No abstract

Discontinuity surfaces develop in carbonate successions in response to a range of environmental changes and represent an integral part of the stratigraphic record. In Palaeozoic shallow epeiric basins that are typified by extremely slow subsidence and intermittent sedimentation, discontinuity surfaces may represent the majority of the time-rock record. A depositional and sequence-stratigraphic model was developed through microfacies analysis and discontinuity surface characterization using three cores in a proximal to distal transect across the Middle to Upper Devonian Iowa Basin. Twelve microfacies are recognized, spanning supratidal to deep subtidal facies tracts. A total of 105 discontinuity surfaces were documented and classified as either submarine omission surfaces, subaerial exposure surfaces or submarine erosional surfaces. Omission surfaces increase in frequency basinward, indicating increased sediment starvation in the offshore direction. Exposure surfaces increase in frequency shoreward, indicating more frequent subaerial exposure in a shallower setting. Erosional surfaces are dominant in the inner and middle ramp and interpreted as the base of storm beds (tempestites); these surfaces are rare in the outer ramp due to its generally deeper setting below storm wave base. Moreover, discontinuity surfaces exhibit systematic groupings stratigraphically (vertically) across the three localities spanning the Devonian carbonate ramp. Zones of either exposuredominated, erosion-dominated or omission-dominated surfaces were recognized and correlated with their landward or basinward equivalents (along with shifts in major facies belts) and interpreted in a sequence-stratigraphic context. This study highlights the importance of including a detailed characterization of both depositional facies and non-depositional discontinuity surfaces in order to better understand the stratigraphic history of a basin. The framework of analysis provided here is particularly useful for marine carbonate strata deposited in epeiric basins, which are especially common in the Palaeozoic and where nondeposition and erosion occur frequently, but can also be applied to other geological time periods and settings.

Using neural probing devices implanted in the brain, neural activity from neural cells can be recorded in-vivo for long term periods. This research goal is to develop and investigate a neural sensing device using nanotechnology which can enhance the quality and longevity of sensing. In this research, two neural electrode designs were employed with nanostructures, which distinguish them from 2-dimensional planar electrode configuration. According to electrochemical simulation, high molecular confinement has been observed on vertically aligned nanowire electrodes, especially those with grid structures. The efficacy of the 3-dimensional nanoelectrode is also discussed in this paper, depending on the molecular diffusion on nanoelectrodes.