Page 1 Page 2 Page 3 Page 4 Page 5 Page 6 Page 7 Page 8 Page 9 Page 10 Page 11 Page 12 Page 13 Page 14 Page 15 Page 16 Page 17 Page 18 Page 19 Page 20 Page 21 Page 22 Page 23 Page 24 Page 25 Page 26 Page 27 Page 28 Page 29 Page 30 Page 31 Page 32 Page 33 Page 34 Page 35 Page 36 Page 37 Page 38 Page 39 Page 40 Page 41 Page 42 Page 43 Page 44 Page 45 Page 46 Page 47 Page 48 Page 49 Page 50 Page 51 Page 52 Page 53 Page 54 Page 55 Page 56 Page 57 Page 58 Page 59 Page 60Approximate extent of glaciation during last ice age 12,800 –11,500 years before present Geology 10 Fossils are evidence of prehistoric life preserved in sedimentary rocks and provide information about geologic history and evolution. Abundant fossils of fish and other marine organisms, crocodiles, turtles, dinosaurs, mammoths, other mammals and plants have been found. Red Gulch Howe Dinosaur Quarry Crooked Dinosaur Track Site Creek Lance Creek Como Bluff Fossil Butte Twin Buttes Big Cedar Fossil Ridge At different times throughout Wyoming’s geologic history huge amounts of sediments were deposited at the bottom of seas and lakes that covered all or parts of Wyoming. The sediments eventually compressed and solidified into layers of colorful sedimentary rock such as sandstone, limestone, and shale. As the last of the inland seas dried up the Rocky Mountains began to rise, starting about 70 to 80 mya (million years ago). The layers of sediment folded, broke, and tilted during the mountain building process. Streams flowing down the mountains eroded the sedimentary rock, revealing ancient metamorphic rocks that had been pushed up as the mountains rose. Volcanic activity resulted in extensive igneous rocks in the northwestern mountains ofWyoming. During the last million years several ice ages occurred with glaciers carving and shaping many ofWyoming’s mountains. MYA Era Present day water or ice 65–0 251–66 Type of bedrock 540–252 3800–541 Cenozoic Mesozoic Paleozoic Precambrian Unconsolidated materials Sedimentary Igneous Igneous Sedimentary Sedimentary Sedimentary Igneous Metamorphic Well-known fossil sites Data Go Interactive