scholarly journals Sedimentary response of a structural estuary to Holocene coseismic subsidence

Author(s):  
Laura C. Reynolds ◽  
Alexander R. Simms ◽  
Thomas K. Rockwell ◽  
Yusuke Yokoyama ◽  
Yosuke Miyairi ◽  
...  

Stratigraphic evidence for coseismic subsidence has been documented in active-margin estuaries throughout the world. Most of these studies have been conducted in subduction zone or strike-slip settings; however, the stratigraphic response to coseismic subsidence in other tectonic settings would benefit from further study. Here we show evidence of late Holocene coseismic subsidence in a structural estuary in southern California. Below the modern marsh surface, an organic-rich mud containing marsh gastropods, foraminifera, and geochemical signatures indicative of terrestrial influence (mud facies) is sharply overlain by a blue-gray sand containing intertidal and subtidal bivalves and geochemical signatures of marine influence (gray sand facies). We use well-established criteria to interpret this contact as representing an abrupt 1.3 ± 1.1 m rise in relative sea level (RSL) generated by coseismic subsidence with some contribution from sediment compaction and/or erosion. The contact dates to 1.0 ± 0.3 ka and is the only event indicative of rapid RSL rise in the 7 k.y. sedimentary record studied. Consistent with observations made in previous coseismic subsidence studies, an acceleration in tidal-flat sedimentation followed this abrupt increase in accommodation; however, the recovery of the estuary to its pre-subsidence elevations was spatially variable and required 500−900 years, which is longer than the recovery time estimated for estuaries with larger tidal ranges and wetter climates.

2006 ◽  
Vol 66 (2) ◽  
pp. 288-302 ◽  
Author(s):  
W. Roland Gehrels ◽  
Katie Szkornik ◽  
Jesper Bartholdy ◽  
Jason R. Kirby ◽  
Sarah L. Bradley ◽  
...  

AbstractCores and exposed cliff sections in salt marshes around Ho Bugt, a tidal embayment in the northernmost part of the Danish Wadden Sea, were subjected to 14C dating and litho- and biostratigraphical analyses to reconstruct paleoenvironmental changes and to establish a late Holocene relative sea-level history. Four stages in the late Holocene development of Ho Bugt can be identified: (1) groundwater-table rise and growth of basal peat (from at least 2300 BC to AD 0); (2) salt-marsh formation (0 to AD 250); (3) a freshening phase (AD 250 to AD 1600?), culminating in the drying out of the marshes and producing a distinct black horizon followed by an aeolian phase with sand deposition; and (4) renewed salt-marsh deposition (AD 1600? to present). From 16 calibrated AMS radiocarbon ages on fossil plant fragments and 4 calibrated conventional radiocarbon ages on peat, we reconstructed a local relative sea-level history that shows a steady sea-level rise of 4 m since 4000 cal yr BP. Contrary to suggestions made in the literature, the relative sea-level record of Ho Bugt does not contain a late Holocene highstand. Relative sea-level changes at Ho Bugt are controlled by glacio-isostatic subsidence and can be duplicated by a glacial isostatic adjustment model in which no water is added to the world's oceans after ca. 5000 cal yr BP.


1964 ◽  
Vol 206 (4) ◽  
pp. 805-810 ◽  
Author(s):  
Raul C. Schiavi

The comparative effect of anterior and posterior hypothalamic lesions on the development of sexual maturation of prepubertal female rats was investigated. Lesions by electrocoagulation were made in the medial hypothalamus of 45 rats at 25–26 days of age. Thirty-nine animals of the same age constituted the sham-operated and nonoperated controls. A hastened appearance of vaginal opening and first estrus, a significant increase in uterine weight, precocious ovarian luteinization, and premature sexual cycles were observed following both types of lesions. Sham-operated rats and animals with lesions in other parts of the brain did not show evidence of precocious sexual maturation.


