Optically Stimulated Luminescence (OSL) dating of loessic sediments and cemented scree in northwest...

http://hol.sagepub.com

The Holocene

DOI: 10.1177/0959683608093538 2008; 18; 1101 The Holocene

Peter Wilson, Peter J. Vincent, Matt W. Telfer and Tom C. Lord northwest England

Optically stimulated luminescence (OSL) dating of loessic sediments and cemented scree in

http://hol.sagepub.com/cgi/content/abstract/18/7/1101 The online version of this article can be found at:

Published by:

http://www.sagepublications.com

can be found at:The Holocene Additional services and information for

http://hol.sagepub.com/cgi/alerts Email Alerts:

http://hol.sagepub.com/subscriptions Subscriptions:

http://www.sagepub.com/journalsReprints.navReprints:

http://www.sagepub.co.uk/journalsPermissions.navPermissions:

http://hol.sagepub.com/cgi/content/refs/18/7/1101 Citations

at Univ of Ulster at Jordanstown on October 23, 2008 http://hol.sagepub.comDownloaded from

http://hol.sagepub.com/cgi/alerts

http://hol.sagepub.com/subscriptions

http://www.sagepub.com/journalsReprints.nav

http://www.sagepub.co.uk/journalsPermissions.nav

http://hol.sagepub.com/cgi/content/refs/18/7/1101


component of the British Quaternary stratigraphy and at several

sites the age and significance of the loess has been assessed

through application of luminescence dating techniques (eg,

Wintle, 1981; Gibbard et al., 1987; Parks and Rendell, 1992;Murton et al., 2003; Clarke et al., 2007). These studies havedemonstrated that whilst most of the loess is of late Devensian–

early Holocene age (~26–9 ka BP), isolated pockets of pre-

Devensian and early- to mid-Devensian loess occur.

In northwest England loess occurs on the outcrop of

Carboniferous limestone, within the limit of the British ice sheet at

the LGM. Aeolian silts were identified as soil parent materials in

parts of the Yorkshire Dales andWestmorland during the 1950s and

1960s (Pigott and Pigott, 1963; Bullock, 1964, 1971; Furness and

Introduction

Loess is terrestrial, silt-rich, aeolian sediment and has a discontin-

uous global distribution (Catt, 1988; Pye, 1995). In mainland

Europe loess is abundant in those areas that were close to the mar-

gins of the last glacial maximum (LGM) ice sheets and is regarded

as a product of aeolian reworking of glacial and glacifluvial

deposits. Extensive loess accumulations also occur in the south

and east of Britain but most of these loess deposits are less than 1

m in thickness (Catt, 2001). Nevertheless, loess is an important

*Author for correspondence (e-mail: [email protected])

Optically stimulated luminescence (OSL)dating of loessic sediments andcemented scree in northwest EnglandPeter Wilson,

1* Peter J. Vincent,

2Matt W. Telfer

3

and Tom C. Lord4

( 1Environmental Sciences Research Institute, School of Environmental Sciences, University of Ulster,

Coleraine, Co. Londonderry BT52 1SA, UK; 2formerly Department of Geography, University of

Lancaster, Lancaster LA1 4YB, UK; 3Oxford University Centre for the Environment, South Parks Road,

Oxford OX1 3QY, UK; 4Lower Winskill, Langcliffe, Settle BD24 9PZ, UK and Centre for North-West

Regional Studies, University of Lancaster, Lancaster LA1 4YB, UK)

Received 30 October 2007; revised manuscript accepted 21 February 2008

Abstract: Optically stimulated luminescence (OSL) dates are reported for silts and very fine sands believed to

be loessic sediments from northwest England. At three sites loessic sediments were initially interpreted as pri-

mary aeolian deposits, and at two other sites as loess incorporated into the matrix of cemented scree. However,

the results of OSL dating indicate a more complex pattern of accumulation than originally hypothesized and

have prompted reconsideration of these materials. Whatever the process(es) and underlying cause(s), it is evi-

dent that significant amounts of soil erosion occurred on the limestone uplands earlier than previously thought.

All but one of the ages fall entirely within the Holocene period and suggest that these deposits contain

reworked, rather than primary loess. Four of the five sites are characterized by non-Gaussian dose distributions,

and consequently equivalent doses have been estimated using a range of appropriate age models. The implica-

tions of differences in the ages derived from the fine silt and fine sand fractions of the samples are considered.

Three processes, namely aeolian transport, overland flow and subsoil piping, are invoked to account for the

reworking of loess, although their relative contributions cannot be quantified. At one site the inclusion of lime-

stone clasts within the reworked loess strongly suggests that the sediment can be regarded as loess-derived col-

luvium. Human impacts on the landscape and climate shifts, either separately or in combination, are considered

to have been the most likely mechanisms that triggered loess erosion.

Key words: Loess, loessic sediments, cemented scree, karst landforms, optically stimulated luminescence dat-

ing, Lateglacial, Holocene, northwest England.

The Holocene 18,7 (2008) pp. 1101–1112

© 2008 SAGE Publications 10.1177/0959683608093538 at Univ of Ulster at Jordanstown on October 23, 2008 http://hol.sagepub.comDownloaded from


King, 1972). More detailed investigation of these materials on the

limestone around Morecambe Bay (Vincent and Lee, 1981) demon-

strated similarity to loess deposits elsewhere, and it was thought that

the silt derived from deflation of glacigenic sediments in

Morecambe Bay as Lake District and Irish Sea ice wasted follow-

ing the LGM. Further understanding of these discontinuous but

nevertheless important and widespread deposits is required; in par-

ticular absolute age estimates are needed to place the materials in a

secure chronological context. We report optically stimulated lumi-

nescence (OSL) dates from the loess, and offer a preliminary assess-

ment of their significance and implications. The past decade has

seen extensive methodological developments of loessic optical dat-

ing, and its application to loess sediments worldwide (eg, Watanuki

et al., 2005; Roberts, 2006, 2007; Wang et al., 2006; Zhang andZhou, 2007; Stevens et al., 2007), but the dates presented in thispaper are the first from such sediments in northwest England.

In many areas of its outcrop in northwest England the

Carboniferous limestone is characterized by cliffs below which there

is scree, some being cemented by calcium carbonate and thus com-

prising a form of calcrete (Sweeting, 1966, 1972; Vincent, 1982,

1985; Vincent and Lee, 1982; Goudie, 1983). At Arnside Knott

(Figure 1), Vincent (1982, 1985) showed that fine quartz grains,

assumed to be of loessic origin, and scree are intimately mixed and

cemented, suggesting that either the scree and loess accumulated

contemporaneously, or that the loess was added to existing scree

prior to cementation. Such material has proven difficult to date

owing to the open nature of the chemical system and possibly multi-

phase development of the matrix. However, optical dates have been

reported from quartz grains included within calcareous tufas and

groundwater discharge deposits from the USA (Rich et al., 2003;Mahan et al., 2007). We report initial attempts to date the cementedscree deposits using similar methodologies. A crucial assumption is

that the burial event, and thus the age obtained by the OSL dating is

considered to be the cementation of the scree, irrespective of whether

the quartz was deposited prior to, or coevally with, the cement.

