportunities are evaluated in light of these results.

Butterflies Recorded on Flattop Mountain, Anchorage, Alaska

Eleven species of butterflies were recorded on Flattop Mountain, Anchorage, Alaska, during a four-day period in July 2006: Colias philodice vitabunda (Clouded Sulphur), Pieris angelika angelika (Arctic White), Lycaena dorcas arcticus (Dorcas Copper), Plebejus glandon bryanti (Arctic Blue), Plebejus idas alaskensis (Northern Blue), Plebejus optilete yukona (Cranberry Blue), Boloria charliclea butleri (Purplish Fritillary), Boloria alaskensis alaskensis (Mountain Fritillary), Speyeria mormonia bischoffii (Mormon Fritillary), Oeneis bore mckinleyensis (White-veined Arctic), and Carterocephalus palaemon skada (Arctic Skipperling). Based on previously published distribution maps, the records for Plebejus idas and P. optilete represent range extensions; P. optilete was relatively common in sheltered valleys on the mountain.

Anthropology of displacement: Case of conservation induced displacement and its impact on indigenous people in Simlipal Tiger Reserve, Odisha

Displacement is a growing concern in globalized world; it is said that for any development project the cost has to necessarily be borne by the displaced and affected population. In the state of Odisha, particularly where displacement due to development projects are rampant, of late the foreign investors have identified the low, flat-topped mountains buried with some high deposits of the best quality bauxite in the world. According to estimates, the buxite makes more than two trillion dollars, that is, twice the value of India's GDP, $1.243 trillion in 2009 (Padal and Das 2010) Therefore, to construct infrastructural projects such as multipurpose river valley, mining, industrial, sanctuaries, national park etc.) in the forest areas, the state at present has been diverging maximum forest lands, while displacing more than lakhs of age old forest dwellers. They are the ones who pay the price and get displaced from everything attached to them. This paper tries to explore the impact of conservation induced displacement in Simlipal Tiger Reserve and the Resettlement & Rehabilitation practices in the Kapanda Banbasa & Ambadiha resettlement colony using some of the anthropological methods and approaches.

Parakari a New Genus of the Family Baetidae (Insecta: Ephemeroptera) from Guyana Highlands

Baetidae is one of the most diverse families of Ephemeroptera. In South America this family now encompasses 27 genera and more than 130 species. The Guyana region is known for its extraordinary diversity and high level of endemism, which is, above all, remarkable at the tops of the isolated flat-topped table mountains – tepuis. Recently various international speleological expeditions to Churí-tepui explored the cave systems of this mountain. Here we describe a new genus of Baetidae recently found during the mentioned expeditions to Churí-tepui and Auyán-tepui. Parakari n. gen. can be distinguish from the other genera of this family, among other characters, in the nymphs by the absence of abdominal gills I, tarsal claws with subapical denticle larger than the others, right mandible with prostheca bifid and pectinate and with incisors positioned in obtuse angle to mola area, lingua with a tuft of setae, segment II of maxillary palpi with a concavity and a hole apically and segment II of labial palpi with a strong distomedial projection. In the adults the hind wings are absent and genitalia with segment II of forceps with a constriction, segment III elongate and long. Two new species are included in this genus; each one was collected at different tepui. A key and illustrations are included.

Colluvic Umbrisols As a Result of the Erosion Process of Rolling and Hilly Country in Agricultural Area

Abstract Agricultural activity, especially agricultural mechanization, leads to acceleration of erosion in rolling and hilly country. The level of the erosion process, already during territorial observations, may be assessed by the thickness of the humus horizon. In the vicinity of Bytów, the deluvial humus horizons have even achieved thickness of 100 cm. These horizons are also richer in organic matter than humus horizons located on flat-topped mountains and mountain sides. Deluvial horizons are characterized by a somewhat less acid reaction, sometimes even neutral, and somewhat greater dehydration of the sorption complex by alkaline cations.

