82 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



"sand" near shore and "mud" off shore, showing 

 an outward gradation of sediments. 



Agassiz (1878, p. 1) found the fauna of the 

 Yucatan Bank to be identical with that of the 

 Florida Bank, being characterized by the same 

 species of echinoderms, mollusks, crustaceans, 

 corals, and fishes. 



From Tampico southward beyond Veracruz 

 volcanic rocks are found near shore, and possibly 

 igneous rocks will be found in the adjacent Gulf 

 waters. Therefore, the sediments in this area 

 should be somewhat different from those off 

 southern coastal Texas and from those associated 

 with the limestone of the Campeche Banks to the 

 east. The coastal plain is exceedingly narrow 

 locally, and the beach sands give way to near- 

 shore patches of coral. In many places mud 

 extends out on the shelf beyond the coral. 



YUCATAN PENINSULA 



The beach sands along the west and north 

 shores of the Yucatan Peninsula do not spread 

 far from shore except locally where sand and mud 

 are found out to the edge of the shelf. To the 

 southwest of the peninsula the sand becomes 

 mixed with near-shore coral patches. 



Numerous local patches of coral occur over the 

 Campeche Banks, and in other places the bottom 

 is very similar to the Florida Bank. The hard 

 limestone is locally covered with a thin veneer of 

 detrital sediments. The Globigerina ooze prov- 

 ince joins the Campeche Banks apparently with 

 the blue mud absent between these calcareous 



sediments. 



CUBA 



Corals are common at the outer edge of the 

 narrow shelf off the northern coast of Cuba. 

 Beyond these corals the Florida Straits contain 

 calcareous mud with the exception of a local area 

 to the northwest of Cuba where pteropod ooze 

 has been found. 



A bottom sample taken in 20 fathoms of water 

 at 24°25' N. lat. and 82°26' W. long, was sub- 

 jected to a chemical and spectrographic analysis. 

 Also, use was made of electrolytic separation in a 

 mercury cathode cell to concentrate the trace 

 elements. No unusual trace elements were found, 

 and the common elements were in approximately 

 the same abundance as has been determined by 

 others who analyzed the skeletal material of 

 organisms which contribute to sediment formation. 



MEXICAN BASIN 



The upper surface of the floor in the deepest 

 part of the Gulf consists of foraminiferal ooze. 

 The few available cores show the underlying sedi- 

 ment to be clay, silt, and sand, which is cross- 

 bedded and ripple-marked in some cores. The 

 origin of this detrital material is unknown as is 

 also the origin of the basin forming the Gulf. 

 Turbidity currents may have brought much sedi- 

 ment to the central Gulf. Such an origin is 

 further suggested by the presence of continental- 

 shelf Foraminifera in the Mexican Basin sediments. 



Agassiz (1888, pp. 280-282) quoted Murray who 

 observed that the globigerine and pteropod ooze 

 found in the central Gulf of Mexico differed 

 materially from that found in the oceanic basins. 

 Diatoms, radiolarians, and sponge spicules com- 

 prise the siliceous organisms but represent only a 

 small percentage of the bottom deposits. Fish oto- 

 liths were found at depths from 392 to 1,568 fath- 

 oms. The globigerine ooze was found to extend 

 northward to the Mississippi River slope where it 

 was replaced by dark, rich muds containing "a 

 number of interesting forms of annelids, mollusks, 

 ophiurous and sea-urchins, characteristic of the 

 continental Gulf slope, and typical of mud 

 deposits" (idem., p. 282). 



CONCLUSIONS 



The Gulf of Mexico, with a surface area of 

 615,000 square miles, offers many rewards for 

 research in geology, biology, and oceanography. 

 Continued drilling at the extreme margins of the 

 Gulf may produce new local data as greater depths 

 are reached by the drill, but much of the search 

 must be made far from shore. To date most of the 

 geophysical prospecting has been in the very shoal 

 areas where present methods of development may 

 apply. The use of geophysics to study the tec- 

 tonics of the Gulf largely lies in the future. 

 Therefore, it seems that present aid in solving the 

 many problems of the Gulf of Mexico must come 

 from the oceanographer who can give other 

 scientists new data from soundings, bottom 

 samples, and the physical characteristics of the 

 water. 



While the time and manner of the origin of the 

 Gulf basin are still undetermined, present evidence 

 favors the existence of a shallow Gulf, the "plate" 

 of Suess and Schuchert. Assuming that Llanoria 