Author(s):  
Hla Hla Aung

An earthquake with magnitude 5.9 occurred in the east of Falam on 16th April, 2020 at 11:45:23 (UTC). The epicenter is situated at latitude 22.789°N, longitude 94.025°E, 38 km ESE of Falam, at the depth of 10 km. Focal mechanism solution for this event is normal faulting (USGS). The epicentral location is in the Kabaw Valley along which Kabaw fault runs through in N-S direction. The Kabaw fault is situated in forearc region at the eastern base of N-S trending Rakhine Western Ranges under which the India oceanic plate is obliquely subducting beneath the Burma continental plate. The 2020 M 5.9 Falam earthquake occurred along two closely linked tectonic settings: north-eastward oblique subduction zone and north-south trending Kabaw fault zone system in the forearc region.The Falam earthquake ruptured the Tripura segment, one of the segments of India subduction zone, located approximately between latitude 22°-24°N according to the geographical location. This event is a rare intraplate earthquake and a subduction-induced strike-slip earthquake that ever occurred for the recent time in Myanmar. The shock was felt by cities of Gangaw, Kalemyo, Kalewa, Mandalay, Kyauk-se, Monywa. This earthquake was preceded by a loud sound and shaking lasts 1 minute. A few aftershocks of magnitude >3.5 followed the main shock in the vicinity of the epicenter. The vibration spread a wide area along Rakhine Yoma and Myanmar lowland area. The investigation of field survey from social media was found that the event reaches Modified Mercalli Intensity scale VIII based on people’s perception, indoor effects and damaged buildings. Damage is severe in some poorly built structures and upper parts of stupa and pagodas.


Geosphere ◽  
2021 ◽  
Author(s):  
Robert C. Witter ◽  
Adrian M. Bender ◽  
Katherine M. Scharer ◽  
Christopher B. DuRoss ◽  
Peter J. Haeussler ◽  
...  

Active traces of the southern Fairweather fault were revealed by light detection and ranging (lidar) and show evidence for transpressional deformation between North America and the Yakutat block in southeast Alaska. We map the Holocene geomorphic expression of tectonic deformation along the southern 30 km of the Fairweather fault, which ruptured in the 1958 moment magnitude 7.8 earthquake. Digital maps of surficial geology, geomorphology, and active faults illustrate both strike-slip and dip-slip deformation styles within a 10°–30° double restraining bend where the southern Fairweather fault steps offshore to the Queen Charlotte fault. We measure offset landforms along the fault and calibrate legacy 14C data to reassess the rate of Holocene strike-slip motion (≥49 mm/yr), which corroborates published estimates that place most of the plate boundary motion on the Fairweather fault. Our slip-rate estimates allow a component of oblique-reverse motion to be accommodated by contractional structures west of the Fairweather fault consistent with geodetic block models. Stratigraphic and structural relations in hand-dug excavations across two active fault strands provide an incomplete paleoseismic record including evidence for up to six surface ruptures in the past 5600 years, and at least two to four events in the past 810 years. The incomplete record suggests an earthquake recurrence interval of ≥270 years—much longer than intervals <100 years implied by published slip rates and expected earthquake displacements. Our paleoseismic observations and map of active traces of the southern Fairweather fault illustrate the complexity of transpressional deformation and seismic potential along one of Earth’s fastest strike-slip plate boundaries.