Landscape metrics indicate differences in patterns and dominant controls of ribbon forests in the Rocky Mountains, USA

AbstractQuestion: Do landscape metrics reflect differences in dominant factors controlling ribbon forest patterns among sites?Location: West Flattop Mountain, Glacier National Park, Montana (Flattop); Medicine Bow Mountains, Wyoming (Medicine Bow); Park Range, Colorado (Park Range).Methods: High‐resolution aerial photography was used to delineate ribbon forest patches, and to calculate landscape metrics to distinguish between long, narrow, regular patterns expected from strong microtopographic control, and smaller, more compact, and variable patterns expected from wind‐snowdrift interactions.Results: All but two metrics were significantly different (P<0.05) among the three sites. The rank and magnitude of differences indicated that ribbons at Flattop and Park Range are more similar to each other than to those at Medicine Bow. Flattop ribbons were also more elongated, narrower and less variable than those at Park Range, suggesting differences in the type and strength of structural control. Previous research showed that Flattop ribbons occupy regular lithologic ridges, while our observations of ribbons and analysis of geologic maps suggests weaker and less consistent microtopographic control at Park Range, and dominant wind‐snowdrift interactions with little to no microtopographic influence at Medicine Bow.Conclusions: Landscape metrics indicate differences in pattern among sites that reflect differences in dominant factors influencing ribbon forest development and maintenance. Explanations of ribbon forest dynamics are site‐specific and are more complex than is currently recognized. The sites vary in the level of endogenous versus exogenous control of ribbon patterns, and consequently in the sensitivity of this phenomenon to climate.

Herbaceous ecosystems on the Guayana Shield, a regional overview

AbstractAims Ecosystems dominated by herbaceous plant communities are amongst the most diversified landscape units in the Guayana (Guiana) Shield region. This paper aims to present a synthetic overview of the wide array of herbaceous ecosystems found in the region in an attempt to furnish a more concrete baseline for a better understanding of the pattern of variation, and to clarify some of the differences that occur in the vegetation of the area.Location The Guayana Shield region, and the area of north‐eastern South America extending between the Orinoco River to the North and the Amazon River to the South (c. 8° N to 1° S).Methods Floristic and ecological field data gathered from over 300 study sites located at different altitudinal levels in the Venezuelan Guayana and the northern Brazilian Amazon are evaluated and interpreted in the light of personal observations and existing literature.Results The diversification pattern includes physiognomic as well as floristic variation and shows two opposing tendencies in relation to their altitudinal location: grass‐dominated meadows (savannas) predominate in the macrothermic lowlands, whereas non‐gramineous, broadleaved herbaceous communities are dominant in the mesothermic highlands of the Guayanan mountains. In detail, the biogeographic region of Guayana (Guiana) consists of three easily recognized altitudinal levels, each of which contains a highly characteristic set of landscape types with their associated ecosystems and endemic plant communities. Between 0 and c. 500 m a.s.l. the extensive macrothermic (mean annual temperature, MAT > 24 °C) lowlands are found, where an enormous – still largely unexplored – diversity of forest types represents the main plant cover of the plains, peneplains, glacis and piedmont slopes. Sparsely distributed within this forest cover are numerous herbaceous ecosystems, ranging from true grass savannas to unusual and poorly understood meadows developed on extremely oligotrophic white sandy soils dominated by non‐gramineous genera of Rapateaceae and Xyridaceae. In the intermediate submesothermic (MAT 24–18 °C) Guayana uplands, extending roughly between 500 and 1500 m a.s.l., the grasslands of the Gran Sabana in south‐eastern Venezuela reach their upper altitudinal limit. At the same altitudinal level, however, several distinct herbaceous communities are found, in which other genera of Rapateaceae, together with Bromeliaceae and Xyridaceae, are predominant. Finally, at the uppermost altitudinal level, i.e. in Pantepui (which includes the characteristically flat topped mountain summits (tepuis) of the Guayana highlands) between 1500 and 3000 m a.s.l., encompassing a range of meso‐ to submicrothermic temperature regimes (MAT 18–8 °C), the extensive herbaceous ecosystems are developed either on deep organic soils (peat) or on open sandstone surfaces. These high‐tepui meadows present a considerable physiognomic diversification and are formed by a variety of endemic genera of the Rapateaceae, Bromeliaceae, Xyridaceae, Eriocaulaceae and Cyperaceae families, often dominated by locally endemic species on each of the larger tepui massifs. In contrast, grass dominated plant communities are very rare and restricted to only a few high‐tepui sites.Main conclusions A marked floristic and ecologic differentiation of herbaceous ecosystems in the Guayana Shield region can be recognized. The ecological differentiation results primarily from the wide spectrum of variations in the substrate found at the various altitudinal levels of the Guayana Shield region. A possible explanation for the present‐day pattern of herbaceous vegetation types may be the following: Non‐gramineous meadows representing ancient species pools of Guayana‐centred families had evolved successful colonization strategies in occupying extremely nutrient poor sites at all altitudinal levels. In contrast, the more modern grass savannas, which preferentially occupy the peripheral Guayana landscapes, are restricted to richer soil conditions with better internal drainage and water retention conditions.

