Mesozoic and Cenozoic Strata of the Colorado Plateau

The Wingate Formation is about 300ft thick in the area of Canyonlands, and lies conformably atop the Chinle Formation. The Wingate, like most of the Glen Canyon Group, is composed of typical eolian deposits, including fossil dunes and small playa or oasis deposits. The most common track type in the Wingate are small theropod Grallator tracks, typically 15-20cm long. These are about "twice the size of the diminuative, yet abundant, Grallator tracks found in the upper part of the Chinle Group" (Lockley and Hunt, 1995, p. 115). Based on a formula which relates foot length to hip height, these Grallator track makers were probably about 3-4 ft tall at the hips. Near the top of the Wingate, larger theropod tracks, Eubrontes (up to 35-40cm long), are known. Eubrontes tracks are about twice the size of Grallator. Lockley and Hunt notes that "in contrast with the underlying Chinle Group, in which dinosaurs were few and other kinds of archosaurs were many, the Wingate evidence suggests a vertebrate community dominated by bipedal theropod dinosaurs. The pronounced earliest Jurassic dinosaur radiation is thus, in our view, showing up clearly in the track record" (p. 116).

The Kayenta is a thin layer (about 200-600ft) of weakly inclined fluvial sandstone, sandwiched between two massive eolian sandstones, the Kayenta and the Navajo. The Kayenta preserves both dinosaur fossils (such as Dilophosaurus) and footprints, as well as the fossils of the mammal-like reptile tritylodont (Baar, p. 171).

Vertebrate footprints attributed to therapod dinosaurs are dominant by Kayenta time. Some of the Kayenta dinosaur tracks are very small and bird-like, such as the ichnogenus Anomoepus, with relatively slender, widely-splayed digits, and "pigeon-toed," inwardly rotated tracks. Most ichnologists attribute Anomoepus to ornithopod theropods rather than early birds because Anomoepus tracks found in late-Triassic/early-Jurasic strata of the Connecticut Valley "occasionally show five-toed front footprints, as well as heel (metatarsal) and pelvic impressions. This shows that the animal sometimes switched from bipedal to quadrupedal progression and even to a stationary crouching position" (Lockley and Hunt, 1995, p. 125-126). Anomoepus tracks have also been reported from late-Triassic/early-Jurasic strata in Europe and Africa. Similar tracks are present in early Jurassic strata of Hungary (Komlosaurus), China (Schizograllator), South Africa, and Morrocco (Argoides) (p. 126).

During the Jurassic period, large portions of Arizona, Colorado, Utah and New Mexico were covered by massive, windswept dune fields. At places within the Navajo are small lenses of limestone thought to have originated in small interdune lakes. The resulting sediments, the Navajo Sandstone (NS), document the existence of this huge desert sand sea. At its thickest, the Navajo is approximately 730 meters (2400ft) thick, over twice as thick as the CS. Baar writes:

Fossils, although very rare, have been found in the Navajo Sandstone. These include a Protosuchus-like primitive crocodilian, tritylodonts (mammal-like reptile), the small theropod Segisaurus, and the small prosauropod Ammosaurus (Lockley and Hunt, 1995, p. 130).

Despite the extreme rarity of fossils, the NS preserves an abundant and varied vertebrate track fauna. Again, dinosaur tracks dominate. The lower part of the Navajo contains tracks of theropods ranging from <10cm to about 50cm in length. The smallest of these tracks are very bird-like, with slender, widely splayed digits. Also present are four-toed tracks, about 25cm long, that Lockley and others attribute to a prosauropod trackmaker (ibid., p. 134). Others tracks in the lower Navajo display 5 digit impressions, and have been attributed to mammal like reptiles. These include Brasilichnium and, possibly, Navahopus. Brasilichnium is also known from the early Jurassic Botocatu Formation of Brazil, and it is these tracks for which the ichnogenus was named by Leonardi.

