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Zone C (zone + c)
Selected AbstractsEvolution of an accretionary complex along the north arm of the Island of Sulawesi, IndonesiaISLAND ARC, Issue 1 2004Yusuf Surachman Djajadihardja Abstract Seismic reflections across the accretionary prism of the North Sulawesi provide excellent images of the various structural domains landward of the frontal thrust. The structural domain in the accretionary prism area of the North Sulawesi Trench can be divided into four zones: (i) trench area; (ii) Zone A; (iii) Zone B; and (iv) Zone C. Zone A is an active imbrication zone where a decollement is well imaged. Zone B is dominated by out-of-sequence thrusts and small slope basins. Zone C is structurally high in the forearc basin, overlain by a thick sedimentary sequence. The subducted and accreted sedimentary packages are separated by the decollement. Topography of the oceanic basement is rough, both in the basin and beneath the wedge. The accretionary prism along the North Sulawesi Trench grew because of the collision between eastern Sulawesi and the Bangai,Sula microcontinent along the Sorong Fault in the middle Miocene. This collision produced a large rotation of the north arm of Sulawesi Island. Rotation and northward movement of the north arm of Sulawesi may have resulted in southward subduction and development of the accretionary wedge along North Sulawesi. Lateral variations are wider in the western areas relative to the eastern areas. This is due to greater convergence rates in the western area: 5 km/My for the west and 1.5 km/My for the east. An accretionary prism model indicates that the initiation of growth of the accretionary prism in the North Sulawesi Trench occurred approximately 5 Ma. A comparison between the North Sulawesi accretionary prism and the Nankai accretionary prism of Japan reveals similar internal structures, suggesting similar mechanical processes and structural evolution. [source] Fault configuration produced by initial arc rifting in the Parece Vela Basin as deduced from seismic reflection dataISLAND ARC, Issue 3 2007Mikiya Yamashita Abstract The Parece Vela Basin (PVB), which is a currently inactive back-arc basin of the Philippine Sea Plate, was formed by separation between the Izu-Ogasawara Arc (IOA) and the Kyushu-Palau Ridge (KPR). Elucidating the marks of the past back-arc opening and rifting is important for investigation of its crustal structure. To image its fault configurations and crustal deformation, pre-stack depth migration to multichannel seismic reflection was applied and data obtained by the Japan Agency for Marine-Earth Science and Technology and Metal Mining Agency of Japan and Japan National Oil Corporation (Japan Oil, Gas and Metals National Corporation). Salient results for the pre-stack depth-migrated sections are: (i) deep reflectors exist around the eastern margin of KPR and at the western margin of IOA down to 8 km depth; and (ii) normal fault zones distributed at the eastern margin of the KPR (Fault zone A) and the western margin of the IOA (Fault zone B) have a total displacement of greater than 500 m associated with synrift sediments. Additional normal faults (Fault zone C) exist 20 km east of the Fault zone B. They are covered with sediment, which indicates deposition of recent volcanic products in the IOA. According to those results: (i) the fault displacement of more than 500 m with respect to initial rifting was approximately asymmetric at 25 Ma based on PSDM profiles; and (ii) the faults had reactivated after 23 Ma, based on the age of deformed sediments obtained from past ocean drillings. The age of the base sediments corresponds to those of spreading and rotation after rifting in the PVB. Fault zone C is covered with thick and not deformed volcanogenic sediments from the IOA, which suggests that the fault is inactive. [source] Orthodontic movement in bone defects augmented with Bio-Oss®JOURNAL OF CLINICAL PERIODONTOLOGY, Issue 1 2001An experimental study in dogs Abstract Objective: To study if it was possible to move, by orthodontic means, a tooth into an area of the jaw that had been augmented with Bio-Oss®. Material and Methods: 5 beagle dogs were used. The 1st, 2nd, and 4th mandibular premolars on each side were removed. The defect at the left 4th premolar site was filled with a biomaterial (Bio-Oss®) while the corresponding defect in the right side was left for spontaneous healing. 