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  Rocks of Mechanical Origin – Rudaceous        Sedimentary particles of mechanical (terrigenous) origin are classified according to their size. Particles larger than  2 mm  constitute  gravel  (Latin-rudite), those between  2 and 1/16 mm  constitute  sand  (Latin-arenite), while those  finer than 1/16 mm  constitute  silt and clay  (Latin-lutite). Accordingly, sedimentary rocks of mechanical origin are classified broadly into three groups:  Rudaceous, Arenaceous  and  Lutaceous  (aka  Argillaceous ). Rudaceous Sedimentary Rocks  (Conglomerates and Breccias) Unconsolidated sediments coarser than 2 mm are grouped under the term gravel. Indurated gravels are called conglomerates. While the particles constituting a conglomerate are essentially rounded, a breccia consists of gravel-size clasts which are angular. The term rubble is applied to an assemblage of loose angular fragments of gravel size.      Conglomerates may be classified either in a purely descriptive way (example: chertconglo

  Classification of sedimentary rocks      After transportation and deposition loose sediments are consolidated into sedimentary rocks by a process called diagenesis. The sedimentary rocks thus formed may be broadly divided into two groups: Exogenetic and Endogenetic      Exogenetic  rocks are the products of fragmentation of the source rock outside the basin of sedimentation.  Endogenetic  rocks are produced out of precipitation from solution within the basin. The exogenetic and endogenetic rocks can be distinguished by their textures. While the endogenetic rocks show an interlocking or crystalline fabric (‘non-clastic’ texture), the exogenetic rocks show discrete framework grains separated by voids. The latter texture is called ‘clastic’ from the Greek clastos, meaning broken      Classification of sedimentary rocks into  clastic  and  non-clastic , though popular among sedimentologists, may at times lead to ambiguity. A chemically precipitated sediment for example, may also be trans

  Residual deposits What is it? The residual deposits are the insoluble products of rock weathering which have escaped transportation. They are found over the rocks from which they have been formed. The rocks belonging to this class are made up of two components. Unaltered minerals from the original rock The insoluble products of chemical weathering. Its texture? The residual sediments are composed of unsorted and angular materials as they have not suffered transportation. The grain size of the deposits are determined by the nature and grain size of the weathered rock.  Some of its types: (a) Terra Rossa: This deposit is found in limestone countries in arid regions. Terra rossa is a reddish clayey soil covering the limestone country rock. constituting the insoluble residue of clay and other mineral matter after removal of the limestone by solution. In areas of comparatively high rainfall, the terra rossa is washed into depression, swallow holes and caves soon after its formation. The b

  What is a sedimentary texture?      The term texture refers to the pattern formed within a sedimentary rock by the constituting grains. This can best be studied under a microscope. Classification of sedimentary texture      In sedimentary rocks of  Mechanical origin , formed by weathering, erosion, transportation, deposition followed by diagenesis & Lithification, the framework grains are joined together, either by finer fragmental particles or by chemically precipitated cement. The former is called  matrix  and the latter, c ement . The pattern formed by framework grains, matrix and cement is called (a) Clastic texture . Sandstones show this kind of texture.      The texture of a rock of  Chemical origin  is produced wholly by chemically precipitated materials. No inter-granular space is to be found in such a rock. Limestones of orthochemical origin show this kind of (b) Non clastic texture .      Allochemical limestones, produced by fragmental pieces of calcareous material join

  Unravel the Earth’s Secrets: A Comprehensive Geology Guide What is Geology? Geo  – Earth,  logy  – science, so geology can be simply defined as science of Earth. From the center of the core to the exosphere (outermost layer of the atmosphere) anything to every that happens naturally can be studied under the subject called Geology. It was also called as  Rock Science , as most of the data source for the subject is from rocks. Subject covers Origin of Earth (Dynamic Geology), Process of formation and alteration of landforms (Geomorphology) Evolution of life (Palaeontology) Study of rocks (Petrology) Civil engineering construction (Engineering geology) Exploitation of minerals (Mining geology) Oil & Gas (Petroleum geology) Study of physical properties of earth (Geophysics) Earths chemical properties study (Geochemistry) and the list goes on., Key Concepts of Geology We need to know about the types of rocks found in vast areas of the earth, plate tectonics and the chronology of the e