GEOLOGY OF THE GULF OF MEXICO 



By S. A. Lynch,^ Agricultural and Mechanical College of Texas 



The lower Gulf coast and the inner continental 

 shelf of the Gulf of Mexico are the sites of oil 

 fields in Veracruz, Tamaulipas, Texas, Louisiana, 

 and Florida. Therefore, hundreds of geologists, 

 geophysicists, and engineers are engaged in inves- 

 tigations of the structure, geologic history, and 

 sedimentology of the fringe of the Gulf of Mexico. 

 Due to the economic necessity for research to 

 discover new trends and new provinces of petro- 

 leum accumulation and to the many data contin- 

 uously being furnished by the drill and geophysics, 

 great strides have been made in the knowledge of 

 the continental shelf and the adjacent Coastal 

 Plain of the United States. Even though these 

 economic studies were of the coastal area and con- 

 tinental shelf, they have encouraged thought con- 

 cerning the origin and geologic history of the Gulf 

 of Mexico. 



A modern study of the Gulf Stream was initi- 

 ated by the United States Coast Survey in 1846, 

 and some work in the Gulf of Mexico was started 

 soon thereafter. During the last century, many 

 capable students of geology have studied the geo- 

 logical history of the Gulf of Mexico, but there is 

 still much diversity of opinion concerning its 

 origin and manner of development. 



EARLY CONCEPTS 



Early European writers initiated the idea of 

 North and South America being tied together by 

 a continuous mountain sj'stem, and this century- 

 old concept is still popular in Europe. Suess 

 (1885, pp. 283-285) described the Gulf of Mexico 

 bottom as an elevated "plate" and considered 

 this plate the foreland of the Antillean chain. 

 He believed the present deep Gulf did not exist 

 in Paleozoic time, but an old metamorphosed 

 and deformed basement formed a somewhat flat 

 platform that continued southward the low-lying 



' Contribution from the Department of Geology of the Agricultural and 

 Mechanical College of Texas, Oceanographic Series No. 18. 



' Head, Department of Geology, Agricultural and Mechanical College of 

 Texas, College Station, Texas. 



259534 O— 54 6 



central area of the United States. The present 

 Gulf of Mexico was formed by the collapse of the 

 plate during Cretaceous and later time, and the 

 general outline of the Gulf was "not influenced by 

 the course of the mountainfolds unless perhaps in 

 the west by the approach of the Mexican ranges 

 to the coast of Vera Cruz" (1885, p. 551). The 

 plate of Suess has influenced geologic thought con- 

 cerning the origin of the Gulf for the past three- 

 score years. 



Spencer (1895, pp. 103-140) not only believed 

 that the whole tract of the Caribbean Sea, the 

 Antilles, and the Gulf of Mexico constituted an 

 ancient continental region, but he attempted to 

 restore the topography of the submerged conti- 

 nent. Using available soundings, Spencer found 

 drowned valleys which he considered of prime 

 importance in establishing the existence of a 

 continental region which ever since the Miocene 

 had executed vertical fluctuations of an amplitude 

 of many thousands of meters. In discussing the 

 area, he stated, "the Gulf of Mexico appears to 

 have been a plain, with the fjords and embayments 

 reaching nearly to its greatest depths" (1895, p. 

 119). Thus, Spencer agreed with Suess, at least 

 in part, and postulated a Gulf floor more than 

 12,000 feet above its present deepest position. 



Hill (1898, pp. 3-5) believed the Gulf of Mexico 

 is more closely related to North America than to 

 Central or South America. He declined to con- 

 sider most of the Antilles as other than true 

 oceanic formations and refused to believe that 

 there is any connection between the northern 

 Antilles and Barbados-Trinidad, the latter being 

 by him assigned to the South American mainland. 

 He saw that the Gulf is nearly surrounded by low 

 plains composed of nearly horizontal, uncon- 

 solidated sediments deposited in an enlarged 

 Gulf of Mexico. This border of plains is in direct 

 contrast to the Caribbean and its mountainous 

 periphery. 



Willis (1929, p. 328) held that basins are per- 

 manent, and he did not believe the Gulf of Mexico 



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