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and petroleum accumulations are part of the pattern. Much work remains to
be done to reconcile the hypotheses of plate tectonics with the detailed evi-
dence available from petroleum geology.

INTRODUCTION

Our purpose in this chapter is to pass in review the topics of earlier chapters
and seek to relate them to broad concepts of sedimentary basin development
and the occurrence of petroleum. These are geological concepts to which
petroleum, as a natural substance, contributes significant data. Exploration
for petroleum, and the development of petroleum fields, has provided us
with regional and detailed geology of areas that would otherwise have waited
decades before investigation. In particular, it has provided us with some
knowledge of the geology of the continental shelves.
The 19th Century work on coal mines, railways and canals, brought great
advances in geology; but some of the concepts developed from surface and
near-surface work on land have been maintained despite contrary evidence
from subsurface work offshore as well as on land during the last 30 years or
so. It seems to have been generally accepted that the regressive sequences of
sedimentary basins indicate uplift, and that their deformation was due to
major tectonic events. Anticlines were (and perhaps still are) widely attributed
to horizontally directed compressional stress. The evolution of sedimentary
basins (and, to some extent, geosynclines) seems to have been regarded as in-
volving three stages: subsidence, uplift and deformation, with the last two,
perhaps, concurrent. While geologists were confined to the land, such a se-
quence of events was logical and consistent with the evidence available to
them. But the discovery of anticlines offshore under the continental shelves
has shown that they can occur in young sedimentary rocks without uplift
and orogeny.
The world-wide search for petroleum has shown that just as a petroleum
province has a character, so we have similar characters in petroleum provinces
in different continents. The United States Gulf Coast province has much in
common with the Niger delta, and many areas of South-East Asia: the West-
ern Canada basin has much in common with northern Mexico and south-east
Libya: the North Sea has much in common with the Gippsland basin of south-
east Australia, the north-west shelf of Australia, and northern Alaska. Many
of these similarities are so close that we feel entitled to believe that the prin-
ciples of petroleum geology that apply to one, apply also to the others like
it. This is not to deny individuality to fields, but to assert that we are concerned
to discover the guiding principles of geology that govern the generation, migra-
tion, and accumulation of petroleum.