The diversification of animals during the Cambrian Period is one of the most significant evolutionary events inEarth’s history. However, the sequence of events leading to the origin of ‘modern’ ecosystems and the exacttemporal relationship between Ediacaran and Cambrian faunas are uncertain, as identification of the Ediacaran–Cambrian boundary and global correlation through this interval remains problematic. Here we review thecontroversies surrounding global correlation of the base of the Cambrian and present new high-resolutionbiostratigraphic, lithostratigraphic and δ13C chemostratigraphic data for terminal Ediacaran to basal Cambrianstrata in the Zavkhan Basin of Mongolia. This predominantly carbonate sequence, through the Zuun-Arts andBayangol formations in southwestern Mongolia, captures a distinct, negative δ13C excursion close to the top ofthe Zuun-Arts Formation recognized as the BAsal Cambrian carbon isotope Excursion (BACE). In this location,the nadir of the BACE closely coincides with first occurrence of the characteristic early Cambrian protoconodontProtohertzina anabarica. Despite recent suggestions that there is an evolutionary continuum of biomineralizinganimals across the Ediacaran–Cambrian transition, we suggest that this continuum is restricted to tubular forms,and that skeletal taxa such as Protohertzina depict ‘true’ Cambrian representatives that are restricted entirely tothe Cambrian. Employing the first appearance of the trace fossil Treptichnus pedum to define the base of theCambrian suffers significant drawbacks, particularly in carbonate settings where it is not commonly preserved.As T. pedum is the only proxy available to correlate the Cambrian Global boundary Stratotype Section and Point(GSSP) defined at Fortune Head, Newfoundland, we suggest that the GSSP be redefined elsewhere, in a newstratigraphic section that contains secondary markers that permit global correlation. We propose the nadir of theBACE as the favored candidate to define the base of the Cambrian. However, it is essential that the BACE becomplemented with secondary markers. In many global sections the nadir of the BACE and the first occurrence ofthe genus Protohertzina are closely juxtaposed, as are the BACE and T. pedum. Hence these taxa provide essentialbiostratigraphic control on the BACE and increase potential for effective global correlation. We also recommendthat an Auxiliary boundary Stratotype Section and Point (ASSP) be simultaneously established in order toincorporate additional markers that will aid global correlation of the Ediacaran–Cambrian boundary. The BAY4/5 section through the upper Zuun-Arts and Bayangol formations yields key shelly fossils and δ13C values and istherefore an ideal candidate for consideration as the GSSP for the Ediacaran–Cambrian boundary.