Cutaneous lesions of the nose

Skin diseases on the nose are seen in a variety of medical disciplines. Dermatologists, otorhinolaryngologists, general practitioners and general plastic and dermatologic surgeons are regularly consulted regarding cutaneous lesions on the nose. This article is the second part of a review series dealing with cutaneous lesions on the head and face, which are frequently seen in daily practice by a dermatologic surgeon. In this review, we focus on those skin diseases on the nose where surgery or laser therapy is considered a possible treatment option or that can be surgically evaluated

Microbially originated wrinkle structures on sandstone and their stratigraphic context: Palaeoproterozoic Koldaha Shale, central India

Wrinkle structures on sandstone beds are abundant and present in diverse forms in the Palaeoproterozoic Koldaha Shale, Vindhyan basin, central India. The inferred palaeogeography of sedimentation ranges from offshore marine to terrestrial, the wrinkled sandstones belonging to the relatively deeper marine part. Good preservation of ultramicroscopic microbial elements within these sandstones strongly supports a microbial mat origin of the wrinkles, which was facilitated by development of an oxygen depleted condition immediately beneath the sediment-water interface, as depicted in early pyrite growth. Later, impermeable shale encasing the sandstone beds arrested further scope for destruction of the microbial elements. Trapping of fine detritus by microbial filaments is documented by the invariable occurrence of a silty clay veneer on the wrinkled surfaces, and by its characteristic texture. Wrinkle morphology has been classified and an attempt has been made to understand the origin of each of the varieties, and to visualize the processes that acted upon the microbial mats to produce the wrinkle structures in their specific palaeogeographic context. The general palaeogeographic bias in occurrence of the sandy wrinkles is well reflected in their concentration in the lower part of the highstand systems tracts (HST's), one superposed above the other, comprising the Koldaha Shale. The smaller-scale palaeogeographic control is indicated by compartmentalization of two wrinkle varieties in the upper and the basal intervals of the HST's, and overlapping occurrence of other varieties in the medial interval with apparent preference for either the upper or the lower levels. © 200

Facies and depositional sequence of the Mesoproterozoic Rohtas Limestone: Eastern Son valley, Vindhyan basin

Paleogeography and process-related facies analysis of the shelf-originated Rohtas Limestone of early Mesoproterozoic age has been attempted. Lithology, structure, microfabric and TOC are the mainstay of facies classification. The Rohtas Limestone consists of seven facies; out of which the organic-rich black shale and the crinkle laminated limestone facies dominates the basal part, reveal distinctive fabric of microbial mat origin and represents outer shelf products. With gradual shoaling, the crinkle laminated limestone facies gains importance and locally turns into the nodular limestone facies through early diagenetic modification. The grey shale facies, poor in organic content, replaces them further upward. The other three facies, viz., the thinly laminated heterolithic facies, typified by close alternations between black shale and limestone, the planar laminated limestone facies and the wavy laminated limestone facies alternate with the grey shale facies, progressively dominating the top part of the succession. While the heterolithic facies records deposition across the paleochemocline, the planar laminated and the wavy laminated limestone facies document deposition in shallow agitated shelf. Confined between a condensed zone below and an unconformity above, the overall coarsening upward Rohtas Limestone records development of a HST. (c) 200

Microbial mat-induced sedimentary structures in siliciclastic sediments: Examples from the 1.6Ga Chorhat Sandstone, Vindhyan Supergroup, MP, India

This paper addresses macroscopic signatures of microbial mat-related structures within the 1.6 Ga-old Chorhat Sandstone of the Semri Group - the basal stratigraphic unit of the Vindhyan succession in Son valley. The Chorhat Sandstone broadly represents a prograding succession of three depositional facies ranging from shallow shelf to coastal margin with aeolian sandsheet. The mat-mediated structures were generated because of plastic or brittle deformation of sand, turned cohesive and even thixotropic because of microbial mat growth. Mat growth also favoured abundant preservation of structures that usually have low preservation potential. Prolific growth of microbial mat in the subtidal to intertidal zone of the Chorhat sea was facilitated due to lack of grazing and burrowing activities of organisms in the Precambrian. It further indicates low rate of sedimentation between the storms, as also attested by frequent superposition of storm-beds, even near the storm wave base. It also reduces erosion and that, in turn, would imply low sediment concentration in flows leading to development of bedforms that are likely to be smaller in size and isolated from each other in a single train in contrast to those that form in mat-free sands

Mg-rich ferric illite in marine transgressive and highstand systems tracts : examples from the Paleoproterozoic Semri Group, central India

This paper focusses upon two glauconitic sandstones in the Paleoproterozoic Deoland Formation and Chorhat Sandstone, both belonging to the Semri Group, central India. In both the cases glauconitic minerals occur in sandstones deposited in the marine realm, within a transgressive systems tract (TST) for the former unit and within a highstand systems tract (HST) for the latter. The proportion of glauconitic minerals increases in the paleo-offshore direction. Petrography reveals selective early glauconitization of detrital K-feldspars along their fringes, cleavages and the fractures created by volume expansion during progressive alteration, leading to the generation of peloids with small relics of the precursors. XRD and mineral chemistry reveal a structure typical of glauconite, and more akin to Mg-rich ferric illite. The mineral chemistry of the glauconitic mineral phases remains the same whether the glauconitization process was incipient or at an advanced stage