Stony Mountain Research Articles

섬 어촌 풍도의 지역재생과 어민역량 강화 사례 연구

Pungdo, an island fishing village located in Ansan, Gyeonggi-do, is a representative island that is undergoing population extinction. Pungdo is an island composed of stony mountains, made of pebbles and rocks, and has no beach, and fishing is not possible due to poor fishery resources. Wildflowers are outstanding from February to April, but due to the short period, tourism resources centered on wildflower enthusiasts are also poor. On the other hand, there are not many local fishermen and there are few outside tourists, so it has the advantage of less damage to resources and quietness compared to other islands. This study is based on literature research and the contents of listening to various opinions through in-depth interviews with fishermen. In addition, the strengths and weaknesses, opportunities and threats of Pungdo were analyzed through the human geography characteristics and SWOT analysis of Pungdo, and directions were presented. The sustainability of Pungdo is presented through five proposals to strengthen the fishermen's competency of Pungdo. Pungdo is a typical case of Korean island fishing villages represented by low fertility and aging population, and through this, we will analyze the case of island fishing villages and suggest alternatives and measures to make it a prosperous island fishing village with contents.

<strong>A broadly sampled 3-loci plastid phylogeny of <em>Atraphaxis</em> (Polygoneae, Polygonoideae, Polygonaceae) reveals new taxa: II. <em>Atraphaxis</em> <em>selengensis</em> <em>spec. nov.</em>, and <em>A. davurica</em> Jaub. & Spach from Russian Transbaikalia</strong>

Maximum Likelihood (ML) and Bayesian analyses (BI) applied for 3-plastid loci (cpDNA trnL(UAA) intron, trnL–trnF IGS, and rpl32–trnL(UAG) IGS regions) / 55 tips of Atraphaxis revealed a subclade of two endemics from Transbaikalia (Dahuria) which are often mistaken for A. pungens and A. frutescens but phylogenetically distant from both. Atraphaxis selengensis is a species new to science which inhabits dune sands along the Selenga and Chikoy rivers and has specific morphology of perianth, fruits, ochreas, leaf blades, and pollen. Atraphaxis davurica inhabits stony mountain steppe in Buryatia and Chita region and differs from A. pungens and A. frutescens by longer ochreas, fruits, styles and stigmas extended to ends. Two varieties recognized by Ledebour in plants from Russian Transbaikalia have no clear morphological and molecular distinctions, but the plants from Khentei-Chikoy Highlands subtly differ in leaf ratio (length/width), bark colour, and a single-nucleotide substitution in trnL–F region. These plants are described as A. davurica var. chikoensis var. nov. Morphological descriptions of A. selengensis and A. davurica are supplied with LM and SEM images and a distributional map. Atraphaxis frutescens and A. pungens are absent from Russian Transbaikalia but distributed in Altai, Tuva, Khakassia, Mongolia and China.

Late Ordovician climate and sea-level record in a mixed carbonate-siliciclastic-evaporite lithofacies, Williston Basin, USA

The Late Ordovician late Katian was a period of generally warm, transitional greenhouse to icehouse climate with sea-level oscillations dominated by moderate-amplitude eustasy. This study aims to improve the understanding of the climatic and sea-level fluctuations prior to the end-Ordovician glaciation, using a comprehensive core, wireline log, and thin-section dataset spanning the topmost Red River-Stony Mountain Formation within the subsurface of North Dakota, Williston Basin, North America. Eleven facies are identified, interpreted, and grouped into four facies associations, including salina to peritidal evaporative, restricted-marine subtidal, open-marine subtidal, and open-marine deeper water. Stratigraphic trends, basin-wide facies variations, and correlation of individual surfaces for ~380 km across the study area, suggest that the facies were deposited under different climatic and sea-level regimes as part of the long-term Stony Mountain sequence. The sequence (37–52 m) is bounded by anhydrites (basin center) and their correlative thin exposure-related breccias (updip proximal basin), and contains a set of high-frequency sequences (HFS; 2–26 m) that can be traced across the study area. The lowstand systems tract (LST) anhydrites formed in a shallow and well‑oxygenated setting under an arid climate during relatively short periods of the basin restriction. The sea-level rise during the early transgressive system tract (TST) resulted in a higher evapotranspiration rate and an increasingly humid climate that peaked during the late TST with the input of siliciclastics off the Transcontinental Arch. The increased precipitation and runoff resulted in quasiestuarine circulation. Return to semi-arid conditions characterizes the highstand systems tract (HST), with increasingly more restricted, shallow-marine and oxygenated setting with antiestuarine circulation. The work provides insight into the interaction of siliciclastic input, climate, and sea-level changes on depositional dynamics and sequence architecture of a mixed carbonate-siliciclastic-evaporite succession that formed in a tropical epicontinental basin setting prior to the end-Ordovician glaciation.

