Geomorphological and Statistical Assessment of Tilt-Block Tectonics in the Garhwal Synform: Implications for the Active Tectonics, Garhwal Lesser Himalaya, India

Active tectonics is manifested in geomorphological features such as drainage basins and drainage patterns. Geomorphic parameters asymmetry factor (AF) and transverse topography symmetry factor (T) is calculated for 94 third order basins of the Garhwal synform to decipher the tilt-block tectonics based on remote sensing and geographical information system (GIS) techniques. The quantitative analysis of the AF suggests that all the 94 basins are asymmetric and gentle to steeply tilted, indicating active tectonics and early and late stage of development, respectively. The mean vector magnitude (θv) of T suggests the migration of the basin stream towards the south in most basins (60%), suggesting a unidirectional tilting of the tectonic block. The χ2 test for statistical significance indicates that the θv is significant for southern and northern limb basins. The χ2 test affirms that the third order basin position on either side of the main channel of the river basin influences the tilt direction. The regional tectonics suggests migration of the Lansdowne klippe towards the south, as the majority of third order basins show southward tilt. The study provides a quick appraisal of tilting in the tectonic blocks of active margins, such as in the Himalayas.

Introduction: Active Margins in Transition—Magmatism and Tectonics through Time: An Issue in Honor of Arthur W. Snoke

The evolution of active margins through time is the record of plate tectonics as inscribed on the continents. This themed issue honors the eclectic contributions of Arthur W. Snoke (Fig. 1) to the study of active margins with a series of papers that amply demonstrate the broad scope of active margin tectonics and the diverse methods that tectonic geologists employ to decipher their histories. Taken together, this set of papers illustrates the diversity of boundary conditions that guide the development of active margins and the key parameters that regulate their evolution in time and space.

Profile of Tinea Corporis and Tinea Cruris in Dermatovenereology Clinic of Tertiery Hospital: A Retrospective Study

Background: Tinea corporis and cruris are dermatophytes that infect the skin, and they are caused by Trichophyton sp., Microsporum sp., and Epidermophyton sp. Dermatophyte fungal-infect keratin-containing skin classified by the body’s location, such as tinea corporis (skin besides haired area, body, hands, or feet) and tinea cruris (groin & perineal region). Purpose: To evaluate the clinical profiles and treatments of tinea corporis and cruris at Dermatology and Venereology (DV) outpatient clinic Dr. Soetomo General Academic Hospital in 2018. Methods: A retrospective-descriptive study based on medical records of DV outpatient clinic Dr. Soetomo General Academic Hospital, Surabaya. Data collected from August to December 2019. Tinea corporis and cruris profiles evaluation based on age, sex, occupation, precipitating factors, complaints, illness duration, family history, lesion’s location and description, and therapy. Result: A total of 164 patients (35 tinea corporis, 76 tinea cruris, and 53 tinea corporis and cruris), predominantly female, age 46–55 years, came treatment less-than-a-month cases, excessive sweating, itching, tinea corporis lesion’s location on the face and body, tinea cruris in groin, tinea corporis and cruris on body and groin, erythematous macules, firm borders, active margins, scales, central healing, positive KOH 10–20% examination, miconazole cream therapy 2%, griseofulvin therapy, griseofulvin oral and ketoconazole cream 2% combination therapy. Discussion: Tinea corporis and cruris are common in females as their history and symptoms supported by the characteristics of laboratory examination, the presence of hyphae in potassium hydroxide (KOH) 10–20%. Most patients were prescribed with oral griseofulvin, especially in large lesions cases.

