Sedimentary Rocks

Kamal roslan mohamed Geologi UKM Kamal roslan mohamed Geologi UKM Proses luluhawa akan menghakis batuan yang terdedah menjadi serpihan atau pecahan batuan yang lebih kecil, dan pecahan baru ini akan dibawa oleh agen pengangkut (air dan angin) ke kawasan lain. Pecahan batuan ini akhirnya akan terkumpul di lembangan pengendapan baru, iaitu membentuk sedimen baru. Sedimen sebegini dipanggil sedimen terrigenous atau sedimen klastik.

Berita Sedimentologi, 2019

The upper part of Tapak Formation in Kali Cimande of Banyumas area shows a good example of tidal flat succession. The interval consists of alternating sandstones, siltstone and mudstone that show a fining and thinning upward bedding pattern and includes sand flat, mixed flat and mud flat sedimentary facies. The sand flat facies is characterized by medium-grained sandstone, moderately sorted, with cross-lamination sedimentary structures and bioturbation trace fossils (Skolithos) found mostly on the top of sandstone layer. The mixed flat facies is characterized by an alternation of thin layered sandstones with mudstone and siltstone, with lenticular, wavy, and flaser sedimentary structures. This facies contains many forms of bioturbations, such as Planolites, Thallasinoides, Lockeia, and Ophiomorpha. The mud flat facies is characterized by repeated claystone and thin sandstone intercalation, where the ratio of clay content being more than 95 % of the total layers, and contains abundant Lockeia trace fossil. The Upper Tapak Formation in Banyumas basin has moderate reservoir potential.

Jump to navigationJump to search Middle Triassic marginal marine sequence of siltstones (reddish layers at the cliff base) and limestones (brown rocks above), Virgin Formation, southwestern Utah, USA Sedimentary rocks on Mars, investigated by NASA's Curiosity Mars rover Steeply dipping sedimentary rock strata along the Chalous Road in northern Iran Sedimentary rocks are types of rock that are formed by the deposition and subsequent cementation of that material at the Earth's surface and within bodies of water. Sedimentation is the collective name for processes that cause mineral or organic particles (detritus) to settle in place. The particles that form a sedimentary rock by accumulating are called sediment. Before being deposited, the sediment was formed by weathering and erosion from the source area, and then transported to the place of deposition by water, wind, ice, mass movement or glaciers, which are called agents of denudation. Sedimentation may also occur as minerals precipitate from water solution or shells of aquatic creatures settle out of suspension. The sedimentary rock cover of the continents of the Earth's crust is extensive (73% of the Earth's current land surface [1]), but the total contribution of sedimentary rocks is estimated to be only 8% of the total volume of the crust. [2] Sedimentary rocks are only a thin veneer over a crust consisting mainly of igneous and metamorphic rocks. Sedimentary rocks are deposited in layers as strata, forming a structure called bedding. The study of sedimentary rocks and rock strata provides information about the subsurface that is useful for civil engineering, for example in the construction of roads, houses, tunnels, canals or other structures. Sedimentary rocks are also important sources of natural resources like coal, fossil fuels, drinking water or ores. The study of the sequence of sedimentary rock strata is the main source for an understanding of the Earth's history, including palaeogeography, paleoclimatology and the history of life. The scientific discipline that studies the properties and origin of sedimentary rocks is called sedimentology. Sedimentology is part of both geology and physical geography and overlaps partly with other disciplines in the Earth sciences, such as pedology, geomorphology, geochemistry and structural geology. Sedimentary rocks have also been found on Mars.

The study area is situated in the folded zone of the Zagros Basin where sediments of the Sachun Formation (Paleocene-Lower Eocene) were deposited in a shallow marine environment and consist of interstratified carbonate, shale and evaporite. The Sachun Formation is conformably overlain by the dolomite-dominated Jahrom Formation and unconformably downlaps the Tarbur Formation carbonates (Alavi in Am J Sci 304:1-20, 2004). The Sachun Formation consists mainly of secondary gypsum, which precipitated from the hydration of precursor anhydrite rock. The succession of the Sachun Formation has been divided into three units: the lower red clastic unit, the middle evaporite unit, and the upper carbonate unit. In the middle unit gypsum, several structures are distinguished; e.g. nodular, nodular-banded, and laminated-banded lithofacies with enterolithic and chicken-wire structures. These associations were deposited in a sabkha or shallow water type of depositional environment. Petrographic investigations confirm that the evaporites of the Sachun Formation are mostly composed of secondary gypsum, with rare anhydrite relics. Five microfacies were distinguished according to the gypsum fabrics. The textural relationships of the carbonate and sulfate minerals indicate that some of these anhydrites were formed as a result of a replacement processes of carbonate sediments associated with evaporites. The textures are considered to be a by-product of anhydrite hydration, which is in turn rehydrated from primary gypsum. The evaporites indicate deposition during a regressive lowstand systems tract, whereas the carbonates indicate deposition under shallow water marine conditions during a highstand systems tract. The Sachun Formation succession deposits are in a quite stable arid climate within a rapidly subsiding basin.

Initial Reports of the Deep Sea Drilling Project, 13, 1973

Generally rocks can be divided into three major types based on the process of their formation. These are; Igneous rocks, sedimentary rocks and metamorphic rocks. Igneous rocks are formed by the solidification and cooling of magma in volcanic areas, while sedimentary rocks are formed by low temperature accumulation of sediments in tectonic basins and topographical sinks. Metamorphic rocks on the other hand are formed by application of temperature and pressure on pre-existing rocks. Metamorphic rocks therefore form at great depths, but exposed on the surface due to erosion and epirogenic movements. Each of these three rock types can be further classified in terms of; chemistry, how the form and environment of formation. The distributions of these major rock types are critical in regional mapping of natural resources. Igneous is coined from word " ignis " meaning fire and therefore these rocks are good indicators of volcanism and are there associated with geothermal resources and hydrothermal deposits like porphyry copper, and gold etc. sedimentary rocks especially the organic sediments on the other hand are good source rocks and are associated with resources like coal and oil. Sediments are also good proxies for environmental reconstruction, since fossils can be well preserved in these deposits. Metamorphic environments are associated with Gemstones and alteration minerals which form good index minerals as geobarometers and geothermometry. In this paper we look mainly into igneous and metamorphic rocks, their distribution, plate margins and geothermal resources.