A New Species of the Genus Conophyma Zubovsky (Orthoptera, Acrididae) from Tajikistan

A new species Conophyma nazarovaesp. n. (Orthoptera, Acrididae) is described from Tajikistan (Western Pamirs, Rushan Mt. Range). The species was found on the stony mountain slopes in the semi-savanna zone at an altitude of 3000–3300 m.

“I Know It’s Not Saving a Life, but I Know I’m Doing Good…”: The Peer Offender Prevention Service (POPS) at Stony Mountain Institution, Canada

ABSTRACT There is a growing literature on prisoner peer support and mentoring to which this work contributes. This paper examines a form of prisoner peer mentoring at Stony Mountain Institution in the province of Manitoba, Canada. The Peer Offender Prevention Service (POPS) employs prisoners to provide support and mentorship for other prisoners throughout the prison. Based on interviews with POPS members and the POPS coordinator, this paper examines how the POPS initiative works and how POPS members feel about their experiences. We show that the work of POPS members is based on relationships, emotions, listening, compassion, and mutual aid among prisoners, all of which tends to be inhibited by the prison. This paper also analyzes the barriers that POPS members encounter and the challenges that the POPS initiative faces in the prison. In our discussion, we invoke the idea of fast policy to caution against the implementation of such programs in situations where sufficient resources, continuity, mentorship, and commitment are not established.

New Constraints on the Timing and History of Breccia Dikes in the Western San Juan Mountains, Southwestern Colorado

In the western San Juan Mountains, clastic (breccia) dikes crop out in Paleozoic to Cenozoic rocks. The dikes are tabular to bifurcating masses up to several meters thick and are exposed on northwest or northeast trends for up to several kilometers. They are matrix- to clast-supported with angular to rounded pebble- to boulder-sized fragments that in most dikes are dominated by Proterozoic igneous and metamorphic rocks. U-Pb age analyses (n = 3) reveal a range of zircon ages in all samples with several containing high proportions of 1820 to 1390 Ma zircons. The majority of Proterozoic zircons are interpreted as direct contributions from basement rocks during breccia dike formation and emplacement. Field relations and U-Pb zircon analyses reveal that breccia dikes formed in intervals from 65 to 30 Ma (Ouray) and 27 to 12 Ma (Stony Mountain); some dikes are closely allied with mineralization. The dikes formed at depths over 500 meters where Proterozoic basement was fragmented, entrained, and transported to higher structural levels along with pieces of Paleozoic to Cenozoic rocks. A close spatial relationship exists between breccia dikes and latest Mesozoic to Cenozoic plutons. This is best exemplified near Ouray where clastic dikes share similar trends with ~65 Ma granodiorite dikes, and there is a clear transition from intrusive rocks to altered-brecciated plutons, and finally to breccia dikes. The preponderance of evidence supports breccia dike formation via degassing and explosive release of CO2-charged volatiles on deep fractures related to emplacement of 70 to 4 Ma plutons or mantle melts. In addition to breccia dikes, several post-80 Ma events in the region involved explosive release of volatile-charged magmas: 29-27 Ma calderas, ~25 Ma diatremes, and ~24 Ma breccia pipes. Causal factors for production of these gas-charged magmas remain poorly understood, but partial melting or assimilation of altered and metasomatized lithospheric mantle could have played a role.

