Wind transport of foraminiferal tests into subaerial dunes: an example from western Ireland

Abstract

INTRODUCTION

The empty tests of dead foraminifera behave as sedimentary particles and are subject to transport, although their different shapes and effectively low density means that their hydraulic equivalence is greater than that of spherical quartz grains (see Haake, 1962). Their estimated traction velocities range from c. 4 cm s⁻¹ to c. 13 cm s⁻¹ (Snyder et al., 1999). The presence of calcareous foraminiferal tests in a fossil sedimentary deposit would normally be taken as an indication of deposition in a marine environment. However, it has long been known that wind can transport tests from a carbonate beach into adjacent carbonate dunes as in Dogs Bay, Connemara, Eire (Murray, 1973) and Abu Dhabi, Persian Gulf (Murray, 1970). The purpose of this Notebook is to provide some details of the Dogs Bay occurrence and to comment on how such deposits might be recognized in the rock record.

In western Ireland the coastal geology consists of hard rocks, yet the beaches are commonly composed primarily of calcareous bioclastic sands (Guilcher & King, 1961; Keary, 1967). Dogs Bay (Lat. 53° 24′ N Long. 9° 58′ W) lies on the west-facing side of a tombola which is approximately 200 m wide and 400 m long. The tombola is made up of sand dunes that are mainly vegetated except along the margins adjacent to the beaches. Dogs Bay is exposed to Atlantic storms and the surface layer of the beach is reworked on each tidal cycle. Both the beach and the dunes are composed of . . .