A working hypothesis was that the loess and cementation of the

screes are of deglacial/Lateglacial age (~18–11.5 ka BP). Between

~18 and 16 ka BP and in the Loch Lomond Stade (12.9–11.5 ka

BP) severe climatic conditions prevailed (Marshall et al., 2002)and aeolian sediments of Lateglacial age in other parts of England

indicate a vigorous wind regime (Bateman, 1995, 1998). A further

hypothesis was that the loess had derived from deflation of

glacigenic sediments in Morecambe Bay (Vincent and Lee, 1981)

and area-wide outwash deposits. The assumption then is that it is

highly likely that loess blanketed the landscape of northwest

England, and that the present-day absence of loess from many

areas is probably a result of widespread and severe erosion (cf.

Catt, 1977, 1978).

Methods

Field locationsFollowing extensive investigations into the distribution of loess

deposits on the karst of northwest England, three sites were

selected on the grounds of having a significant depth of silty

deposits, and occurring in relatively undisturbed locations. At

Asby Scar (NY 650 097; 370 m OD), Farleton Fell (SD 544 801;

225 m OD) and New Close (Malham; SD 908 645; 365 m OD)

(Figure 1), pits set within shallow topographic depressions sur-

rounded by limestone pavements carrying rundkarren were exca-

vated to bedrock (Figure 2). Below thin (~10–15 cm) Ah horizons,

all the exposures consisted of structureless yellowish brown

(10YR5/4) sandy silt loam and silt loam beneath which was an

irregular bedrock surface at a depth of ~80 cm. Scarce, small (baxes <5 cm) angular clasts of limestone were present in the lower-

most 20 cm of the Farleton Fell pit, otherwise the loess was clast

free. From each pit one sample was removed for OSL dating from

~30 cm above the loess–bedrock interface by hammering light-

tight PVC tubes horizontally into the loess. Laser granulometry

was performed on each sample with a Malvern Mastersizer 2000™

at Oxford University. The samples from Farleton Fell and New

Close are remarkably similar, and are predominantly silts (Table 1).

The sample from Asby Scar has a slightly coarser modal value, and

a significant very fine to medium sand component.

Blocks of cemented scree (~30 cm × 30 cm × 30 cm), in which

clast b axes were generally <10 cm, were collected from near the

surface of scree exposures at Arnside Knott (SD 455 772; 65 m

OD) and Giggleswick Scar (SD 806 652; 220 m OD) (Figure 1),

using a hammer and chisel, and were stored in opaque plastic bags.

Analysis protocolsDosimetryFor all samples, dosimetry was provided by Inductively Coupled

Plasma Mass Spectrometry and Atomic Emission Spectrometry

(ICP-MS/-AES) following lithium metaborate fusion. For the

cemented screes, samples of both the matrix and limestone scree

clasts were isolated for analyses, in addition to a ‘bulk’ sample which

approximated the correct composition of the cemented scree, to

investigate potential inhomogeneities. An appropriate geological ref-

erence standard (SCO1) was also prepared and analysed, and results

suggested that extract and analysis procedures were satisfactory.

In addition, for the cemented scree samples, in situ NaI gammaspectrometry was conducted with an ORTEC Digibase™. A ham-

mer and chisel were used to excavate a 5 cm wide slot into a section

of the cemented scree into which the NaI probe was inserted. A sec-

tion of scree was selected with as low a proportion of void space as

possible (estimated at <5%) in order to best approximate the geom-

etry of the calibration of the gamma spectrometer. All OSL samples

were stored in light-tight conditions, and the outer rind of the tubes

and blocks discarded to exclude possible light contamination.

De determinationCarbonates and organics were removed from samples by HCl and

H2O2. The scree samples, with significant limestone clasts, were

reacted with HCl only until the matrix had dissociated, liberating

the enclosed quartz. All samples were subsequently sieved, and the

90–212 µm fraction was selected from the cement of the scree

1102 The Holocene 18,7 (2008)

Figure 1 The outcrop of Carboniferous limestone in northwest

England showing locations (1–5) of the loess and cemented scree sam-

ples. Inset shows location of northwest England within Great Britain



Peter Wilson et al.: OSL dating of loessic sediments and cemented scree 1103

Figure 2 (a) Part of Asby Scar showing limestone pavement with rundkarren. Loessic sediments underlie the vegetated area right of centre.

(b) Profile in loessic sediments at Asby Scar. The sample for OSL dating was removed from the bottom of the exposed face. The survey pole

divisions are 20 cm



samples to maximize the available material. For the loess samples,

both a fine silt fraction (~4–11 µm, which accounted for 12–25%of the sediment) and a very fine sand fraction (90–125 µm,accounting for 2–5% of the sample) were prepared, the former

being sampled from suspensions based on Stokesian settling times.

The coarser fractions, sampled in case the luminescence properties

of this grain-size proved favourable to the silts, were subsequently

density-separated at 2.7 g/cm3and treated with HF for 45 min

before a final sieving. For analysis, 3 mm aliquots of quartz were

mounted onto 9.6 mm aluminium discs with Silkospray™ silicone

spray. The fine-grained (silt) samples were treated with excess

35% H2SiF

6for two weeks to remove non-quartz components,

before being evaporated from suspension onto the discs.

All samples were measured at the Oxford Luminescence Dating

laboratories with the Single Aliquot Regeneration (SAR) proto-

cols (Murray and Wintle, 2000, 2003; Wintle and Murray, 2006),

using a Risø TL-DA-15 with stimulation from blue diodes (nomi-

nally 20 mW/cm2at 420±20 nm) and IR laser diodes (nominally

400 mW/cm2at 830±10 nm). All samples were preheated at 240°C

for 10 s prior to 130°C OSL measurements, and 220°C for 10 s

prior to the measurement of a 3.6 Gy test-dose, although preheat

tests did not suggest a strong preheat dependence. Stimulation

light from blue diodes was filtered with a Schott GG420 filter, and

measured with a 9235QA photomultiplier tube protected with two

3 mm Hoya U-340 filters. ‘De(t) plots’ of resultant equivalent dose

(De) against signal integration time (Huntley et al., 1985; Bailey,

2000) were used to select an appropriate integral for estimation of

the luminescence response; at very short integration times with the

fine-grained samples, the dimness of the signals led to poor dose

recovery results, attributed to the relatively poor counting statis-

tics. On this basis, the OSL intensity was estimated from the inte-

gration of the first 1.5 s (channels 1–5) of luminescence with the

last 2.6 s (channels 240–250). Dose rates were corrected for the

fine-grained samples according to the recommendations of

Armitage and Bailey (2005).

All samples were tested for evidence of feldspar contamination

using the ratio of OSL to post-IR OSL (Duller, 2003); although

originally designed for discriminating single grains of quartz and

feldspar, it has since been used extensively on multiple grain

aliquots as an indicator of quartz purity (eg, Chase and Thomas,

2006; Armitage et al., 2006; Carr et al., 2006). A few of the finesand aliquots from this study showed significant depletion, and

these were rejected from further analysis. However, all of the silt

samples showed evidence of feldspar contamination (OSL:post-IR

OSL ratios typically around 50–70%) after the initial two-week

treatment in H2SiF

6, and were thus treated for a further two weeks.

Even after this treatment, some evidence of IRSL response was evi-

dent (Figure 3), and thus alternative methods of isolating a quartz

signal were required.

The ‘double-SAR’ (‘post-IR blue’) procedure outlined by

Roberts and Wintle (2001) and Banerjee et al. (2001) aims tominimize the effects of the feldspar contribution to the bulk OSL

signal, and the accompanying risk of Deunderestimation, by

preceeding each OSL measurement with an IRSL ‘wash’.

