Article: Fish oblique to bedding in early diagenetic concretions from the Cretaceous Santana Formation of Brazil – implications for substrate consistency
David M. Martill
A large number (> 1 per cent.) of fossil fish from the Santana Formation (?Albian, Lower Cretaceous) of north-east Brazil, occurs at a high angle, or even vertical, to bedding. Petrographic and taphonomic analyses of such occurrences indicate that the laminated argillaceous sediments were soupy and allowed sinking dead fish to penetrate the sediment to depths greater than the total body length of the fish. Density contrasts between the dead fish and the surrounding sediment were negligible, and penetration was largely a result of acceleration due to the high density contrast between the fish and the water column. A commonly recurrent angle of fish to bedding of approximately 45° reflects the gliding angle achieved during forward descent with pectoral fins extended.