Some 75% of the rocks at the Earth’s surface are sedimentary in origin, and these include the familiar sandstones, limestones and shales, and the less common but equally well-known salt deposits, ironstones, coal and chert. Sedimentary rocks of the geological record were deposited in the whole range of natural environments that exist today. The study of these modern environments and their sediments and processes contributes much to the understanding of their ancient equivalents. There are some sedimentary rock types; however, for which there are no known modern analogues, or their inferred depositional environments are only poorly represented at the present time.

formations or indeed on any other process in which time played an integral and fundamental role. The advent of radionuclide dating, with the attendant absolute measure of age, changed the views of geology and processes that can occur in ways that have been of major significance. In addition, the radionuclides allow a direct comparison of absolute age to the prior proxies. Accordingly, not only had one available a true age dating but also a proxy scale that could be tie <...>

Sedimentary rock-hosted disseminated gold ores lithologically and chemically similar to those of Carlin-type deposits of the western United States are present in the Yauricocha district, central Peru. The Purisima Concepcion deposit is located in the core of a steeply plunging anticline several hundred meters beyond large pipe-shaped Cu-Zn-Pb-Ag-Au replacement orebodies in limestone bordering a late Miocene granodiorite stock. The central part of the stock is potassium-silicate altered and contains high-salinity fluid inclusions.

The study of sedimentary rocks has come a long way in the past 200 years. In the nineteenth century, they were regarded as the matrix in which fossils occurred and their study, as far as it went, was mainly tied up with the understanding of stratigraphy. Sedimentary rocks had clearly been deposited through time in some way, but little attention was paid to asking exactly how. There was a general appreciation of the idea that ancient processes and conditions of deposition were probably similar to those prevailing at the present day (actualism and uniformitarianism), but, with a few notable exceptions, detailed study concentrated on description of the rocks as materials, rather than as products of dynamic processes and environments. This attitude prevailed until the middle of the twentieth century, although pioneering studies had, by then, used sedimentary structures as indicators of top and bottom (way-up) in deformed successions and as a means of deducing palaeocurrent directions. <...>