Helping San Diego, California and beyond since 1997.
Do you need
volunteer, community service, work, military or court hours?
|
|
Helping San Diego, California and beyond since 1997.
|
|
Click here and add this page to your favorites!
|
Encyclopedia Britannica - Main :: COM-COR |
|
|
CONGLOMERATE (from the Lat. conglomerare, to form into a ball, glomus, glomeris; so also the general term " conglomeration " for a miscellaneous collection of things, gathered together in a mass) , in petrology, the term
rock
rock
Scotland , which are thousands of feet in thickness, consist largely of andesite, porphyrite, granite, diorite and porphyry , along with vein-quartz, quartzite and various kinds of gneiss. Soft and friable rocks, on the other hand, such as shale, mica-schist and coal, are rarely found in any quantityas pebbles in conglomerate
diameter , more frequently they are a foot or less. The cementing matrix in which the pebbles are embedded usually bears some resemblance in composition to the nature of the pebbles, but contains a larger proportion of the softer ingredients, such as clay, mica, weathered felspar, calcite and dolomite. Often it resembles a felspathic or calcareous sandstone; if limestone fragments are common it may be highly calcareous, or may be in large measure dolomitic. Often the matrix is stained red by compounds of iron. The " brockram " of the north of England is a well-known Permian limestone-conglomerate . The Dolomitic Conglomerate is a similar rock, but of Triassic age. Both of these are often extensively dolomitized and pass into breccias, where their fragments are angular and unworn. The pebble beds of the Bunter (Triassic period) are also familiar to geologists. They cover extensive areas in the mid-lands of England, and are well seen at Budleigh Salterton on the south
coast
Conglomerates are rarely well bedded, showing at most a rude stratification, but they may contain intercalations of finer materials such as sandstone and shale, which indicate the bedding clearly. In these fossils may be found, but they do not often occur in the conglomerates themselves, as the conditions are generally unsuitable for the preservation of organic remains. The pebbles, however, may be highly fossiliferous, and sometimes important evidence is provided by this means as to the age of the'eonglomerate. On account of the imperfect stratification it is often very hard to estimate the thickness of conglomerates, and this difficulty is increased by the fact that many of them must have been laid down as sloping banks of pebbles and not as flat layers of deposit. Conglomerates are merely consolidated gravels, and have originated mostly on seashores or in shallow waters near land. They are typical shore formations, and are especially frequent where one series of stratified rocks rest upon an older group unconformably. Other conglomerates occur along with fine-grained red sandstones, salt beds and such rocks as accompany desert deposits. We may compare them with the accumulations of pebbles which cover extensive areas of existing deserts. A quite distinct group of conglomerates characterizes regions where the rocks are much broken and sheared; these may very closely resemble true conglomerates, but have really been produced by the mashing together of rock masses along zones of fracture and movement
movement
End of Article: CONGLOMERATE (from the Lat. conglomerare, to form into a ball, glomus, glomeris; so also the general term " conglomeration " for a miscellaneous collection of things, gathered together in a mass) If you wish, you can link directly to this article.
<a href="http://jcsm.org/StudyCenter/Encyclopedia/COM_COR/CONGLOMERATE_from_the_Lat_cong.html"> CONGLOMERATE (from the Lat. conglomerare, to fo... </a> |
|
|
(Previous) CONGLETON, HENRY BROOKE PARNELL, 1ST BARON (177... |
(Next) CONGO |
|
Sponsored Advertisements