498 O. H. HERSHEY GEOLOGICAL RECONNAISSANCE IN NICARAGUA 



entirely of the alluvium of the river and of beach deposits. The river 

 has two mouths, and all the land bordering on them is very low, prob- 

 ably only a foot or 18 inches above ordinary high-tide level. Very little 

 of it is marshy, although there are a few small lagoons back of the beach. 

 No evidence was seen here of the recent elevation of the coast mentioned 

 by Crawford. 



In ascending the Wanks Eiver, on May 11, 1910, when it was prob- 

 ably at its lowest stage, the following observations were made : As far 

 up as the Indian village of Living Creek, said to be 56 miles from the 

 mouth of the river, but probably about 45 miles, the stream is from 100 

 to 150 yards wide and apparently rather deep. It winds about in great 

 curves in a broad delta plain. The banks are steep and very gradually 

 increase in height. At the Colimer ranch, said to be 12 miles from the 

 mouth, the bank is 6 feet high, of which the lower 4 feet consist of light- 

 brown sand, the next 8 inches of black and dark reddish material like a 

 buried soil, and the upper 16 inches of brown sandy alluvium. Shells of 

 species now living in the river are abundant in the upper stratum, less so 

 in the dark layer. From the edge of the bank on the north side of the 

 river level savannas extend back several miles. 



In the vicinity of Living Creek the banks were 10 to 12 feet high. 

 In ordinary years the river apparently does not reach the top, but occa- 

 sionally it overtops them a few inches and floods the alluvial plain for a 

 short time. The alluvium as seen from a boat seems largely clay below, 

 passing to silt above. It is in bands of reddish brown, dark gray, and 

 light brown. Bars of light-colored sand appear on the inner sides of 

 curves. No gravel was seen below tlie village, but bars of fine gravel 

 appear a short distance above it. The river continued to be about 100 

 yards wide and to have steep 10-foot banks of banded alluvium, but 

 there is said to be higher ground at a. distance of several miles back 

 from it. We had apparently passed out of the Modern delta proper into 

 a broad, alluvium-floored valley, in which the river winds as in the 

 delta. The country bordering the valley is said to consist of low ridges 

 and may be the dissected remnant of some older delta deposit. The 

 tropical vegetation on the banks and the fact that I traveled in a small 

 boat prevented me from seeing any part of these ridges for many miles 

 after we were said to have entered the valley between them. 



At Sawa the banks are 18 to 20 feet high and no higher land can be 

 seen from the village. An extensive bar between the stream and the 

 bank consists of fine gravel, largely white quartz. The alluvium in the 

 banks is partly sand, partly the claylike banded material. Fine gravel 

 appears in places at the foot of the sandy bank. 