Lithologic, structural, and geomorphic controls on ribbon forest patterns in a glaciated mountain environment

So-called “ribbon forests” have been attributed to snowdrift patterns and fire history without reference to geomorphology [Vegetatio 19 (1969) 192.]. This paper illustrates how site conditions of geomorphology and geology explain the origin of ribbon forests. In Glacier National Park, MT (USA), regional tectonic uplift associated with the Laramide Orogeny produced structural features that amplify lithologic differences. Pleistocene glaciation scoured deeply along the strike of bedding planes, highlighting this pattern and in some cases producing fine-scale parallel finger lakes between forested ribbon strips. Twelve ribbon forest sites on both sides of the Continental Divide were closely studied on stereoscopic aerial photographs, and several of these sites were examined in the field or from helicopter overflights. In all cases, geologic and geomorphic conditions explain the location and distribution of the ribbon forests. Change-detection of the distribution of trees versus nontree-covered surfaces in an area of ribbon forest on Flattop Mountain, a complex uplifted synclinal structure, was undertaken using panchromatic, low-altitude aerial photographs from 1966 to 1991. Areas changed from forest to meadow and from meadow to forest in roughly equal amounts in a generally random spatial pattern. No evidence was seen to suggest that the creation of one ribbon eventually created another downwind, as suggested by Billings. Aerial photograph interpretation, field examination and soils analyses of forest ribbons and adjacent unforested meadows clearly illustrated that trees occupy higher, parallel to subparallel, well-drained sites where the spatial pattern is in turn a distinct reflection of the spatial pattern of structure and stratigraphy. Meadows occupy topographically lower positions between ridges where erosion along bedding plane strike was concentrated. Topography sets conditions that allow tree growth in certain locations while precluding it in immediately adjacent areas. Ribbon forests there are thus a spatial manifestation of the interaction between structure, lithology, and topography.

The Game Drives of Rocky Mountain National Park

Communal game drives were a cost-effective way for pedestrian hunters to obtain large amounts of meat and hides. Although once common across North America, nearly all traces of game drives have been removed by modem agriculture practices. Thus, the two high-altitude sites in Colorado reported on in this volume are significant because their features are largely intact and their occupations can be reliably dated. Chapter 1 is a thorough overview of ethnohistoric game drives and hunting practices across North America. Chapter 2 focuses on the Trail Ridge Game Drive site located at the forest-tundra ecotone at 3,4653,500 m asl. Natural topography and constructed stone walls were employed to funnel herds to hunters waiting in blinds. Pellet-group studies suggest that the intended prey were elk or mule deer. Projectile points indicate intermittent occupation between the late Paleoindian and late prehistoric periods. Charcoal from two blinds was radiocarbon dated to 4590 ? 60 B.P. (Beta-85363) and 2610 ? 60 B.P. (Beta-75998), while granite weathering dates indicate that the walls were built or repaired numerous times. Chapter 3 discusses the extensive Flattop Mountain Game Drive site situated at 33503720 m asl. Features include 14 stone drive walls, 848 cairns, 90 blinds, and a possible hunter's bed. Numerous projectile points ranging from Paleoindian through protohistoric styles have been recovered in this vicinity since the 1920s, and these, as well as all other lithic tools, pottery and debitage, were analyzed. Fifteen radiocarbon samples collected within blinds date between ca. 4300 and 200 B.P. Chapter 4 places the two sites within a continental perspective. Both were used intermittently beginning in the Paleoindian period, and their features were maintained by various parties up to the protohistoric period. The appendixes address lichenometry, granite weathering, radiocarbon dating, pellet-group surveys, early artiay be disap ointed howev r, at the inco lusive i g. They may also be frustrated, as I was, by its a tic and repeti ve style and its limited and idiosynic selection among rel vant sources. fact collections, and descriptive data for all projectile points. This report is well organized and the numerous photographs, drawings, and graphs make it a valuable addition to the library of anyone interested in hunter-gatherer ecology in North America.

