A Hoxnian interglacial doline infilling at Slade Oak Lane, Denham, Buckinghamshire, England

Abstract

Site investigations for the M25 motorway at Denham proved a maximum depth of 37.5 m of deposits filling an enclosed hollow up to 40 m across beneath a small seasonally dry valley near Higher Denham. This previously unknown very steepsided hollow is infilled with gravel and sand, partially laminated clayey silt and pebbly clay. Within these deposits a bed of organic clay mud up to 4.5 m in thickness is present. Resistivity survey of the hollow proves that it is completely enclosed.Palaeobotanical investigation shows that the organic sediment contains fossil pollen, spores and macroscopic remains. The pollen spectra indicate that the sediments accumulated during the later half of the Hoxnian interglacial Stage (Ho III/IV). Macroscopic remains include ‘relict’ species Dulichium arundinaceum, and Brasenia schreberi, the latter being new to the Hoxnian Stage. The evidence for waterlevel fluctuation during the interglacial at the site is discussed.The origin of the hollow is considered and the conclusion reached is that it is a doline formed by solution of the underlying Chalk bedrock. The infilling of the basin is attributed to collapse, solifluction and slope wash of local material under cold climates before and after the interglacial. The interglacial sediment is a shallow water pool accumulation. The hollow is thought to have been formed originally as a solution pipe beneath the Thames' Gerrards Cross Gravel, rapid drainage of a neighbouring glacial lake causing the major collapse in the late Anglian Stage. Subsequent infill took place during the later part of the Anglian, Hoxnian and Wolstonian Stages and possibly even later.Heavy mineral analyses of the silt-rich sediment above and beneath the interglacial deposits are appended and indicate that it is almost all of local Reading Beds material.

Karst Evolution of the Garraf Massif (Barcelona, Spain): Doline Formation, Chronology and Archaeo-palaeontological Archives

“…Solution dolines are the most commonly studied of the karst landforms, having been described in detail since the end of the nineteenth century (Cvijic, 1893), while collapse sinkholes are perhaps the most spectacular, with the tiankengs in the karst areas of China providing the best examples (Zhu and Waltham, 2005). Recently, many studies conducted in different karst regions have proposed new models for the full evolutionary sequence of doline development (Gibbard et al, 1986;Bruxelles et al, 2008Bruxelles et al, , 2012Luzón et al, 2008;Siart et al, 2010).…”

“…More common is the use of these sediment-filled depressions for archaeological and palaeoenvironmental reconstruction (Gibbard et al, 1986, Bruxelles et al, 2008Siart et al, 2010;Bruxelles et al, 2012). Most of these reconstructions have been conducted in ancient Mediterranean landscapes (Marriner and Morhange, 2007;Fouache et al, 2008), where the abundance of karst regions without running surface water and any associated sediment accumulations has hindered reconstruction owing to the absence of corresponding non-karst archives.…”

On the history of Brasenia Schreb. in the European Pleistocene

“…However, these two plants seem to be associated not only today, but were also in the past. This is confirmed by numerous macrofossil finds of Brasenia and Dulichium occurring together in sediments across Europe (Jessen and Milthers 1928;Hall 1978;Velichkevich 1982;Gibbard et al 1986). Therefore, Brasenia is not the only known case of a puzzling extinction on the European continent.…”

East–West European Middle Pleistocene correlation – the contribution of the first British record of Aracites interglacialis Wieliczk.

“…Gilson is the first such sequence from the English Midlands where a discontinuous sequence has been found. This discontinuous sedimentation has been attributed to water-level changes resulting from groundwater fluctuations (Gibbard & Aalto 1977, Gibbard et al 1986, Boreham & Gibbard 1995, Boreham et al 1999. The evidence from a range of sites indicates that at the beginning of the Hoxnian temperate event, water levels were initially low, but that they rose during in the latter half of the period, beginning at the start of Ho III, thereby increasing accommodation space for sediments to accumulate.…”