The extent to which persistent, rather than transient, fissures (wide planar voids) can exist along upper crustal faults is important in assessing fault permeability to mineral and hydrocarbon-bearing fluids. Variscan (late Carboniferous) faults cutting Dinantian (Lower Carboniferous) limestones on the Gower peninsula, South Wales, host clear evidence for fissures up to several metres wide. Evidence includes dendritic hematite growth and elongate calcite growth into open voids, spar ball and cockade breccia formation, laminated sediment infill and void-collapse breccias. Detailed mapping reveals cross-cutting geometries and brecciation of earlier fissure fills, showing that fissures were formed during, rather than after, active faulting. Fissures therefore probably formed by geometric mismatch between displaced fault walls, rather than by solution widening along inactive faults.

The Mississippian–Pennsylvanian Global Stratotype Section and Point (GSSP) are hosted within a shallow-water, dominantly carbonate succession in the lower part of the Bird Spring Formation at Arrow Canyon, Nevada, USA. The boundary is marked by the first appearance datum (FAD) of the conodont Declinognathodus noduliferus sensu lato . It is shown that the boundary interval is punctuated by numerous subaerial hiatuses represented by palaeokarstic surfaces and palaeosols, which divide strata at this location into fourth-order glacio-eustatic cycles. A well-developed palaeosol horizon occurs <1 m above the FAD of D. noduliferus . It also coincides with a very marked facies change and a second-order shift in cycle-stacking patterns. These characteristics violate International Commission on Stratigraphy guidelines, which state that GSSPs should be chosen in sections showing continuous sedimentation and lacking vertical facies changes at or near the boundary. Because the Mid-Carboniferous is an icehouse interval, cyclostratigraphy is a powerful tool for high-resolution correlation. A comparison of the cyclostratigraphy of Mid-Carboniferous strata at Arrow Canyon and in northern England indicates that a large number of glacio-eustatic sea-level oscillations are not recorded at Arrow Canyon and that this section contains over 25 missed beats of Milankovitch band duration equating to a hiatus of ≥1 Ma.

FLÜGEL, E. 2004. Microfacies of Carbonate Rocks. Analysis, Interpretation and Application. xx + 976 pp. Berlin, Heidelberg, New York: Springer-Verlag. Price Euros 99.95 (+ VAT at local rate), SFr 169.00, £77.00, US $99.00 (hard covers). ISBN 3 540 22016 X - Volume 143 Issue 1

GILI, E., NEGRA, M. E. H. & SKELTON, P. W. (eds) 2003. North African Cretaceous Carbonate Platform Systems. NATO Science Series IV. Earth and Environmental Sciences Vol. 28. x+252 pp. Dordrecht, Boston, London: Kluwer Academic Publishers. Price Euros 105.00, US $116.00, £72.00 (hard covers). ISBN 1 402 01606 9 - Volume 142 Issue 3

ABEGG, F. E., HARRIS, P. M. & LOOPE, D. B. (eds) 2002. Modern and Ancient Carbonate Eolianites: Sedimentology, Sequence Stratigraphy, and Diagenesis. SEPM Special Publication no. 71. v + 207 pp. Tulsa: SEPM (Society for Sedimentary Geology). Price US 90.00. ISBN 1 56576 079 4 - Volume 141 Issue 1

ALSHARHAN, A. S. & SCOTT, R. W. (eds) 2001. Middle East Models of Jurassic/Cretaceous Carbonate Systems. SEPM Special Publication no. 69. iv+364 pp. Tulsa: SEPM (Society for Sedimentary Geology). Price US 100.00 (members), plus shipping and handling; hard covers. ISBN 1 56576 075 1. - Volume 139 Issue 3

RETTALACK, G. J. 1997. A Colour Guide to Paleosols. xi + 175 pp. New York, Chichester, Weinheim, Brisbane, Singapore, Toronto: John Wiley & Sons, Inc. Price £34.95 (hard covers). ISBN 0 471 96711 4. - Volume 135 Issue 2

