78 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



that sediments off shore were remarkably uni- 

 form. Out to a distance of some 40 miles from 

 shore a combination of fine sand and coarse silt 

 with an average diameter of 100 microns was 

 found; this material was extremely well sorted. 

 On the outer shelf the sediments were much finer, 

 the average diameter being about 1 micron, and 

 they were poorly sorted. In water over 11,000 

 feet deep in the central part of the Gulf foramini- 

 feral ooze at the surface was underlain, beginning 

 at 2 feet depth, by alternating clay, silt, and sand, 

 the silt and sand being extremely well sorted. 



A core taken in the Mexican Basin in 1947 is 

 of unusual interest. Trask, Phleger, and Stetson 

 (1947, p. 461) reported that: 



The upper foraminiferal zone, 50 cm. in thickness, is 

 characterized by a subtropical planktonic fauna . . . 

 Between depths of 50 and 68 cm. in a zone of red clay or 

 red mud, the fauna is transitional between cold and 

 warm water faunas. Between depths of 74 and 78.5 

 cm., at the top of the zone of banded clay and silt, the 

 fauna is definitely sub-Arctic . . . Between 78.5 cm. and 

 125 cm., the fauna is cold-water in type but is warmer 

 than that between 74 and 78.5 cm.; and from 125 to 128 

 cm., at the bottom of the core, the fauna is definitely 

 sub- Arctic. 



Trask (1948, p. 683) mentioned that ice-age 

 deposits showing crossbedding or ripple marks 

 were found in the coarse elastics of two cores taken 

 in the central Gulf of Mexico. In other cores 

 "well-sorted sand zones, one and three feet, 

 respectively, were encountered at depths of more 

 than three feet beneath the surface of the sedi- 

 ments. Such deposits, if hardened into rock and 

 formed in a geosyncline, would be taken as 

 compatible with the idea of shallow-water depo- 

 sition. Yet they were encountered in 11,000 

 feet of water." 



The Fish and Wildlife Service of the United 

 States Department of the Interior, cooperating 

 with the Agricultural and Mechanical College 

 of Texas, is making a systematic survey of the 

 Gulf of Mexico. Much of the physical ocean- 

 ography is being done by the Texas A. and M. 

 Department of Oceanography, and the Depart- 

 ment of Geology is cooperating in the study of 

 Gulf problems of marine geology. Samples of 

 sediments obtained early in 1952 are now being 

 studied. 



SEDIMENTARY PROVINCES 



The major sedimentary provinces of the Gulf 

 are shown on the map in figure 16. The basic 



data for this map were collected from many 

 sources, including the publications of Agassiz, 

 Carsey, Gunter, Kindle, Lowman, Murray, Phleg- 

 er, Price, Shepard, .Stetson, Trask, and Weaver, 

 and by personal communications from individuals 

 principally W. A. Price, Department of Ocean- 

 ography, Agricultural and Mechanical College of 

 Texas. Unfortunately, the data resulting from 

 some 600 cores taken from the Atlantis in 1946 

 are not yet available. Also, the systematic 

 exploration of the Gulf now in progress will 

 provide many bottom samples from the whole 

 Gulf area, and these data will make possible 

 more detailed sediment maps in the future. 



The recent sediments are divided into lithologi- 

 cal units which form somewhat indefinite zones 

 parallel to the coast and extending outward on 

 the continental shelf. In general, sands and 

 shales predominate from Florida west and south 

 to Cabo Rojo, Mexico, while limestone forms a 

 wide platform west and north of the Yucatdn 

 Peninsula and west of Florida. 



EASTERN GULF 



Modern calcareous sediments were thought by 

 Agassiz (1888, p. 286) to cover the continental 

 shelf on the west side of Florida. The charts of 

 this area show "sand and shells" and are therefore 

 deceiving. Samples from this region that were 

 examined by Shepard (1932, p. 1021) "were lacking 

 in quartz-sand and the use of sand as a textural 

 term seemed questionable." Little sediment goes 

 to the Gulf in streams from the Florida Peninsula, 

 and the shore deposits consist largely of calcium 

 carbonate secreted by organisms. Even the 

 Apalachicola River does not discharge an appre- 

 ciable amount of clay and silt. However, some 

 quartz sand is found relatively near shore from 

 Mississippi eastward across Alabama and the 

 panhandle and near shore along the northern part 

 of the west coast of Florida. Also, recently, num- 

 erous sand bars have been found on the northern 

 part of the continental shelf west of the Florida 

 Peninsula. 



The area off shore from Alabama and the pan- 

 handle of Florida has detrital sediments which 

 show the influence of the southern Appalachians. 

 These sediments contain an abundance of ilmenite, 

 staurolite, kyanite, zircon, tourmaline, and silli- 

 manite, and only minor amounts of magnetite, 



