Pyrite framboids interpreted as microbial colonies within the Permian Zoophycos spreiten from southeastern Australia

Two types of pyrite framboids (PF, probably sulphate-reducing bacteria) have been foundwithin the Zoophycos spreiten, hosted in the Guadalupian (Middle Permian) glaciomarine greywackeof the Westley Park Sandstone Member within the Broughton Formation from the southern SydneyBasin of southeastern Australia. They are composed of non-sheathed (PF1) and sheathed (PF2)sub-micron balls, respectively. Chemically, the sub-micron balls consist of iron, sulphur, carbon andoxygen. Both PF1 and PF2 occur in rhythmic alternationwithin the thick, light-grey and thin, dark-greyminor lamellae of Zoophycos spreiten. The framboids from the minor lamellae are highly abundant andoccur in an orderly arrangement of equal density and in a good state of preservation.Within Zoophycosspreiten no homogeneous filling, fecal pellets, or any sign of re-exploitation of the minor lamellae havebeen recognized. No similar framboids have been observed outside Zoophycos spreiten. Therefore, theframboids are interpreted as the pyritized remains of microbial colonies within Zoophycos spreiten.The trace Zoophycos would be a multifunctional garden thatmay have been carefully constructed by theZoophycos maker, where different microbial colonies were orderly and carefully planted and culturedwithin different minor lamellae. Further, it is proposed that the Zoophycos maker had a symbioticrelationship with microbial colonies on the mutual basis of food supply and redox conditions. The factthat the overlying spreiten cut the underlying ones indicates that the Zoophycos from the study area isof an upward construction. The rhythmic alternation of both the thick, light-grey and thin, dark-greyminor lamellae within Zoophycos spreiten may be suggestive of a gardening manner of the Zoophycosmaker responding to the warm and cold changes, food supply in pulses and variations of sedimentationrate for planting and culturing microbial colonies under the conditions of a glaciomarine environmentat the high latitudes.