SubSpread: An integrated approach to understand the signature, mechanics and controls of subaqueous spreading

<p>Subaqueous spreading is a widespread type of mass movement, which involves extensional displacement along a gliding plane and the deformation of the failing layer into a sequence of ridges and troughs. Spreading has been poorly investigated, nonetheless it poses hazard to offshore infrastructures. SubSpread is a new project that will investigate the mechanics of the spreading failure and its geological controls in the subaqueous environment. The first objective of SubSpread is to identify the topographic and sedimentary signature of subaqueous environment. We have compiled a global database of subaqueous and subaerial spreads that includes information on physiography, geomorphology, sedimentology and geotechnical properties, where available. A preliminary analysis of the database reveals that spreading morphologies occur on both passive and active margins, especially in the headwall area of translational retrogressive slides. Potential causes of spreading include seismic loading (also glacially induced), sediment loading, and increased pore pressure generated by migration of fluid or gas. The latter may induce loss of shear strength and the formation of a weak layer, particularly in gentle open slopes. Information compiled in this database will also be used to develop a numerical model that can better understand the mechanics and rheological aspects of submarine spreading, focusing on the role played by pore pressure generation. The Tuaheni slide complex in the Hikurangi Margin of New Zealand is being used as a case-study in view of the wealth of geophysical and sedimentological data that are available. The final part of the SubSpread project will test whether the morphometric and sedimentological signature of spreading can provide information on past seismicity. In this case, the test site will be Lake Tekapo in the South Island of New Zealand.</p>

Middle Triassic high-K calc-alkaline effusive and pyroclastic rocks from the Zagorje-Mid-Transdanubian Zone (Mt. Kuna Gora; NW Croatia): mineralogy, petrology, geochemistry and tectonomagmatic affinity

This study uses mineralogical, petrological, geochemical, and Sr and Nd isotope data along with K-Ar ages to infer the petrogenesis and geodynamic evolution of Middle Triassic high-K calc-alkaline lavas and their associated pyroclastics of Mt. Kuna Gora in NW Croatia. Their analogue mineralogy and bulk-rock geochemistry testify to the coeval origin of both rock types. Sanidine and plagioclase accompanied by inor augite and Ti-bearing magnetite are the major phases found in a matrix of devitrified volcanic glass and plagioclase microlites. Hydrothermal anddiagenetic processes in the pyroclastics originated the formation of chlorite and white mica, and mixed-layer clay minerals, respectively. Petrography reveals the following crystallization order: spinel→clinopyroxene→plagioclase→alkali-feldspar±Fe-Ti oxides. Geochemical and isotopic data suggests that the studied rocks had a complex origin that included the contamination of subduction-generated magmas by lithospheric mantle melts. This presumes an interplay between fertile arc mantle, subducted continental crust, and depleted or ocean island basalts-like mantle. A low degree of crustal contamination stands as a last step in the formation of such “hybrid” magmas. The subducted Paleotethyan oceanic lithosphere went through processes of partial melting at depths of ~45-49km and pressures of ≤1.6GPa and fractionation that produced melts which gave rise to the studied rocks. In the model we are proposing herein such formed partial melts are related to the demise of the northward subduction of the Paleotethys oceanic lithosphere during the Early to Middle Triassic epoch, which is consistent with an active, ensialic mature volcanic arc developing along Laurussian southern active margins.

The location and Potential Assessment of the Ore Regions in the South-Western Part of the Koryak Highland

