1,721,129 research outputs found
Miocene high-frequency rhtmic sediment successions between astrochronology and diagenesis.
No full textHow facies and diagenesis affect fracturing of limestone beds and reservoir permeability in limestone-marl alternations
No full textFades and diagenetic heterogeneities in carbonate reservoir rocks affect both, fracture distribution and fracture permeability. Many studies focussed on fracture patterns in limestone-marl alternations, as e.g. fluid flow models, are based on laterally continuous beds. Here we examine 4010 fractures in multiple layers of limestone-marl alternations using a modified scan-line method. The studied successions belong to the Blue Lias Formation (Hettangian-Sinemurian), exposed on the coast of the Bristol Channel, United Kingdom. We combine methods of sedimentology and structural geology with rock physics to gain a better understanding of the role of fades, diagenesis and petrophysical properties (tensile and compressive strength, hardness, porosity) on the distribution of fractures (fracture orientation, density, spacing and height). Fracture distribution varies significantly despite similar bed thicknesses, indicating that planar bedding planes (i.e. well-bedded limestones, WBL) and beds with bedding plane irregularities (i.e. semi-nodular limestones, SNL) must be distinguished. SNL show higher percentages of non-stratabound fractures (67%) while they are more stratabound in WBL (57%). Additionally, beds with variable bed thicknesses (in scale of 15 m long beds) exhibit a wide range of fracture spacing, whereas fractures in beds with more continuous bed thicknesses are more regularly spaced. Considering all lithologies, the percentage of non-stratabound fractures increases proportionally with CaCO3 content. Three subsections studied in detail reveal different main sedimentological and diagenetic features (from early lithified over differentially compacted to physically compacted). All of them are characterised by dissimilar percentages of stratabound and non-stratabound fractures in limestone beds and marl interbeds. Our findings demonstrate that the distribution of fractures in individual well-bedded limestones is not necessarily representative for successions of limestone marl alternations; multiple layers should therefore be studied in outcrop analogues as basis for fluid flow models of reservoirs composed of such lithologies. (C) 2014 Elsevier Ltd. All rights reserved.Deutsche Forschungsgemeinschaft (DFG) [PH 189/2-1
A standardized database of Last Interglacial (MIS 5e) sea-level indicators in Southeast Asia
Full text linkMarine Isotope Stage 5e (MIS 5e; the Last Interglacial, 125 ka) represents a process analog for a warmer world. Analysis of sea-level proxies formed in this period helps in constraining both regional and global drivers of sea-level change. In Southeast Asia, several studies have reported elevation and age information on MIS 5e sea-level proxies, such as fossil coral reef terraces or tidal notches, but a standardized database of such data was hitherto missing. In this paper, we produced such a sea-level database using the framework of the World Atlas of Last Interglacial Shorelines (WALIS; https://warmcoasts.eu/world-atlas.html). Overall, we screened and reviewed 14 studies on Last Interglacial sea-level indicators in Southeast Asia, from which we report 43 proxies (42 coral reef terraces and 1 tidal notch) that were correlated to 134 dated samples. Five data points date to MIS 5a (80 ka), six data points are MIS 5c (100 ka), and the rest are dated to MIS 5e. The database compiled in this study is available at 10.5281/zenodo.5040784 (Maxwell et al., 2021)
Environmental factors influencing skeletal grain sediment associations: a critical review of Miocene examples from the western Mediterranean
No full textHardground development on Miocene ramp succession of the Western Mediterranean area: sea level changes versus trophic resources.
No full textForamol, rhodalgal and bryomol sediments are not necessarily temperate-water carbonates.
No full textTropical foramol carbonates – Environmental factors influencing skeletal grain sediment associations
No full textLa risposta di una rampa carbonatica rhodalgal/bryomol alla ciclicità eustatica ad alta frequenza: il Miocene calcareo dell’Appennino centrale
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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