Taphonomy of ghost shrimps (Decapoda: Axiidea: Callianassidae) associated with their burrows within a middle Miocene mud volcano complex of Persian (Arabian) Gulf, Kuwait

Abstract

Shallow-marine strata of the Ghar Formation exposed along the Kuwait arch in the north of Kuwait contains fields of mud volcanoes associated with an assemblage dominated by pectinid bivalves and callianassid ghost shrimps. The depositional palaeoenvironment is interpreted to be intertidal to subtidal with the water depth not exceeding 50 m and with normal to hypersaline conditions. Based on the microfossil assemblage a middle Miocene age (early Langhian) is inferred, suggesting a longer stratigraphic span of the formation despite the previous studies treating the Ghar Formation as strictly early Miocene. Callianassid body fossils and numerous trace fossils assignable to Ophiomorpha have been identified. Ghost shrimp remains consisting of isolated cheliped elements are assigned to Neocallichirus (s.l.), which is the likely producer of Ophiomorpha burrows as documented by cheliped elements present within burrows and in the substrate around them. Stable isotopes discrimination modelling confirmed that fluids in the substrate were derived from at least two sources implying the presence of active mud volcanoes in the environment inhabited by ghost shrimps. Effusive activity of mud volcanoes further enhanced disarticulation and fragmentation of callianassid remains. The micritic matrix of ghost shrimp exoskeletons is indicated to have resulted from a mixture of local seawater with fluid of continental origin. This ghost shrimp occurrence is the first formal report of fossil decapod crustaceans from Kuwait.