Актуальность рассматриваемой темы в том, что орогенные пояса материковой части Камчатского края насыщены полезными ископаемыми, приуроченных к поясам, образованным последовательным приростом окраин континента от древних с северо-запада к юго-востоку. Такими поясами с месторождениями Ag, Au, Sn, Hg, S являются Северо-Западно-Корякский олигоценовый и Южно-Корякский миоценовый, образованные на северной и южной границе Центрально-Корякской окраины позднемелового континента. Они сформированы в олигоцене и миоцене изолированными вулканогенами локальных андезитовых полей, прорванных гранитоидами тектонической активизации. С ними связаны рудные площади, локализация которых позволит обеспечить прирост запасов разрабатываемых россыпей платиноидов. Цель работы заключается в установлении тектонических закономерностей образования вулканогенов, связанных с ними рудных районов и получения новых данных по их прогнозу. В Северо-Западном поясе оформилась металлогеническая зона с Уннэйваямским, Гайчаваямским и Пальматкинским районами, сопряжёнными с одноименными вулканогенами, в Южно-Камчатском с Ветроваямским вулканогеном. Методология и методы исследования. Методология заключена в глыбово-клавишной структуре литосферы и её земной коры на активных окраинах континента. Методика основана на установлении системной связи структурных элементов геолого-геофизической системы тектоника-вулканогены . Результаты работ и их анализ. Предложена схема закономерностей размещения известных и прогнозируемых рудных районов, узлов юго-запада Корякского нагорья. Они обусловлены глыбово-клавишной тектоникой и локализованы в звеньях серии продольных субпараллельных разновозрастных региональных структур СВ простирания, последовательно наращивающих континент к юго-востоку. Звенья являются дискретными и определяют размеры рудных районов. Рассмотрены выделяемые звенья Северо-Западно-Корякского олигоценового и Южно-Корякского миоценового поясов. В первом СЗ поперечными межглыбовыми разломами литосферы образованы вулканогены гнездового типа. Они возникли на пересечении фундамента позднего мела и южной окраины сопредельной Пенжинской СФЗ поперечными межглыбовыми разломами. В пересечениях образуется литосферный столб вещества гранитоидной активизации верхней мантии и позднемелового осадочного разреза фундамента. Делается вывод, что в Южно-Корякском поясе вулканоген является линейным, образованным заключением линейного СВ Ветроваямского выступа фундамента и чехла между двумя поперечными межглыбовыми разломами. В нём рудоносными вторичными кварцитами создан Ильпинский рудный район с крупными месторождениями самородной серы с Ag, Au, Hg, S. Орогенный вулканизм на активных окраинах континентов сопряжён с основными элементами тектоники и магматизма, создавшими условия образования минерагенических таксонов. На примерах орогенных поясов олигоцена и миоцена очевидна роль геотектонических и металлогенических аспектов авторской методологии глыбово-клавишной структуры литосферы активных окраин. Она эффективна в прогнозе рудных площадей и их оценке последующими геологоразведочными работами. The relevance of the work is that the orogenic belts of the mainland of the Kamchatka Territory are saturated with minerals confined to the belts formed by the successive growth of the continental margins from the ancient ones from the north-west to the south-east. Such belts with deposits of Ag, Au, Sn, Hg, S are the Northwest Koryak Oligocene and South Koryak Miocene, formed on the northern and southern borders of the Central Koryak margin of the Late Cretaceous continent. They are formed in the Oligocene and Miocene by isolated volcanogens of local andesitic fields, broken by granitoids of tectonic activation. Ore areas are associated with them, the localization of which will ensure an increase in the reserves of developed placer deposits. The purpose of the work is to establish tectonic patterns of formation of volcanogens, associated ore regions and obtain new data on their forecast. In the North-Western zone, a metallogenic zone took shape with the Unneivayamsky, Gaichavayamsky and Palmatkinsky regions, associated with the same named volcanogenes, in the South Kamchatka - with the Vetrovayamsky volcanogen. Methodology and research methods. The methodology lies in the block-key structure of the lithosphere and its earths crust on the active margins of the continent. The methodology is based on establishing a systemic connection between the structural elements of the geological and geophysical system tectonics-volcanogens. The results of the work and their analysis. A scheme of patterns of distribution of known and predicted ore regions, nodes of the south-west of the Koryak upland is proposed. They are caused by block-key tectonics and are localized in the links of a series of longitudinal subparallel regionally different age structures of NE strike, successively expanding the continent to the southeast. The links are discrete and determine the size of the ore regions. The distinguished links of the Northwest Koryak Oligocene and South Koryak Miocene belts are considered. In the first northwestern region, nesting volcanogens are formed by transverse interblock faults of the lithosphere. They arose at the intersection of the Late Cretaceous foundation and the southern edge of the adjacent Penzhinsk structural-facial zone with transverse interblock faults. At the intersections, a lithospheric column of granitoid activation matter of the upper mantle and the Late Cretaceous sedimentary section of the basement is formed. It is concluded that the volcanogen in the South Koryak belt, has a linear nature, formed by the conclusion of a linear NE of Vetrovayamsk ledge of the basement and cover between two transverse interblock faults. There ore-bearing secondary quartzites created the Ilpinsk ore region with large deposits of native sulfur with Ag, Au, Hg, S. The orogenic volcanism on the active margins of the continents is associated with the basic elements of tectonics and magmatism, which created the conditions for the formation of minerogenic taxons. The role of geotectonic and metallogenic aspects of the authors methodology of the block-key structure of the active lithosphere margins is evident on the examples of the orogenic Oligocene and Miocene belts. It is effective in forecasting ore areas and evaluating them with subsequent exploration works

