at SciVerse ScienceDirect

Quaternary Geochronology 12 (2012) 11e22

Contents lists available

Quaternary Geochronology

journal homepage: www.elsevier .com/locate/quageo

Research paper

Meteoric 10Be concentrations from saprolite and till in northern Sweden:Implications for glacial erosion and age

Karin Ebert a, Jane Willenbring b,c,*, Kevin P. Norton c,d, Adrian Hall e, Clas Hättestrand a

aDepartment of Physical Geography and Quaternary Geology, Stockholm University, SwedenbDepartment of Earth and Environmental Science, University of Pennsylvania, Philadelphia, PA, USAcGFZ-Potsdam Section 3.2, Potsdam, Germanyd School of Geography, Environment and Earth Sciences, Victoria University of Wellington, Wellington, New Zealande School of Geography and Geosciences, University of St Andrews, St Andrews, KY16 9AL, UK

a r t i c l e i n f o

Article history:Received 24 November 2011Received in revised form18 May 2012Accepted 21 May 2012Available online 1 June 2012

Keywords:MeteoricCosmogenicBeryllium-10SaproliteTillGeochemistryGlaciated shield areaNorthern Sweden

* Corresponding author.E-mail address: erosion@sas.upenn.edu (J. Willenb

1871-1014/$ e see front matter � 2012 Elsevier B.V.doi:10.1016/j.quageo.2012.05.005

a b s t r a c t

We examine 10Be concentration in two pit profiles in the Parkajoki area at w67�N on the northernFennoscandian shield in northern Sweden. Due to repeated cover by cold-based, non-erosive ice sheets,the area retains many relict non-glacial features, including tors and saprolites. In the examined pitprofiles, gruss-type saprolite developed from weathering of intermediate igneous rocks is overlainunconformably by Weichselian till.

Our results show that 10Be concentrations found in the till greatly exceed the levels of 10Be that canhave accumulated since deglaciation at w11 ka and are comparable to those reported from Pliocene andEarly Pleistocene tills in North America. Old tills with grussified boulders at depth were excavated in theParkajoki area and correlations with neighbouring parts of Finland indicate a Middle Pleistocene or olderage. Evidence from pit excavations and geochemistry shows that the underlying saprolites have beentruncated by glacial erosion and that previously weathered material has been incorporated into the tillsequence. Hence, 10Be inventories in the tills are dominated by material recycled fromMiddle Pleistoceneor older soils, near-surface sediments and saprolite, and cannot be used to date the periods of tilldeposition. The retention of relict 10Be in the tills nonetheless confirms minimal glacial erosion.

Concentrations of meteoric 10Be in the saprolites are lower than any reported saprolite concentrationsmeasured in other settings. Uncertainty in the pre-glaciation 10Be concentrations in the saprolites makesage determinations difficult. One possibility is that that the saprolite had higher 10Be concentrations inthe past but that saprolite formation ended after glaciation and burial by till and that the 10Be hassubstantially decayed. Modelling of the meteoric 10Be depth profiles in this case suggests that thesaprolites in the Parkajoki area were formed at a minimum of 2 Ma. Erosion of the saprolite allows anolder age of up to w5 Ma, with up to 250 cm of material removed and incorporated into later tills. Asecond possibility is that concentrations of meteoric 10Be in the saprolite were originally lower, withformation of the saprolite in a period or periods of ice- and permafrost-free conditions before 0.8 Ma.

� 2012 Elsevier B.V. All rights reserved.

1. Introduction

In many formerly glaciated areas, glacial erosion has strippedpre-glacial weathering mantles to leave bare bedrock surfaces.However, in zones of cold-based ice cover, pre-glacial landscapeelements were preserved under the ice sheet (Kleman, 1994;Staiger et al., 2005). In these zones of selective and limited glacialerosion, pockets or extensive areas of saprolites may survive(Bouchard and Pavich, 1989; Hall, 1985, 1986; Lundqvist, 1985;

ring).

All rights reserved.

Paasche et al., 2006) and reworked saprolite may be a prominentcomponent of glacial tills (Feininger, 1971; Peuraniemi et al., 1997).Such materials provide opportunities to reconstruct formerclimates during weathering (Migo�n and Lidmar-Bergström, 2001),to establish the character of pre-glacial terrain (Hall and Sugden,1987; Lidmar-Bergström et al., 1997) and to determine depthsand rates of pre-glacial and glacial erosion (Glasser and Hall, 1997;Stanford et al., 2002).