El limite entre el Jurasico Medio y Superior en la Cuenca Lusitanica es desigual, a semejanza de lo que ocurre en otras cuencas peri-atlanticas, y esta asociado a lagunas estratigraficas que se prolongan por lo menos durante el intervalo Calloviense superior-Oxfordiense inferior. En la parte oriental de la cuenca, las zonas internas de las rampas carbonatadas se encuentran truncadas por superficies de erosion (paleocarst), asociadas a una fuerte laguna estratigrafica. La disconformidad esta formada y cubierta por depositos ferruginosos, carbones y carbonatos pedogenicos. Estos sedimentos pasan gradualmente y hacia techo a carbonatos lacustres y a carbonatos de lagoon confinado (probablemente del Oxfordiense medio). Hacia occidente, los carbonatos de la rampa externa del Jurasico Medio pasan sin discontinuidad sedimentaria evidente, pero con laguna estratigrafica, a los sedimentos del Malm (probablemente Oxfordiense medio). Estos presentan caracteristicas de exposicion subaerea mucho menos pronunciada que en la parte E de la cuenca; consisten principalmente de carbonatos marinos-marginales, con clara influencia de agua dulce, asociados a carbonatos marinos someros con emersion intermitente. Este articulo realza algunas caracteristicas especificas relacionadas con la transicion Jurasico Medio-Superior, que merecen ~cr comparadas -con- otros acontecimientos contemporaneos en otras cuencas, en particular en las cuencas Ibericas. Merecen especial atencion la asimetria de las sucesiones de facies detectada entre las zonas oriental y occidental de la Cuenca Lusitanica y los marcadores paleoclimaticos variados y contrastantes que aparecen entre estas secuencias. Se sugiere una posible fluctuacion climatica durante el Oxfordiense.

Paleokarst refers to karstic (dissolution-related) features formed in the past, related to an earlier hydrological system or landsurface. Karst is a term used to describe distinctive terrains whose landforms and hydrology result from a combination of high rock solubility and well-developed secondary porosity. Karst systems have been intensively studied and the hydrological principles of their formation are well understood. Thus, in studying paleokarsts, it is possible to employ the knowledge of present-day systems to understand ancient ones. Indeed this is one of the few occasions when “diagenesis” can be related to hydrology and hydrogeology, allowing some predictive element. There are two main drawbacks encountered in studying paleokarsts which frustrate attempts to apply karst-science to interpret them. Firstly, many paleokarsts are encountered in the subsurface, particularly during hydrocarbon exploration, and interpreting paleokarst style from limited seismic or borehole data is very difficult. Recognizing and interpreting paleokarsts in the subsurface is difficult but a variety of techniques can be applied. Modelling a paleokarstic reservoir is particularly difficult and it is likely that some fractured reservoirs may be paleokarstic in origin.

Paleosols— that is, soils formed on a landscape of the past are now being widely recognized in the geological record, and are potentially very powerful tools for a variety of paleoenvironmental purposes. They have also been used as indicators of porosity evolution in ancient limestones. A variety of criteria is used for recognizing paleosols. Some are not replicated by sedimentological or other diagenetic processes and so provide unique and diagnostic evidence. Paleosols can be recognized based on their biological features, color, destratification, horizonation and boundaries, granulometrics, mineral assemblages, macrostructures, and micromorphology. Many of the features used to recognize paleosols are subtle and prone to alteration during diagenesis, but surprisingly little work has been carried out on these problems. The physical effects of burial diagenesis, such as compaction and pressure solution, are relatively easily recognized as overprints. Many major changes can occur very early in the burial history of the paleosol, and two common situations require consideration. The first is that of an aggrading floodplain, and second, a paralic setting during a transgression.

An abstract is not available for this content so a preview has been provided. As you have access to this content, a full PDF is available via the 'Save PDF' action button.