Geochemistry of Late Ordovician dalmanelloid brachiopods from Laurentia: testing the effects of paleolatitudinal gradient

Dalmanelloid brachiopod shells were collected from the Upper Ordovician Lexington Formation (lower Katian) of Kentucky, Sheguindah Shale (middle Katian) on Manitoulin Island, Ontario, and the Stony Mountain Formation (upper Katian) in the Winnipeg area, Manitoba. They were investigated to test the hypothesis of paleo-latitudinal zonation of the shelly benthos. A multi-technique approach was applied to evaluate the petrographic and geochemical (isotopic and elemental) preservation of the secondary layer of shells. Preliminary conventional microscopy, cathodoluminescence (CL), and scanning electron microscopy (SEM) confirmed the retention of primary shell ultrastructure (prismatic low-Mg calcite). The geochemical diagenesis proxies (e.g., Sr, Mn, Fe, and ΣREE) show insignificant correlations with the δ18O and δ13C values, thus supporting the preservation of at least near-primary geochemical compositions. Among the three lots of shells, the mean δ18O value is the highest in those from the Lexington Formation (–4.5‰ ± 0.3‰ VPDB), lowest from the Stony Mountain Formation (–6.8‰ ± 0.4‰ VPDB), and intermediate from the Sheguindah Shale (–6.0‰ ± 0.8‰ VPDB). The relative gradient in δ18O increase is in agreement with the paleo-latitudinal gradient, with Kentucky in subtropical, southern Ontario in mid-tropical, and southern Manitoba in subequatorial latitudes. The Lexington Formation shells also have the highest mean δ13C value (0.8‰ ± 0.2‰ VPDB) and relatively high P contents (170 ± 27 ppm), suggesting higher organic productivity, which is consistent with previous interpretation of frequent upwelling of nutrient-rich cool waters along the southeastern margin of Laurentia during the Katian. The Lexington shells also have a lower mean Th/U (0.6 ± 0.6), which is consistent with blooming organic productivity that likely led to more consumption of oxygen in the water column.

Quantitative interpretation using conventional and facies-based pre-stack inversion — A thin dolomite reservoir case study in Cabin Creek Field, Williston Basin

Cabin Creek Field, on the southwestern flank of the Williston Basin, is one of 14 hydrocarbon fields within Cedar Creek nticline. The field was initially discovered in May 1953 and developed by Shell starting with primary production followed by water flooding beginning in the late 1950s. In 1999, Encore purchased Shell’s interests and focused on infill drilling. In 2010, Denbury Resources acquired Encore giving it the potential to undertake enhanced oil recovery operations in the Rockies. Production is from the Ordovician Red River, Silurian Stony Mountain, Interlake, and Mississippian Mission Canyon Formations. The objective of the Cabin Creek reservoir characterization is to document reservoir heterogeneity within the target reservoirs and to facilitate development of the CO2 flood. The goal of this integrated case study is to generate a representative reservoir model that combines the structural framework and porosity prediction within the Red River Formation. This paper focuses on utilizing and comparing conventional and facies-based pre-stack inversion methods to characterize the porosity at the reservoir level.

Ichnology and depositional environments of the Upper Ordovician Stony Mountain Formation in the Williston Basin, Canada: Refining ichnofacies and ichnofabric models for Epeiric Sea carbonates

