Paper No. 30
Presentation Time: 9:00 AM-6:00 PM
UPPER CRETACEOUS (SANTONIAN) AMBER FROM THE INGERSOLL SHALE (EUTAW FORMATION), EASTERN ALABAMA: MODES OF OCURRENCE, CHARACTER, FOSSIL INCLUSIONS, AND PALEOBOTANICAL AFFINITY
A new amber-rich deposit has been identified in the Upper Cretaceous (Santonian) Eutaw Formation, exposed in eastern Alabama, U.S.A. Amber occurs as common parautochthonous clasts (up to 360 g of amber/m3 of sediment) and in direct association with plant parts in the lower part of a thin (<90 cm), narrow (<30 m), carbonaceous, pyritiferous, clay lens known informally as the Ingersoll shale. This richly fossiliferous clay lens, which also contains common feathers and a diverse terrestrial paleoflora, was deposited in a restricted tidal channel within a transgressive estuarine bayhead-delta system. Factors contributing to the accumulation and preservation of amber include close proximity to resin-producing swamp vegetation, concentration of resin clasts and resin-bearing plant parts after limited transport, rapid burial caused by continuous tidal laminite deposition, and reducing substrate conditions. Amber clasts are relatively transparent and contain common organic inclusions such as plant and fungal debris and terrestrial arthropod remains. The latter include mites, scale insects, and a spider in association with its web. In situ amber rods, recognized in various plant parts (stems, leafs, cones, and cone scales), and chemotaxonomic evidence derived from pyrolysis GC-MS analyses—specifically the occurrence of methyl callitrisate and related homologues—indicate that amber was derived from tree species belonging to the family Cupressaceae. Comparison of other Cretaceous amber deposits from around the world indicate that Ingersoll amber is most similar to Turonian amber of central
New Jersey with respect to lithologic associations, depositional conditions, and paleobotanical affinities.