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THE QUALITY OF THE BOTTOM
A GLOSSARY OF TERMS
WILLIAM H. BERNINGHAUSEN
Oceanographic Analysis Division
U. S. NAVY HYDROGRAPHIC OFFICE
WASHINGTON 25, D. C.
Price 20 cents
Notations of bottom types which appear on navigation charts
are a valuable source of data used in compiling bottom sedi-
ment charts. The correct and consistent interpretation of
these notations in terms of the sediment classification (Mud,
Mud-Sand, Gravel, Shell and Coral) used on U. S. Navy Hydro-
graphic Office bottom sediment charts is essential in main-
taining high standards of reliability. This glossary indicates
how bottom sediment notations are reconciled to this classi-
This glossary is designed for use in the Hydrographic Office
training programs which include instruction in the preparation of
bottom sediment charts. It defines bottom type notations given on
navigation charts in an effort to make more uniform their interpreta-
tion and use in bottom sediment charts produced by this Office. In
addition, the glossary should assist researchers in comparing and
evaluating notations and symbols which appear on navigation and bottom
Rear Admij^l, U. S. Navy
THE QUALITY OF THE BOTTOM
Various kinds of charts are compiled to describe, in one way or
another, the type or quality of the ocean bottom. The commonest type
is a chart which shows the relative size of the particles that make up
the bottom sediments. For this purpose the U. S. Navy Hydrographic
Office uses the standard categories of mud, sand, gravel, and rock.
The two additional sediment categories used are shell and coral;
however, these do not relate directly to size but indicate origin and
chemical composition. Other charts of a more specialized nature may
be made in addition to the standard bottom sediment chart, such as
charts showing the presence or proportion of calcium carbonate or the
distribution of globigerina.
The chief sources of data used in compiling bottom sediment charts
are navigation charts. To use these sources effectively, one needs to
know (with as much precision as possible) the meaning of the various
abbreviations used on these charts to indicate the type or quality of
the bottom. This glossary was compiled to meet this need.
The following list is based on the International Hydrographic Bureau,
Glossary of Cartographic Terms, 1951 and the U. S. Navy Hydrographic
Office Chart No. 1, "Nautical Chart Symbols and Abbreviations," 1957.
The definitions herein are based, for the most part, on "Websters New
Collegiate Dictionary," 1954, "The Glossary of Geology and Related
Sciences," American Geological Institute, 1957, and H. O. Pub. No.
220, "Navigation Dictionary," 1956.
Often some indication of the type or quality of the bottom is given
by landforms of the adjacent coast and by other notations not usually
classified under the general heading "Quality of the Bottom." Such
symbols can be found in H. O. Chart No. 1, page 1, "The Coastline"
and page 12, "Dangers."
The abbreviations and terms are listed in the order given in the
H. O. Chart No. 1, rather than in alphabetical order. On nautical charts
the initial letter of the abbreviation of names is in capitals and the
initial letter of the abbreviation of adjectives is in small letters. When
these abbreviations appear on a chart, they may or may not be followed
by a period depending on the date of the chart.
1. Grd. Ground; the bottom of the ocean; the sea floor.
2. S. Sand; loose detrital material consisting of small but
easily distinguishable separate grains ranging between
0.0025 and 0.0787 inch (0.0625 and 2.0000 millimeters)
3. M. Mud; pelagic or terrigenous detrital material consisting
of particles smaller than sand; that is, an undifferen-
tiated sediment made up of particles mostly within the
silt-clay range smaller than 0.0025 inch (0.0625 milli-
4. Oz. Ooze; an unconsolidated deep sea deposit composed of
30 percent or more of the shells (tests) of foraminifera,
diatoms, and other marine organisms, for example,
diatom ooze and globigerina ooze.
5. Ml. Marl; a calcareous clay which may include silts and
sand. This sediment is classed as mud-sand.
6. CI. Clay; fine-grained sediments with particle size smaller
than approximately 0.00008 inch (0.004 millimeter).
