OOZE. The fine homogeneous sediment. like mud, but softer and more sticky, forming a plas tie floury substance, which constitutes a large portion of the bottom in the deeper parts of the ocean. As this ooze is principally made up of the shells of (11obigtritut bulloides, a surface foraminifer, it is generally called 'gloldgerina ooze.' As early as 1850 Pourtales stated that at depths of 257 fathoms are still liv ing in immense numbers." Ilv stated that at great depths in the strait of Florida the bot tom is covered by a chalk-like layer, which re solves itself into a mass of Foraminifera. and their fragments more or less comminuted. This forma tion extends, he says, almost uninterruptedly in the whole bed of the Gulf Stream, in the greater depths of the Gulf of Mexico, in the deep eltan Ilds which intersect the Bahama Banks. and then up the Atlantic coast from about the 100 fathom curve outward, or from the inner limit of the Gulf Stream, which nearly eoineides with it, and so over the greater part of the Atlantic basin. The discovery of this formation belongs to the year 1853, when it was found almost si multaneously by Lieutenants Craven and Alatlit, then in the Coast Survey, and exploring the Gulf Stream. It became more extensively known somewhat later by the soundings made fur the Atlantic telegraph. The Foraminifera most abundantly represented in this bottom are of the genus Globigerina. Then occurs in order of fre quency Rotalina cultrata ; then set oral Textu larhe. Marginulime, etc. It is now pretty gen erally admitted that these rhizopods live and die in these great depths. But that animals liv ing near the surface also isintribute a large proportion is proved by the numerous shells of mollusks, teeth of fishes, etc.. contained in it. The Challenger expedition explorations estab lished that the pelagic bottom deposits are not derived from the shores of the continent. but are formed in the deep water of the central regions of the great ocean basins, and consist of organic oozes and a reddish clay. They are chiefly made up of the calcareous and siliceous remains of organisms that have fallen to the bottom from the surface waters, along with (day and volcanic diThris iu a more or less advanced state of I 1 e composithm. There is little or no traee of me chanical action on their components, their ac cumulation is relatively slow, and among them there do not appear to be ally ac cumulations of materials identical with the ma rice stratified rocks of the eontinental areas. It seems doubtful, says Thirray. whether the de posits of the abysmal areas have in the past taken any part in the formation of the existing emit inenta I masses.
A 'pteropod ooze' is met with in depths of less than 2000 fathoms in the tropics. and is very largely made up of pteropod and heteropod which also exist in considerable numbers in the deposits around oceanic and other islands.
1 In 'radiolarian and 'diatom' oozes the de posits consist of siliceous skeletons and frustules of surface organisms, which have likewise fallen from the surface waters. A radiolarian ooze has hitherto been met with only in the deepest waters of the western and central Pacific, and diatom ooze appears to be confined to the Southern Ocean, a little north of the Antarctic Circle.
Thus it will be seen. as Agassiz has pointed out, that the eharacter of a marine deposit is largely determined by its distance from land, and again by the nature of the organisms living in the surface waters. The dead shells of ptero pods, foraminifers, radiolarians, and diatoms are heaped up on the bottom, some in one part of the ocean, some in another; and as no other materials reach these distant to cover them. they form characteristic deposits. Depth is, however. an important factor in reference to the composi tion of a deposit in any locality. There seems to he now no doubt that the whole of the car bonate-of-lime shells. such as those of mollusks and foraminifers, are entirely removed by solu tion in very deep water during their fall from the surface to the bottom, or immediately alter reaching the bottom. It is found that, with increasing depth., the pteropod and heteropod shells are the first to disappear from deposits, then the more delicate surface foraminifers, and finally the larger and heavier ones. It is like Wise observed that, the more numerous these shells are in the sin face waters, the greater is the depth at which they will accumulate at the bottom. As a rule, a pteropod ooze or a globi gerina ooze is found in deeper water in the tropics than in temperate regions.
It must be remembered that all the bottom de posits merge into one another, and at times it is difficult to say whether a deposit should be called a red clay, or a radiolarian ooze, or a globigerina ooze, or a blue mud. It was thought by Pourtales and others that. the Globigerina lived in the oozes at the sea-bottom; but the Challenger observations have clearly established that many fo•amminifers have a pelagic mode of life (see I'EL,tOIc ANIMALS), flourishing in the pure currents of the open ocean, nearly all the species being confined to tropical and subtropical waters. There are not more than twenty or twenty-two species of pelagic Foraminifera; yet, says Murray. so numerous are the individuals of the species that they usually make up over 90 per cent, of the carbonate of lime present in the .alennsol.; oozes of the abysmal regions. The individuals belonging to even a dozen of these species far outnumber the individuals belonging to all the other known genera and species of Foraminifera. This is true not only with re gard to their abundance in the deep-sea deposits of the present period, but also to their great development in Tertiary and other geological formations. Murray adds that the species of Foraminifera which live on the bottom in deep water "are habitually under very uniform condi tions, and consequently their shells do not vary in size and thickness with change of latitude like those of the pelagic species. the animals of which are subject to great changes of temperature and salinity in the surface waters." 11mm0uusertY. Poortales, in lleyort of the United Stales Count Surrey, for 1853; Agassiz, Three- Pruines of the Blake (Cambridge. 1888) ; Murray, Report on the Seientifie Results of the Voyage of H. M. S. Challenger. Deep Sea De posils1 (London, 1891).