While virtually all geologists who have studied the Navajo sandstone agree that it is an eolian deposit, Glen Visher has argued that the Navajo may have been deposited subaqeously (Freeman, William E., and Visher, Glenn S., Stratigraphic Analysis of The Navajo Sandstone, Journal of Sedimentary Petrology, v. 45, no. 3 pp 651-668 sept 1975). As Schimmrich has pointed out (internet posting), however, Visher's claim generated four seperate replies in the next two issues of the journal, all of which disputed Visher's claim. For instance, Folk wrote:

The top of the NS is truncated by erosion, and overlain sharply and disconformably by the Carmel Formation (Baar, p. 174). The Carmel Formation is Jurassic in age and is between 200 and 300 feet in thickness in the area of Zion National Park. The Carmel Formation consists in this area of beds of limestone separated by thin sandy limestone beds containing fossils of shallow water organisms. Eastwardly, the Carmel displays evidence of stream and mudflat type deposits. Evaporites are present in some areas (Chronic, 1990, p.36). At least two tracksites have been reported in the Carmel, both containing small to medium size theropod tracks (Lockley and Hunt, 1995, p. 152). Ash beds within the Carmel have yielded dates between 166.3 and 168.0 ± 0.5 Ma (Kowalis, et al. The record of Middle Jurassic volcanism in the Carmel and Temple Cap Formations of southwestern Utah. GSA Bulletin, Vol. 113, No. 3, pp. 373–387).

Near the San Rafael swell area, the Entrada is composed of uniform, "dirty" siltstone and sandstone of marine origin, and is about 850ft thick (Baar, p. 176). To the east and south of this area, this formation grades into a clean white, cross bedded sandstone of apparently eolian origin. Paleocurrent indicators show that the sands were transported from the north/northwest (Tanner, W.F., 1965. Upper Jurassic Paleogeography of the Four Corners Region. Jour Sed. Petrology, v. 35, p. 564-574).

Like the rest of the early to middle Jurassic formations of the Colorado Plateaum fossils are essentially absent from the Entrada, although one specimen of the crocodyliform Entradasuchus spinosus is known (Hunt and Lockley, 1995). Despite the lack of fossils, however, the Entrada contains abundant vertebrate trackways. This fact seems most odd on the flood theory. We know that numerous dinosaurs and other terrestrial vertebrates were alive and well during early to middle Jurassic deposition. Their footprints are everywhere. But why, then, given the extreme violence and rapidity of the flood catastrophe, are their remains absent?

Addendum: 5/16/01: Aside from the vertebrate trackways, there are several other locally abundant types of trace fossils in the Entrada as well. These need to be taken into account when depositional models for the Entrada are considered. These include small horizontal burrows, small plug-shaped burrows, and meniscate trails (Entradichnus meniscus) which are apparently "identical to infaunal trails produced in modern sand dunes by the larvae of tipulid dipteran insects ('crane flies'), which burrow just beneath the sand surface and created back-filled burrows in convex epirelief" (A.A. Ecdale and M. Dane Picard. Trace Fossils in a Jurassic Eolianite, Entrada Sandstone, Utah, USA, in Biogenic Structures: Their Use in Interpreting Depositional Environments. Curran, H.A. ed. SEPM Special Publication No. 35, 1985, pp. 3-12).

The Curtis Sandstone consists of unstructured to horizontally-bedded sandstone, and is 250ft thick in the San Rafael Swell region (Baar, p. 181). Some portions of the Curtis display thin shale layers which are enriched in glauconite, a mineral that forms only in shallow marine environments. Based on molluscan fauna and microfauna evidence, the Curtis is dated as late Jurassic. The Curtis is not laterally extensive (hence the Summerville directly overlies the Entrada in most areas), and thins rapidly away from the San Rafael region. This suggests only a minor transgression of the sea during Curtis deposition. Baar notes, however, that another formation occurs at the same stratigraphic position in southwestern Colorado and northwestern New Mexico, called the Todilto formation. The Todilto was probably deposited in a large lake. The lower portion of the formation is limestone, occasionally with fish fossils, while the upper portion of the formation contains thick beds of evaporite minerals. Though found at the same stratigraphic position as the Curtis, there is no evidence that these two formations were continuous. Chronic (1987) discusses a revealing feature of the Todilto:

Anderson and Kirkland (1960) describe 11-13 laminae cycles which may correspond to the sunspot cycle, as well as 60, 85, 170 and 180 cycles (Origin, varves, and cycles of Jurassic Todilto formation, New Mexico, AAPG Bull. 44, p.37-52).

The Summerville Formation (~75-325ft) consists of thin, horizontally-bedded siltstones and mudstones, with occasional thin beds of white sandstone. In the San Rafael Group, the formation is over 325ft thick. The Summerville preserves mudcracks and ripple marks (Baar, p. 183), and is overlain in some areas by thick evaporite deposits (Chronic, 1990, p. 35). All of this suggests a shallow water, tidal-flat origin for the Summerville. Tracks from the Summerville include two Pterosaur tracks, and a sauropod track which preserves skin impressions (Lockley and Hunt, p. 163).

Distribution of the Morrison Formation. From the Town of Morrison Server.

The Morrison Formation is laterally very extensive (about 1 million km2), and has been found over a large area of the western states, including South Dakota, Idaho, Arizona, New Mexico, Wyoming, Texas and Oklahoma. The Morrison contains massive amounts of dinosaur fossils, and has been described as a bone yard. Several members are recognized, the most prominent being the Salt Wash member, the Recapture Shale Member, the Westwater Canyon Sandstone Member, and the Brushy Basin Shale Member. Along the west side of Dinosaur Ridge, the Morrison Formation is 280 to 320 feet thick. In the area of Arches National Park, the Morrison is approximately 600ft thick. Layers of volcanic ash just above the formation have been radiometrically dated to 147 million years (Chronic, 1990, p. 90).

The Morrison Formation is incompatible with the flood model in several ways. First of all, there is abundant evidence that the Morrison deposits are continental, lake and stream deposits, rather than open marine deposits. Some of the thin limestone beds contain abundant charophyte fossils, a type of algae that lives only in fresh-water lakes (Baar, p. 184). The Morrison preserves well-developed paleosols, complete with: abundant carbonate nodules (Turner and Peterson, 1998), "pseudo-microkarst and microkarst features with vadose and internal sediment fills; root traces, columnar and stacked rhizoconcretions, and Microcodium; circumgranular, desiccation, horizontal, and septarian cracks; brecciation and grainification; and rare blackened pebbles" (Dunagan, p. 24). Some sections also contain bedded gypsum. Lastly, the Morrison is unconformable with the strata above and below it (Morales, p. 247).

The Morrison Formation is certainly one of the more interesting formations in terms of its fossil content. Over much of that area, it has yielded a rich trove of dinosaur fossils, beginning with dinosaur discoveries made near Morrison in 1877. These include several species of Diplodocus, Brachiosaurus, Stegosaurus, Seismosaurus, Allosaurus, Ceratosaurus, Camarasaurus, Camptisaurus, Ornitholestes, and others. Other fossils include crocodiles, lizards, frogs, tiny primitive mammals, freshwater clams, fish, ferns, trees, and even large termite nests [see also: Termite tenacity]! The termite nests are especially interesting significant, since they are apparently presrved in situ, and would have been destroyed by flood conditions.

Tracks are found in the Morrison at least thirty locations (Lockley and Hunt, p. 164), and include those of sauropods, theropods, some ornithisicians, pterosaurs, bird-like theropod, and possibly the only known stegosaur track. Whereas underlying formations of the San Rafael are dominated by small and medium theropods tracks, with a small precentage of sauropods, the Morrison track fauna contain numerous tracks of large sauropods, a smaller proportion but a wider variety of theropod tracks, and a wider size range of ornithopod tracks. The largest sauropod tracks are nearly 1 meter long. The smallest tracks Lockley and Hunt note that dinosaur fossils in the Morrison "are preserved at the base of river channel deposits or in fossil soils where tracks are rarely found, whereas some of the best tracks occur along the shores of alkaline lakes or at the top of river channel sequences where bones are not usually found" (p. 177).