When not separately designated on a bottom sediment
chart, clay is classed as mud.
7. G. Gravel; loose detrital material which consists of frag-
ments ranging in size from approximately 0.08 to 10.08
inches (2 to 256 millimeters).
8. Sn. Shingle; rounded, often flat waterworn rock fragments
(very coarse gravel). Shingle is classed as gravel on
bottom sediment charts.
9. P. Pebbles; small, usually rounded rock fragments ranging
in size from 0.16 to 2.59 (4 to 64 millimeters) in
diameter. Pebbles are classed as gravel on bottom
10. St. Stones; detached particles of rock usually smaller than
10 inches (256 millimeters) in diameter. Stones are
classed as gravel on bottom sediment charts.
11. Rk.,rky. Rock; rocky; the naturally occurring material that
forms the firm, hard, and solid masses of the ocean
floor. On navigation charts the abbreviation Rk. usually
indicates a rocky formation or a single large boulder
which may constitute a danger to navigation.
12. Ck. Chalk; soft earthy limestone of marine origin composed
chiefly of minute shells. It is white, gray, or buff in
color. Chalk is classed as rock on bottom sediment
13. Qz. Quartz; silicon dioxide. The most common inorganic
constituent of the detrital particles on the ocean floor.
14. Co. Coral; the hard calcareous skeletons of certain tiny
marine animals, or the stony solidified mass of a
number of such skeletons. In warm waters colonial
coral forms extensive reefs of limestone. In cool
or cold water coral usually appears in the form of
isolated solitary individuals. Occasionally, large reefs
formed in cold waters by calcareous algae ( Litho-
thamnion ) have been noted on navigation charts as coral.
14a. Co. Hd. Coral head; a mass of coral, usually forming a portion
of a reef. Frequently, coral heads are large enough to
be dangerous to navigation. On the basis of size, coral
heads would be classed as rock, but are shown as coral
on bottom sediment charts.
15. Mad. Madrepore; a branching coral; also any perforated
Md. stone coral. Madrepore is classed as coral on bottom
Mds. sediment charts.
16. Vol. Volcanic.
16a. Vol. Volcanic ash; usually fine-grained material ejected by
Ash a volcano. Volcanic ash is classed as sand on bottom
17. La. Lava; fluid rock such as that which issues from a
volcano or a fissure in the earth's surface; also the
same material solidified by cooling. Since this material
usually is massive, it is classed as rock on bottom
18. Pm. Pumice; an excessively cellular, glassy lava. It is very
light and floats on water until it becomes water logged
and sinks. Pumice is classed as gravel on bottom
19. T. Tufa; a chemical sedimentary rock composed of calcium
carbonate or silica. Tufa is included with rock on bottom
sediment charts. On U. S. Navy Hydrographic charts for
the western coast of France the notation T may mean
tangue, a calcareous deposit derived from a variety of
20. Sc. Scoriae; volcanic slag, pyroclastic ejecta; fragments
of scoriae between 0.16 and 1.26 inches (4 and 32
millimeters) in size are essentially equivalent to
volcanic cinders. Scoriae are classed as gravel on
bottom sediment charts.
21. Cn. Cinders; volcanic cinders (see scoriae).
22. Mn. Manganese; manganese dioxide; the black oxide of a
metal. Manganese dioxide usually is found on the ocean
bottom in the form of nodules. Manganese nodules are
classed as gravel on bottom sediment charts.
23. Sh. Shell; the hard outer covering of an animal. Shell
usually falls within the gravel size limits, but because
of its origin shell usually is classed separately on
bottom sediment charts.
24. Oys. Oysters; sessile mollusks with an unequal, irregular
bivalved shell. Oysters frequently occur in large banks.
Oysters are classed as shell on bottom sediment charts.
25. Ms. Mussels; sessile mollusks with a regular bivalved
shell. Mussels frequently occur in large banks. Mussels
are classed as shell on bottom sediment charts.