Author(s):  
Валерий Викторович Игошев

В статье исследуется серебряный оклад Евангелия из собрания Государственного Русского музея с иконописным изображением Распятия на верхней деревянной крышке. Оклад Евангелия, происходящий из коллекции М. П. Боткина, выполнен в разнообразных техниках и имеет очень редко встречающуюся особенность - иконописное «Распятие» расположено в центральной части верхней крышки в заглублении (ковчеге). Аналогичные оклады Евангелий с иконописными изображениями нередко изготавливались псковскими мастерами в конце XIV- XVI вв. Исследуемый оклад состоит из разновременных серебряных деталей, которые свидетельствуют о его неоднократных переделках и «поновлениях». В центральной части верхней крышки Евангелия на гвоздиках крепятся серебряные золочёные пластины, украшенные надписями и растительным орнаментом, а также - семь узорчатых венчиков, выполненных псковским мастером в середине XVI в. Такие детали изготовлены в технике резьбы (оброна) и заполнены черной эмалью. В это же время сделаны литые детали двух застёжек с кожаными ремнями, скрепляющих деревянные крышки Евангелия. Все эти изящно и тонко исполненные серебряные детали по стилю и технике очень близки к работам псковских мастеров середины XVI в. Вероятно, к XVI в. следует отнести также гладкие накладные серебряные дробницы с гравированными изображениями символов евангелистов и святых. Разновременные дополнения оклада появились при его переделках. Обветшавшие, сломанные или утерянные детали изготавливались заново и заменяли оригинальные части оклада. Во второй половине XVII в. сделаны ажурные серебряные пластины со сканым растительным орнаментом и эмалью, закрывающие поля верхней крышки, выполненные псковским мастером в подражаниt тонким и изысканным образцам эмали по скани работы псковских мастеров XVI в. Во второй половине XVII в. было сделано утраченное иконописное изображение Распятия с фигурами предстоящих и летящими ангелами. В начале XVIII в. был заменён старый книжный блок на новый, а в XIX в. менялся бархат на нижней и верхней крышке Евангелия. Разнообразие деталей, сделанных в разных техниках на протяжении XVI-XVII-XVIII-XIX вв., свидетельствует о многочисленных ремонтах, и в то же время - бережном отношении к древнейшим деталям оклада книги, сохранившимся до нашего времени. The article reflects the research work of the silver oklad, laid on the Gospel book from the Russian Museum’s collection, with the iconographic depiction of the Crucifixion on the top. Originally, the Gospel cover came from the collection of M. P. Botkin and was made in a variety of techniques. It has a rarely encountered feature: the icon of “Crucifixion” is set in the recess, called “covchèg” (or “ark”) located on the top of a book cover. Similar oklads on the Gospel books with the iconographic images were often made by Pskov master jewelers at the end of the XIV-XVI centuries. This oklad consists of different silver parts of different time periods, which testify to its repeated alterations and “improvements.” The central part of the upper board is decorated with gilded silver plates, containing inscriptions, floral ornaments and seven patterned halos. They are made in the middle of 16th century by unknown Pskov jeweler in the technique of carving and decorated with a black enamel. The silver cast parts and pieces of two fasteners with a leather straps are made at the same time period. All these gracefully and finely made details are very similar in style and techniques to the works of the Pskov silversmiths active in the mid-16th century. The silver plaques with images and symbols of the evangelists and Saints engraved on them were made around the same time, but multiple additions and replacements, which were made at different periods appeared during its alterations. Broken or lost pieces were made anew, and they have replaced original, but worn out parts. The openwork silver plates and enameled filigree floral ornaments were made in the second half of the XVII century by the Pskov silversmith in imitation of subtle and exquisite enamel works of the 16th century Pskov masters. The Crucifixion with figures of Saints and flying angels was repainted in the second half of the XVII century. The old book block was replaced with a new one in the beginning of the XVIII century. The velvet, which is covering upper and lower book boards has been changed in the XIX century. Variety of parts were made in different technique styles during XVI - XVII - XVIII - XIX centuries; they show evidence of multiple repairs and, at the same time, show assiduous care for the most ancient pieces of the oklad and the book itself, preserved to our time.


REINWARDTIA ◽  
2016 ◽  
Vol 15 (2) ◽  
pp. 99
Author(s):  
ROSIE PRITCHETT ◽  
AURORA PHILLIPS ◽  
ANI MARDIASTUTI ◽  
ANDREW POWLING

PRITCHETT, R., PHILLIPS, A., MARDIASTUTI, A. & POWLING, A. 2016. Rattan diversity and broad edaphic niches in a tropical rainforest of Buton, Sulawesi, Indonesia. Reinwardtia 15(2): 99 – 110. — This paper attempts to answer the question: how can at least 20 species of rattan palms in the genus Calamus (family Palmae (Arecaceae)) co -exist in a rainforest? A survey of rattans was made in Lambusango Forest on Buton, an island close to south east Sulawesi, in Indonesia. Rattan species and numbers were recorded in 87 quadrats of 30 × 10 m, laid out along linear transects in habitats with a variety of soils. Evidence for edaphic (soil) niches was sought. Different rattan species were found to be adapted to soils with different conductivity and pH values. Standardised mean difference (d) scores were calculated for pairs of species based on their response to soil pH. Of the 66 pairs tested, 61 were found to be significantly different statistically. Such differences suggest, but do not prove, that many species occupy different edaphic niches. It was found that species which show a preference for soils with intermediate pH values (5.0 to 6.5) can grow in soils with a wide range of pH values, implying broad edaphic niches and that competition between these species is weak. Correspondence analysis shows that many species do not distinguish greatly between many soils with intermediate pH values. It is concluded that rattan species show evidence for having different edaphic niches, although the niches for many species are broad. It is speculated that many rattan species may be ecologically equivalent and that a weak version of ecological neutrality theory may apply.


