Db_abstract

Rotation of an Upper Triassic Ghost Ranch, New Mexico Whitaker (Coelophysis) Quarry block: turning over a fragile 12,000 lb block

Describes how staff at the New Mexico Museum of Natural History and Science very carefully turned over its Ghost Ranch Coelophysis block so that it could be prepared from beneath for exhibition.

Item Details

Abstract

New Mexico Museum of Natural History's Coelophysis Quarry block C-8-82 is from the Upper Triassic Rock Point Formation of the Chinle Group at Ghost Ranch, New Mexico. Its maximum dimensions are ~2 m long, ~1.4 m wide, and ~1.1 m deep. The volume is ~2 m, and the mass ~5,440 kg (~12,000 lb). The siltstone is extremely friable, and has intersecting desiccation cracks and joints throughout. The premium fossil horizon is only ~30 cm deep in the block and the highest quality bone is located at the bottom of this horizon. Therefore, it was decided to turn the block over before preparation so the prepared fossils would reside on a 30 cm-thick slab rather than a nearly 1 m-thick boulder and so the best of the material would be most readily exposed.


We describe here the design, construction, and use of a large wooden rocker to gently roll the block 180 degrees. Material costs for the rocker were under $300. Jacks, nylon ratchetstraps, and an electric winch constituted the balance of the hardware already available at NMMNH. Analysis of nonconcurrent forces, rolling resistance, traction, material strengths, and minimization of vibration and flexing of the specimen were essential to the successful roll. The block was rolled on a time scale of less than 1 minute with no damage to its jacket or contents. Time invested in the project totaled 100 hours.