Growth and Vegetation History of Alpine Mires on the Old Man Range, Central Otago, New Zealand

Alpine mires are widespread on the flat-topped mountains of Central Otago, the driest and most continental region in New Zealand. Peat profiles, pollen analyses, and radiocarbon dates are presented for several mires from the Old Man Range as part of a study of the environmental history of this region. Precipitation in the early Holocene may have been up to 30% less than that of the present, and peat accumulation was restricted to topogenous mires. Alpine ombrogenous bogs began growth at ca. 7500 BP. At the same time, forest and tall scrub spread in the adjacent lowlands in response to increasing rainfall, replacing grassland-shrub-lands. Peat accumulation was slow and episodic and declined to very low rates after 3000 BP, probably as a result of cooler winters and drier summers. Low levels of natural fire occurred throughout the Holocene. However, from 750 BP onwards, lowland forest and scrub was severely reduced, subalpine shrubland declined, and snow tussock grassland increased markedly as fires lit by Polynesian hunters swept the region. From A.D. 1850 onwards, European pastoralists introduced sheep and increased the burning of the uplands to improve grazing. Peat accumulation increased in topogenous mires after burning and grazing of the alpine grassland, possibly because of accelerated runoff and nutrient input.

A Deviant Expression of Sphagnum tenerum from the Virginia Tidewater and the Dominican Republic

Sphagnum tenerum var. virginicum, described from coastal Virginia and the Domin- ican Republic, differs from var. tenerum in having branches infascicles of 4-5 and pores consistently in the epidermal cells of stems. Sphagnum tenerum Sull. & Lesq. is common and wide-ranging along the Atlantic Coastal Plain of the eastern United States. It occurs less commonly in the uplands of North Carolina and Tennessee, and perhaps elsewhere inland, and as a rare disjunct in northern South America. The original collection was made by Leo Lesquereux in northern Alabama and issued in 1857 as no. 11 in the first edition of Sul- livant and Lesquereux's Musci Boreali-Americani. The locality and habitat data are skimpy: Ad ri- vulorum per montes Raccoon Alabamae. The Raccoon Mountains were designated as the Sand and Raccoon Mountains on older maps but now merely as the Sand Mountains. They comprise a much dissected plateau that is a spur of the greater Cumberland Plateau. The dissections create a series of more or less flat-topped mountains, with an average elevation of about 1,500 ft. above sea level, rising from a base of 300-400 ft. The soil layer is thin, and there is considerable exposure of sand- stone. The summers are hot and dry, but in late fall to spring there are seasonal rivulets. The Sand Mountains extend southwesterly from Dade Coun- ty, Georgia, through Dekalb and Marshall counties, Alabama, ending near Albertsville. The junior au- thor has collected in the area on several occasions and found Sphagnum tenerum to be rather plentiful in both Dekalb and Marshall counties. Lesquereux's route is uncertain, but he could have collected S. tenerum in either county. The species occurs on nearly all peaks in the area, generally on thin soil seasonally wet from seepage at margins of vegeta- tion mats forming islands on exposed sandstone and also, as Lesquereux noted, along rivulets. In Dekalb Co. S. tenerum occupies the edges of boggy habitats that support Sarracenia, Drosera, and other plants

