1913.1 NATURAL SCIENCES OF PHILADELPHIA. 591 



The water-deposited beds of the island are apparently all included 

 in the Oligocene and Pleistocene; the Miocene and Pliocene are 

 entirely wanting, indicating that the island was not submerged 

 during this time. But a submergence occurred at the end of the 

 Pliocene which permitted the formation of marine deposits in many 

 parts of the island. The movement of the island at present appears 

 to be upward, and the formation of salt pond and mangrove swamp 

 deposits at many places along the coast line is still in progress. The 

 age of the accumulation of the "igneous basement" is set down in 

 the above table as possibly Eocene, not from any fossils which it 

 contains, but because the bedded deposits of the Oligocene appear 

 to overlie it. The volcanic activity continued, however, into the 

 Oligocene during the time of the deposit of the tuffs, and the white 

 limestone itself is intersected by dykes of the igneous material. 

 These deposits will now be described in more detail. 



1. The Igneous Basement. 



This is what Dr. Nugent has called the "trap formation"; it is 

 M. Purves's "porphyrites and volcanic agglomerates," or the 

 'foundation rocks of the island" or "igneous basement" of Spencer. 

 I have used Spencer's term. The rocks included in this formation 

 lie to the west of a line drawn from the head of Five Islands Bay, 

 southeasterly towards English Harbor, and they lie in the southwest 

 part of the island. They are exposed along the coast from the mouth 

 of Five Islands Bay to the southwest corner of the island and thence 

 east to the head of Falmouth Harbor. I inspected this region in 

 company with Mr. Forrest from St. John's to St. Mary's, Old Road 

 (nearly due south of St. John's), and thence along the south coast 

 to St. Mary's Rectory at the southwest extremity, and from 

 there up the west coast to St. Mary's in the Valley, and back to 

 St. John's by the Central Plain. Mr. Tempany showed me his 

 collection of these rocks, which corresponded with those seen on the 

 trip with Mr. Forrest. They consist of massive igneous flows and 

 subaerially deposited ashes, mainly in layers, and with many volcanic 

 agglomerates, consisting of ash and volcanic fragments held together 

 by the material of the flows. Large volcanic bombs occur in this 

 agglomerate with fragments down to fine lapilli and o-sh. The 

 flows are mainly pyroxene andesite, often compact; and also basalt, 

 or the same material as the pyroxene andesite with much olivine. 

 Dykes of compact andesite and basalt intersect the tuffs and agglom- 

 erates. The rocks are prevailingly andesitic, and the tuff and 



