Zoophycosichnogenus distribution and paleoenvironmental analysis: examples from the Mississippian Mobarak formation (Alborz Basin, Iran)

Zoophycos is a characteristic trace fossil in the Mississippian in the Alborz Basin deposits of north Iran, and is described for the first time in the Mobarak Formation. The vertical distribution of the carbonate deposits bearingZoophycosprovided the basis for distinguishing three distinct types of sedimentary sequences includingZoophycos(type A, B, and C) in shallow marine sediments of Mobarak Formation. Type A is composed of rare to common density of small to medium lobedZoophycos. Type B is characterized by common density of medium lobedZoophycos. This ichnogenus in type A and B is associated withPalaeophycus. The low diversity and bioturbation of the trace fossils would be the result of a stressful environment characterized by optimal water circulation and high-energy conditions. Type C consists of abundant density of large lobedZoophycos. Type C is associated withChondritesandplanolites. The high diversity and bioturbation of the trace fossils in type C than type A and B would be the result of a calm environment characterized low-energy conditions. Under low sedimentation rate, stable paleoenvironment, dysaerobic conditions, and high amount of benthic food, the size ofZoophycosis the biggest, whereas in the high sedimentation rate, unstable paleoenvironment, aerobic conditions, and shortage of benthic food, the size ofZoophycosis small.