Paleoecologic and Biostratigraphic Significance of Trace Fossils From Shallow- to Marginal-Marine Environments From the Middle Cambrian (Stage 5) of Jordan

The Hanneh Member (Cambrian Stage 5) of the Burj Formation and the Umm Ishrin Formation of Jordan represent a transgressive-regressive succession that contains twenty-eight ichnotaxa, including vertical burrows (Arenicolites isp., Diplocraterion isp., Gyrolithes polonicus, Rosselia isp., Skolithos linearis, escape trace fossils), horizontal simple burrows and trails (Archaeonassa fossulata, Gordia marina, Helminthoidichnites tenuis, Palaeophycus tubularis, Planolites beverleyensis, P. montanus), plug-shaped burrows (Bergaueria sucta), horizontal branched burrows (Asterosoma isp., Phycodes isp., Treptichnus cf. T. pedum), bilobate structures (various ichnospecies of Cruziana and Rusophycus), and trackways and scratch marks (Diplichnites isp., Dimorphichnus cf. D. obliquus, Monomorphichnus isp.). Eleven trace fossil assemblages are identified. The Arenicolites isp. and Diplocraterion isp. assemblages occur in transgressive tidal dunes and bars whereas the Rosselia isp. assemblage characterizes areas between tidal dunes. The Cruziana salomonis assemblage reflects a wide variety of environmental settings including channels within tidal-bar complexes, bottomsets of tidal dunes, and interdune areas. The Gordia marina assemblage is resent between dune patches. The Gyrolithes polonicus assemblage penetrates into firmground mudstone below the maximum flooding surface. The Bergaueria sucta, Archaeonassa fossulata, Rusophycus aegypticus and Cruziana problematica assemblages occur in different subenvironments of the progradational delta. Cruziana salomonis and Rusophycus burjensis, originally considered indicative of an early Cambrian age, are actually middle Cambrian in their type locality. Occurrences of Cruziana jordanica and Rusophycus aegypticus provide evidence that these ichnospecies are of the same age in Jordan and may co-exist in terms of stratigraphic distribution with C. salomonis and R. burjensis.