The method can be used to derive not only a blue-stimulated SAR

estimate of Devalue for each aliquot, but an IRSL-stimulated D

e

estimate, which is assumed to be feldspar dominated, and thus

subject to the usual concerns of anomalous fading and internal

dosimetry associated with feldspar dating. Overestimations of the

IRSL-derived Dehave been observed and attributed to sensitivity

changes between the natural and first regeneration point (Roberts

and Wintle, 2003), and thus this study has concentrated on the

post-IR blue signal. Even then, the technique has yielded varied

results. It is not possible to guarantee that the post-IR blue signal

is exclusively from quartz (Banerjee et al., 2001), and some stud-ies have reported age underestimations using the technique when

compared with chemically purified quartz (Thomas et al., 2003)or other OSL signals (Berger et al., 2004). The post-IR blue sig-nal is also apparently sensitive to the length of IR exposure used

and the temperature of stimulation (Zhang and Zhou, 2007), and

a high degree of preheat sensitivity has been demonstrated for

some loessic samples (Roberts, 2006). However, a number of

studies have suggested that the careful application of the tech-

nique may provide reliable estimates of De, based either on inde-

pendent age control (Banerjee et al., 2001; Watanuki et al.,2005), or by comparison with other luminescence methods

(Roberts, 2006; Wang et al., 2006). Some authors, indeed, haverecommended routinely incorporating an IR stimulation prior to

each OSL measurement to minimize the effect of suspected

feldspar contamination at both the single grain (Olley et al.,2004) and single aliquot level (Nanson et al., 2005; Wintle andMurray, 2006).

This study has adopted the recommendations of Roberts (2006)

regarding preheat conditions, and that of Zhang and Zhou (2007)

regarding the use of room temperatures for the IR stimulation. IR

bleach times were determined experimentally using the methods of

Zhang and Zhou (2007) (see Figure 4a); our data show less time

dependency to IR stimulation than the samples presented in that

study. At exposure times over 1000 s, however, there is an overall

deterioration in signal/noise of these already dim samples, and thus

reproducibility is affected. From these observations, a room tem-

perature IR stimulation for 100 s was used prior to each measure-

ment. Following the initial IR ‘wash’, no depletion of OSL to

further IRSL was observed, although the post-IR blue OSL signal

decays only to a level considerably above the typical background

for this instrument (Figure 3), as observed by Duller (2003), which

is likely to be feldspar derived. However, the standard practice of

subtracting a ‘late-light’ background correction for all SAR meas-

urements is assumed to account for this, and the quickly decaying

initial luminescence signal is assumed to be quartz-dominated. Dose

recovery tests (Roberts et al., 1999; Murray and Wintle, 2003) havebeen performed on all samples, except the coarse-grained material

extracted from Arnside Knott, which was used in its entirety in De

measurement. Averages from three aliquots of each are reported,

and all except Farleton Fell (at 21.3 ± 0.89 Gy, a 6.5% overesti-

mate) are within 1 standard deviation of unity. The ability of all

samples to recover an applied 20 Gy β doses (Figure 4b) suggeststhat the basic SAR protocol is appropriate, although it must be noted

that a dose recovery test will not reveal whether there is still an

unstable feldspar component in the post-IR blue signal.

1104 The Holocene 18,7 (2008)

Table 1 Grain size data for the pit-sampled sediments

Grain size (%)

Clay Silt Very fine sand Fine sand Medium sand Coarse sand

<2 µm 2–62.5 µm 62.5–125 µm 125–250 µm 250–500 µm 500–1000

µm

Asby Scar 11.7 53.4 11.2 11.8 10.3 1.6

Farleton Fell 18.0 74.0 5.3 1.2 1.0 0.5

New Close 16.2 72.0 7.2 2.1 1.6 1.0



Results

Loess depositsThe results of the luminescence age determinations are presented

in Table 2 and Figure 5. The luminescence intensity of all samples

was small, but the Asby Scar fine sand sample yielded a De

distribution that was unimodal, unskewed and tightly clustered

(Figure 6a), and the Defor this sample is provided by the Central

Age Model (CAM) of Galbraith et al. (1999). This is a simple sta-tistical technique to derive a single estimate of D

efrom a range of

values, in which it is assumed that the true palaeodoses are not nec-

essarily equal. The age derived from the fine silt confirms that this

is a mid-Holocene deposit, although the silt yields a slightly older

date (7.6 ± 0.7 ka BP) than the sand fraction (5.6±0.29 ka BP).

The coarser-grained component of samples from the Farleton

Fell and New Close pits show overdispersed bimodal Dedistribu-

tions (Figure 6b and c). Although these distributions may reflect

poor bleaching conditions at the time of deposition or variations in

β microdosimetry, the clear bimodalism is interpreted as most

likely reflecting extensive postdepositional reworking (Bateman

et al., 2003). Although no direct evidence of burrowing animalswas evident in the loess profiles at any site, rabbits are likely to

have been present in northern England from the twelfth century

AD following their introduction by the Normans, and other bur-

rowing animals may have been active throughout the Holocene. In

addition, some root material was evident, even at a depth of 50

cm. Such strong bimodalism on multiple-grain aliquots such as

these supports the earlier suggestion that very few grains of these

samples contribute to the luminescence. For these samples the

Finite Mixture Model (FMM), which identifies populations from

mixed sediments, has been applied (Galbraith and Green, 1990;

Rodnight et al., 2005). The silt fractions from Farleton Fell and

New Close yielded tightly clustered, normal distributions, and the

resultant ages are congruent with the older component of the sand

fraction.

Two possible interpretations can be made of this observation. It

may be a pedogenetic or diagenetic phenomenon, which would

imply that some of the sand fraction had been transported down-

wards through the soil profile; alternatively, it could be considered

that one or other of the Dedistributions is inaccurate. The down-

ward movement of the coarser fraction of a soil is contrary to usual

translocation processes, which normally involve the movement of

silts and clays, but such re-distribution has been reported in

periglacial environments (Locke, 1986). However, it is not clear

how such a mechanism could have operated in Holocene Britain. If

it is accepted that these distributions are accurate reflections of the

palaeodose of the sediments, then the implication is that the true

depositional age at the sample depth of 50 cm is the older compo-

nent (ie, around 10 ka BP) with subsequent translocation of fine

sands having occurred more recently than the younger component

(~4.5 ka BP at New Close and ~7 ka BP at Farleton Fell).

Furthermore, this suggests that loess was still being introduced to

these sites during the mid Holocene. Conversely, discrepancies

between fine (4–11 µm) and medium (38–53 µm) silt have beenreported for one sample from Pegwell Bay (Clarke et al., 2007). Inthis case, a larger D

efor the coarser fraction was attributed to par-

tial bleaching. As discussed above, the Dedistributions from the

samples in this study are considered to be more likely attributable

to mixing than poor bleaching, but rigorously testing these

hypotheses will require further sampling from various depths

within the soil profiles, and single grain measurements to improve

understanding of dose distributions; such work is ongoing.

