| OCR Text |
Show 222 4.5. Conclusions The rences proximity of the K-T interval is indicated of the Cretaceous Porochara sp., and about 18 m the last in the ostracod upper/lower coal of undoubted dinosaur bones is at 175 assemblage above the base of the formation there. appearance of the smooth mixed type 1 and over a occur and range of sequence contact. The last appearance m above the base of the formation at North Horn Mountain, and the last appearance of dinosaur level. The last stratigraphic charophyte fossils, Platychara compressa by changes below the by Immediately eggshells, type 2 eggshells which occur eggshells is at 202 m beneath the bone is the last extremely were 19 and 27 m, rare at that respectively, above the bone. Several fossil groups disappear one by one in the lower coal sequence in pattern typical of gradual extinction (Archibald, 1996). Changes particular faunal assemblage composition of single fossil group would be inconclusive a of evidence indicates that sufficient this stratigraphic interval conceivable that the K-T pollen indicate merely change our an to indicate boundary environmental the K-T biostratigraphic Mountain, which disappearance of by itself. However, the any preponderance in diverse fossil groups occurred in proximity to the K-T is located at change. boundary. the in the changes may have coincided with and across or a a boundary. It is level in the section where If so, the local environmental disguised a If this horizon entirely much change larger environmental represents the K-T boundary, data indicate that the last Cretaceous groups at North Horn were present only a few meters below, were no longer |
