The Cambrian period of geological history spans from approximately 545 to 490 million years ago (mya). During this period many signifigant changes occurred in Oklahoma as well as around the world. This period was marked by a kind of biological "big bang" known by most as the Cambrian Explosion, where life on earth literally exploded onto the scene.
During this period of time Oklahoma was under a shallow continental shelf sea just below the equator on the continent of Laurentia. Most of the continental landforms were located near the equatorial regions which allowed the ocean currents to flow mainly near the polar latitudes. The result of this was a generally warm Cambrian climate without significant ice development at the poles.
Locations of landmasses during Cambrian Earth
Cambrian life was confined to the oceans and the first hard skinned and shelled invertebrates appeared. Trilobites were the dominant lifeform in the ocean as well as brachiopods, sponges, echinoderms, etc... The first vertebrate ancestors, chordates, also occured. Evidence of these early life forms may be found in exposed Cambrian sedimentary rock in the southern Oklahoma Arbuckle and Ouachita Uplifts.
During the late pre-Cambrian and early Cambrian, the southern part of Oklahoma tried to separate from the northern part. This resulted in a zone of weakness in the earths crust that was exploited by rising magma, some of which erupted at the surface. These erupting magmas changed the sedimentary rocks into metamorphic rocks resulting in thick granites, rhyolites, gabbros, and basalts being formed in southwest and south central Oklahoma. Cambrian igneous rocks may be found most prevelantly in the Wichita Uplift in southwest Oklahoma. Pre-Cambrain igneous rocks (granites and rhyolites formed 1.05 to 1.35 mya) and Cambrian igneous rocks underly all of Oklahoma and all other younger rocks rest upon them.
This website is hosted for free by  .
Get your own
Free Website now!
|