Cemented screesAs for the pit samples, the luminescence intensity of both

cemented scree samples was relatively small, and the relatively

high rejection rates of aliquots from Arnside Knott (33%) and

Giggleswick Scar (19%) are caused largely by aliquots with no

discernible shine-down curve and no regenerative growth. The

low luminescence intensity and the presence of aliquots with no

shine-down or growth suggest that the luminescence signal is

derived from a few, very bright, grains. The remaining rejected


Figure 3 Post-IR blue-stimulated OSL decay (open squares), and

the corresponding IRSL signal (solid triangles) for ten aliquots of the

fine-grained (~4–11µm) sample from Asby Scar. The IRSL signal

persisted despite extensive treatment in 35% H2SiF

6, and thus post-IR

blue stimulation was employed to remove this unwanted component

from the signal

16

18

20

22

24

As

by

Sc

ar

(4–1

1μm

)

Fa

rle

ton

Fe

ll(4

–11μ

m)

Ne

wC

los

e(4

–11μ

m)

As

by

Sc

ar

(90–

12

5μm

)

(90–

12

5μm

)

(90–

12

5μm

)

(90–

12

5μm

)

Fa

rle

ton

Fe

ll

Ne

wC

los

e

Gig

gle

swic

k

Rec

ove

red

do

se(G

y)

b)

0

5

10

15

20

25

30

35

40

1 10 100 1000 10000

Rec

ove

red

do

se(G

y)

Pre-OSL IR stimulation (s)a)

Figure 4 Dose recovery test results for (a) differing IR bleach times

used before the blue stimulation used to measure luminescence for the

SAR protocol (results are the average of one aliquot of each of the

three fine-grained samples), and (b) the average of three aliquots of

each sample using the finalized protocol. There is less dependency of

the length of precedent IR-stimulation than has been shown in other

studies (Zhang and Zhou, 2007), and all samples recover a known

dose (20 Gy) to an acceptable degree



1106 The Holocene 18,7 (2008)

Table2

Experimentaldetailsandresultsfromtheluminescencedatingprogramme

Sample

Size

AliquotsAliquotsAge

De(Gy)Error

Over-

Dosimetry

Age(ka)

Error

fractionanalysedacceptedmodel

dispersion(σ)

analysed

used

Method

K(%)U(ppm)Th(ppm)Measured

Dcosmic

D(Gy/ka)

+Error

(µm)

water

(Gy/ka)

content

and

assumed

error(%)

AsbyScar

4–11

10

10

CentralAge

23.07

1.02

10.4%

ICP-

3.011

0.239

7.6

0.70

Model(CAM)

MS/-AES

1.32

2.99

9.79

25±5

0.21

90–125

15

15

CAM

12.42

0.40

11.2%

2.210

0.088

5.6

0.29

FarletonFell

4–11

10

10

CAM

33.83

1.00

14.0%

3.847

0.277

8.8

0.68

FiniteMixture

21.15

1.47

-ICP

2.07

2.44

10.33

17±5

0.20

7.1

0.59

Model(FMM)

MS/-AES

90–125

16

16

-component1

18.0%

2.965

0.135

FMM-

30.36

2.08

10.2

0.84

component2

NewClose

4–11

10

10

CAM

34.16

1.87

14.4%

3.699

0.264

9.2

0.83

FMM-

12.83

1.14

ICP-

4.5

0.45

90–125

27

25

component1

48.6%

MS/-AES

2.12

2.68

9.81

21±5

0.20

2.865

0.131

FMM-

30.16

1.87

10.5

0.81

component2

ArnsideKnott

ICP-

0.15

1.22

0.7

––

––

MS/-AES

0.21

1.32

0.59

––

––

90–210

24

16

MAM-3

2.95

0.95

55.3%

γ-spectrometry

5±5

0.21

0.718

0.025

4.1

1.30

CAM

6.22

1.03

Mean

0.18

1.27

0.65

8.7

1.47

GiggleswickScar

ICP-

0.33

1.51

3.04

––

––

MS/-AES

0.32

1.42

3.07

––

––

90–210

31

25

MAM-3

5.85

1.65

71.5%

γ-spectrometry

5±5

0.21

1.069

0.037

5.5

1.55

CAM

13.12

2.10

Mean

0.33

1.47

3.06

12.3

2.01

Thedifferentagemodelsandtheirimplicationsarediscussedinthetext.DosimetryhasbeenconductedwithInductively-CoupledPlasmaMassSpectrometryandAtomicEmissionSpectrometry(ICP-MS/-AES)

orgamma(γ)spectrometry,andfine-grainedsampleshavethedoseratecorrectionofArmitageandBailey(2005)applied.



aliquots were those which showed greater than 10% depletion of

the OSL signal following an IRSL bleach, indicating persistent

and unremoved feldspar contamination.

The cemented scree samples demonstrate overdispersed and

strongly skewed ranges of Deestimates (Figure 6d and e). Such dis-

tributions are perhaps not surprising because of inherent difficulties

in dating material of this type, and several contributing factors are

possible. First, the burial event within the cemented scree matrix is

unlikely to have been instantaneous, and the wide spread of Deesti-

mates may imply a multistage development of the cement. As the full

history of carbonate mobilization and remobilization is unknown, the

assumption that the measured dose rate at the site has been consistent

throughout the sample’s history may not be valid. If an aeolian trans-

port mechanism is accepted for the loess incorporated in the cement

(see discussion below), it is likely that the quartz would have been

adequately bleached on deposition. Conversely, if the transport of the

loess into the scree was by overland flow or karstic piping, there can

be less assurance of adequate bleaching. The overdispersed Deval-

ues may simply reflect the difficulty of sampling block material with

sufficient precision, as a substantial block (~20 cm × 20 cm × 20 cm)

was needed to provide sufficient quartz from the cement once a light-

contaminated outer rind had been discarded.

Whilst the relative importance of such factors cannot be quan-

tified, the results of the dosimetry analyses for the scree samples

(Table 3) provide evidence of variations in chemistry that will cer-

tainly result in overdispersion of De. The quartz-bearing calcare-

ous matrix is much enriched in K, U and Th compared with the

enclosed limestone clasts, with the result that the dose from the

matrix (estimated at 20% volume) is between 50% (Arnside) and

300% (Giggleswick) higher than the enclosed clasts (estimated at

80% volume). Coherence between the bulk ICP analysis and

in situ gamma dosimetry is apparently more an artefact of havingsampled the bulk sediment in approximately representative pro-

portions, rather than indicating a homogenous dose environment.

With β radiations contributing approximately 40–50% of the dose

rate from the matrix, such heterogeneity makes overdispersed De

distributions almost inevitable, and estimation of the true dose rate

on a grain-by-grain basis impossible. However, as variability in β

dosimetry is considered the most certain contributing factor to the

overdispersion (although other factors such as partial bleaching can-

not be dismissed), one approach, whilst far from ideal, is to esti-

mate the true dose rate by assuming the bulk ICP/γ-spectrometry-derived dose rate to be approximately representative of an average

quartz grain included in the matrix, and accept that very overdis-

persed Deestimates are unavoidable (Olley et al., 1997).

Furthermore, when luminescence-dating sediments are in close

association with carbonates, there is the risk that disequilibrium,

especially in the uranium series, may have caused a time depend-

ency in dose rates. Various studies have suggested widely differ-

ing significances of this phenomenon. Rich et al. (2003) suggest a45–65% age underestimate because of disequilibrium, but their

method relies on an assumed concentration of U-series isotopes

rather than direct measurement. Other studies of carbonate-rich

environments that have directly measured different products in the

decay chains (eg, Prescott and Hutton, 1995; Olley et al., 1997;Jacobs et al., 2006) have suggested disequilibrium is widespread,but the consensus appears to be that the resultant effect on total

dose rate (and thus age) is relatively small. In the above-cited

examples, only in the case of still-active spring mounds (Prescott

and Hutton, 1995) would the effect on dose rate be in excess of

10%. High-precision γ-spectrometry has not been available forthis study, but considering the inherent difficulties with calculat-

ing a reliable single Deestimate for these samples, and the impre-

cision of the conclusions thus drawn, it is considered that

disequilibrium is likely to be a relatively minor problem.

