Ediacaran fossils from the Innerelv Member (late Proterozoic) of the Tanafjorden area, northeastern Finnmark J. FARMER*, H. P. A. of Earth and Sciences, University of California. Los 405 Hilgard Avenue, CA 90024, U.S.A. Institute of University of Box 558, 22, Sweden fur Postfach 102148, I, Germany Department of Historical Geology and Palaeontology, University, 13, 62, Lund, Sweden P.O. Box Trondheim, Norway (Received March 199I accepted 29 August 199I) - An Ediacaran assemblage dominated by an unidentified species of 1947,along with species of Sprigg 1947, Sprigg 1947, Fedonkin 1982, and Fedonkin is described the first time from Innerelv of the Formation exposed in coastal outcrops west of on Peninsula, in northeastern Finnmark, northern Norway. The fossil assemblage is dominated by discoidal which share certain affinities with the cosmopolitan genera. and However, our specimens differ from these and other discoidal Ediacaran fossils in the absence of radial sculpture. This, with a basically concentric organization, are characteristics shared with from the Dividal Group of northern Scandinavia, the White and northwestern Canada, along with discoidal from the Supergroup, Forest, England, and the Conception Group, Avalon Peninsula, Newfoundland. Our discovery of an assemblage within the Middle Innerelv Member provides support for previous suggestions of a late age for this sequence. This conclusion is consistent with the occurrence of early taxa, including the trace fossil and the problematicalforms and in basal portions of the Lower Formation, within the same stratigraphic section. The lowest faunal in northern Scandinavia Zone, on the of the fossil in Member (Middle Sandstone of the Group, Scandinavia. is a distinctly chambered form that was probably pelagic. In contrast, and genera of the so-called plexus, comprise an informal grouping of probably benthic, taxa that radial and/or concentric organization. In light the nature of taxa, present difficulties in taxonomic interpretation and correlation, and the abundance of cyclomedusoids many Ediacaran assemblages, we suggest that the concept of the Zone,as originally for northern be broadened to include the genera the plexus, of the occurrences in the Member described herein. It is our hope that additional fieldwork provide a basis for refined taxonomic evaluations and biozonation. Fedonkin, press), understanding Introduction of its stratigraphicand spatial distribution is becoming Our knowledge of the pre-skeletal history of increasinglyrefined (Glaessner, 1979;Hofrnann, 1988 cellular animal rests exclusively published Hofmann & in press). descriptions of about one hundred species that of the Ediacaran assemblage were first comprise the Ediacaran fauna, an assemblage of described in Namibia by (1930) and by bodied fossil animals of complex organization that are 1972, 1973). However, the strati- presently known from about 25 localities on five graphic and age significance of the was continents (Glaessner, 1984 Sokolov Ivanovskiy, first brought to attention by Sprigg (1947, 1985; Morris, Hofmann, 1988; based on occurrences in the Ediacara Hills, Flinders Walter, Although the phylogenetic and evolu- Range, South Australia. The probable of the tionary significance of this unique fossil assemblage assemblage was subsequently established late remains controversial Glassner, 1984 Bergstrom, Vendian (Germs, Knoll & Vidal, 1986). Since that 1989 Valentine, 1489 Walter, 1989 time the list of species and localities has continued to grow, and the fauna is now considered be global in * Present address: Research Center, Field, CA U.S.A. distribution. Previous occurrences are J. FARMER AND detail elsewhere (Glaessner, 1979, 1984; Hofmann, The Ediacaran fauna is dominated by discoidal 1988; Hofmann in press). forms that, until recently, were generally regarded With the exception of a recently reported occurrence pelagic 1947, Glaessner Wade, ; of fossils from inter-tillite beds in the see discussion by Narbonne Aitken, 1990, 953). Proterozoic Windermere Supergroup of northwestern. However, recent work suggests that many Ediacaran Canada Narbonne, 1990; Hofmann, discoidal forms (including the cyclomedusoids) Narbonne & Aitken, a consistent feature of the benthic (Seilacher, 1984; Fedonkin, 1985a, assemblage worldwide is that it postdates 1987; Jenkins, Narbonne Aitken. glacial deposits of the late Proterozoic (Glaessner, It also predates the first appearance of The preservation of soft-bodied organisms usually shelly fossils of early Cambrian age. A extinction requires special environmental conditions. However, of most Ediacaran forms appears to have preceded the Glaessner 984) has emphasized that the Ediacaran early Cambrian radiation (Fedonkin, In the fauna is not Under conventional