Ordovician epeiric sea carbonates in intracratonic basins of Laurentia are enigmatic due to their unique depositional settings and the absence of modern analogs. Integrated ichnologic and sedimentologic analysis of the Upper Ordovician Stony Mountain Formation in the Williston Basin of Canada allows recognition of neritic-marine, nearshore-marine, open-lagoon, restricted-lagoon, peritidal sand-shoal and peritidal-flat subenvironments. The Cruziana ichnofacies occurs in neritic (between fair-weather and storm wave bases) and nearshore (around fair-weather wave base) marine environments. The depauperate Cruziana ichnofacies is present in open- and restricted-lagoon environments, indicating a shift from fully marine to stressed conditions. In the open lagoon, composite ichnofabrics related to omission surfaces illustrate the low rates of background sedimentation interrupted by event deposition and early cementation, illustrating the Glossifungites and Trypanites ichnofacies. The decreased size of discrete burrows in the restricted lagoon is attributed to reduced oxygenation under stagnation rather than hypersalinity. The peritidal complex includes high-energy sand shoals and low-energy tidal flats. Only monospecific colonization took place sporadically in associated subtidal environments within the peritidal complex deposits.

ORNAMENTAL PLANTS OF CHECHNYA AND ITS ADJACENT AREAS

The aim of the research is to summarize the scattered information about the types of decorative flora of the Chechen Republic and adjacent territories; to identify highly resistant ornamental plants for cities and settlements of the North Caucasus and other territories of Russia. Discussion. Currently, in a variety of botanical gardens of the North Caucasus grows a large number of decorative plant species, widely used in green construction. However, not all species posses the quality to sufficient resist unfavorable conditions of the changed abiotic and biotic environment. Among the studied, the most valuable and promising for widespread introduction are the species of more than 122 taxa, the decorative effect of which is preserved throughout the year with no signs of aging. Many examples of the targeted use of herbs, tree species, lianas, bulbous plants were cited in the research. We give a large list of Caucasian species for growing on lawns, flowerbeds, flower gardens, alpine and stony mountains, roadsides and parks, urban parks, squares and alleys as a type of gardening. Their decorative properties, vitality, durability, life form and other bio-ecological features, attitude to abiotic factors (soil conditions, illumination, temperature, soil and atmospheric humidification conditions, etc.) were taken into account. Conclusion . We give a large list of ornamental species and various planting techniques of specific species are introduced in conditions of Chechnya and its adjacent territories as well as the methods of implementing in the landscaping practice in other (middle and northern) regions of Russia.

Ecological-taxonomic analysis of the petrophyte flora of Ikhrek (Rutulsky district) surroundings of Republic of Dagestan

The study of petrophytes, as a peculiar group of plants, is important for understanding the history of the flora and nature in general. Their ecological characteristics, taxonomic composition, geographic and genetic relationships and other characteristics carry information about the stages of development of the mountain country and its flora. Rutulsky district is a part of Highland Dagestan and borders on the Republic of Azerbaijan in the South, Akhtynsky and Kurakhsky districts in the East, Tlyaratinsky and Charodinsky districts in the North-West, Kulinsky, Agulsky and Laksky districts of the Republic of Dagestan in the North. The relief of Highland Dagestan, which is the area of our research, is characterized by a large slope, stony and rocky mountains. The following paper contains taxonomic, biomorphic, ecological analyses of petrophyte complexes of the studied area and an analysis of endemism and relict flora of petrophytic complexes. Herbarium material has helped to find the dominant family, genera and species of petrophyte complexes of the area. Biomorphic and environmental groups of petrophyte complexes have been studied. Confinement of petrophytes to different environmental conditions has been established. Endemic, relict and protected species of petrophyte complexes have been identified.

