The Malone Formation is a geologic formation in Texas. It preserves fossils dating back to the Jurassic period.
Description
One of the few geological formations in Texas dating to the Jurassic period, the Malone Formation uncomformably overlies the Permian Briggs Formation, and laterally changes thickness dramatically from 45 meters on the east side to 325 meters in the northwest part of the Malone Mountains. It has been split into two subdivisions: a lower member containing Idoceras suggesting a Kimmeridgian age, and an upper member containing Kossmatia indicating a Tithonian age. Geochronological analysis of detrital zircon suggests an age of 151±2 Ma for the formation, supporting its dating to the late Jurassic.
Depositional environment
The Malone Formation represents a fan-delta system in a shallow marine to marginal marine environment, deposited along the northern edge of the Chihuahua trough (a sedimentary basin mostly located in northeast Mexico). Many fossils found in the formation represent marine invertebrates.
Fossil content
Vertebrates
Remains of vertebrates in this formation are rare and mostly poorly-preserved. Two cycloid fish scales, a pycnodont tooth and bone fragments of 'enaliosaurs' (a classification now obsolete) have been reported from the Malone Formation, but are not well-described.
Invertebrates
Annelids
Bivalves
Bryozoans
Cephalopods
Corals
Echinoderms
Gastropods
Plants
Fossil remains of plants, including driftwood, are abundant in the Malone Formation, but not well preserved.