The Purgatoire Valley tracksite contains tracks on 4 seperate beds. Over 1300 tracks have been mapped at this location, from one outcrop of one of the beds. Some layers at Purgatoire Valley are in fact heavily trampled or 'dinoturbated,' a phenomenon which becomes widespread in late Mesozoic deposits (p. 173). The site has been dubbed dinosaur lake, for the tracks appear to have been made on the shores of a freshwater lake, based on the associated fossils of plants, algae, snails, clams, crustaceans, and fish. Sometime the tracks contain crushed clam shells and flattened plant stems created perhaps when dinosaurs came to the lake shore for a drink. This sight also contains evidence of gragarious behavior in the form of 5 evenly spaced, parallel brontosaur tracks, which extend roughly 100 meters, virtually the whole length of the outcrop. In Cretaceous deposits, parallel trackways of dozens of individuals are known. Apparently these dinosaurs had no problems gathering themselves into herds and taking long walks, even during the final stages of the global flood.

The Dakota Formation (~150ft) is generally thin and highly variable throughout the central Colorado Plateau. Where it is present, it generally consists of a lower unit of sandstone or conglomerate, a middle layer of shale and channel sandstone, and an upper layer of marine shale and sandstone. Several paleosoils and numerous types of burrows have been reported from the Dakota Formation (Joeckel, R.M. Albian-Cenomanian geomorphology and climate in southeastern Nebraska: evidence from deep, plinthic paleosols in the lower to middle Dakota Formation. Abstracts of SEPM 1992 Theme Meeting, Mesozoic of the Western Interior: 35; See also: This Page). Rare fossils include plants (dominately ferns and horsetails) and petrified wood.

The Dakota sandstone is interpreted as a shoreline facies of the Cretaceous Western Interior Seaway. While thin in the Colorado Plateau region, correlative formations are found throughout western North America. Numerous dinosaur tracksites occur in these deposits, and trackways attributed to birds and small, coeleasaur theropods have been found in the Dakota Group as well. Although theropod and large sauropod tracks are present as in the Morrison, a conspicuous feature of these Cretaceous deposits, both in the Colorado Plateau region and elsewhere, is the presence of numerous large ornithopod (Iguanodontid) trackways (~50cm).

Trackways are found at numerous levels. For instance, 18 track bearing levels have been mapped at one site near Eldorado Springs, Colorado (lockley and Hunt, p. 196), 11 at Roxborough State Park, Colorado. However, no body fossils have been found at these sites. Often these exposures show parallel, monospecific trackways (up to 55 at Mosquero Creek) suggesting gregarious behavior. Lockley and Hunt write:

Both to the east and to the north, the Dakota is overlain by shales, but in the North this shale is called the Tropic Shale and in the east it is called the Mancos. These shales were deposited in the Cretaceous Interior Seaway, which stretched north-south from Canada to the Gulf of Mexico. At Mancos, Colorado, this black shale is about 2000ft thick. Fossils from several types of organisms are present, including shark teeth (Bourdon and Graffam), gastropods, foraminifera, ammonites, bivalve molluscs, clams, and others. Baar writes:

Similar black shale deposits are forming today in restricted, poorly-oxygenated marine environments, such the Santa Barbara basin in California and the deep Black Sea (Van Andel, p. 210). To the west and south, the Mancos grades into a shell-rich, near-shore lithofacies of cross-bedded sandstone. Plesiosaurs and mosasaurs have been found. Layers of salt are also present in some portions of the Mancos.