МИКРОСКОПИЧЕСКИЕ ГРИБЫ В ПОЧВАХ И ГРУНТАХ АРКТИЧЕСКИХ ГОРНЫХ СИСТЕМ

Изучено распространение микроскопических грибов в первичных почвах и грунтах арктических горных систем. Отмечено, что изменение интегральных показателей происходит на региональном уровне, когда для различных горных систем в почвах прослеживается снижение численности микроскопических грибов, связанное с широтной зональностью, и на локальном уровне, например, тенденция снижения мозаичности в пределах растительных сообществ в ряду почв от разреженных к климаксовым растительным сообществам. В пределах одной локальной горной системы интегральные показатели зависят в первую очередь от растительных сообществ, которые могут рассматриваться еще и как стадии сукцессии. В разреженных растительных сообществах эти показатели коррелируют с площадью проективного покрытия, а в климаксовых интразональных сообществах на первое место по значимости выходят экологические условия. В пределах одного растительного сообщества особую значимость приобретают микрониши. При сравнении комплексов микроскопических грибов на контрастных горных породах не отмечено существенного влияния подстилающей горной породы на интегральные показатели. Если сравнивать изменение интегральных показателей на высотном градиенте в горах и зональном градиенте в равнинных высокоширотных ландшафтах (зоны полярных пустынь, арктические тундры – типичные тундры – южные тундры), то увеличение в ряду каменистые пустыни – травянистые–кустарничковые – кустарниковые растительные сообщества в пределах одной горной системы происходит строго монотонно, в отличие от наблюдаемого в зональных плакорах, и менее похоже на «экспоненциальное». Видовой состав микроскопических грибов горных систем северных территорий имеет сходство с таковыми как в альпийских, так и в тундровых местообитаниях. На контрастных горных породах влияние материнской породы прослеживается на уровне комплексов микромицетов на начальных стадиях сукцессии. В отличие от наблюдаемого в зонах полярных пустынь, для комплексов микроскопических грибов разреженных растительных группировок и каменистых горных пустынь не показано наличие явления субдоминирования видов. В данных сообществах отмечена внутрибиогеоценотическая горизонтальная неоднородность комплексов почвенных микромицетов. Таким образом, в отличие от зональных растительных сообществ Арктики, комплексы микроскопических грибов в горных системах не демонстрируют правило компенсации.

한양도성 석재공급지 추정을 위한 고문헌 분석 및 암석학적 데이터베이스 구축

이 연구에서는 한양도성 석재공급지 추정을 위해 고문헌을 분석하고 산지탐색 지점에 대한 광역조사를 수행하여 암석학적 기초 데이터베이스를 구축하였다. 고문헌 분석 결과를 종합하면 성돌은 조선 초기에 주로 도성과 인접한 석산에서 조달된 반면 후기로 갈수록 도성 외부의 고정 채석장으로부터 공급되었다. 따라서 고문헌에 기록된 채석 산지를 중심으로 암석학적 조사를 수행한 결과, 산지탐색 전역에 걸쳐 담홍색화강암과 우백질화강암이 분포하였으며, 이들 화강암류는 광물조성 및 지구화학적 거동특성이 거의 유사하였다. 그러나 담홍색화강암은 남산 북사면에서 불암산의 북동방향으로 갈수록 대자율 값이 증가하는 자철석 계열을 보였으며, 우백질화강암은 용마산을 시작으로 남산과 인왕산 등의 편마암 경계부에 주로 나타나고 티탄철석계열의 낮은 대자율 특성을 가졌다. 이상의 내용을 종합할 때, 한양도성 석재공급지 추정을 위한 중요한 암석학적 지시자는 색상과 대자율로 판단된다. 이와 함께 채석장의 석재 양, 운반거리 및 기술력 등을 고려하여 원산지 해석의 신뢰도를 높일 필요가 있다. This study analyzed ancient documents and established petrological database through extensive field investigation of provenance sites to presume stone source areas of the Seoul City Wall. By summarizing the ancient documents, the rampart stone was mostly supplied from a stony mountain adjacent to the City Wall in the early Joseon period, whereas the stone was provided from fixed quarry outside the City Wall in the late Joseon period. As a result of the petrological investigation based on quarries recorded in the ancient documents, pinkish granite and leucogranite were distributed as a whole, and the granitoid rocks are similar in mineralogical compositions and geochemical behavior characteristics. However, the pinkish granite with magnetic-series show that the magnetic susceptibility increased from the north slope of Namsan Mountain to Bulamsan Mountain. The leucogranite with ilmenite-series mainly occurred along the boundary between granite and gneiss from Yongmasan Mountain to Inwangsan Mountain. Consequently, the important petrological indicators for presumption of stone source areas are the rock color and the magnetic susceptibility. In addition to the petrological features, the reliability for provenance interpretation should improve considering stone quantities in the quarries, transportation distance and technical skills.