Age progressive volcanism in the Tasmantid Seamounts

The Tasmantid Seamounts comprise a northerly trending linear chain of submarine volcanoes that extend over more than 1300 km in the middle of the Tasman Basin, located to the east of the Australian continental margin. The volcanoes are situated upon deep oceanic crust of Late Cretaceous/Early Cenozoic age. Several of the volcanoes were built from sea floor depths of more than 4000 m to above sea level, and were then eroded to flat-topped mountains which have subsided to depths as great as 400 m. Basalt samples dredged from Gascoyne, Taupo, Derwent Hunter, Britannia and Queensland Seamounts have been dated by the K-Ar and 40Ar/ 39Ar methods, yielding results in the range 24 to 6.4 Ma, Early to Late Miocene. A progressive younging of the volcanism southward along the seamount chain at an average rate of 67 ± 5mm/year is indicated. The predicted present position of the volcanic focus is at 40.4°S latitude, and between 155° and 156°E longitude, virtually coincident with the epicentre of a recent large earthquake. These results provide strong evidence that the Tasmantid Seamounts represent a hotspot track, effectively recording motion of the Australian plate across the sublithospheric mantle source region for the volcanism. Comparison with results from hotspot traces on the same plate and on the African plate further demonstrate that these hotspots provide a useful frame of reference for plate motions, and that relative movement between individual hotspots must be less than about 5 mm/year.

Geology of Natural Gas in Arkansas Valley, Arkansas: ABSTRACT

The Arkansas Valley is an east-west trending synclinorium bounded on the north by the Ozark uplift and on the south by the Ouachita Mountain anticlinorium. The Valley is an eastward extension of the McAlester basin of southeastern Oklahoma. Pennsylvanian Atoka sediments form the principal outcrops in the Arkansas Valley. The Atoka measures 20,000 feet or more near the Ouachita front. Post-Atoka Pennsylvanian sediments (Hartshorne through Boggy) aggregate 3,000 feet in the western part of the Valley. Cambrian through Pennsylvanian Morrow sediments thicken southward from 5,000 feet or less in the Ozarks to an estimated 25,000 feet of correlatives in the Ouachitas. Little is known of the pre-Pennsylvanian section in the Arkansas Valley because of inadequate drilling densities. Morrow shales, sandstones, and subordinate limestones were deposited mainly under shallow-water marine conditions. Morrow facies changes occur southeastward in the subsurface and eastward on the outcrop. Meagerly fossiliferous dark shales and lenticular sandstones constitute the Atoka in the Valley. Regional Atoka facies changes have not been observed. Numerous east-west trending anticlines and synclines have surface expression in the Arkansas Valley. Many are faulted parallel with their axes. Steeply dipping flanks of the folds are indicated on the surface mostly by sharp ridges, and open synclines are expressed by flat-topped mountains. Folds in the southern part of the Arkansas Valley are tight and asymmetrical, with steeper north flanks. Dips of 50° or more are common. Progressively northward, the structures are less tightly folded and more nearly symmetrical. The folding was initiated during the Ouachita orogeny as early as Middle Pennsylvanian time and terminated after Boggy time. A major fault system marks the structural boundary between the Valley and the Ozarks. These faults are normal and predominantly downthrown toward the south with displacements up to 3,000 feet. The structural boundary between the Arkansas Valley and the Ouachitas is more difficult to define. Faults near the Ouachita front are predominantly downthrown toward the north. High-angle reverse faults and low-angle thrusts are the common types in that region. Major faulting in the Arkansas Valley was not initiated until Atoka time or later. Only dry gas is produced in the Arkansas Valley, chiefly from the Atoka but increasingly from the Morrow. The gas is sweet, generally high in methane and low in nitrogen. Currently there are 41 designated gas fields in the Arkansas Valley. Daily production averages 50 million cubic feet. Cumulative production since the first commercial well in 1902 totals 300 billion cubic feet. Reserves are in excess of 800 billion cubic feet. Pennsylvanian production is expected to be expanded both eastward and southward in the Arkansas Valley. Pre-Pennsylvanian sediments, especially the Mississippian End_Page 126------------------------------ and Arbuckle correlative sections, are prospective targets for oil or gas. End_of_Article - Last_Page 127------------

5. The 200-Inch Hale Telescope

One of the first problems investigated at the start of the 200-inch telescope project was that of a suitable site. Extensive tests of climatic and ‘seeing’ conditions at some dozens of sites in the semi-arid south-western part of the United States led to the selection of Palomar Mountain. This is a flat-topped mountain some 10 x 20 km. in extend located 150 km. south-east of Los Angeles. The altitude of the telescope is 1700 m. Temperature conditions are very stable with a diurnal range of about 6° C. and observing conditions during the past two years have proved to be at least as satisfactory as those at Mount Wilson.