The Cretaceous - Tertiary Boundary

At the end of the Cretaceous period, roughly 65-70% of all marine species living within 20mya of the Cretaceous disappear from the fossil record (Crutzen, P. J. 1987. Acid rain at the KT boundary. Nature 330:108-109). In oceanic sediment cores which preserve the a continuous section through the K-T boundary, over 90% of coccolith genera and planktonic foraminifera disappear abruptly, right at the iridium anamoly (McLean 1985). For instance, see this page for a look at how foraminifera faunas change right at the K-T boundary. Other marine organisms which disappear at the K-T boundary include the ammonites, the mosasaurs, the icthyosaurs, and the plesiosaurs, many groups of animals. In terrestrial environments, the most obvious faunal change at the K-T boundary is the sudden disappearance of all non-avian dinosaurs. Other terrestrial organisms which disappear at the K-T boundary include the pterosaurs. Even if some groups were in decline before the K-T boundary, and indeed at any given time some groups are in decline, it is clear that many of the victims were thriving just prior to K-T event, and did in fact disappear right at the K-T boundary. Many groups which did not become extinct altogether where heavily reduced. These incluide the belemnites, brachiopods, foraminifera, sharks and rays, some bony fish, and other groups. For reasons which are not clearly understood, eutherian mammals, birds, turtles and amphibians were little affected.

Plants were severely affected as well, although the effect seems to have been greatest in North America. At terrestrial K/T sections from Canada to New Mexico, sediments below the boundary are dominated by angiosperm pollen, yet the boundary itself has little or no angiosperm pollen, and instead is dominated by fern spores. Normal pollen counts occur immediately above these boundaries. The spore spike therefore coincides precisely with the iridium spike in time and is equally intense and short-lived. Evidence from modern catastrophes, such as the eruption of Krakatau in 1883, indicate that ferns are the first to recolonize decimated areas. Studies by Hickey and Johnson of nearly 25,000 plant fossil specimens, from over 200 localities in the Rocky Mountains and Great Plains area, indicate that between 79-90% of Cretaceous plants became extinct at the K/T boundary (Johnson, K.R., and Hickey, L.J. 1990. Patterns of Megafloral Change Across the Cretaceous Tertiary Boundary in the Northern Great Plains and Rocky Mountains. Global Catastrophes in Earth History, eds. V.L. Sharpton and P.D. Ward. Boulder, CO.: Geological Society of America. Special Paper 247: 433-434).

The K-T boundary coincides with two 'catastrophic' events, both of which have been cited as causally linked to the K-T extinctions: a major meterorite impact on the Yucatan Peninsula, whcih left a crater approximately 180km in diameter, and the extrusion of the Deccan Traps flood basalt province, which consists of approximately 2 million km2 worth of lava. It is the opinion of this author that the impact, but not the Deccan lava flows, is most likely causally linked to the extinctions at the K-T boundary.

Abundant information about the nature of the K-T event is present in places where K-T boundary deposits are preserved. For instance, in the Cretaceous-Tertiary limestone originally studied by impact proponent Walter Alvarez in Gubbio, Italy, the K-T boundary was identified as a 1cm clay layer seperating Globotruncana-rich limestone below from limestone above in which Globotruncana forams were absent entirely, containing instead a fauna of tiny forams. Whereas the limestone above and below the clay layer contains normal, 'background' levels of Iridium (about 300 ppt), the clay layer right at the K-T boundary was found to contain roughly 30 times as much Iridium. In order to confirm his results, Alvarez studied a similar clay layer at the K-T boundary in Copenhagen. The Iridium spike was found here as well, but was even stronger, about 160 times the background Ir level. Iridium enriched boundary layers have now been described from well over 100 localities, in both continental and marine sediments (Glen, W. 1994. The Mass Extinction Debates. Stanford Unoversity Press, p. 9). Amazingly enough, the Iridium anamoly has even been discovered within the Deccan Traps, in a sediment layer denoted ITIII, between the third (FIII) and fourth (FIV) basalt flows! The three lower flows possess normal magnetism, and are placed within the latest Cretaceous normal chron C30N, while FIV is revesely magnetized, and placed within chron C29R. This sediment or intertrappean layer was formed after the extrusion of FIII, but before extrusion of FIV, which have been Ar-40/Ar-39 dated at 65.5+/-0.7 and 65.4+/-0.7my respectively. Iridium here peaks at almost 1300ppt, while the other intertrappean layers and the basalts themselves possess normal 'background' Iridium levels or around 10ppt (Bhandari, N., Shukla, P.N. et al. 1995. Impact Did not Trigger Deccan Volcanism: Evidence from Anjar K/T Boundary Intertrappean Sediments. Geophysical Research Letters 22: 433-436). Just below the Iridium layer are found ostracods, as well as dinosaur bones and eggshells, again confirming that dinosaurs lived right up until the K/T boundary. Taken together, these facts indicate that the first three flows did not decimate life, even in the immediate area, and that extrusion was not occurring at the precise time of the K/T boundary.

