INTRODUCTION:    Unlike its paleontological record (which only spans some 350 million years), the geological record of Vancouver Island can be traced back perhaps another 70 million years or more, to the Lower Silurian Period of the Paleozoic Era, more than 420 million years ago. The oldest rocks from this period are igneous in nature. They undoubtedly record the initial and explosive birth of the Island in the southwestern Pacific Ocean, and as such form the foundation for the accumulation of volcanic arc (not unlike the modern Hawaiian Islands), oceanic, and clastic wedge (sediments eroded from pre-existing rock) deposits that occurred during the periods of the Paleozoic, Mesozoic, and Cenozoic Eras.    The Cenozoic Era is the last phase of the three major units into which geologic time is divided. It was a time of important continental repositioning and sea-level adjustment -- the result, to a considerable degree, of tectonic movements that had begun prior to the close of the Mesozoic. Shallow seas, which had flooded the interiors of many of the major land masses since the mid-Jurassic Period, now experienced broad recessions as the continents experienced widespread uplift due to the formation of modern mountain systems. These include the creation of the Himalayan chains in the Old World, and the Cordillera in the New, as well as other episodes of mountain building that actively continue to this day.    These realignments and uplifts were accompanied by often dramatic climatic alterations. The modern climatic zones slowly became established, and as the Cenozoic Era progressed, the alternation of cold and warm seasons became ever more sharply defined, especially in the higher latitudes, which began to support permanent modern ice sheets. The warm tropical and subtropical seas, which once lapped at Arctic and Antarctic shores, gradually contracted toward the equator, replaced by colder bodies of water towards each pole. This period of flucuation finally culminated in the great Ice Age, in the latest phase of which we are now living.    Click on the rotating globe to access a geographical map of each Cenozoic Period.

SIMPLIFIED CENOZOIC GEOLOGY OF VANCOUVER ISLAND:
(MINOR VOLCANIC EPISODES OMITTED):

THE PLEISTOCENE PERIOD: GLOBAL:    The Pleistocene is the last and shortest period in the history of the Earth. The episode of cooling that had begun in the lower Neocene had by now reached its climax. As global temperatures fell, the snow and ice that had accumulated in the higher latitudes during the winter months could not entirely melt away during the increasingly cooler summers. Under this weight, the ice began to gradually flow outward from these mountain centres, until at last great sheets of glacial ice extended over wide areas of both the northern and southern hemispheres. Each of these episodes of glacial advance lasted for approximately 100,000 years, alternating with a warmer period of glacial retreat of shorter (~10,000 years) duration, at least a half-dozen times during the past million years. Today, we presumably live near the end of the latest interglacial period that has endured for more than 8,000 years.

VANCOUVER ISLAND: Unassigned Glacial Sediments:    Locally, glacial sediments exposed on Vancouver Island represent only the youngest (Wisconsinan) of the glacial episodes. This is because the last advance of the ice sheet destroyed any trace of the previous advance. Radiocarbon dates indicate that the onset of the Wisconsinan advance slowly began between 25,000-30,000 years ago, but did not leave the Cordillera until some 5,000 years later. Between 14,000 and 14,500 years ago, the ice sheet had attained its greatest size, locally covering the entirety of Vancouver Island except for the tops of the highest mountain peaks and possibly parts of its western coast. Along our eastern coastline, the incredible weight of this ice depressed the land beneath it between 175m (525ft), north of Campbell River, and 75m (225ft) in Victoria to the extreme south. This caused the Strait of Georgia to flow another 10km (6 miles) into the eastern interior of the Island. Thereafter, the ice began to quickly retreat, and by roughly 10,000 years ago Vancouver Island was completely free of glacial ice, except for the few shrinking satellite glaciers that persist to this day.    As this ice sheet advanced and retreated, it deposited sands, clays, and gravels into a wide range of glacial environments; including LAND, RIVER, LAKE, and MARINE settings.

STAGES:                (Ma) Holocene          0 Pleistocene     .01                   2

Glacial Sediments (.01 - .03 Ma): Sedimentary material; Usually poorly sorted glacial gravels, blue-grey clays, & yellow sands. Quadra Sand: Vashon Drift Gold River Drift Port MacNeil Drift Cowichan Head Frm.