Runoff to boreal lakes linked to land cover, watershed morphology and permafrost thaw: a 9‐year isotope mass balance assessment

AbstractStable isotopes of oxygen and hydrogen were measured in water samples collected annually from a representative suite of 50 lakes in northeastern Alberta over a 9‐year period and are interpreted using a steady‐state isotope mass balance model to determine water yield and runoff ratios for the lake watersheds and residence time of the lakes. This isotopic perspective on hydrology of the region provides new insight into the role of land cover, watershed morphometry, climatic drivers and permafrost thaw on lakes. Bog cover, permafrost and presence of thaw features in bogs are found to be the dominant hydrologic drivers, although morphometric properties such as elevation, lake area and drainage basin area are also influential. In addition to quantifying the hydrologic fluxes, the analysis establishes contrasting conditions in more southerly lakes, located in the Stony Mountains and west of Fort McMurray, as compared with more northerly sites in the Birch Mountains, Caribou Mountains and northeast of Fort McMurray, mainly because of contributions from thawing permafrost at the northerly sites. Distinct hydrologic conditions are also noted for Shield systems north of Lake Athabasca where bogs and permafrost are absent. While permafrost thaw is not directly labelled by oxygen and hydrogen isotope composition, isotope mass balance calculations suggest that contributions of up to several hundred millimetres per year are occurring in 14 of the 50 lake watersheds under study. Several of these lakes have water yields in excess of precipitation in some years, and regional groups of lakes display significant correlations between water yield and percentage of bogs that have collapsed. Copyright © 2015 John Wiley & Sons, Ltd.

泾河流域上游土石山区和黄土区森林覆盖率变化的水文影响模拟

泾河流域上游土石山区和黄土区森林覆盖率变化的水文影响模拟

Chapter 9 Coral biogeography in the Late Ordovician (Cincinnatian) of Laurentia

Abstract During the Late Ordovician, Cincinnatian, the epicontinental seas and continental margin of Laurentia provided habitats that were suitable for corals. Biogeographical differentiation occurred within this equatorially placed continent, when corals were introduced to areas that had fundamentally different environments. There were four biogeographical divisions, characterized by distinctive faunas that included some endemic taxa: the Red River–Stony Mountain Province, Richmond Province, Edgewood Province and the less well understood, informal ‘Continental Margin’ Area. In each division, the potential for diversification and the capacity for diversity were determined by factors such as the duration and size of the division, the amount of immigration, the extent of evolution and biogeographical differentiation, faunal responses to changes in sea-level and climate, and the complexity of the ecological structure. The development of multiple biogeographical divisions, each contributing to overall diversity, enhanced the ‘Great Ordovician Biodiversification Event’. During the latest Ordovician mass extinction, there was a reduction of diversity and loss of biogeographical divisions within Laurentia. The divisions were terminated when their characteristic taxa disappeared, in response to major environmental changes associated with glaciation in Gondwana and subsequent global warming.

Effect of rock fragments on macropores and water effluent in a forest soil in the stony mountains of the Loess Plateau, China

Rock fragments exert important effects on soil water movement and macropores.However,they are not well-studied in forest hydrological processes. The results show that the steday effluent is markedly affected by the radius and density of macropores, especially the density of macropores with radii>1.4mm make up only 6.86% of the total,they contribute 67.4% to the variance of steady effluent rates. The area proportion of macropores can better explain the change in steady effluent rates than radii and density of macropores;the steady effluent rate is closely positively related to th area proportion of soil macropores. The increase of the volumetric content of rock fragments in the soil causes increase in the mean radius of the macropores, especially in the density of macropores with radius>1.4mm,but has little effect on the density of macropores with radius<1.4mm.These results show that the effects of rock fragments on the water effluent rate are exerted by affecting the radius and density of macropores to some extent. Key words: Macropore, steady effluent, rock fragment, stony mountains, Loess Plateau.

