New OSL dating of UK loess: indications of two phases of Late Glacial dust accretion in SE England and climate implications

Abstract

2007. New OSL dating of UK loess: indications of two phases of Late Glacial dust accretion in SE England and climate implications.ABSTRACT: Windblown dust deposits or loess, locally known in the UK as brickearth, blanket many parts of southern England outside the limits of the British and Irish Ice Sheet. The best-studied loess exposures occur in Kent, southeast England, where the deposits are believed to be Late Glacial in age. New sedimentological evidence is presented for phases of accretion with two distinct units, a calcareous brickearth exhibiting periglacial cryoturbation and a non-calcareous, massive brickearth. Optically stimulated luminescence (OSL) dating has been applied to chemically isolated modal quartz silts to derive a chronology for sediment accretion and to better understand the palaeoclimatic significance of these deposits. # British

Reply: Evidence for episodic dust accretion in SE England

“…These petrographic observations show that illuvial clay coatings around old root channels and voids are developed throughout the thickness of the upper 'non-calcareous' brickearth horizon and even into the top of the lower 'calcareous' brickearth layer. This supports Prof. Catt's view that Holocene pedogenesis should be more significant than was apparently indicated in our paper.With regard to our discussion of differentiation of the upper and lower brickearth horizons as two distinct units, this again is supported by much more petrological and mineralogical observation that was presented in Clarke et al (2007). This involved detailed observations of grain fabrics by scanning electron microscopy (SEM), as well as high-resolution backscattered scanning electron microscopy (BSEM) and optical petrographic analysis of polished thin sections, X-ray diffraction analysis of bulk and clay mineralogy, and particle size analysis, taken through the entire sequence at both study sites.…”

Two hundred years of engineering geology

“…A study of Quaternary Brickearth is nearing completion. This is being reported in a series of papers in the literature (for example, Northmore et al, 1996, Jefferson et al, 2001, Clarke et al, 2007, Milodowski et al, 2008. A study on Glacial Tills is underway.…”

The limitations of Quaternary lithostratigraphy: an example from southern Ireland

“…The aeolian sand unit probably formed under a periglacial, rather than interglacial, climate (e.g. Kasse 2002;Clarke et al 2007) and is thus more closely associated with the overlying breccia (element 4) than the underlying 'beach' (element 2) (Farrington 1966). (4) Periglacial 'Lower Head' (interpreted as a soliflucted slope deposit, element 4) is present at many locations and sometimes directly overlies the rock platform.…”

“…Aeolian sand has been recorded in an uppermost stratigraphic position at many other extra-glacial sites in southern Britain (e.g. Scourse 1996;Clarke et al 2007). An aeolian origin is supported by the laminated and well-sorted sand, and sediment draping over larger, angular fragments that are probably derived by rockfall.…”

“…The capping sand unit at Ballycroneen Strand and Cnoc na nAcrai is considered to be the lateral equivalent of the breccia unit, and deposited by enhanced wind activity in an exposed extra-glacial (periglacial) environment (e.g. Clarke et al 2007;Kolstrup 2007). …”