[Note: dates cited by V. Courtillot et al. indicate a slightly older (66.5-67 Ma) age for flows FI-FIII. (Cosmic markers, 40Ar /39 Ar dating and paleomagnetism of the KT sections in the Anjar Area of the Deccan large igneous province. Earth and Planetary Science Letters 182 (2000) 137-156).]

These boundary layers are enriched not only in Iridium, but also in other elements which are rare on the earth's surface, including nickel, cobalt, chromium, arsenic, antinomy and selenium. Impressively, the chemical composition of the boundary clay cannot be matched to any terrestrial source, but happens to match quite well the composition of type 1 carbonaceous chondrites, a type of meterorite. This similarity in composition is based on the analysis of several elemental ratios present in the boundary clay, such as platinum/iridium and gold/iridium (Alvarez, W., and Asaro, F. 1990. An Extraterrestrial Impact, Scientific American. October.), the relative abundances of ruthenium and rhodium, and ratios of osmium 186/osmium 187 (Luck, J.M., and Turekain, K.K. 1983. Osmium 187/Osmium 186 in Manganese Nodules and the Cretaceous-Teriary Boundary. Science 222: 613-615), and the relative abundances of 53Cr/ 52Cr (Shykolyukov, A. and Lugmair, G.W. 1998. Isotopic evidence for the Cretaceous-Tertiary impactor and its type. Science 282: 927-929), all of which correspond remarkably well with the ratios in carbonaceous chondrites and are sharply different from the ratios found on earth and on the moon. Yet another line of evidence suggesting a meteoric source for the K-T boundary clay is the presence of 18 amino acids which are not found on earth, but which have been found in carbonaceous chondrites (Dingus and Rowe, The Mistaken Extinction, p. 63; Zhao & Bada, 1989, Nature, 339, 464-465). Note that although life on earth uses only 20 amino acids, these are only a small subset of all amino acids.