Fore-arc building and destruction: a critical interplay between fluid flow, megathrust strength and tectonic underplating

<p>Subduction zones are the loci of huge mass transfers, including accretion and erosion processes responsible for the long-term formation (and destruction) of fore-arc margins. Study of now-exhumed deep portions of the fore-arc crust revealed km-scale tectonic units of marine sediments and oceanic crust, which have been underplated (i.e. basally accreted) to the overriding plate. However, geophysical observations of this deep process in active subduction zones are unclear and the dynamics of tectonic underplating, as well as its existence, along most of active margins remain controversial. We attempt to shed light on this critical process from the plate interface where tectonic slicing is triggered, to the surface where topographic variations are expected in response to such a mass transfer.</p><p>Using high-resolution visco-elasto-plastic thermo-mechanical models, we present with unprecedented details the dynamics of formation, preservation and destruction of underplated crustal nappes at 10-40-km depth in subductions zones. Our results show that subduction segments exhibiting an increasing frictional behaviour control deep accretionary dynamics and that the long-term frictional zonation of the plate interface is stable due to a positive feedback between fluid distribution and effective stress. As a result, discrete underplating events follow one after another for tens of Myr, leading to the formation of a thick duplex structure supporting a coastal topographic high. The rise of this high topography is cadenced by Myr-scale uplift-then-subsidence cycles, characterising each underplating event and the subsequent period of wedge re-equilibration. This periodical evolution is significantly modified by changing the rheological properties of the material entering the subduction zone, suggesting that tectonic underplating is likely a transient process active along most of active margins, depending on severe variations of the hydro-mechanical properties of the plate interface at Myr timescale.</p>

Seismic strengthening of diatom-rich sediments: A comparison of slope sediments from Chilean lakes and the Japan Trench margin

<p>Earthquakes are a main trigger of subaqueous landslides and surficial sediment remobilization at ocean margins and lake basins. If the earthquake loading is insufficient to lead to sediment failure, the subsequent dewatering and inherent compaction may enhance the shear strength of sedimentary slopes, a process termed „seismic strengthening“, which is believed to be especially relevant for the upper 10s of meters. This mechanism has been suggested to explain the observed paucity of submarine landslides on active margins when compared to the short recurrence of strong earthquakes in such settings. However, only few field studies were dedicated on this topic and little is known about which settings are especially prone to seismic strengthening.</p><p>Here, we present geotechnical data from diatom-rich sedimentary slopes in Chilean lakes and at the Japan Trench margin. We use the overburden-normalized undrained shear strength as an indicator of consolidation state. In Chile, this data is derived from in-situ dynamic cone penetrometer measurements, whereas the Japan data is obtained by lab vane shear tests on sediment cores. Both settings show extremely elevated shear strength of about ~5-10 times higher than expected for normally-consolidated sediment in the upper meters of a sequence. Significant overconsolidation is confirmed by one-dimensional compression tests, providing overconsolidation ratios of ~2-8 (Chilean lakes) and 4-9 (Japan Trench). For each setting, the shear strength profiles of sites with different sedimentation rates show very similar trends when they are normalized over the sediment age instead of over overburden stress. As older sediments experienced more earthquakes, this apparent age-dependency may form a new argument supporting the hypothesis of seismic strengthening. Following previous lab experiments on mixtures of diatoms and clayey-silt, we postulate that a high susceptibility to seismic strengthening in both settings is caused by the abundance of diatom frustules which are typically characterized by a high particle interlocking and surface roughness. On the Japan Trench margin, biogenic opal forms ~15% in dry weight, and given the hollow structure of diatom frustules, we infer that diatoms take up a considerable space in the in-situ sediment texture. We conclude that seismically active margins with diatom-rich sediments have a reduced susceptibility to submarine landslide hazards.</p>