With a data set such as this, precise dating of the cementation of

the scree is not possible, but some broad conclusions can be drawn.

Two age models have been considered for estimating the most suit-

able Devalue: the CAM, and the three-parameter Minimum Age

Model (MAM-3) (Galbraith et al., 1999), which aims to representthe true palaeodose amongst a population with positively skewed

distributions and has been widely used in settings where the bleach-

ing history is questionable (eg, Rodnight et al., 2005). If the overdis-persion is primarily due to imprecise sampling or the observed βmicrodosimetry, then the CAM may provide the most suitable esti-

mate of the palaeodose. Given the absence of zero-aged or very

young aliquots, however, the MAM-3 model at least provides a min-

imum age for the final formation of the cemented scree. What can

still be concluded is that the cementation of the screes at Arnside

Knott and Giggleswick Scar is probably a Lateglacial or early-/mid-

Holocene phenomenon, and was completed by ~4–5 ka BP.

Discussion

None of the dates of ‘loess’ deposition fall within the

deglacial/Lateglacial period (Table 2, Figures 5 and 7) and our

working hypothesis, that these deposits represent primary, aeolian

silt deposits, is no longer considered tenable. By ~8 ka BP, sea lev-

els in Morecambe Bay approximated modern levels (Roberts et al.,2006), whilst a well-developed woodland vegetation characterized

the region by ~9 ka BP (Walker, 2004), removing both the likely

source of primary loess and the open-ground conditions necessary

for aeolian transport pathways to operate effectively. Whilst British

coversands (an aeolian facies coarser than loess) as young as ~11

ka BP have been reported (Bateman, 1995, 1998), Clarke et al.(2007) conclude that primary loess deposition at Pegwell Bay in

Kent ceased ~15 ka BP. Collations of luminescence dates of

European loess also suggest a cessation of primary loess accumu-

lation by ~15 ka BP (Singhvi et al., 2001). The Holocene agesreported in this study must lead us to the conclusion that this is not

primary loess. An alternative model proposes the reworking of

loess and its likely trigger mechanisms during the early/mid

Holocene. Precedents for loess reworking include loess-rich


Figure 5 OSL ages from the three pit samples, illustrating the

multimodal nature of the sands dated, and the discrepancies between

the silt and sand fractions



1108 The Holocene 18,7 (2008)

Figure 6 Dose distributions for the loessic samples, displayed as radial plots (Galbraith, 1988), for (a) Asby Scar. The difference between fine

sand-sized (solid triangles) and silt-sized (open circles) aliquots is apparent. The Central Age Model estimates are shown with bounding 1-sigma

uncertainties for the fine sand (in black) and silt (grey). Even allowing for the differing effects of dosimetry on the different grain-sizes this repre-

sents a significant discrepancy in age. (b) Farleton Fell and (c) New Close are multimodal coarse-grained samples, with the two components iso-

lated by the Finite Mixture Model, and their 1-sigma uncertainties, highlighted. (d) Giggleswick Scar and (e) Arnside Knott show overdispersed

De distributions, and widely different results between Minimum Age Model (MAM-3) (black line with uncertainties marked), and the Central Age

Model (CAM) in grey. The safest interpretation is that the MAM-3 estimate provides a minimum age

Table 3 Concentrations of the important radiogenic elements from bulk, matrix and clasts from the cemented screes, determined by ICP and

gamma (γ) spectrometry

K (%) U (ppm) Th (ppm) Dose rate

(Gy/ka)

Arnside in situ γ-spectrometry 0.21 ± 0.01 1.32 ± 0.13 0.59 ± 0.06 0.753 ± 0.027

Bulk ICP-MS/-AES 0.15 ± 0.01 1.22 ± 0.12 0.70 ± 0.07 0.682 ± 0.023

Matrix ICP-MS/-AES 0.28 ± 0.01 1.33 ± 0.13 2.30 ± 0.23 0.938 ± 0.032

Clast ICP-MS/-AES 0.02 ± 0.01 0.46 ± 0.05 1.02 ± 0.10 0.626 ± 0.022

Giggleswick in situ γ-spectrometry 0.33 ± 0.02 1.51 ± 0.15 3.04 ± 0.30 1.077 ± 0.037

Bulk ICP-MS/-AES 0.32 ± 0.02 1.42 ± 0.14 3.07 ± 0.31 1.049 ± 0.035

Matrix ICP-MS/-AES 0.58 ± 0.03 1.05 ± 0.11 3.81 ± 0.38 1.254 ± 0.047

Clast ICP-MS/-AES 0.05 ± 0.01 1.34 ± 0.13 0.82 ± 0.08 0.406 ± 0.009



alluvial sediments in theWeald (Burrin, 1981) and the Thames val-

ley (Gibbard et al., 1987), colluvial loess associated with snow-patches on Farleton Fell (Vincent and Lee, 1982) and OSL-dated

mid-Holocene colluviated loessic sediments from Europe (Lang,

1994, 2003; Kadereit et al., 2002). We therefore consider that oursites contain colluvial deposits derived from reworked loess, rather

than primary loess.

At our three pit sites the colluvium occurs in shallow topo-

graphic depressions adjacent to areas of limestone pavement with

rundkarren (Figure 2a). Exposed pavements with rundkarren indi-

cate areas of formerly covered karst (Sweeting, 1966, 1972; Ford

and Williams, 1989); we suggest that this cover may have been the

primary loess. Therefore the pavements are evidence of localized

loess erosion and the Holocene dates constrain the timing of collu-

vium accumulation in the depressions. Further evidence for

Holocene loess erosion is provided by Furness and King (1972)

who report silt-rich topsoil buried beneath 43 cm of silt loam on

Farleton Fell, within 200 m of our site. Because of the early/

mid-Holocene ages for both the colluvium and cemented scree, we

postulate that the addition of loess to the scree was also a conse-

quence of the reworking of primary loess. At Giggleswick Scar

there is the possibility that the loess is primary rather than second-

ary, resulting from deflation of glacigenic sediments in the

Lateglacial. The MAM-3 scree dates are minimum ages for cemen-

tation and are compatible with the findings of Strong et al. (1992)and Howard et al. (2000) from other Yorkshire sites for cementa-tion of coarse debris under cool temperate (Holocene) conditions.

Three processes can account for loess reworking: aeolian trans-

port, overland flow and subsoil piping between the developing

rundkarren and the overlying loess. At Giggleswick Scar, aeolian

transport is the preferred mechanism for loess incorporation into the

scree, irrespective of whether it is primary or secondary, because

there is no catchment area above the Scar to facilitate overland flow

and no limestone pavement with rundkarren. At Arnside Knott and

the three pit sites, all processes could have operated but at present

we have no means of quantifying their respective contributions.

However, at Farleton Fell small clasts of limestone were found in

the lowermost 20 cm of the pit. If these are not derived from in situweathering of the bedrock, this may be further evidence that the sed-

iment can be regarded as loess-derived colluvium (cf. Lang, 1994,

2003; Pye, 1995; Kadereit et al., 2002). The mechanisms that trig-gered loess erosion by overland flow and aeolian transport have to

explain the removal of vegetation and exposure of the loess; human

activities and/or climate shifts were probably of significance.

