PLEASE ONLY TAKE PHOTOS, LEAVE WHAT YOU FIND FOR OTHERS TO ENJOY ALSO.
The Columbia Basin is a large, triangular mountainous region in southeastern British Columbia that is drained by the Columbia and Kootenay rivers. It includes the Main Ranges of the Rocky Mountains to the east, the Purcell Mountains, the Selkirk Mountains and, to the west, the Monashee Mountains.
The Columbia Basin does not correspond to a coherent geologic region -- in fact, it is crossed by a fundamental geologic boundary that separates Laurentia, ancient North America, from exotic terranes that collided with Laurentia during the Mesozoic.The strata making up the Rocky Mountains are largely limestones and shales of Palaeozoic age, deposited as a thick apron on the seaward side of Laurentia. Even though these rocks are faulted and upthrust, they have not been significantly altered or metamorphosed and their contained fossils are generally well preserved.
The rocks of the Purcell and Selkirk mountains are mainly sandstones and grits of late Cryptozoic (late Precambrian) age. These rocks are commonly highly deformed and metamorphosed, and locally they are intruded by younger granites. They were deposited on the margin of ancient North America. The Monashees and related mountain ranges in the western Columbia Basin are made up of a variety of rocks including exoticterranes of Late Palaeozoic and Mesozoic volcanics and sedimentary rocks, as well as large masses of granites.
During the Jurassic, Laurentia, with its thick packages of late Cryptozoic and Palaeozoic strata, collided with large exotic terranes that had formed out in the palaeo-Pacific Ocean during the late Palaeozoic. This collision pushed the entire package of Palaeozoic rock eastward in a series of overlapping faults to form the Rocky Mountains. The late Cryptozoic rocks were squeezed and faulted up to form the structures now seen in the Purcell and Selkirk mountains. The colliding terranes on the west were shoved onto the granitic basement, making the crust much thicker, altering and heating it, and causing the melted rocks to be intruded as large granitic masses.
Lower Cambrian Trilobites
Brown and grey shales that make up the Lower Cambrian Eager Formation in the vicinity of Cranbrook and Fort Steele contain numerous fragments and many complete specimens of olenellid trilobites. These trilobites are invariably the oldest trilobites found at localities on all continents, but they are fully formed trilobites and not obviously primitive. These fossils have been avidly collected by amateurs and professionals since 1921, when they were first made known to palaeontologists by Colonel C.H. Pollen of Cranbrook.
The most abundant trilobite in the Eager Formation is Olenellus -- which has a large, semi-circular head, a body of 15 segments (of which the third is much longer than the others), a long spine on the 15th segment, and a minute tail. A less common olenellid trilobite is Wanneria -- which has a large head lacking conspicuous furrows, and a broad body without an expanded third segment.
The shales of the Eager Formation are widely exposed in the valleys of the Kootenay and Columbia rivers but, by far, the most fossiliferous site is located on Crown Lands leased to the Cranbrook Rifle Club, located just outside Fort Steele. Abundant collections from this site proved critical to the recently completed Ph.D. thesis by Lisa Bohach, who was able to place them in the upper part of the Lower Cambrian, but not the uppermost. Bohach also used these rich collections to establish a new classification of olenellid trilobites based on the different growth history (ontogeny) of major groups.
In order to log this Earthcache please email/message me the answers the following questions and perform the two mandatory photo tasks:
1) What type of rock is it that you are looking at to find fossils? (Answer in cache page)
2) What are 2 types of trilobites found in this region? (Answer in cache page)
2) Include a photo of a fossil you found at the location in your geocache log. (MANDATORY)
3) Include a picture of yourself and/or your GPS at the Earthcache site in your log or when you send me your answers. (MANDATORY)