September, 1916. 
This document was produced 
by scanning the original publication. 
Ce document est le produit d'une 
numerisation par balayage 
de la publication originale. 
Canada 
Geological Survey 
Museum Bulletin No. 24 
GEOLOGICAL SERIES, No. 33. 
Late Pleistocene Oscillations of Sea-level in the Ottawa Valley. 
By W. A. Johnston. 
introduction: 
It has long been known that during late Pleistocene time an 
arm of the Atlantic extended westward far up the St. Lawrence 
and Ottawa valleys. Extensive deposits of marine clays, known 
as the Champlain or Leda clays, and old sea beaches, at con- 
siderable heights above sea-level, have long been known to occur 
in the St, Lawrence and Ottawa valleys and have furnished 
evidence that the land had been depressed relatively to sea-level 
and had subsequently emerged. It is known that stratified 
sands and clays holding fossil marine shells occur in the Ottawa 
valley at various altitudes up to at least 480 feet above the sea 
and that old sea beaches occur at higher altitudes; but there has 
been doubt regarding the upper limit of marine submergence 
because of contradictory opinions expressed by different in- 
vestigators. It is known that the upper limit of the marine 
deposits rises gradually towards the north, but altitudes of the 
raised beaches in this region have been determined at very few 
localities so that comparatively little is known regarding the 
extent and character of the differential uplift which affected this 
portion of Canada during late Pleistocene time. (Pleistocene 
time is herein considered to have ended and Recent time to have 
