THE GREAT FAULT TROUGHS OF THE ANTILLES 99 



3,932 m. have been obtained within 20 km. of the coast. There 

 is no evidence of important seismic activity along this branch 

 zone east of Jamaica, and therefore, if the channel be due to fault- 

 ing, as seems probably, a condition of at least temporary stability 

 has been attained. 



The Cayman Islands-Sierra Maestra-North Haiti Fault Zone. — 

 This fault zone extends along the north side of the Bartlett 

 Trough, crosses the Island of Haiti between Manzanillo Bay and 

 Samana Bay, and, in the vicinity of Mona Passage, joins the fault 

 zone which forms the south side of the Brownson Trough. 



The Sierra Maestra range, after closely following the straight 

 east-west coast of southern Cuba, continues westward as a sub- 

 marine ridge, which, bearing slightly toward the south, reappears 

 above the surface in the Cayman Islands and almost reaches the 

 surface in the Misteriosa Bank. It culminates in the Pico del 

 Turquino which rises abruptly from the sea to an altitude of 

 2,000 m. The precipitous southern slope of the range is continued 

 below sea-level to depths of over 6,000 m., forming one of the most 

 magnificent fault scarps known. At the base of this scarp, which 

 forms the north side of the great Bartlett Trough, there is a narrow 

 subordinate trough or series of elongated depressions containing 

 four of the deepest soundings obtained in these waters; and it is 

 interesting to note that these soundings are located opposite points 

 where the top of the scarp is relatively high. The four soundings 

 are: 5,501 m. immediately southeast of Misteriosa Bank; 6,269 m., 

 32 km. south of the Cayman Islands; 5,724 m., 35 km. south of 

 Cape Cruz; and 6,412 m., 50 km. south of Turquina Peak. In 

 passing south from Turquina Peak there is a precipitous descent 

 to something more than 2,286 m. below sea-level, and then an ascent 

 to 1,582 m. below sea-level before the descent to 6,412 m. is made 

 (see profile. Fig. i). Farther east there are other submerged peaks 

 or ridges near the base of the scarp. 



Vaughan has referred to the precipitous profiles along the south 

 shore of Cuba as indicative of faulting and states that this interpre- 

 tation is supported by the geologic structure.^ The La Cruz marl 



^ T. W. Vaughan, "Some Littoral and Sublittoral Physiographic Features of 

 the Virgin and Northern Leeward Islands and Their Bearing on the Coral Reef 

 Problem," Jour. Wash. Acad. Sci., Vol. VI (1916), p. 56. 



