ABSTRACT

The Kilranny Conglomerate, Ardwell Flags, Whitehouse Formation, and Barren Flags succession was deposited near the Northwest margin of the Caledonian Geosyncline. The Kilranny Conglomerate (0-500 ft) has been interpreted in the literature as a "slide conglomerate" and the Ardwell Flags (1000 ft) as a deep-water turbidite formation. A reinterpretation is necessary because in the Kilranny Conglomerate the consistent imbrication of discoidal pebbles, and the clay-free nature of the sandy gravel layers, indicate deposition was in relatively shallow water by strong southwest-flowing ocean currents. Similarly the current-ripple thin sandstones, intraformational flat-pebble conglomerates, and intraformational sandstone folds in the Ardwell Flags at the Ardwell foreshore were all formed by a trong, southeast-flowing ocean current system; in situ algal mats prove that water depth was shallow.

Many graded, sandy limestones in the limestone flysch sequence (165 ft) in the lower part of the Whitehouse Formation contain cross-bedded dunes previously unrecorded in graded limestones. The dunes were deposited in the lower flow regime. A dune division is added to the sequence of five internal divisions described by Bouma (1962) in the ideal graded sandstone or limestone bed.

Graded sandstones in the 90-ft flysch-like sequence in the middle part of the Whitehouse formation and in the 800-ft Barren Flags flysch occur transitionally below and above the 180-ft upper Whitehouse fossiliferous deltaic red and green mudstone section. The delta was built to the southeast and east based on current directions in cross-bedded conglomeratic sandstone and limestone scour channels. Flutes on both Whitehouse and Barren graded sandstones indicate consistent "longitudinal," southwest-flowing currents, perpendicular to the direction of delta-building, and approximately parallel and adjacent to the inferred geosynclinal margin. Therefore, the currents are unlikely to represent axial turbidity current flows. The regional slope probably dipped southeastward from the geosynclin l margin towards the axial portion. The graded sandstones may have been deposited in relatively shallow water from waning ocean bottom currents that flow southwest across the regional southeast paleoslope, rather than by gravity-controlled, down-slope turbidity currents.