26. Spg. Sponge; a Porifera, a sessile invertebrate with a
skeleton formed of a mass of elastic fibers (spongin)
27. Grs. Grass; seagrass, seed-bearing marine plants found in
brackish and saline shallow water. They attain lengths
to 8 feet. Occasionally, the notation Grs. on a navigation
chart may refer to seaweed or kelp. The presence of
grass usually denotes a mud-sand bottom.
28. Wd. Weeds; seaweed, a plant growing in the sea, especially
28a. Kelp; brown algae of the order Laminariales, including
the largest known algae. Kelp typically grows on a rock
or stone bottom. They attain their greatest size in cold
waters, with lengths to 100 feet and blades 4 or more
29. Sea tangle; tangle; any of various seaweeds or kelps,
especially of the genus Laminaria .
30. Ballast; broken stone or gravel which has been used in
a vessel to improve its stability or control the draft.
31. Spicules; minute calcareous or siliceous bodies that
support the tissues of various invertebrates, such as,
sponges, radiolarians, and holothurians.
32. Fr. Foraminifera; minute one-celled marine organisms
which secrete a calcareous test (shell), or the test of
such an organism. Foraminifera may be an important
constituent of some deep sea deposits. If the Foraminif-
era constitute 30 percent or more of the samples, the
sediment is referred to as foraminferal ooze. On the
basis of size, foraminiferal ooze usually is classified
as mud-sand on bottom sediment charts.
33. Gl. Globigerina; a very common form of sediment-producing
Foraminifera. Globigerina ooze covers large portions
of the deep ocean bottom. On the basis of size a
globigerina ooze is classified as mud-sand.
34. Di. Diatoms; microscopic algae which secrete siliceous
tests (shells). Diatomaceous ooze covers large areas
of the ocean bottom. Diatomaceous ooze is classed as
mud on bottom sediment charts.
35. Rd. Radiolaria; minute marine protozoans which have a
siliceous skeleton of spicules and radiating threadlike
pseudopodia. Radiolarian ooze contains large propor-
tions of radiolarian skeletons and is an important
constituent of the deep ocean deposits. Radiolarian ooze
is classed as mud on bottom sediment charts.
36. Pt. Pteropods; pelagic, swimming-type gastropods in which
the foot is modified into a pair of winglike lobes or
fins. Pteropod ooze contains conspicuous shells of these
pelagic molluscs and is an important constituent of
the deep ocean deposits. Pteropod ooze usually is classed
as mud on bottom sediment charts.
37. Po. Polyzoa; Broyozoa, a colonial animal that secretes a
calcareous, horny, or membranous covering in a multi-
tudinous variety of forms and structures. Bryozoa may
form insignificant colonies on shells, or they may be
an important constituent of a reef.
38. Cirripeda; barnacles.
38a. Fucus; rockweed, any of a genus of olive-green or
brown algae. Fucus grows attached to rocks; hence the
38b. Mattes; an uneven growth of seagrass.
39. fne. Fine.
40. crs. Coarse.
41. sft. Soft.
42. hrd. Hard.
43. stf. Stiff.
44. sml. Small.
45. lrg. Large.
46. stk. Sticky.
47. brk. Broken.
47a. Ground (shell); shell that has been ground up by wave
or current action. Broken shell.
53. fly. Flinty; resembling flint, a dense, fine-grained form of
silica which is very tough and breaks with a conchoidal
fracture and cutting edges.
54. glac. Glacial.
55. Tenacious; sticky, coherent.
56. wh. White.
57. bk. Black.
58. vi. Violet.
59. bu. Blue.
60. gn. Green.
61. yl. Yellow.
62. or. Orange.
63. rd. Red.
64. br. Brown.
65. ch. Chocolate.
66. gy. Gray.
67. It. Light.
68. dk. Dark.
69. Ca. Calcareous; limey, containing lime.
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