Rl. Thomas et al., RECENT DEFORMATION IN THE BOTTOM SEDIMENTS OF WESTERN AND SOUTHEASTERN LAKE-ONTARIO AND ITS ASSOCIATION WITH MAJOR STRUCTURES AND SEISMICITY, Geographie physique et quaternaire, 47(3), 1993, pp. 325-335
Geophysical surveys, undertaken in the Toronto-Burlington corridor of
western Lake Ontario and in the Rochester Basin of southeastern Lake O
ntario, revealed the presence of features affecting the young lake-bot
tom sediments. In the western part of the lake, they include inferred
pop-ups in bedrock, and plumose structures, dark linear patterns, and
linear belts of circular to elliptical signatures in the modern mud. I
n southeastern Lake Ontario the glacial and post-glacial sediments dis
play vertical separations of on the order of 10-15 m. Pop-ups are tect
onically-induced structures. The features in the modern mud commonly p
arallel the orientation of P-stresses measured in Paleozoic rocks near
by and, along with the pop-ups, are spatially related to an aeromagnet
ic lineament. Furthermore, all of these features occur within a seismi
cally active belt. The vertical displacements of the layered glacial a
nd post-glacial sediments, within the Rochester Basin, are located alo
ng the southern margin of the postulated WSW extension of the seismica
lly active St. Lawrence rift system and are interpreted to be due to f
aulting. The geologically young age of the sediments affected by the v
arious deformational features, along with the characteristics of the f
eatures themselves, suggest that the lake-bottom sediments surveyed in
this study may have recorded the effects of neotectonic processes.