Several of our dates fall within the Mesolithic period; others cor-

respond with the Neolithic and Bronze Age (Figure 7). Abundant

archaeological evidence exists for human occupation in the

Pennines and the Lake District in the early/mid Holocene (eg,

Higham, 1986; Manby et al., 2003) but pollen analytical data showthat human impact on vegetation and soils was rather limited prior

to the early Neolithic (~6–5.5 ka BP; Pigott and Pigott, 1959, 1963;

Oldfield, 1963; Tinsley, 1976; Bartley et al., 1990; Atherden, 1999).In contrast, Simmons et al. (1981) and Simmons and Innes (1987)have argued for significant modification of early woodlands by

Mesolithic cultures, and Smith (1986, 1991) considers that clear-

ance of woodland and reworking of friable soils by both wind and

water took place in the Malham area during that time. In the south-

ern Pennines, Redda and Hansom (1989) reported a14C date of

5860 ± 120 years BP (SRR-2518) on charcoal from beneath land-

slide debris. They considered that burning of woodland vegetation

had occurred in the late Mesolithic period and that this may have

contributed to slope instability. Human impacts on the limestone


Figure 7 Summary diagram showing age ranges of OSL dates set against cultural phases, periods of climate deterioration in the northeast Atlantic

region shown in black (O’Brien et al., 1995; Bond et al., 1997), and wet shifts/phases identified from ombrotrophic bogs in northern Britain shownin black (Hughes et al., 2000; Barber et al., 2003; Langdon et al., 2003)



uplands during the early Neolithic might have involved the creation

of cleared areas for small-scale cultivation and grazing (Evans,

2004). Thus, in northern England there are strong indications of

human interference in the Mesolithic and early Neolithic but no

unequivocal evidence for this being the cause of loess reworking.

From a variety of proxy environmental data, millennial- to sub-

millennial climate shifts are known to have characterized the

Holocene. Greenland (GISP2) ice core records (O’Brien et al.,1995), and North Atlantic marine sediments (Bond et al., 1997)demonstrate several shifts to cooler and more disturbed climate.

Some of these show good correspondence with major wet shifts

recorded in ombrotrophic bogs in northern Britain and across a

wide area of mid-latitude Europe (Figure 7; Hughes et al., 2000;Barber et al., 2003; Langdon et al., 2003) suggesting climatechanges were spatially coherent and resulted from a regional forc-

ing factor, most probably perturbations of North Atlantic thermo-

haline circulation. However, no consistent association between

loess erosion/deposition and known phases of climate deterioration

is evident, partially because of the relatively large dating uncer-

tainties. It is currently not possible to resolve specific climate

events because of the low precision.

Conclusions

Application of OSL dating to the ‘loess’ and cemented scree of

northwest England has provided new data and new insights con-

cerning these discontinuous but widespread deposits. A more

complex pattern of accumulation than originally hypothesized is

indicated, necessitating a reconsideration of these materials.

Despite the preliminary nature of this work, a number of impor-

tant conclusions can be drawn.

(1) Fine sands and silts extracted from the sites in this study

proved suitable for optical dating, although at most sites broad

and/or multimodal distributions of replicate estimates of palaeo-

dose are likely to reflect postdepositional reworking, poor bleach-

ing and/or microscale variations in dosimetry. Appropriate models

have been used to provide the Dein such cases.

(2) The ‘loess’ and cementation of the screes are not of

deglacial/Lateglacial age as was previously thought. Despite the

methodological complications discussed above, the OSL ages indi-

cate they are predominantly of Holocene age. This indicates that

loess reworking must have occurred during the early/mid Holocene.

(3) Dates from the cemented scree support the results of Strong

et al. (1992) and Howard et al. (2000) for Holocene calcrete for-mation in northern England.

(4) Conclusive information concerning the underlying

cause(s) of loess erosion and the process(es) of reworking is cur-

rently difficult to establish. Whatever the stimulus for disturbance,

more massive and widespread soil erosion occurred on the lime-

stone uplands earlier than conventionally thought. Loess rework-

ing may have resulted from aeolian transport, overland flow

and/or subsoil piping; at one site sediment composition strongly

suggests we are dealing with loess-derived colluvium.

(5) It is important that a greater range of ‘loess’ sites is dated

in order to test and refine the spatial and temporal/stratigraphic

components of our findings. Such work is presently underway.

Acknowledgements

Funding was provided by Robert White (Yorkshire Dales National

Park), the British Geomorphological Research Group, theManchester

Geographical Society, and an Aggregate Levy Sustainability Fund

grant to the North Craven Historical Research Group. Kilian

McDaid at the University of Ulster prepared Figures 1 and 7 for pub-

lication. Richard Bailey at the Oxford University Centre for the

Environment is thanked for discussion regarding the interpretation of

the OSL data, and the comments of an anonymous referee helped us

improve the manuscript.

References

Armitage, S.J. and Bailey, R.M. 2005: The measured dependence of

laboratory beta dose rates on sample grain size. RadiationMeasurements 39, 123–27.Armitage, S.J., Botha, G.A., Duller, G.A.T., Wintle, A.G., Rebelo, L.P.

andMomade,F.J. 2006: The formation and evolution of the barrier islands

of Inhaca and Bazaruto, Mozambique.Geomorphology 82, 295–308.Atherden, M.A. 1999: The vegetation history of Yorkshire: a bog-

trotter’s guide to God’s own county. The Naturalist 124, 137–56.Bailey, R.M. 2000: The interpretation of quartz optically stimulated

luminescence equivalent dose versus time plots. RadiationMeasurements 32, 129–40.Banerjee, D., Murray, A.S., Botter-Jensen, L. and Lang, A. 2001:

Equivalent dose estimation using a single aliquot of polymineral fine

grains. Radiation Measurements 33, 73–94.Barber, K.E., Chambers, F.M. and Maddy, D. 2003: Holocene

palaeoclimates from peat stratigraphy: macrofossil proxy climate

records from three oceanic raised bogs in England and Ireland.

Quaternary Science Reviews 22, 521–39.Bartley, D.D., Jones, I.P. and Smith, R.T. 1990: Studies in the

Flandrian vegetational history of the Craven district of Yorkshire: the

lowlands. Journal of Ecology 78, 611–32.Bateman, M.D. 1995: Thermoluminescence dating of the British cov-

ersand deposits. Quaternary Science Reviews 14, 791–98.—— 1998: The origin and age of coversand in north Lincolnshire,

UK. Permafrost and Periglacial Processes 9, 313–25.Bateman, M.D., Frederick, C.D., Jaiswal, M.K. and Singhvi, A.K.

2003: Investigations into the potential effects of pedoturbation on

luminescence dating. Quaternary Science Reviews 22, 1169–76.Berger, G.W., Melles, M., Banerjee, D., Murray, A.S. and Raabs,

A. 2004: Luminescence chronology of non-glacial sediments in

Changeable Lake, Russian High Arctic, and implications for limited

Eurasian ice-sheet extent during the LGM. Journal of QuaternaryScience 19, 513–23.Bond, G., Showers, W., Cheseby, M., Lotti, R., Almasi, P.,

deMenocal, P., Priore, P., Cullen, H., Hajdas, I. and Bonani, G.

1997: A pervasive millennial-scale cycle in North Atlantic Holocene

and glacial climates. Science 278, 1257–66.Bullock, P. 1964: A study of the origin and development of soils overCarboniferous limestone in the Malham district of Yorkshire.Unpublished M.Sc. thesis, University of Leeds.

Bullock, P. 1971: Soils of the Malham Tarn area. Field Studies 3,381–408.

