Geological Ages of the Earth
(refer to chart toward bottom of this page)

by Alan Hagen

People living in, visiting, or merely spotting Lloydminster on a map would not realize that the prosperity of this community is linked closely to the sea. Today Lloydminster is more than 1,000 miles from the sea, but at various times throughout the distant past this area, and indeed all of Alberta and Saskatchewan, was submerged. The earth and the seas are never stagnant; they are constantly, although almost imperceptibly, changing.

During the Devonian Period the land masses were positioned such that the equator stretched across the North American continent from the southwest to the northeast; from southern California through Ungava Bay and crossing the southern tip of Greenland. The Devonian sea covered all of Saskatchewan and Alberta. The environment of most of Saskatchewan and part of Alberta would be described as shallow marine or continental shelf with the remainder being deep marine.

The Devonian Period is often referred to as the Age of the Fishes. This North American sea was warm and tropical, it teemed with life, and had extensive reef systems. A cross section of animal life includes: Corals (Cnidaria), bryzoids, shellfish (Brachiopods); Molluscs of the class Cephalopoda: Ammonoids, Nautilus which still survives today and Orthocerus a squid like animal that was a precursor to the octopus, squid and cuttlefish; Arthropods such as trilobites, and Eurypterids which resembled scorpions; Echinodermata: Cystoids, Blastoids and Crinoids which are animals which resemble plants in appearance with a "stalk" and a "bud", Crinoids are often referred to as "sea lilies". Jawless fish with cartilage skeletons were developing into jawed, bony fish although cartilage would never go entirely out of fashion (e.g. sharks and rays). However, more importantly to the Lloydminster economy were the microscopic plants and animals whose metamorphosed remains we pump out of the earth as oil. You need only to go to a pond and scoop a bucket full of water to see how plentiful these types of organisms are.

Periodic regressions in the Devonian sea also resulted in the formation of evaporites such as gypsum rock, potash and, particularly important to the Lloydminster area, halite (rock salt). Some of these rock salt deposits were dissolved by water within the earth creating traps when the sedimentary layers above collapsed. 

The Mississippian Period 360 - 320 million years ago

During the Mississippian Period the western sea transgressed (advanced) far onto the North American continent. The sea covered the southern edge of Canada’s Arctic islands at its northern extremity, most of the Hudson Bay region in the east, and in the southeast to the western border of Florida. The continent itself had sifted slightly to the north as in the southwest the equator remained in southern California, but in the northeast it was near the eastern tip of Labrador, and past to the south of Greenland. Although the sea covered more of the continent than in the Devonian, Saskatchewan and Alberta were entirely within the shallow marine environment. The island arc in the west continued but, possibly, not as actively.

The animals of the period followed a generic evolutionary progression; there were no large extinctions, but some of the fishes were becoming uncomfortable in their environment. It is theorized that some fish in an effort to escape anaerobic (oxygen depleted) environments took to the land and skittered their way to another pool; repeating this process as each subsequent pool became unlivable. In order to facilitate this puddle jumping the fish developed strong fleshy fins. This continued until amphibians had evolved. The fossilized remains of amphibians are found for the first time in Mississippian rock. However interesting these developments are, it is the sea’s prolific production of microscopic plants and animals that provides the oil we extract.

 Below Lloydminster there is approximately 200 million years of sedimentary rock missing. Lower through mid-Cretaceous rocks of the Mannville Group are sitting directly on Mississippian or Devonian rock; Mississippian rock has been completely eroded in some areas.

The Cretaceous Period 144 - 66 million years ago

North American development continued as islands and microcontinents accreted to form the Western Cordillera. This cut the sea off to the west, but did not prevent the sea from transgressing from the north and south. There were several transgression/ regression cycles which occurred during this period. These cycles coupled with the rapid erosion of the cordillera resulted in the deposition of huge sandstone, silt/mudstone, and shale formations.  North America had moved significantly north but retained a tropical climate. The equator was now well south as North America was nearing its present position. The continent was tilted slightly to the east with the 30 degree north latitude crossing the Gulf States.

The evolution of life has progressed relatively steadily, some believe. The Cretaceous was the last great stand of the dinosaurs and was the age of the Tyrannosaurus rex. Pterosaurs were gradually replaced by birds and large formidable reptiles roamed the seas. In the Lloydminster area, Cretaceous sediments had not achieved sufficient burial nor had they been subject to sufficient tectonic stress to produce the heat necessary to cook the oil out of these rich sediments. Nevertheless, these rocks provide the traps for the oil that migrated out of the Devonian and Mississippian deposits.

Note: Two parts of the geological record are missing underneath Lloydminster.   One is a section from the lower Mississippian to the lower Cretaceous ( a period of almost 200 million years) during which the area was exposed to the process of erosion.  It is believed that enormous volumes of sediments must have been eroded away.  A second section, from the Eocene to the present, also may have been eroded - a layer that may have been as much as 9 kilometers thick.

For a more detailed representation of the Geological Strata from where most of the oil is produced in this area - click here.

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