SEDIMENTOLOGY AND PALEONTOLOGY OF THE NASH DINOLAND QUARRY (EARLY JURASSIC PORTLAND FM), GRANBY, MA

Nash Dinoland is a privately owned and operated quarry that has sold dinosaur footprints for 70 years. The quarry is located in Granby, Massachusetts and exposes 1.3m of rock of the Early Jurassic (ca. 200MA) Portland Formation. Although footprints have been sold worldwide, Nash Dinoland has never been scientifically examined in depth. Thus, the paleontology and sedimentology of the site are poorly constrained. A preliminary examination has been conducted to better constrain these aspects of the site.

Various lines of evidence indicate that the depositional environment was a hypoxic lake bed. The rock, which is primarily siltstone to fine-grained, oscillation-ripple-marked sandstone, has a dark gray to black color on fresh surfaces, which is indicative of hypoxic aqueous environments. Furthermore, no invertebrate bioturbation has been observed and fossilized fish, when found, are rare and fragmentary. The paucity of fish and invertebrate burrows indicates low dissolved oxygen content for aqueous macroorganisms. Large concentrations of poorly preserved, water-transported plant material occur on bedding planes, and suggest a cause for the hypoxia. No subaerially-produced sedimentary structures, such as desiccation cracks or raindrop impressions were observed, indicating that subaerial exposure did not occur.

There are four dinosaur ichnotaxa present at the site, including the theropod prints Anchisauripus, Eubrontes, Grallator and the ornithischian print Anomoepus. Theropod ichnotaxa comprise the vast majority of footprints, with only a few ornithischian footprints being present. Despite the fact that aqueous conditions predominated, no swim tracks were observed. Thus the animals must have waded through water shallower than their hips, or they would have become buoyed up and produced tracks with the characteristic swim track morphology seen at other sites. Estimates of maximum water depth were obtained by using equations for dinosaur hip height, which was calculated from the lengths of the smallest footprints (ca. 9.6 cm). Based on these calculations the water depth probably did not exceed ca. 38 cm.