The K-T boundary clay is also contains several other types of 'impact products.' These include microtectites and impact glass, shocked quartz and zircon crystals, and microdiamonds. Each of these have been found in association with known impact structures, although in much smaller quantities than are found in the K-T boundary. Shocked quart with multiple planar fractures are diagnostic of impact, and are not produced by volcanic eruptions or regional metamorphism [they have been produced by nuclear tests, however]. Tectites from the K-T boundary have been dated at 64.5+/-0.1my and 64.75my (Izett, G.A., Dalrymple, G.B., et al. 1991. Ar-40/Ar-39 Age of Cretaceous-Tertiary Boundary Tectites from Haiti. Science 252: 1539-1542; Hall, C.M., York, D. et al. 1991. Laser Ar-40/Ar-39 Step Heating Ages From Cretaceous-Tertiary Boundary Glass Spherules. Eos 72: A531). A feldspar from the Hell Creek, Montana K-T boundary section has yielded an age of 64.6+/-0.2my (Hall, 1991). Melt rock from the Chicxulub crater itself has been dated at 64.98+/-0.05 and 65.2+/-0.4my (Swisher, C.C.I., Grajales-Nichimura, J.M., et al. 1992. Coeval Ar-40/Ar-39 Ages of 65.0 Million Years Ago from the Chicxulub Crater Melt Rock and Creteaceous-Tertiary Boundary Tectites. Science 257: 954-958; Sharpton, V.L., Dalrymple, G.B., et al. 1992. New Links Between the Chicxulub Impact Structure and the Cretaceous-Tertiary Boundary. Nature 359: 819-821). Just as isotopic analyses have been used to match K-T boundary material to an extraterrestrial source, similar chemical and isotopic analyses have been used to demonstrate that the glass spherules are derived from source rocks in the area of Chicxulub crater (Sigurdsson, H.S., D' Hondt, S., et al. 1991. Glass From the Cretaceous-Tertiary Boundary in Haiti. Nature 349: 482-487; Blum, J.D., Chamberlain, C.P., et al. 1993. isotopic Comparison of K/T Boundary Glass with Melt Rock From Chicxulub and Manson Impact Structures. Nature 364: 325-327).

This is confirmed by isotopic dating of 43 zircons from Chicxulub melt rock, and from K/T boundary clays in the Raton Basin, the Haitian Beloc Formation, and a site in Saskatchewan. Zircons in these locations range from heavily fractured to unaltered. U-Pb concordia dates reported by Tom Crough and Bruce Bohor showed that the least disturbed zircons yield ages of 545+/-5my, and that the most heavily disturbed zircons yield ages of 65+/-3my, strongly suggesting that zircons scattered in K/T boundaries over a significant portion of the world were originally part of a single igneous body which cystallized in the Cambrian and was disturbed 65mya. J.L. Powell (Night Comes to the Cretaceous, 1998) writes:

"In all, Krogh and his colleagues studied 43 K-T zircons. A few seemed to point to an age of 418 million years for the parent rock; several others scatter randonmly when plotted on the Concordia diagram, indicating that they have had a more complex history, perhaps having lost lead twice. But . . of the 43 zircons from all four sites, 30 fall exactly on a straight line . . . These 30 zircons, found at four sites seperated by thousands of kilometers and representing three completely different geologic settings - A Chicxulub breccia, Haitian tectites, and K-T boundary clays from two locations, one 3,500km away from the Yucatan - plot precisely on a single straight line with a coefficient of correlation of 0.998. When all 43 zircons are included, even those that obviously have a more complex history, the correlation coefficient is still a remarkably high 0.985" (p. 120).

"This point is absolutely critical: Zircons that originated in a volcanic eruption 65 million years ago would have crystallized at that time. They would possess, and would display, an original age of 65 million years - not 550 million years. Subsequent lead loss would make them appear younger than 65 million years, not older. . . Because 65 million year old zircons could not produce this result, neither the zircons nor the clay itself could have come from a 65 million year old volcanic eruption" (p. 119).

There is now a great deal of additional evidence for the violent effects of the K/T impact. 900m-thick impact breccia deposits are present 100 km from the crater (e.g., Sharpton et al., 1996). On Albion Island, about 360km from Chicxulub, an ejecta blanket about 15m thick is found at the K/T boundary, and contains fragments as large as a car. Tsunami deposits containing decimeter-size rip-up clasts are found along continental shelves in Texas and northern Mexico (e.g., Bourgeois et al., 1988). Gravity-flow deposits occur at the K-T boundary in Cuba (Iturralde-Vinent, 1992), Chiapas (Montanan et al., 1994), and Belize (O'Campo et al., 1996). Disturbed K-T boundary units are also reported in Haiti (Maurrasse and Sen, 1991) and in Deep Sea Drilling Project (DSDP) sites at the base of the Campeche Escarpment (Alvarez et al., 1992).