THE NEOCENE PERIOD: GLOBAL:    The Neocene Period witnessed the final modern assembly of the world's continents. The Indian subcontinent was by then colliding with the southernmost edge of the Asian plate, buckling up huge amounts of oceanic sediments which in turn fused Asia into a single land mass and began the construction of the Himalayan mountain system. At the same time the Alps, Pyrenees, and Carpathian mountains were acquiring their present form as the African continent continued to move steadily northward, creating a shallow ocean basin between them that would one day be called the Mediterranean. As a result of these and other continental movements, including the opening of colder circumpolar seaways, especially south of Cape Horn (South America) and the Cape of Good Hope (Africa), the late Neocene was chiefly characterized by a rapid deterioration in worldwide climatic conditons. This would eventually lead to the formation of great ice sheets during the forthcoming Pleistocene Period. VANCOUVER ISLAND:    With the final completion of the Cordilleran mountain-building phase during the late Paleocene, volcanic activity had shifted further to the west. Possibly in conjunction with realignments in the offshore geology, this next episode of uplift was responsible for the construction of both the Coastal Ranges of British Columbia and the mountains in the interior of Vancouver Island.

The Carmanah Assemblage:    The Carmanah Assemblage represents the accumulation of slope sediments into the Tofino Basin, from the erosion of older rocks on the west coast of Vancouver Island. The formations represent a trend from thick accumulations of slump debris formed in deep offshore waters, to deposition into a very shallow water environment, both MARINE settings.

STAGES:                (Ma) Pliocene          2 Miocene           5

Sooke Formation (18 - 25 Ma): Sedimentary rock; sandstone interbedded with local coquina (rocks composed of broken and abraded shell fragments) of shallow water bivalves, with minor interbeds of shale, siltstone, and sandstone, indicating deposition of coarse-grained debris along slope into relatively shallow water; <100m (<330ft) depth, <200m (<660ft) unit thickness.

THE PALEOCENE PERIOD: GLOBAL:    The beginning of the Paleocene Period marked the transition from the Mesozoic Era to the Cenozoic. During this interval of time the continents continued to migrate from the Pangean supercontinent that had existed, in one form or another, since the mid-Jurassic Period, toward their modern positions. In particular, Africa and the southern continents (Antarctica, Austarlia, and India) experienced the most important realignments, each of them being propelled northeastwards relative to Antarctica.    These adjustments, obviously, also brought about profound changes in the world's oceans, causing many of them to either appear, grow in size, or vanish altogether, as well as maintaining the higher sea levels that were so characteristic of the last third of the Cretaceous Period. The North and South Atlantic continued their expansion, as did the Arctic and Antarctic Oceans. Likewise, as many of the continents began to subside, the oceans surrounding them invaded deeper into Europe as far as the Russian plateau and southern Asia, and swallowed many of the outlying regions of both the Americas and large portions of Africa. VANCOUVER ISLAND:    In comparison to the great activity that marked the last 40 or so million years of the Cretaceous Period, the Paleocene was a time of relative stability for the geology of Vancouver Island. During this time the Insular Superterrane had, at long last, become permanently fixed to the western edge of North America, and there is no evidence to suggest that from the Eocene stage onward this region moved any further east. All post-Eocene movement seems to have been limited to a general northward movement along the Island's west coast.

The Carmanah Assemblage:    The Carmanah Assemblage represents the accumulation of slope sediments into the Tofino Basin, from the erosion of older rocks from the west coast of Vancouver Island. The formations represent a trend from thick accumulations of slump debris formed in deep offshore waters, to deposition into a very shallow water environment, both MARINE settings.

STAGES:                (Ma) Oligocene        25 Eocene           38 Paleocene        55

Hesquiat Formation (25 - 33 Ma): Sedimentary rock; massively-bedded shale melange (mixture of broken rock) with irregular interbeds of sandstone and conglomerate, indicating massive slumping and redeposition of coarse-grained debris along slope into relatively deep water; 200m - 1000m (660ft - 3300ft) depth, 1100m (3630ft) unit thickness. Escalante Formation (33 - 42 Ma): Sedimentary rock; massively bedded basement conglomerate, interbedded with shale and conglomerate melange (mixture of broken rock), and beds of sandstone and conglomerate, indicating massive slumping and redeposition of coarse-grained debris into relatively deep water; <1000m (<3300ft) depth, <150m (<495ft) unit thickness.

Unassigned and Informal Appian Way Formation:

STAGES:                (Ma) Oligocene        25 Eocene           38 Paleocene        55

Unassigned and Informal Appian Way Formation (45? - 50? Ma): Sedimentary rock; thinly-bedded layers of dark, silty shale, interbedded with layers of pale sandstone and gritty, concretionary shale and/or siltstone, indicating deposition of relatively coarse-grained sediments into deep water; >200m (>660ft) depth, unmeasured unit thickness.