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Trail142Fault & river & arch
TECTONIC FAULTING: Mitten Park Fault, Harpers Corner, Dinosaur National Monument --- Spectacular vertical fault with adjacent folding of sedimentary layers in the lower left corner of the picture.
Wasp
This specimen of a fossil wasp comes from Eocene strata of the Fossil Lake (Wyoming) and its body plan is quite similar to modern representatives of this type of organism. On display at the Field Museum of Natural History, Chicago.
I70 ThrustFault
TECTONIC FAULTING: Thrust fault along Interstate-70, Silverthorne --- Younger rocks on the very bottom of this picture have been thrust under older rocks. The fault line ascends slowly from the lower right edge of the picture to beyond the center where some folding of the layers at the fault contact can be seen.
Platyceramus platinus
Dinosaurs are not the only group of organisms to disappear above Cretaceous strata. Inoceramids, a family of large bivalves, are also extinct and not found in Cenozoic layers. Remains of fish have been found preserved within some specimens of this giant clam, leading to the suggestion of possible commensalism or symbiosis. Specimen on display at the Denver Museum of Nature and Science.
Rt40 WolfordMtnThrustFault
TECTONIC FAULTING: Thrust fault at Wolford Mountain east of Rt.40 north of Kremmling --- Trees take root in the older Precambrian rocks outcropping over the top half of the mountain, but do not grow in the younger Cretaceous Pierre shale outcropping over the lower half.
Underprints
“Brontosaur bulges." Mid-way through the picture we can observe four bulges in a sandstone layer, depressing downward the underlying layers. These have been interpreted as a dinosaur trackway viewed in cross-section. A large sauropod left these “underprints" by deforming soft sediment while walking. Very specific conditions (e.g, sediment cohesiveness, rate of sedimentation, exposure vs submergence) are necessary for the preservation of footprints in the rock record. Scale bar is 40 cm long. Photo taken at Dinosaur Ridge, Golden, Colorado.
Dinosaur Ridge Trackway
The Dinosaur Ridge Tracksite, in Golden, CO, preserves two main types of dinosaur footprints. Both are tridactyl (with three toes). They have been colored in with charcoal to enhance their visibility. The tracks with a wider aspect and thick toes were made by ornithopod dinosaurs. They were left by animals of different sizes (possibly adults and juveniles). The narrow-toed tracks were made by theropods. See if you can recognize the different tracks. This outcrop exposes the surface of a sandstone bed in the Lower Cretaceous South Platte Formation of the Dakota Group.
Palm fronds
Fossil impressions of palm fronds exposed on a verticalized bedding surface of fine sandstone in the Maastrichtian Laramie Formation, near Golden CO. The integrity of individual fronds implies that minimal decomposition took place prior to burial. Scale bar is 40 cm long.
Coccoliths
Calcareous nannofossils (coccoliths) are among the tiniest fossils preserved in the sedimentary record, measuring around 5 to 10 microns. The image (plate) shows petrographic microscope photos of some of the most characteristic coccoliths of the Cretaceous/Paleogene (K/Pg) boundary. This boundary is associated with one of the most studied mass extinctions in the geological record, which has been correlated to a major catastrophic event. Photos 1 to 4 show nannofossils of the Upper Cretaceous (Maastrichtian) that are thought to have gone extinct at the K-Pg catastrophic event. Photos 5 to 7 are of Cretaceous survivors that show continuous distribution into the Paleogene (Danian). These last species are considered adapted to cold water and eutrophic environments (r-selected taxa). Photos 8 and 9 show Paleogene taxa, not present below the boundary. (Photos by E. Belia)
BurningMtn
ENERGY SOURCES: Burning Mountain, New Castle --- Burning coal seam heats up the ground so there is a horizontal bare streak across the hill that is too warm for vegetation to grow.