KINNEYIA-TYPE WRINKLE STRUCTURES ON SANDSTONE BEDS: NOT MICROBIALLY INDUCED BUT DEFORMATION FEATURES CAUSED BY SYNSEDIMENTARY EARTHQUAKES

ABSTRACT A category of wrinkle structures, often termed Kinneyia structure or Runzel marks, comprises bedding plane features consisting typically of anastomosing, low-relief, flat-topped ridges with intervening depressions. Topographic relief is usually less than a millimeter. They are locally common on the upper surfaces of fine- to medium-grained sandstone beds interbedded with mudstone deposited in offshore settings, especially in Precambrian and lower Paleozoic strata but as young as Cretaceous. For more than the last two decades these wrinkle structures have been widely regarded as due to microbial mats, and have been taken as evidence for dominance in the Proterozoic of microbially stabilized sediment and, in the Phanerozoic, a matground marine benthic ecology which gradually gave way to a mixground ecology. The detailed morphology and cross-cutting relationships demonstrated by a range of specimens of Proterozoic, Cambrian, and Silurian age, however, cast this interpretation into doubt. The relationship between the wrinkled surface and bioclasts such as shells and both prior- and later-formed scour surfaces, and horizontal and vertical burrows show that these wrinkles did not develop due to the surface topography of microbial mats or compaction of microbial mats during burial, but instead formed at the top of a sand bed at the interface with an overlying layer of mud. Deformation is ascribed to vibration from low-magnitude earthquakes. The presence in some units of small-scale sedimentary dikelets and crack arrays that formed later after some stiffening, along with locally associated seismites and other evidence for nearby faulting, show that syndepositional tectonic activity was not unexpected and support the interpretation that this category of wrinkle structures is a type of seismite.

Investigations on Electrochemical Performance of Hausmannite Manganese Oxide Nanoparticles in KOH and Na2SO4 Electrolytes for Energy Storage Applications

The hausmannite phase manganese oxide nanoparticles (NPs) were prepared by a simple chemical reflux method. Powder X-ray diffraction shows the well-crystalline structure of Mn3O4 spinel. Fourier-transform infrared spectroscopy study exhibited the Mn–O functional group vibrations in the hausmannite NPs. UV–visible spectroscopy study reveals that the optical bandgap energy of the manganese oxide nanoparticles is about 3.1[Formula: see text]eV. The scanning electron microscopy (SEM) analysis shows that the surface morphologies of the manganese oxide nanoparticles are wrinkle structures. Cyclic voltammetry studies were carried out to the electrode of Mn3O4 NPs in KOH and Na2SO4. The charge–discharge analysis and impedance spectroscopy method analysis were made on Mn3O4 NPs to understand the electrochemical performance. The ability of synthesized Mn3O4 NPs electrodes was analyzed and compared with the existing materials for the supercapacitor applications.

Tunable Optical Diffusers Based on the UV/Ozone-Assisted Self-Wrinkling of Thermal-Cured Polymer Films

Tunable optical diffusers have attracted attention because of the rapid development of next generation stretchable optoelectronics and optomechanics applications. Flexible wrinkle structures have the potential to change the light path and tune the diffusion capability, which is beneficial to fabricate optical diffusers. The generation of wrinkles usually depends on an external stimulus, thus resulting in complicated fabricating equipment and processes. In this study, a facile and low-cost method is proposed to fabricate wrinkle structures by the self-wrinkling of thermal-cured polymer for tunable optical diffusers. The uncured polydimethylsiloxane (PDMS) precursors were exposed to UV/ozone to obtain hard silica layers and then crosslinked via heating to induce the wrinkle patterns. The wrinkle structures were demonstrated as strain-dependent tunable optical diffusers and the optical diffusion of transmitted light via the deformable wrinkle structures was studied and adjusted. The incident light isotropically diffused through the sample at the initial state. When the wrinkle structures deformed, it showed a more pronounced isotropic optical diffusion with uniaxial tensile strain. The optical diffusion is anisotropical with a further increase in uniaxial tensile strain. The proposed method of fabricating wrinkles by UV/ozone-assisted self-wrinkling of thermal-cured polymer films is simple and cost-effective, and the obtained structures have potential applications in tunable optical diffusers.

Biological mats in siliciclastic sediments of the Paleoproterozoic Gunflint Formation, northwestern Ontario, Canada

The Gunflint Formation of northwestern Ontario, Canada, contains an extensive array of stromatolite morphologies and associated fossilized bacteria. It, and correlative units in the United States, provided some of the most persuasive early interpretations of stromatolites and evidence of Precambrian bacterial life. This study examined the siliciclastic rocks in the Gunflint Formation and discovered a multitude of features formed by the development of cohesive biogenic mats on bedding surfaces. In former shallow subtidal depositional settings, evidence of mat erosion was most common, with the presence of various types of wrinkle structures. Microscopically carbonaceous layers and rip-up fragments representing mats and their eroded remnants are well preserved. This emphasizes the abundance of bacterial life in the shallow nearshore of the Gunflint Formation about 1.88 billion years ago and further indicates an increased flux of reductants was necessary during this time period to establish low oxygen levels in the ocean.

Regulating surface wrinkles using light

Regulating existing micro and nano wrinkle structures into desired configurations is urgently necessary yet remains challenging, especially modulating wrinkle direction and location on demand. In this work, we propose a novel light-controlled strategy for surface wrinkles, which can dynamically and precisely regulate all basic characteristics of wrinkles, including wavelength, amplitude, direction and location (λ, A, θ and Lc), and arbitrarily tune wrinkle topographies in two dimensions (2D). By considering the bidirectional Poisson's effect and soft boundary conditions, a modified theoretical model depicting the relation between stress distributions and the basic characteristics was developed to reveal the mechanical mechanism of the regulation strategy. Furthermore, the resulting 2D ordered wrinkles can be used as a dynamic optical grating and a smart template to reversibly regulate the morphology of various functional materials. This study will pave the way for wrinkle regulation and guide fabrication technology for functional wrinkled surfaces.

The roles of wrinkle structures in the veins of Asian Ladybird and bioinspiration

The deployable hind wings of the Asian ladybird beetle (Harmonia axyridis) play important roles in their flight. Wrinkle structures of veins are found on the bending zones of the hind wings of H. axyridis. This paper investigates the effect of the wrinkle structures of the veins of the hind wing on its deformation. Based on the nanomechanical properties of the veins, morphology of the hind wing, surface structures of veins and microstructures of the cross sections, including the veins and wing membranes, we establish four three-dimensional coupling models for hind wings with/without wrinkles with different and uniform reduced modulus. Relative to the bending and twisting model shapes, Model I, which includes the wrinkle structure and different reduced-modulus veins, has much more flexibility of passive deformation to control wing deformations. The results show that both the wrinkle structures in the bending zone and varying reduced modulus of the veins contribute to the flight performance of bending and twisting deformations of the hind wings, which have important implications for the bionic design of the biomimetic deployable wing of micro air vehicles (MAVs).