Sedimentary Rocks

Sediments

Loose, unconsolidated rock particles and ions (i.e., charged atoms) dissolved in aqueous solutions.

Sedimentary Rocks

Constitute about 75% of all rocks exposed at the surface of the Earth formed when the particles are cemented together or when crystals precipitate from the solutions.

Importance of Sedimentary Rocks (particularly sandstone)

They host petroleum deposits and most of the uranium used for generating nuclear energy.

Types of Sedimentary Rocks

There are three types: Clastic (or detrital), Biochemical, and Chemical.

Clastic Sedimentary Rocks

Constitute more than 75% of the total sedimentary rocks.

Clastic Sedimentary Rocks

These rocks are formed from cemented grains and particles derived from the breakdown of preexisting rocks of any type (e.g., igneous, sedimentary, or metamorphic).

Classification of Clastic Sedimentary Rocks

Based mainly on the size of the grains.

Conglomerate

A clastic sedimentary rock formed by gravel with rounded grains.

Breccia

A clastic sedimentary rock formed by gravel with angular grains.

Gravel

Grains bigger than 2 mm in diameter: granules, pebbles, or boulders.

Sandstone

A clastic sedimentary rock formed by grains between 1/16 and 2 mm in diameter.

Quartz Sandstones

Sandstones formed mostly by grains of the mineral quartz.

Arkoses

Sandstones formed mostly by grains of the mineral feldspar.

Graywackes

Sandstones that include high amounts of fine-grained clay.

Silt

Grains between 1/256 and 1/16 mm in diameter.

Clay

Grains smaller than 1/256 mm in diameter.

Siltstones

Formed from cemented silt grains.

Claystones

Formed from cemented clay grains.

Mudstones

Siltstones and claystones are sometimes collectively called ___.

Shale

A mudstone that easily splits in different layers.

Biochemical Sedimentary Rocks

Formed from the remains of organisms.

Peat

Commonly brown and porous, formed from plant fragments that are still visible.

Bituminous Coal

Black without distinguishable plant remains, formed from plant fragments.

Fossiliferous Limestone

Formed from fossil shells and coral and is the most common biochemical sedimentary rock.

Chemical Sedimentary Rocks

Formed by precipitation from aqueous solutions.

Common Chemical Sedimentary Rocks

Limestone (CaCO3), dolostone (CaMg(CO3)2), chert (SiO2), rock salt (NaCl), and rock gypsum (CaSO4·2H2O).

Limestone

__ is the rock that most commonly is responsible for the development of karst topography.

Chocolate Hills

Made out of limestone, which is a type of sedimentary rock, located in Bohol, Philippines.

Zambales Ophiolite

Consists of igneous, metamorphic, and sedimentary rocks.

Zambales Ophiolite Lithology

Includes peridotite, gabbro, diabasic dike complex, diorite, pillow basalt, pelagic limestone, sandstone, and mudstone.

Zambales Ophiolite Distribution

Occupies the greater part of Zambales province; Mayantoc, Tarlac; Barlo and Sual, Pangasinan.

Zambales Ophiolite Description

An east-dipping complete sequence of oceanic crust and mantle material, located at the western portion of Central Luzon spanning 160 km N-S and 40 km at its widest (E-W) portion.