English

English

Stability strategies and hydrodynamic behavior of liberosessile solitary rugose corals (Ordovician; Red River–Stony Mountain Province, North America)

In the Late Ordovician Red River–Stony Mountain Province of North America, four closely related genera of solitary rugose corals are represented exclusively by liberosessile species: Salvadorea, Grewingkia, Deiracorallium, and Lobocorallium. These rugosans benefitted from innovative and in some cases unique strategies involving corallum form, which improved stability with respect to the substrate and currents, and took advantage of water flow during life. Trochoid form was a compromise for ensuring adequate stabilization of the corallum by sediment, while keeping the calice rim sufficiently elevated above the substrate. In life orientation with the convex cardinal side of the corallum facing down, triangulate and trilobate cross-sectional shapes offered resistance to lateral tipping or rotation. Depressed coralla resisted gravity-induced subsidence or tilting. With the convex side facing downcurrent, the streamlined shape of compressed and triangulate forms improved stability by reducing drag. Trilobate form may have had a drag-reducing “splitter plate” effect. Strategies for drag reduction were especially beneficial for corals inhabiting relatively high-energy environments, but the greatest significance may have been in reducing fatalities due to dislodgement during storms. The hydrodynamic behavior of coralla in life position, especially if leaning downcurrent, resulted in beneficial water flow. Vortices ascending from the substrate on the downcurrent side provided the polyp with water drawn from both the mainstream and the substrate surface. Such circulation facilitated feeding, enhanced the quantity and variety of food, and delivered other necessary substances. Wastes and gametes could be effectively expelled from the polyp and removed downcurrent without entrainment into the food-bearing flow. Functional analysis of the fascinating range of corallum forms in the Red River–Stony Mountain Province provides insight into paleobiology and paleoecology, which is applicable to many Paleozoic solitary rugosans.

Geochemistry and tectonic significance of the Stony Mountain gabbro, North Carolina: Implications for the Early Paleozoic evolution of Carolinia

Carolinia comprises a collection of Neoproterozoic–Early Paleozoic magmatic arc and sedimentary terranes that were amalgamated and accreted to Laurentia in the early to middle Paleozoic. In central North Carolina, mafic rocks of the Stony Mountain gabbro intrude sub-aqueous volcanic and sedimentary rocks and submarine epiclastic sedimentary rocks of the Albemarle Group. The age of the Stony Mountain gabbro is constrained to the Early Cambrian–Middle Ordovician. Field relations indicate that the gabbro represents the final phase of magmatism following the eruption and deposition of the Neoproterozoic–earliest Cambrian Albemarle Group, yet the gabbro pre-dates regional metamorphism and tectonism related to the Late Ordovician accretion of Carolinia to Laurentia. The Stony Mountain gabbro has a sub-alkaline basaltic composition, variable TiO 2, MgO and Ni/Cr values. The rocks have a geochemical signature typical of island-arcs; the degree of LREE enrichment, prominent negative Nb anomalies and Nb/Th ratios are all features of low-K to medium-K tholeiitic basalts in modern island-arc, subduction-related lavas. Isotope data are dominated by juvenile compositions that are consistent with derivation from lithospheric and asthenospheric sources during decompression melting of the mantle. The Stony Mountain gabbro records subduction zone magmatism in a rifted island arc setting and can be modeled as the product of ~ 10–15% hydrous partial melting of variable mixtures of MORB- and OIB-like mantle sources overprinted by a minor subducted-slab derived hydrous fluid component. By analogy with modern settings the rocks of the Stony Mountain gabbro are comparable to MORB-like to OIB-type enriched rocks from the Lau Island and Sumisu Rift and are interpreted to have formed within an evolving Early Paleozoic island arc–back arc rift–basin system. The presence of an Early Cambrian arc–back arc rift system in Carolinia is broadly coeval with arc–back arc volcanism in other peri-Gondwanan blocks of the Appalachians and may be related to the Early Paleozoic opening of the Rheic Ocean.