Burrin, P.J. 1981: Loess in the Weald. Proceedings of the Geologists’Association 92, 87–92.Carr, A.S., Thomas, D.S.G. and Bateman, M.D. 2006: Climatic and

sea level controls on Late Quaternary eolian activity on the Agulhas

Plain, South Africa. Quaternary Research 65, 252–63.Catt, J.A. 1977: Loess and coversands. In Shotton, F.W., editor,

British Quaternary studies: recent advances. Oxford University Press,221–29.

–––– 1978: The contribution of loess to soils in lowland Britain. In

Limbrey, S. and Evans, J.G., editors, The effect of man on the land-scape: the lowland zone. Council for British Archaeology, ResearchReport 21, 12–20.

–––– 1988: Loess – its formation, transport and economic signifi-

cance. In Lerman, A. and Meybeck, M., editors, Physical and chemi-cal weathering in geochemical cycles. Kluwer, 113–42.–––– 2001: The agricultural importance of loess. Earth-ScienceReviews 54, 213–29.Chase, B.M. and Thomas, D.S.G. 2006: Late Quaternary dune accu-

mulation along the western margin of South Africa: distinguishing

forcing mechanisms through the analysis of migratory dune forms.Earth and Planetary Science Letters 251, 318–33.

1110 The Holocene 18,7 (2008)



Clarke, M.L., Milodowski, A.E., Bouch, J.E., Leng, M.J. and

Northmore, K.J. 2007: New OSL dating of UK loess: indications of

two phases of Late Glacial dust accretion in SE England and climate

implications. Journal of Quaternary Science 22, 361–71.Duller, G.A.T. 2003: Distinguishing quartz and feldspar in single grain

luminescence measurements. Radiation Measurement 37, 161–65.Evans, H. 2004: Where is the Cumbrian Neolithic? In Cummings, V.

and Fowler, C., editors, The Neolithic of the Irish Sea: materiality andtraditions of practice. Oxbow Books, 123–28.Ford, D. and Williams, P. 1989: Karst geomorphology and hydrol-ogy. Unwin Hyman.Furness, R.R. andKing, S.J. 1972: Soils inWestmorland I sheet SD 58(Sedgwick). Soil Survey of England and Wales, Soil Survey Record 10.Galbraith, R.F. 1988: Graphical display of estimates having differing

standard errors. Technometrics 30, 271–81.Galbraith, R.F. and Green, P.F. 1990: Estimating the component

ages in a finite mixture. Nuclear Tracks and Radiation Measurements17, 197–206.

Galbraith, R.F., Roberts, R.G., Laslett, G.M., Yoshida, H. and

Olley, J.M. 1999: Optical dating of single and multiple grains of quartz

from Jinmium rock shelter, northern Australia, part 1, Experimental

design and statistical models. Archaeometry 41, 339–64.Gibbard, P.L., Wintle, A.G., and Catt, J.A. 1987: Age and origin of

clayey silt ‘brickearth’ in west London, England. Journal ofQuaternary Science 2, 3–9.Goudie, A.S. 1983: Calcrete. In Goudie, A.S. and Pye, K., editors,

Chemical sediments and geomorphology: precipitates and residua inthe near-surface environment. Academic Press, 93–131.Higham, N.J. 1986: The northern counties to AD 1000. Longman.Howard, A.J., Macklin, M.G., Black, S. and Hudson-Evans, K.A.

2000: Holocene river development and environmental change in

Upper Wharfedale, Yorkshire Dales, England. Journal of QuaternaryScience 15, 239–52.Hughes, P.D.M., Mauquoy, D., Barber, K.E. and Langdon, P.G.

2000: Mire-development pathways and palaeoclimatic records from a

full Holocene peat archive at Walton Moss, Cumbria, England. TheHolocene 10, 465–79.Huntley, D.J., Godfrey-Smith, D.I. and Thewalt, M.L.W. 1985:

Optical dating of sediments. Nature 313, 105–107.Jacobs, Z., Duller, G.A.T., Wintle, A.G. and Henshilwood, C.S.

2006: Extending the chronology of deposits at Blombos Cave, South

Africa, back to 140 ka using optical dating of single and multiple

grains of quartz. Journal of Human Evolution 51, 255–73.Kadereit, A., Lang, A., Hönscheidt, S., Müth, J. andWagner, G.A.

2002: IR-OSL-dated colluvial sediments as a key to Holocene land-

scape reconstruction. Case studies from SW-Germany. Zeitschrift fürGeomorphologie Supplement-Band 128, 191–207.Lang, A. 1994: Infra-red stimulated luminescence dating of Holocene

reworked silty sediments. Quaternary Science Reviews 13, 525–28.–––– 2003: Phases of soil erosion-derived colluviation in the loess

hills of south Germany. Catena 51, 209–21.Langdon, P.G., Barber, K.E. andHughes, P.D.M. 2003: A 7500-year

peat-based palaeoclimatic reconstruction and evidence for an 1100-year

cyclicity in bog surface wetness from Temple Hill Moss, Pentland Hills,

southeast Scotland. Quaternary Science Reviews 22, 259–74.Locke, W.W. 1986: Fine particle translocation in soils developed on

glacial deposits, southern Baffin Island, N.W.T., Canada. Arctic andAlpine Research 18, 33–43.Mahan, S.A., Miller, D.M., Menges, C.M. and Yount, J.C. 2007:

Late Quaternary stratigraphy and luminescence geochronology of the

northeastern Mojave Desert. Quaternary International 166, 61–78.Manby, T.G., Moorhouse, S. and Ottaway, P. 2003: The archaeol-ogy of Yorkshire: an assessment at the beginning of the 21st century.(Charlesworth Group) Yorkshire Archaeological Society, Occasional

Paper No. 3.

Marshall, J.D., Jones, R.T., Crowley, S.F., Oldfield, F., Nash, S.

and Bedford, A. 2002: A high resolution Lateglacial isotopic record

from Hawes Water, northwest England climatic oscillations: calibra-

tion and comparison of palaeotemperature proxies. Palaeogeography,Palaeoclimatology, Palaeoecology 185, 25–40.Murray, A.S. and Wintle, A.G. 2000: Application of the single-

aliquot regenerative-dose protocol to the 375 degrees C quartz TL sig-

nal. Radiation Measurements 32, 579–83.

–––– 2003: The single aliquot regenerative dose protocol: potential

for improvements in reliability. Radiation Measurements 37, 377–81.Murton, J.B., Bateman, M.D., Baker, C.A., Knox, R. and

Whiteman, C.A. 2003: The Devensian periglacial record on Thanet,

Kent, UK. Permafrost and Periglacial Processes 14, 217–46.Nanson, G.C., Jones, B.G., Price, D.M. and Pietsch, T.J. 2005:

Rivers turned to rock: late Quaternary alluvial induration influencing

the behaviour and morphology of an anabranching river in the

Australian monsoon tropics. Geomorphology 70, 398–420.O’Brien, S.R., Mayewski, P.A., Meeker, L.D., Meese, D.A.,

Twickler, M.S. andWhitlow, S.I. 1995: Complexity of Holocene cli-

mate as reconstructed from a Greenland ice core. Science 270, 1962–64.Oldfield, F. 1963: Pollen-analysis and man’s role in the ecological

history of the south-east Lake District. Geografiska Annaler 45,23–40.

Olley, J.M., Roberts, R.G. andMurray, A.S. 1997: Disequilibria in

the uranium decay series in sedimentary deposits at Allen’s Cave,

Nullarbor Plain, Australia: implications for dose rate determinations.

