412 ANNUAL KEPORT SMITHSONIAN INSTITUTION, 1908. 



or Amotape hills (see pi. 2). The lithologic characters of the 

 beds vary considerably, consisting of shales, sandstones, conglomer- 

 ates, and in some places beds filled with shells and occasionally 

 there are coral reefs. The changes observed in the nature of the 

 formation are due to the varying distance from the shore at which 

 they were deposited and to the deepening and shallowing of the 

 water during the time of sedimentation. It is probable that the 

 materials were derived from the mountainous area which during 

 Tertiary time formed the ocean shore to the east, approximately 

 where now are the foothills of the Andes. 



The strata of the formation are not much lithified and the shales 

 and sandstones grade into each other and into conglomerates. In 

 the Brea hills the Amotape formation has been uplifted in an 

 anticline, giving good exposures where the stream valleys have been 

 eroded. The thickness of the beds has not been studied carefully, 

 but from the outcrops seen it is safe to say that on the average it is 

 not less than 1,000 meters, although the thickness may be much less 

 in some places and greater in others, depending upon the distance 

 from the Tertiary shore. 



Fossils are very abundant and well preserved at many places, one 

 of the most noticeable being a large oyster which is found in such 

 great numbers that it is used locally for burning lime. 



The principal mineral substance which is exploited at the present 

 time is petroleum, of which there are superfiicial indications at two 

 places called la Brea and la Breita. The productive localities are 

 Negritos, Lobitos, and Zorritos located on the coast. Besides these 

 some prospecting has been done farther inland. It has been reported 

 that coal has been found at various localities within the limits of 

 this formation. That which the writer examined at Bahia de la Cruz 

 is a lignite, and prospecting failed to reveal a bed of any importance. 

 The writer has been assured that north of Sullana, at the base of 

 the Brea hills, a good quality of lignite has been found and of suf- 

 ficient thickness to warrant its extraction. However, the bed has 

 never been worked and further exploration would be necessary to 

 prove its commercial value. The Amotape formation contains va- 

 rious mineral salts, especially gypsum, which render the water 

 obtained from it unfit for domestic uses. The formation extends 

 throughout the plains region from the Ecuadorian border southward 

 into the table-land to the east of Pita. Undoubtedly it extends far- 

 ther south, but the exposures are obscured by drifting sands and 

 have not been studied by the writer. It may be noted in this con- 

 nection that Wolf in his geologic map of Ecuador has erroneously 

 indicated a recent formation in the plains region to the north of the 

 Brea hills. 