Interestingly, a small piece (2.5 mm) of material found in sediments of K/T age in DSDP Site 576 in the Pacific Ocean, about 9000 km west of the Chicxulub crater, is thought to be a portion of the impacting meteorite. The material has been partially altered since burial, but still has a high Iridium content (690 ng/g). General concentrations of elements are said to be similar to concentrations in weathered meteorites of the types called CV, CO and CR carbonaceous chondrites (Kyte, F.T. 1998. A meteorite from the Cretaceous/ Tertiary boundary. Nature 396: 237-239).

The Claron Formation, also referred to as the "Pink Cliffs," forms the highest "step" of the Grand Staircase. This formation is also known as the Wasatch Formation. This formation, which is about 500ft thick in Bryce Canyon, but up to several thousand feet in Wyoming, was deposited in a lacustrine, or perhaps a playa lake, environment, which expanded and contracted several times. This lake filled basins on either side of the Uinta Uplift in northern Utah (Baars, p. 210), with conglomerate rich alluvial fans adjacent to the uplift grading into sandy and then mudstone textures away from the uplift. The alluvial fan deposits contain small carbonate particles derived from the Uinta Uplift, and which Davis (p. 195) takes as evidence of an arid depositional environment, since such particles would easily dissolve if theyt remained suspended in water for any length of time. Some members of the Wasatch Formation contain layers of volcanic ash which can be radiometrically dated. The "K-spar tuff" at the junction between the upper and middle units of the Fossil Butte Member, which is roughly in the middle of the Wasatch, has been dated at 50.2 +/- 1.9 mya (Buchheim and Eugster, 1998).

In southwestern Wyoming, the Wasatch Formation encloses and intertongues with the famous Green River Shale, which is underlain by the main body of the Wasatch, and overlain by the Bullpen Member. Some members of this lacustrine and/or playa lake deposit contain several hundred meters worth of paper-thin couplets of light and dark sediment layers. Many of these couplets, of which there are several million, are interpreted as yearly or semi-yearly deposits, with the dark layers representing winter conditions, during which very little terriginous sediment is carried by streams into the depositional environment. Essentially identical structures are observed to form in some modern lakes as yearly deposits.

Also notable are the salt deposits and dessication cracks within the Wilkins Peak Member, sandwiched between the Tipton and the Laney members This sequence suggests that the area experienced deep water conditions as the Tipton was deposited, followed by dry, evaporative conditions at the end of Wilkins Peak time, and then back again to deeper water during the deposition of the Laney Member, and then back to dry, dessication conditions at the end of Green River deposition.

The Wasatch contains fossils of plants, leaves, and pollen, freshwater fish and gastropods, crocodiles and other reptiles (McGrew and Casilliano, p. 20). Palynological analysis of the Green River Formation reveal abundant spores and pollen of conifers, angiosperms, ferns and lower plants (Cushman, R., Palynostratigraphy and Age of the Green River Formation in Fossil Basin, Wyoming). Also present are dinoflagellates and acritarchs. These palynofossils and the vertebrate fossils in the intertonguing Wasatch Formation are of Eocene age.

Several apparent Presbyornis nesting-sites, as well as the trackways of these birds, have been reported in shoreline facies within the Green River Formation (Leggitt and Buchheim, 1997; McGrew, 1980). Also present, for the first time in the column we've been discussing, is an increasingly diverse, but still quite 'primitive,' mammalian fauna, including Lambdotherium, the primitive horse Orohippus (Breithaupt, 1990), the Mesonychid Haplodectes (X. Zhou and P. Gingerich), the primate Chiromyoides (P. D. Gingerich and J. A. Dorr), and many others. Small mammal and amphibian trackways are known also, including one of the only known trackways of a frog (Lockely and Hunt, 1995, p. 255). The fauna of the Wasatch is drastically different from that of the underlying Mesozoic strata, not only because of the presence of early members of some modern mammalian families, but also because the dominant land animals of Mesozoic, the dinosaurs, have vanished completely.