The Mygatt-Moore Quarry where Mymoorapelta was first found has been dated between 151.89 and 152.47 million years old, firmly placing it within the Brushy Basin Member of the Morrison Formation. The broader paleoenvironment of the area has been interpreted as a riparian (riverine) ecosystem with abundant flora and a high water table, with the quarry itself having been interpreted as an attritional accumulation of dinosaur fossils at a seasonal waterhole. This has allowed it to become one of the most fossil abundant sites in the United States, with the site notably preserving plants, pollen, coprolites, and even skin impressions preserved alongside dinosaur fossils. The quarry's abundant plant fossils include horsetails, cycads, Gingkoales, Czekanowskiales, and many different Coniferales represented by leaf, wood, and pollen fossils. Invertebrates represented in the quarry include gastropods and, most notably, fossils of fossil crayfish.
