of plankton organisms. The Inorganic deposits are 

 referred to as RED CLAY and the organic deposits 

 as OOZES. Pelagic deposits are classified in the 

 following way: 



I. Inorganic deposits. Those which contain less 

 than 30 per cent of organic remains are known 

 as red clay. 



II. Organic deposits. Those which contain more 



than 30 per cent of material of organic origin 

 are known as oozes. This class is further 

 subdivided into: 



1. Calcareous oozes. These contain more 



than 30 per cent calcium carbonate, which 

 represents the skeletal material of vari- 

 ous plankton animals and plants . The 

 calcareous oozes may be further divided 

 into three types, depending upon a charac- 

 teristic type of organism present in the 

 sediment, namely: 



Globigerina ooze, in which the calcium 

 carbonate is in the tests of pelagic 

 foraminifera. 



MARINE SEXTANT . A sextant designed primarily for 

 marine navigation. On a clamp screw sextant the 

 position of the tangent screw is controlled by a 

 clamp screw; on an endless tangent screw sextant 

 the position of the index arm and the vernier or 

 micrometer drum is controlled by an endless tangent 

 screw. A vernier sextant provides a precise read- 

 ing by means of a vernier used directly with the 

 arc, and may have either a clamp screw or an endless 

 tangent screw for controlling the position of the 

 tangent screw or the index arm. A micrometer drum 

 sextant provides a precise reading by means of a 

 micrometer drum attached to the index arm, and has 

 an endless tangent screw for controlling the posi- 

 tion of the index arm. A marine sextant is gener- 

 ally used with the visible horizon as the horizon- 

 tal reference. (17) 



MARINE SNOW . Suspended living and dead organic 

 material and inorganic debris of the sea which is 

 present in concentrated amounts at density boundar- 

 ies such as the thermocline. (35) 



MARINE SURVEY. See OCEANOGRAPHIC SURVEY 



b. Pteropod ooze, containing conspicuous 

 shells of pelagic molluscs . 



c. Coccolith ooze, containing large num- 

 bers of coccoliths and rhabdoliths 

 that form the protective structures 

 of the minute Coccolithophoridae. 



Siliceous oozes. These are pelagic 

 deposits which contain a large percentage 

 of siliceous skeletal material produced 

 by planktonic plants and animals . The 

 siliceous oozes are subdivided into two 

 types on the basis of the predominance of 

 the forms represented, namely: 



MARINE WEATHER OBSERVATION . The weather as observed 

 from a ship at sea, usually taken in accordance 

 with procedures specified by the World Meteoro- 

 logical Organization. The following elements 

 usually are Included: total cloud amount; wind 

 directi-on and speed; visibility; weather; pressure; 

 temperature; selected cloud-layer data, that is 

 amount, type, and height; pressure tendency; sea- 

 water temperature; dew-point temperature; state of 

 the sea (waves); and sea ice. Also included are 

 the date and time, and the name, position, course, 

 and speed of the ship. (24) 



MARINOSTAT . A controlled - environment facility 

 (Hopkins Marine Station, Pacific Grove, California.) 



b. 



Diatom ooze, containing large amounts 

 of diatom frustules, hence, produced 

 by plankton plants . 



Radiolarian ooze, containing large 

 proportions of radiolarian skeletons 

 formed by these plankton animals. 



The terrigenous deposits are found near shore and 

 generally contain at least some coarse material of 

 terrigenous origin. They cover a wide range in 

 depth and a great variation in color, texture, and 

 composition. The color may range from white to 

 black with the addition of blue, yellow, or red, or 

 mixtures of these. Several systems of classifica- 

 tion have been used without wide application due 

 to the dependance of terrigenous deposits on local 

 conditions. On the basis of texture they may be 

 classified as follows: 



1. Sand. More than 80 per cent of the 

 material coarser than 62 microns in 



diameter. 



2. Silty sand. Between 50 per cent and 80 

 per cent coarser than 62 microns . 



3. Sandy silt. More than 50 per cent 

 coarser than 5 microns and more than 20 

 per cent coarser than 62 microns. 



4. Silty mud. More than 50 per cent coar- 

 ser than 5 microns and less than 20 per 

 cent coarser than 62 microns. 



5. Clayey mud. Less than 50 per cent coar- 

 ser than 5 microns. (13) 



MARK IX SHORE WAVE RECORDER . The Mark IX was de- 

 signed as a general purpose wave measuring instru- 

 ment for permanent installation. The principal 

 component is a differential pressure potentiometer, 

 used as the transducer. The movement of a pressure 

 sensitive brass bellows is magnified by a potentio- 

 meter contact lever which, in the normal position 

 of zero differential pressure, divides the resist- 

 ance of the potentiometer windings equally. Varia- 

 tions of differential pressure cause the potentio- 

 meter contact arm to move across the windings. The 

 position variation of the potentiometer arm is con- 

 verted to a proportional current by the bridge cir- 

 cuit and recorded. (35) 



MARKER BUOY . 1. A temporary buoy used in survey- 

 ing to mark a location of particular interest, such 

 as a shoal or reef. 



2. Station buoy. (17) 



MARL . A general term for calcareous clay or cal- 

 careous loam. A calcareous clay or intimate mix- 

 ture of clay and particles of calcite or dolomite, 

 usually fragments of shells. In America the term 

 Marl is chiefly applied to incoherent sands but 

 abroad, compact impure limestones are also called 

 marls. (27) 



MARS (MOBILE ATLANTIC RANGE STATION) ■ An acoustic 

 navigation system. See also STAR for principle of 

 operation description. (35) 



73 