Radiation Measurements 27, 433–43.Olley, J.M., Pietsch, T. and Roberts, R.G. 2004: Optical dating of

Holocene sediments from a variety of geomorphic settings using sin-

gle grains of quartz. Geomorphology 60, 337–58.Parks, D.A. and Rendell, H.M. 1992: Thermoluminescence dating

and geochemistry of loessic deposits in southeast England. Journal ofQuaternary Science 7, 99–107.Pigott, C.D. and Pigott, M.E. 1963: Lateglacial and post-glacial

deposits at Malham, Yorkshire. New Phytologist 62, 317–34.Pigott, M.E. and Pigott, C.D. 1959: Stratigraphy and pollen analysis

of Malham Tarn and Tarn Moss. Field Studies 1, 84–101.Prescott, J.R. and Hutton, J.T. 1995: Environmental dose rates and

radioactive disequilibrium from some Australian luminescence dating

sites. Quaternary Science Reviews 14, 439–48.Pye, K. 1995: The nature, origin and accumulation of loess.

Quaternary Science Reviews 14, 653–67.Redda, A. and Hansom, J.D. 1989: Mid-Flandrian (Atlantic) land-

slide activity in the south Pennines. Proceedings of the YorkshireGeological Society 47, 207–13.Rich, J., Stokes, S., Wood, W. and Bailey, R. 2003: Optical dating of

tufa via in situ aeolian sand grains: a case example from the Southern

High Plains, USA. Quaternary Science Reviews 22, 1145–52.Roberts, D.H., Chiverrell, R.C., Innes, J.B., Horton, B.P., Brooks,

A.J., Thomas, G.S.P., Turner, S. and Gonzalez, S. 2006: Holocene sea

levels, last glacial maximum glaciomarine environments and geophysical

models in the northern Irish Sea Basin, UK.Marine Geology 231, 113–28.Roberts, H.M. 2006: Optical dating of coarse-silt sized quartz from

loess: evaluation of equivalent dose determinations and SAR proce-

dural checks. Radiation Measurement 41, 923–29.–––– 2007: Assessing the effectiveness of the double-SAR protocol in

isolating a luminescence signal dominated by quartz. RadiationMeasurements 42, 1627–36.Roberts, H.M. and Wintle, A.G. 2001: Equivalent dose determina-

tions for polymineralic fine-grains using the SAR protocol: applica-

tion to a Holocene sequence of the Chinese loess plateau. QuaternaryScience Reviews 20, 859–63.–––– 2003: Luminescence sensitivity changes of polymineral fine

grains during IRSL and [post-IR] OSL measurements. RadiationMeasurements 37, 661–71.Roberts, R.G., Galbraith, R.F., Olley, J.M., Yoshida, H. and

Laslett, G.M. 1999: Optical dating of single and multiple grains of

quartz from Jinmium rock shelter, northern Australia, part 2, results

and implications. Archaeometry 41, 365–95.Rodnight, H., Duller, G.A.T., Tooth, S. and Wintle, A.G. 2005:

Optical dating of a scroll-bar sequence on the Klip River, South

Africa, to derive the lateral migration rate of a meander bend. TheHolocene 15, 802–11.Simmons, I.G. and Innes, J.B. 1987: Mid-Holocene adaptations and

later Mesolithic forest disturbance in northern England. Journal ofArchaeological Science 14, 385–403.Simmons, I.G., Dimbleby, G.W. and Grigson, C. 1981: The

Mesolithic. In Simmons, I.G. and Tooley, M.J., editors, The environ-ment in British prehistory. Duckworth, 82–124.Singhvi, A.K., Bluszcz, A., Bateman, M.D. and Rao, M.S. 2001:

Luminescence dating of loess-palaeosol sequences and coversands:




methodological aspects and palaeoclimatic implications. Earth-Science Reviews 54, 193–211.Smith, R.T. 1986: Aspects of the soil and vegetation history of the

Craven district of Yorkshire. In Manby, T.G. and Turnbull, P., editors,

Archaeology in the Pennines: studies in honour of Arthur Raistrick.BAR British Series 158, 3–27.

–––– 1991: Contrasted pedogenic pathways in the Craven Highlands

of North Yorkshire. Proceedings of the North of England SoilsDiscussion Group 26, 69–73.Stevens, T., Armitage, S.J., Lu, H. and Thomas, D.S.G. 2007:

Examining the potential of high sampling resolution OSL dating of

Chinese loess. Quaternary Geochronology 2, 15–22.Strong, G.E., Giles, J.R.A. andWright, V.P. 1992: A Holocene cal-

crete from North Yorkshire, England: implications for interpreting

palaeoclimates using calcretes. Sedimentology 39, 333–47.Sweeting, M.M. 1966: The weathering of limestones: with particular

reference to the Carboniferous limestones of northern England. In

Dury, G.H., editor, Essays in geomorphology. Heinemann, 177–210.–––– 1972: Karst landforms. Macmillan.Thomas, P.J., Murray, A.S. and Sandgren, P. 2003: Age limit and

age underestimation using different OSL signals from lacustrine quartz

and polymineral fine grains.Quaternary Science Reviews 22, 1139–43.Tinsley, H. 1976: Cultural influences on Pennine vegetation with

particular reference to North Yorkshire. Transactions of the Instituteof British Geographers 1, 310–22.Vincent, P. 1982: Some observations on the so-called relict karst of

the Morecambe Bay region, north-west England. Revue de GéologieDynamique et de Géographie Physique 23, 143–50.

–––– 1985: Quaternary geomorphology of the southern Lake District

and Morecambe Bay area. In Johnson, R.H., editor, The geomorphol-ogy of north-west England. Manchester University Press, 159–77.Vincent, P. and Lee, M.P. 1981: Some observations on the loess

around Morecambe Bay, north-west England. Proceedings of theYorkshire Geological Society 43, 281–94.–––– 1982: Snow patches on Farleton Fell, south-east Cumbria.

Geographical Journal 148, 337–42.Walker, M.J.C. 2004: A Lateglacial pollen record from Hallsenna

Moor, near Seascale, Cumbria, NW England, with evidence for arid

conditions during the Loch Lomond (Younger Dryas) Stadial and early

Holocene. Proceedings of the Yorkshire Geological Society 55, 33–42.Wang, X., Lu, Y. and Zhao, H. 2006: On the performances of the sin-

gle-aliquot regenerative-dose (SAR) protocol for Chinese loess: fine

quartz and polymineral grains. Radiation Measurements 41, 1–8.Watanuki, T., Murray, A.S. and Tsukamoto, S. 2005: Quartz and

polymineral luminescence dating of Japanese loess over the last 0.6 Ma:

comparison with an independent chronology. Earth and PlanetaryScience Letters 240, 774–89.Wintle, A.G. 1981: Thermoluminescence dating of late Devensian

loesses in southern England. Nature 289, 479–80.Wintle, A.G. and Murray, A.S. 2006: A review of quartz optically

stimulated luminescence characteristics and their relevance in single-

aliquot regeneration dating protocols. Radiation Measurements41, 369–91.

Zhang, J.F. and Zhou, L.P. 2007: Optimization of the ‘double SAR’

procedure for polymineral fine grains. Radiation Measurements42, 1475–82.

1112 The Holocene 18,7 (2008)



Optically Stimulated Luminescence (OSL) dating of loessic sediments and cemented scree in northwest...

Documents

Transcript of Optically Stimulated Luminescence (OSL) dating of loessic sediments and cemented scree in northwest...