A GEOLOGICAL RECONNAISSANCE IN HAITI 749 
through the high range and through the hills of Las Cahobes beds 
north of that place is very distinctive. 
Successive uplift and periods of quiescence brought about the 
terracing of this region and the dissection of the plain. Erosional 
remnants standing as high as the old surface are numerous. Appar- 
ently only recently has the Artibonite River passed out of the 
plain region through the Montagnes Noires farther west. 
Elevated coral reefs and marginal deposits.—The same successive 
elevations and periods of quiescence which brought about the 
Fic. 1o.—Terraces of the central plain 
terracing of the central plain region has also terraced the coast, a 
well-known feature of the islands of the Antilles. On many of 
these terraces are coral reefs and marginal sands, while coral 
débris is common. Near St. Marc is an elevated deposit which 
contains innumerable specimens of Strombus gigas. 
IGNEOUS ROCKS 
SYENITE-GRANITE 
The igneous rocks of Haiti present quite a range from almost a 
true granite to basalt. The oldest igneous rocks are the more acid, 
the youngest the more basic. 
The oldest rocks are the syenites and granites which occupy 
the large areas or belts more or less parallel with the axis of the 