3 months later, an orthodontic device was inserted in each side of the mandible. The device was designed to allow distal, bodily movement of the 3rd premolars. When the experimental teeth had been moved into the extraction sites of the 4th premolars, the animals were sacrificed and biopsies of the premolar-molar regions of the mandible sampled. The tissues were prepared for histological analysis using standard procedures. In the sections, 3 zones were identified: zone A=the bone tissue within the distal portion of the previous extraction site (4th premolar), zone B=the pressure side of the 3rd premolar, zone C=the tension side of the 3rd premolar. The area occupied by mineralized bone, Bio-Oss® particles and bone marrow was determined by a point counting procedure. The width of the periodontal ligament as well as the percentage of the root surface (in zone B) that exhibited resorption was determined. Results: The findings demonstrated that it was possible to move a tooth into an area of an alveolar ridge that 3 months previously had been augmented with a biomaterial. It was also demonstrated that 12 months after grafting, Bio-Oss® particles remained as inactive filler material in the not utilized part of zone A. The biomaterial was not present in zone C but present in small amounts in zone B. Conclusion: During the orthodontic tooth movement the graft material (Bio-Oss®) was degraded and eliminated from the part of the alveolar ridge that was utilized for the experiment. In the non-utilized part of the ridge the biomaterial, however, remained as a seemingly inactive filler material. [source] Middle Archean ocean ridge hydrothermal metamorphism and alteration recorded in the Cleaverville area, Pilbara Craton, Western AustraliaJOURNAL OF METAMORPHIC GEOLOGY, Issue 7 2007T. SHIBUYA Abstract A hydrothermally metamorphosed greenstone complex, capped by bedded cherts and banded iron formations (BIFs), is exposed in the Cleaverville area, Pilbara Craton, Western Australia. It has been interpreted as an accretionary complex characterized by both a duplex structure and an oceanic plate stratigraphy, and is shown to represent a 3.2 Ga upper oceanic crust. Three metamorphic zones are identified in the basaltic greenstones. The metamorphic grade increases from sub-greenschist facies (zones A and B) to greenschist facies (zone C) under low-pressure conditions. The boundaries between three mineral zones are subparallel to the bedding plane of overlying chert/BIF, and metamorphic temperature increases stratigraphically downward. The zones correspond to the thermal structure of ocean-floor metamorphism, at a mid-ocean ridge. The uppermost greenstone in the study area is more pervasively altered and carbonatized than the modern upper oceanic crust. This indicates the enrichment of CO2 in the metamorphic fluid by which widespread formation of carbonate occurred, compared with a narrow stability region of Ca-Al silicates. It is, therefore, suggested that the Archean hydrothermal alteration played a more important role in fixation of CO2 than present-day ocean-ridge hydrothermal alteration, as an interaction between sea water and oceanic crust. [source] Perfusion, viability, and pedicle dependence in acute and delayed rat island skin flapsMICROSURGERY, Issue 2 2007Ewa Komorowska-Timek M.D. Purpose: Although surgical delay phenomenon has been widely investigated, its pathophysiology has not been fully elucidated. Methods: In 25 Spraque,Dawley rats, an 8 × 8 cm2 epigastric skin flap consisting of 4 vertical zones A through D (farthest from vascular pedicle) was outlined. All animals were perfused twice with colored fluorescent microspheres: immediately before and after flap elevation (Acute, n = 10) and before and after pedicle ligation on POD 8 (Delayed, n = 15). Results: After acute flap elevation, peripheral perfusion dropped significantly in zone C (0.29 ± 0.01 vs. 0.19 ± 0.04 ml g,1 min,1; P < 0.01) and zone D (0.33 ± 0.09 vs 0.01 ± 0.01 ml g,1 min,1; P < 0.01), while global flap perfusion remained unchanged. Total and regional blood flow did not change in the Delayed group after pedicle ligation. Conclusions: Elevation of a pedicled flap caused significant decrease in distal flap perfusion while maintaining proximal and total flap perfusion. Eight-day delay was adequate to establish sufficient flap perfusion independent of the vascular pedicle. © 2007 Wiley-Liss, Inc. Microsurgery, 2007. [source] | |||||||||||||