The Sirius Passet Lagerstätte (early Cambrian) of North Greenland

The Sirius Passet biota is the oldest major Cambrian lager-statte in Laurentia {Nevadella Zone, equivalent to Series 2, stage 3 of the developing chronostratigraphic scale for the Cambrian). The locality on the northern coast of Greenland (latitude 82°47.6' N, longitude 42°13.3' W) was discovered in 1984 and preserves an assemblage of about 40 species dominated by weakly sclerotized arthropods and lobopodi-Other forms include articulated Halkieria evangelista, the oldest described annelid, palaeoscolecidans and early cycloneuralians, but many species await description. Fine details of soft tissues such as mineralized digestive glands and muscle fibres, gut traces and limbs are commonly visible, but their preservation is variable between individuals and species, reflecting the different life styles and taphonom-ic histories of the various faunal elements. The Sirius Passet locality lies in the transition between the southern shelf succession and a northern deep water trough, forming the southern margin of the trans-arctic Franklinian Basin, in a geological setting reminiscent of that of the younger Burgess Shale. Fossiliferous fine-grained, siliciclastic sediments accumulated in close proximity to the degraded, abrupt scarp of an extensive aggradational carbonate platform (PortQeld Formation). The eroded carbonate platform was transgressed in the early Cambrian, with the fine-grained Sirius Passet sediments considered to have accumulated in an oxygen-deficient, sheltered, pocket in the upper slope coarse-sediment bypass zone. The northern deep water trough of the Franklinian Basin forms the locus of Ellesmerian deformation with the Sirius Passet locality lying within a zone of southerly directed thrusts and folds. Porphyroblasts of chloritoid are characteristic of the mudstones, indicating temperatures in excess of 300°C.