EDIACARAN BIOTA ON BONAVISTA PENINSULA, NEWFOUNDLAND, CANADA

Journal of Paleontology, Jan 2008 by Hofmann, H J, O'Brien, S J, King, A F

Renews Head Formation.-The Renews Head Formation gradationally and conformably overlies the Fermeuse Formation. It differs from the latter by its greater silt and sand content, its pyritic, rusty-weathering lenticular bedding, and the presence of impoverished or starved current ripples, pseudonodules, waterescape structures, and small sand dykes. This formation records another coarsening- and thickening-upward succession. It represents a second major cycle within the group, but one of prograding deltaic sedimentation that passes upward and laterally (above the deep basin and slope) into terrestrial conditions represented by the Gibbett Hill Formation (Signal Hill Group).

The Renews Head Formation is divisible into three main lithofacies: (A-r) black shale with numerous laminae of rusty brown-weathering gray silty sandstone, (B-r) thin- to medium-bedded lenticular sandstone intercalated with black shale, and (C-r) distinctive, very thick to extremely thick (>3 m) beds of cross-bedded, laminated, and structureless gray sandstone units interbedded with black shales and thin sandstones. The coarse-grained sandstones are, in places, associated with granule and small pebble layers. Facies (C-r) is commonly incised or present in facies (A-r) and (B-r) and is interpreted as major channelized sand lobes and sheets, which are possible deltafront deposits related to delta-top sedimentation recorded in the overlying Gibbett Hill Formation that crops out beyond the map area (see O'Brien and King, 2004a). Shale-rich units in the formation bear Aspidella terranovica.

PALEONTOLOGY

Fossil assemblage and localities.-In a 1978 reconnaissance mapping and paleontological investigation of eastern Bonavista Peninsula, one of the authors (King) noted that 1) the siliceous rocks of Goodland Point, Catalina, resembled the Mistaken Point Formation, 2) the mudstones of Catalina were comparable with the Trepassey Formation, and 3) the shale sequence of Melrose matched the Fermeuse Formation. At that time, only the shales were found to be fossiliferous, yielding very poorly preserved sphaeromorph acritarchs and nonseptate filamentous microfossils near Port Union (Hofmann et al., 1979). As a result of more recent work, Ediacaran fossils were discovered in this area (O'Brien and King, 2004a).

The main occurrence of the Ediacaran biota on the Bonavista Peninsula is limited to the Catalina Dome (Fig. 1). Discoidal fossils have also been observed at English Harbour, 20 km south of Catalina, and at Maberly, 10 km to the north. The exposed units belong to the Conception and St. John's groups, with fossiliferous horizons in the Mistaken Point, Trepassey, Fermeuse, and Renews Head Formations.

The general geographic and stratigraphic distributions of the fossiliferous localities were given by O'Brien and King (2004a), as was a summary of their morphologic diversity. The same authors have since provided a more detailed inventory of their occurrence (O'Brien and King, 2005), but the present paper is the first to more fully describe and illustrate the Ediacaran fossils on the Bonavista Peninsula. Figure 2 presents a graphic summary of the more than a dozen constituent elements of this assemblage.

The fossils are best observed on dip slopes of shoreline outcrops. The discovery site, also the one showing the greatest diversity of fossils in the new assemblage, is located in the Murphy's Cove Member of the Mistaken Point Formation (Locality 5), and is illustrated in Figure 3. The fossils are protected under provincial legislation, but remain exposed to the elements (wave and ice action, cliff collapse, algal and bacterial growth, human activity).