GEOLOGY OF THE PROVINCES OF BARAHONA AND AZUA. 187 



LAND FORMS. 

 PROVINCE OF BARAHONA. 



The surface of the Province of Barahona consists mostly of numerous 

 hogback ridges whose trend ranges from east to southeast. Most of the 

 rock of these ridges is hard white limestone, in beds that are generally in- 

 clined northward more or less steeply. The parallel ridges are probably in 

 large part the result of step faulting, a type of structure known to prevail in 

 this part of the island. The mountain tops as seen from a distance are 

 generally of even profile, but here and there isolated peaks extend above 

 the general summit. Some of the peaks visited consist of volcanic rock. 

 The highest mountain ridges are generally 1,000 to 1,500 meters above sea 

 level, and probably no peaks are as high as 2,000 meters. Between the 

 mountains are more or less extensive valleys that include local savannas. 

 Most of those in the interior have less rainfall than the coastal region and 

 some are said to be poorly watered and either treeless or covered with low 

 shrubbery of the mesquite and cactus type. 



The most striking topographic feature in the Province is Enriquillo 

 Basin, a valley 12 kilometers broad, extending from the Bay of Neiba 

 northwestward across the Haitian border to the sea at Port-au-Prince. 

 A part of the interior is depressed and is occupied by Lake Enriquillo, 

 a body of salt water whose surface lies (in June, 1919) about 44 meters 

 below sea level. To the west, in the Republic of Haiti, is the smaller 

 Etang Saumatre, a lake said to be less salty than Enriquillo. Extending 

 around Lake Enriquillo is a terrace of limestone having an altitude of 

 about 35 meters above sea level and 79 meters above the lake. The 

 upper part of this terrace is a mass of corals underlain by marly limestone 

 consisting largely of shells. The Quaternary age of the fossils denotes an 

 uplift of the valley from beneath the sea in comparatively recent time. 

 The barrier to the east against the slowly flowing waters of Rio Yaque del 

 Sur is so slight that they are used by the inhabitants for irrigating parts 

 of the intervening area. In times of flood the river actually overflows the 

 country and temporarily drains into Lake Enriquillo, and the Barahona 

 Company proposes to irrigate some 160 square kilometers of this land by 

 water diverted from the river through a tunnel to be cut through a low 

 hill near the village of Alpargatal. 



The general aspect of the lower valley of the Yaque suggests that its 

 delta deposits may have separated Lake Enriquillo from the Bay of Neiba, 

 the lake having been in comparatively recent geologic time an arm of the 

 sea. The actual separation probably took place during the regional eleva- 

 tion that formed one of the latest diastrophic movements. 



The east end of Lake Enriquillo is bordered by a broad mud flat that 

 rises very gently eastward to a barren waste of sandy "saladas," which 



