Dinosaur stumble preserved in trackways, Utah, USA
Posted on homepage: 1 October 2010 (GMT+10)
Scientists have described a trackway of a theropod dinosaur beautifully preserved in soft mud, now turned to stone, within Lower Jurassic strata at St George in south-western Utah, USA (figure 1).1 As well as leaving a trail of footprints, they report the dinosaur left intermittent tail drags, and in one place sat in the mud and left impressions of both of its hands, its feet, its tail, and its buttocks.2 The tracks were found in the Whitmore Point Member of the Moenave Formation at the Dinosaur Discovery Site at Johnson Farm, St George.
The report focused on connecting the dinosaur traces with the anatomy, posture and behaviour of birds, citing as evidence the rotation of the dinosaur’s forearm and the way it sat in the mud. However, in their preoccupation with the unsubstantiated speculation of birds evolving from dinosaurs the authors overlooked the obvious evidence of huge watery catastrophe recorded by the fossils and the rocks.
The Whitmore Point Member is a 20-m-thick deposit of mudstone, shale and sandstone strata, and has abundant horizons containing dinosaur trackways (figure 2), including tracks of theropods that were larger and smaller than the ones described in the report.3 The strata also contain clawmark tracks, indicating times when the animals were swimming in deep water and just managing to scratch their claws along the sand on the bottom.4 The sediment beds are also packed with body fossils including megaplants, sharks, lungfish, coelacanths, ray-finned fish, crustaceans, clams and dinosaur remains. To preserve such an abundance of body fossils and footprints requires rapid sedimentation in order to prevent the degradation processes that would normally destroy them.
The paper documents other features within the strata that point to rapid sedimentation in association with moving water, including ripples, tool marks, flute marks, rill marks and load casts.5 Many different kinds of ripples were present including current ripples, symmetrical ripples, wind-driven ripples, interference ripples, wave-formed ripples and mega ripples. Tool marks are formed on the surface of sedimentary beds by objects being dragged along by the water. They are often prominent as casts protruding on the underside of the overlying bed. Tool marks can be continuous as a result of the object being continually dragged by the current, or they can be intermittent because the object is repeatedly picked up by the current and bounced along the bottom. Flute casts are bulges that look like a spoon or flute on the bottom of sandstone beds. They form when sediment fills a scoop-shaped depression on the underlying surface; a depression caused by fast-flowing turbulent flow. Rill marks are dendritic channels that form on the downstream side of objects sitting on the surface in the presence of flowing water. Load casts are rounded blobs of sand that have oozed into the finer sediment in the underlying bed, showing that both beds were soft and unconsolidated, and indicating rapid sedimentation.
As well as rapid deposition in flowing water, the sedimentary formation points to waters rising in the area at the time. The Whitmore Point Member is part of the 100-m-thick Moenave Formation, and for such a thickness of strata to have been preserved requires the water level to have been continually rising with respect to the land surface by the same amount. The increasing depth was needed to accommodate the sediment and prevent it being eroded and transported out of the area.
Within a biblical geological context, trackways provide a significant classification criteria to help decide when the sediments were deposited.6 To make trackways the animals needed to have been alive. This means the tracks were either made before the waters of Noah’s Flood covered the earth, or after the animals had come off the ark and repopulated the earth. The tracks could not have been made during the Recessive stage of the Flood because by that time every air-breathing, land-dwelling animal had perished.
The sedimentary deposits at St George are of such an immense size, both vertically and geographically, that they could not have been deposited after the Flood—that would have required too large a catastrophe. In other words, the trackways point to their being formed during the Flood as the waters were rising on the earth—the Inundatory stage. They preserve the frantic efforts of the animals trying to flee from the rising waters, running, stumbling and falling in the mud as they fled; even occasionally swimming in a situation of rapid sedimentation and highly variable water levels.
- Haynes, M., Hands down, fossil find an important one, The Salt Lake Tribune, http://www.sltrib.com/Utah/ci_11828632, 6 March 2009. Return to text.
- Milner, A.R. et al., Bird-like anatomy, posture, and behavior revealed by an Early Jurassic theropod dinosaur resting trace, PLos ONE 4(3):e4591, doi:10.131/journal.pone.0004591, 2009; www.plosone.org/article/info:doi/10.1371/journal.pone.0004591, 6 March 2009. Return to text.
- Milner, et al., ref. 2, pp. 2, 4. Return to text.
- For another example see: Walker, T., Terrible lizards trapped by terrible Flood, Journal of Creation 21(3):18, 2007. Return to text.
- Milner, et al., ref. 2, p. 2. Return to text.
- Walker, T.B., A biblical geologic model; in: Proceedings of the Third International Conference on Creationism, Walsh, R.E. (Ed.), Creation Science Fellowship, Pittsburgh, PA, pp. 581–592, 1994. Return to text.