262 S. Powers — Notes on Hawaiian Petrology. 



basalt from the beach is a fine-grained augite basalt free 

 from olivine. 



Maui. — The volcano of West Maui, as judged from the 

 exposures and stream pebbles, has been built largely of 

 olivine basalt. Covering portions of the eroded older 

 rocks there is a veneer of trachyte as described later. 



West Maui contains one feature not observed else- 

 where. Deposits of fragments of subangular to rounded 

 stratified material are found in Launiopoko, Waikapu, 

 and Iao valleys and these streams are at present engaged 

 in cutting into these deposits which rest unconformably 

 on the sides of the older valleys. Ukumehame and 

 Olowalu gulches were not examined and therefore it is 

 not known whether or not the fragmental material is 

 found there. None was seen in Kanaha Gulch above 

 Lahaina. 



The conglomerate, as it may be called, in each case 

 fills an older, precipitously V-shaped valley and has be- 

 come so well consolidated that it stands in vertical cliffs. 

 In Launiopoko Gulch it occurs at an elevation of 1220 

 feet above sea-level on the west side of the stream just 

 below the first water tunnel. In one vertical section 20 

 feet are exposed, showing blocks y 2 foot to 5 feet in 

 length in a sandy or tuffaeeous matrix. Near the second 

 tunnel, at an elevation of 1,360 feet, a thickness of 40 feet 

 of the conglomerate, showing very coarse, unsorted 

 blocks, occurs at and above the present stream bed. 

 Toward the head of the gulch, at an elevation of 2,150 

 feet, 20 feet of conglomerate is exposed and in it are 

 fragments of a true breccia 6 by 5 by 4 feet in diameter 

 and lenses of water-worn pebbles. 



Waikapu Gulch presents similar beds. Gravels occur 

 at the entrance, near the flume, on the south side of the 

 valley at an elevation of 1,000 feet and in the bottom of 

 the gulch, 200 feet below. The deposits continue up the 

 valley to an elevation of 900 feet, but they were not ob- 

 served above the intake tunnel, elevation 1,050 feet, al- 

 though at this place they form cliffs 60 feet high. The 

 dip of the conglomerate beds is downstream at an angle 

 of 6 degrees. The beds are sorted into coarse and fine, 

 the subangular blocks in the former being 6 to 12 inches 

 long, those in the latter 2 to 3 inches. 



At the entrance to the Iao valley gravels are found at 

 an elevation of 550 feet, 25 feet above the stream. 

 Coarser gravels occur in a 20-foot vertical exposure at 



