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Colluvium is generally associated with most steep slopes. It consists of rock waste or <br />rock debris where the principal means of movement is gravity. It occurs at the base of <br />cliffs or as sheets of debris mantling the slopes of the valley sides. <br />GEOMORPHOLOGY <br />Hillslope forms are controlled by the erodabiliiy of the bedrock, which in turn is <br />influenced by: 1) lithology, 2) jointing, 3) surface and subsurface flow of water, <br />4) mass movements, and 5) base level. <br />The rocks in the study area have remained relatively stable since their deposition and <br />are nearly horizontal. The entire landscape was uplifted with the rest of Colorado <br />during the past 25 million years with more rapid uplifting in the more recent past. This <br />action has resulted in energizing the regions modern rivers that have cut deeply into the <br />stack of sedimentary layers. The force of running water on rocks of different abilities <br />to resist weathering and erosion has produced a rich abundance of layered, canyons, <br />ridges and flat-topped hills. <br />PALEONTOLOGY AND PALEOECOLOGY <br />The rocks of the Mesaverde Formation were deposited near the shore of the. <br />Cretaceous Interior Seaway as the shoreline began to retreat to the northeast. The <br />Mesaverde is characterized by interbedded carbonaceous shales, coals, siltstones and <br />sandstones that formed in a marginal marine environment of swamps arid lagoons <br />landward of the shoreline.. <br />Biostratigraphic zone data compiled from outcrop and cored sections in Colorado and <br />New Mexico has been used to Correlate the rock units of the Mesaverde. Intertonguing <br />nonmarine and marine rocks of Campanian and Maestrichtian age are present in <br />northwestern and eastern Colorado. Coexisting ammonite and palynomorph zones <br />allow definition of upper Campanian, lower Maestrichtian, and upper Maestrichtian <br />palynomorph intervals on the basis of the ammonite-based stages. Likewise, coexisting <br />vertebrate (dinosaur and mammal) and palynomorph zones allow definition of upper <br />Maestrichtian palynomorph intervals on the basis of the vertebrate-based stages. <br />(Newman 1987). These methods of ihvestigation have been used to place the <br />Mesaverde Formation into the Upper Campanian and Lower Maestrichtian stages or <br />approximately from 75.5 to 71.2 million years ago (Gill and Cobban 1966a). <br />This places the age of the Mesaverde about six million years before the great <br />impact that marked the and of the Mesozoic and beginning of the Cenozoic Era. There <br />was a great change in life on earth at the end of the Cretaceous Period Mesozoic Era <br />when dinosaurs and many other life forms became extinct. This event also provided <br />great opportunities for the life that did survive. Mammals under went an impressive <br />diversification and development in the early Tertiary Period. To better understand the <br />magnitude of this event, it is important that we know as much about the environment <br />and life that existed at this time before the impact. <br />4 <br />