TRIASSIC INSECT REMAINS FROM THE VIRGINIA SOLITE QUARRY - HOW FAR DID THEY SINK?

The Solite Quarry, situated on the Virginia-North Carolina border, contains outstanding artificial exposures of the Upper Triassic Cow Branch Formation. Different horizons within the quarry are still yielding a remarkable fauna and flora that includes abundant, well-preserved and frequently complete insects. Numerically dominated by aquatic forms, these constitute the earliest known aquatic insect assemblages. Moreover, many extant orders and families of insects are represented. By contrast the tetrapod remains largely represent less well-known taxa which are confined to Triassic times. These include abundant remains of the small protorosaur Tanytrachelos, sometimes with soft tissue preservation, and the rare, enigmatic gliding form, Mecistotrachelos. Plant remains are the most abundant fossils and typically comprise fragments of foliage and/or seeds of cheirolepidaceous conifers, dipteridaceous ferns, bennettitaleans and ginkgophytes. One particular bedding plane extends for tens of meters and displays densely packed fronds over its surface.

Most researchers have interpreted the fossiliferous deposits from the Solite Quarry in terms of Van Houten cyclicity. The black well-laminated sediments containing the insects and soft body fossils are typically considered to have been buried under anoxic conditions in a deep water environment. However, data recently collected from the Solite Quarry has been used to suggest an alternative depositional model where the insects were buried in a shallow, littoral environment; one that might have been inhospitable to many aquatic life forms.

Here we conduct a preliminary assessment of the nature and distribution of the fossils, particularly the plants and insects, to determine whether the taphonomy can provide any further insight into the depositional environment. In particular, the prevalence of coleopterans, abundant belostomatid instars, and completeness of smaller taxa suggest near-shore affinities for the insect assemblage. The preservation of vertebrates likewise indicates an absence of current, but not necessarily deep conditions, especially as fish are comparatively rare and small.