models, East European and in the the preservation of soft-bodied organisms requires first appearance of Ediacaran fossils is tillites early mineralization, controlled by representing the Proterozoic (Varangerian) glaci- rate, the abundance of organic matter, and salinity ation, but the first appearance the putative (Allison, But lithofacies associations, modes of foraminiferan, preservation, and the diversity inferred lifestyles Glaessner, 1979). represented argue against the importance of such The generally age of the processes in Ediacaran based radiometric dates, brackets it within the The late Proterozoic was a unique time in range Ma (Glaessner, 1979). However, un- evolution, with an absence of preda- published zircon dates an earlier age of tors. limited of sediment by burrowing 565 3 Ma for the fauna of the Mistaken organisms, and low levels of atmospheric oxygen Point Formation, Newfoundland (Benus, (Glaessner, 1979 Walter, 1989).Extrinsic factors Although knowledge does not support a account, in part, far many of the unusual biological detailed stratigraphic based an Ediacaran 1982) and features fossils, the widespread occurrence of this distinctive (Fedonkin, c) of the Ediacaran fauna. However: assemblage has proposals for the formal recent and functional suggest that recognition of a geological period (see the Ediacaran organisms may have also possessed discussion by Mount, 1989) termed the intrinsic properties which favoured their preservation, Vendian 1972: Sokolov & Fedonkin, including having been composed of stiffer materials Ediacaran (Jenkins, (Cloud than comparable living species Glaessner. and the having possessed a body The (Varangerian) and Ediacarian architecture (Seilacher, 2989). In addition, microbial have also been proposed as stages of the Vendian mats were more widespread during the Vendian and Series (Sokolov. 1973). Guidelines of may have enhanced the preservation of soft-bodied boundary working group forms by promoting early (Gehling, suggest that the Ediacaran assemblage should be Gall, considered Precambrian in age (Cowie, but formal stratigraphic nomenclature and type localities 2. Stratigraphy are still under evaluation (Harland 1982 Morris, 1987; Narbonne The late Proterozoic to early Cambrian sequences of The Ediacaran fauna as a whole has been described northern Norway, consist of from a variety of (Glaessner, 5000 of and shallow-water including shallow and carbonate marine strata (Reading, 1965 Siedlecka Iithotopes (Goldring & 1967; Germs, 1972; 1967, 1971 Siedlecka, 1985). the Fedonkin, 1981; Gehling, 1983; Jenkins, Ford & (Fig. I the stratigraphic Gehling, 1983, and this report), muddy, basin interval is subdivided, oldest to youngest, as (Narbonne Aitken, and sub- follows: the Vendian ; marine fan (Ford, Anderson & 1981; Siedlecka, Morris, Gibson, Tetter Fedonkin. 1984; (Vendian), Vestertana (late Cambrian), Benus, 1989; Most occurrences and Groups Ordovician). are preserved as soft-bodied impressions in General stratigraphic and age relationships have been sequences as either low established by the correlation tillites within the casts (hyporeliefs) on the bases of beds, or as and Mortensnes formations (Fig. 2) of the on the upper surfaces of beds (Glaessner Lower Vestertana Group (Edwards, 1975, Wade, Glaessner, 1984; Seilacher, These tillites are correlated to the late Proterozoic Finnmark 183 (= Varangian, or glaci- transgressive, fining-upward sequence believed to ation, recognized throughout Scandinavia represent a transition to shallow conditions (Reading Walker, 1966; Banks, 1970, addition to the framework 1973b). described above, a generalized frame- The Member is by Innerelv work has also begun to emerge 1985;Siedlecka, Member with a contact marked by the based primarily on (Vidal, 1979, presence of several dark, pyritic mudstones and tine- strornatolites & Siedlecka, grained, lenticular sandstones. On Digermul Pen- trace fossils (Banks, 1970, a; Crimes, insula, the Innerelv Member is about 275 thick arid and the first appearance of consists of two shallowing-upward sequences, each and other shelly fossils 1967; representing a transition from offshore marine (quiet 1967; Glaessner, 1979). basin, below wave-base), to wave-influenced, The youngest division of the Proterozoic is the subtidal and intertidal deposition (Banks, 1973 Vendian Period (Sokolov & Fedonkin, erected basal part of the Innerelv Member consists of green for sequences underlying the East European Platform. and red shales containing occasional Stratigraphic criteria for defining the base of interbeds of fine-grained, red sandstone. Near Vendian remain controversial. As defined, (Fig. I), the Middle Innerelv Member the beginning of Vendian Period was placed at consists of interbedded greenish-grey