2002 ◽  
Vol 74 (3) ◽  
pp. 519-531 ◽  
Author(s):  
JOÃO B. S. COSTA ◽  
YOCITERU HASUI ◽  
RUTH L. BEMERGUY ◽  
ADILSON V. SOARES-JÚNIOR ◽  
JAVIER M. C. VILLEGAS

The Marajó Basin area presents geologic and geomorphologic features chiefly due to the Mesozoic extension and post-Miocene neotectonics. The extension event with an Early and a Late Cretaceous phases originated four sub-basins that constitutes the Marajó Basin, with a thick continental clastic sequence showing marine influence. NW and NNW normal faults and NE and ENE strike-slip faults controlled the basin geometry. The extension, related to the Equatorial Atlantic opening, propagated into the continent along crustal weakness zones of the Precambrian Tumucumaque, Amapá and Araguaia orogenic belts. The neotectonic event is a strike-slip regime which developed transtensional basins filled in by Upper Tertiary shallow marine (Pirabas Formation) and transitional sequences (Barreiras Group), followed by Quaternary fluvial deposits and transitional sequences derived from the Amazon and Tocantins rivers and the Marajoara estuary. The current landscape has a typical estuarine morphology. The coast morphology presents sea-cliffs on transitional Upper Tertiary sequences, while inwards dominate hills sustained by Mid-Pleistocene lateritic crust, with a flat erosive surface at 70 m. In the eastern Marajó Island several generations of paleochannels associated with fluvial-estuarine sequences are recognized, while a fluvial-marine plain is widespread on its western side.


2009 ◽  
Vol 147 (2) ◽  
pp. 281-298 ◽  
Author(s):  
A. H. N. RICE ◽  
D. M. WILLIAMS

AbstractAnalysis of pelites with detrital white-micas in the Clew Bay–Galway Bay segment of the Irish Caledonides indicates that b0data from whole-rock and < 2 μm fractions generally show differences smaller than the errors of the method, irrespective of (001) illite crystallinity values, probably due to metamorphic recrystallization. Intermediate pressure metamorphism of the Ordovician–Silurian Clew Bay Group indicates slow subduction, allowing partial thermal re-equilibration before exhumation. In contrast, the Croagh Patrick Group Laurentian shelf-sediments underwent high-pressure alteration, suggesting rapid subduction/exhumation, synchronous with strike-slip faulting. The Murrisk Group, which underwent high-intermediate pressure metamorphism in an Ordovician back-arc, forms a separate terrane to the Croagh Patrick Group to the north and also to the Ordovician Lough Nafooey and Tourmakeady groups and Rosroe Formation in the south, in which low-intermediate pressure alteration occurred. These, together with the Silurian North Galway Group, may have undergone heating due to movement over or deposition on the hot Gowlaun Detachment as the Connemara Dalradian was exhumed. The South Connemara Group also underwent a high-pressure alteration, consistent with its inferred subduction environment. Evidence of contact alteration, due to known or inferred buried late- to post-Caledonian granitoid plutons, has been found in the Clew Bay, Louisburg–Clare Island, Croagh Patrick, Murrisk and South Connemara groups. These show evidence of lower-pressure alteration than the surrounding country-rocks.


1987 ◽  
Vol 65 (11) ◽  
pp. 1453-1462 ◽  
Author(s):  
H. Meyer

A review is presented on the experimental observations and the theoretical progress made in investigating the quantum diffusion in solid H2. The mechanisms of resonant ortho–para conversion and of quantum tunneling are discussed. It is pointed out that the ortho-H2 clustering reaction process, by which quantum diffusion is detected, needs to be better understood to account for the dependence of the observed reaction-time constant τ on temperature and on ortho-H2 concentration. The general trends in the experimental results are reviewed, and the discrepancies between various determinations of τ are discussed. Further experiments are suggested as well as computer simulations for the clustering procedure. A review is also given on the status of quantum diffusion of HD in solid H2. Recent observations on recombination rates of H and on depolarization rates of muons in H2 that show evidence of quantum effects are briefly mentioned.


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