A Late Triassic theropod track assemblages from the basal Wingate Sandstone, western Colorado: implications for regional correlation and the megatracksite concept

ABSTRACT

A previously known, but undocumented small Grallator ichnofauna associated with the basal Wingate Sandstone Formation is a typical Late Triassic assemblage. The tracks are very narrow with high length/width ratios, and strong mesaxony (high anterior triangle: length/width ratios). The assemblage reveals at least 88 similar-sized tracks resolved into a minimum of 24 trackways. Trackway pace lengths and speed estimates vary. The tracks occur at least 6.5 metres above the base of the aeolian Wingate Sandstone, but are associated with a thin current rippled surface indicative of a phase of fluvial activity. The trackways show preferred orientations mainly parallel to the direction of current flow indicators, and thus suggest progression along a drainage. The stratigraphic occurrence correlates with other basal Wingate ichnofaunas, at distances up to 240 km to the north, associated with a break in aeolian deposition ~ 7.0 metres above the base of the cliff-forming Wingate Sandstone. Such regional scale correlation of a distinctive track-bearing unit allows for the definition of a ‘basal Wingate megatracksite’.

KEYWORDS:

• Late Triassic
• megatracksite
• Wingate Formation

Acknowledgments

The survey of the Bedrock site was conducted in 2021 under Bureau of Land Management permit COC 076204 issued to the senior author ML. We thank an anonymous reviewer and Historical Biology Editor Gareth Dyke for their reviews and comments on the MS

Disclosure statement

No potential conflict of interest was reported by the author(s).