There are a variety of pore types in unconventional resource mudstones and shales. The currently preferred method by geologists and petrophysicists is to examine and analyze these mudstones and shales by argonion and focused ion-beam milling to produce an ultrasmooth surface, coupled with observation under the field emission scanning electron microscope (FESEM). Potential issues with Ar-ion milled/FESEM preparation and imaging include (1) the small size of sample cubes for upscaling, (2) loss of structural fabric during the milling–imaging process, (3) fewer non-inorganic pore types observed than when observed with an unpolished surface, (4) analog use of pores from one shale to another, although the pore types and composition might differ, and (5) the creation of potential artifacts related to desiccation and rock expansion because of core retrieval and sample preparation. Conventional FESEM images obtained from freshly broken surfaces reveal much more textural detail than those obtained from ion-milled (polished) surfaces. Although conventional FESEM methodology may share some of the same limitations as Ar-ion beam-milled/FESEM technology, FESEM methodology should not be overlooked because it provides a more cost-effective and potentially more accurate analysis for estimating porosity and determining pore types and their distribution in shales. Comparison of FESEM images from ion-milled and fresh, non-ion-milled surfaces reveals that organic matter and internal organoporosity are best viewed on ion-milled surfaces, but shale microfabric and non-organoporosity is best viewed under non-milled surfaces. Complete FESEM imagery for shale characterization should include both types of analyses. AbstractThere are a variety of pore types in unconventional resource mudstones and shales. The currently preferred method by geologists and petrophysicists is to examine and analyze these mudstones and shales by argonion and focused ion-beam milling to produce an ultrasmooth surface, coupled with observation under the field emission scanning electron microscope (FESEM). Potential issues with Ar-ion milled/FESEM preparation and imaging include (1) the small size of sample cubes for upscaling, (2) loss of structural fabric during the milling–imaging process, (3) fewer non-inorganic pore types observed than when observed with an unpolished surface, (4) analog use of pores from one shale to another, although the pore types and composition might differ, and (5) the creation of potential artifacts related to desiccation and rock expansion because of core retrieval and sample preparation. Conventional FESEM images obtained from freshly broken surfaces reveal much more textural detail than those obtained from ion-milled (polished) surfaces. Although conventional FESEM methodology may share some of the same limitations as Ar-ion beam-milled/FESEM technology, FESEM methodology should not be overlooked because it provides a more cost-effective and potentially more accurate analysis for estimating porosity and determining pore types and their distribution in shales. Comparison of FESEM images from ion-milled and fresh, non-ion-milled surfaces reveals that organic matter and internal organoporosity are best viewed on ion-milled surfaces, but shale microfabric and non-organoporosity is best viewed under non-milled surfaces. Complete FESEM imagery for shale characterization should include both types of analyses.

Las Tablas de Daimiel, Spain, is one of the scarce, freshwater wetlands areas still preserved in southern Europe. The wetland is fed by surface and groundwater. We studied the Quaternary sedimentary record of Las Tablas in a drill hole that penetrated 38.5 m of shallow-lake and fluvial deposits. Differences in the dominantly micritic muds indicate three main stages of development. In the lowest stage, unit A, (Lower? to Middle Pleistocene) the slightly saline wetland developed under a relatively arid climate that favored slow flow movement of the fluvial system and the disconnection of the ponded areas. In the intermediate stage, unit B, (Middle to Upper Pleistocene) extensive peat developed during wetter conditions. Biosiliceous sediments (diatoms and sponge spicules) also accumulated in this swampy setting. In the latter stage, unit C, (Upper Pleistocene to Holocene) palustrine carbonates formed in a freshwater environment with desiccation events, followed by fluvial reworking of the lake margins. Lithification of these deposits was relatively fast (<10,000 yr). The studies of the core, including mineralogy, petrography, stables isotopes, and pollen analyses, indicate that these sediments are similar to those of ancient palustrine sequences. Therefore, Las Tablas can be considered as a recent analogue for freshwater palustrine systems that have no marine influence. These systems are very sensitive to changes in climate or base level, and their study is needed to better understand the terrestrial sedimentary record. Study is needed also to determine how to preserve these wetlands. Las Tablas de Daimiel constituyen uno de los escasos humedales de agua dulce que aún se conservan en el sur de Europa, concretamente en España. El humedal está abastecido por aguas superficiales y subterráneas. El registro sedimentario Cuaternario de Las Tablas, se ha estudiado mediante un sondeo en el que se cortaron 38.5 m de depósitos lacustres someros y fluviales, esencialmente carbonatos micríticos. Las características de los sedimentos permiten diferenciar tres principales etapas de sedimentación. En la primera etapa, unidad A, (Pleistoceno Inferior? a Medio) el humedal era ligeramente salino y se desarrolló bajo un clima relativamente árido que favoreció el flujo más lento del sistema fluvial, permitiendo la desconexión de las zonas encharcadas. En la etapa intermedia, unidad B, (Pleistoceno Medio a Superior) el amplio desarrollo de turberas indica condiciones más húmedas, en las que dentro de las áreas pantanosas también se depositaron sedimentos biosilíceos (diatomeas y espículas de esponjas). En la última etapa, unidad C, (Pleistoceno Superior a Holoceno) los sedimentos característicos son carbonatos palustres formados en un ambiente de agua dulce con eventos de desecación seguidos de posterior retrabajamiento de los márgenes lacustres por canales fluviales. La litificación de estos depósitos fue relativamente rápida (<10000 años). El estudio llevado a cabo en el sondeo (mineralogía, petrografía, isótopos estables, análisis polínicos) indica que estos sedimentos son similares a las secuencias palustres del registro geológico. Por tanto, Las Tablas de Daimiel pueden considerarse como un análogo reciente para sistemas palustres de agua dulce que no tengan influencia marina. Estos sistemas son muy sensibles a cambios climáticos y/o del nivel de base, por lo que su estudio es necesario para conocer mejor el registro sedimentario continental, pero también para preservar estos humedales.