Dating of pre-glacial saprolites in glaciated terrain remains,however, in its infancy, with saprolite age often constrained onlythe age of overlying glacial deposits. The pioneering isotopework ofPavich et al. (Bouchard and Pavich, 1989; Pavich et al., 1985)demonstrated the potential of meteoric 10Be for estimating

K. Ebert et al. / Quaternary Geochronology 12 (2012) 11e2212

saprolite age, including those in former glaciated areas but hasremained largely undeveloped. Moreover, previous work along thesouthern margin of the former Laurentide ice sheet has shown thatold tills may retain substantial inventories of meteoric 10Be thatprovide important evidence of glacial reworking of old, weatheredand near-surface materials and that, where tills have been buriedand cut-off from replenished 10Be from the surface, can be used toestimate till age from isotope decay (Roy et al., 2004; Balco et al.,2005; Staiger et al., 2006; Balco and Rovey, 2010).

In this paper, we examine meteoric 10Be inventories in soilprofiles through till and saprolite at 67�N in an area of minimalglacial erosion. The study area lies in arctic northern Sweden andrepresents the northernmost location yet studied in this context.First, we characterise the stratigraphy, geochemistry and 10Bedistribution in the profiles. Next, we consider questions of the ageand origin of the saprolite and till materials and estimate depths ofglacial erosion. Finally, we explore the site criteria that might allowmore precise dating of buried saprolites using the decay of meteoric10Be.

2. Geology and geomorphology of the study area

The Parkajoki area lies near the Sweden-Finland border innorthern Fennoscandia (Fig. 1). The shield here is mainly composedof Paleoproterozoic (1.75e1.96 Ga) granite and granodiorite, with

Fig. 1. Northern Sweden and Parkajoki area, and location in Fennoscandia. The lower right fi(compiled from Nordkalott Project, 1986; Kleman et al., 1997; Hättestrand, 1998; Hättestra

smaller bodies of dolerite, gabbro and mica schist (GeologicalSurvey of Sweden, 2011). Parkajoki is a part of the huge inselbergplains that cover more than 30,000 km2 in the northern Swedishpart of the shield (Ebert and Hättestrand, 2010) and situated ona palaeosurface at 250e400 m a.s.l., the so-called Muddus plains(Wråk, 1908; Lidmar-Berström, 1996; Ebert et al., 2011).

The area is rich in landforms and regolith older than the lastice cover. Pre-Late Weichselian tills and interstadial organic sedi-ments are preserved on both sides of the Sweden-Finland border(Hirvas, 1991; Robertsson, 1997). Old weathering features,including granite tors (Hättestrand and Stroeven, 2002) and insel-bergs (Ebert and Hättestrand, 2010; Ebert et al., in press), togetherwith saprolites (Nordkalott project, 1986; pers. comm. with RobertLagerbäck, SGU) are common, and indicate very limited glacialerosion due to repeated covers of cold-based and non-erosive ice(Fig. 2).

Parkajoki was located near the former ice divide zone of thelarge Fennoscandian ice sheets, during the Last Glacial Maximumand earlier glacial phases (Kleman et al., 1997). However, duringmore restricted Quaternary glaciations, ice sheets were centeredover the elevation axis of the Scandinavian mountain range, c.200 km west of the Parkajoki area (Kleman and Stroeven, 1997)with ice extending over the Parkajoki area. The last (Weichselian)glaciation commenced around 115 ka, and final deglaciation wascompleted at w11 ka (Stroeven et al., 2002).

gure shows the main ice drainage directions as imprinted in the drumlinized landscapend and Stroeven, 2002).

Fig. 2. Parkajoki area, with sampling sites and tor localities (tor localities from Hättestrand and Stroeven, 2002).

K. Ebert et al. / Quaternary Geochronology 12 (2012) 11e22 13

The study area lies today at the southern edge of the discon-tinuous permafrost zone (Rapp, 1982) but permafrost extendedfarther south in the colder conditions of Quaternary interstadials(Pitkäranta, 2009). Parkajoki today has a mean annual temperatureof �1.7 �C and mean annual precipitation of 520 mm, much of itfalling as snow. Present rates of weathering and soil formation inLapland are slow, as indicated by weathering of rock outcrops(André, 2002), estimated as <1.6 m Ma�1 for the last 605 ka atParkajoki (Stroeven et al., 2002), and by the limited development ofpodzols in Holocene sands (Mokma et al., 2004).

An estimate of the duration of ice cover in northern Swedenbased on modelled threshold marine oxygen isotope cut-off values(Kleman and Stroeven, 1997) was later corroborated using thedifferent decay rates of in situ-produced cosmogenic 26Al and 10Be(Li et al., 2007). Using these data, it has been estimated that theParkajoki area was covered by ice during 60e80% of the last700,000 years and during 40e50% of the time in the earlyQuaternary (Hättestrand and Stroeven, 2002). Hence, ice-free

conditions permitting meteoric 10Be influx have prevailed in Par-kajoki area for 156e312 ka since the start of the Middle Pleistoceneat 781 ka. Chemical weathering is possible only under ice-freeconditions when permafrost is absent. In northern Sweden, appli-cation of the cirque glaciation threshold of Kleman et al. (2008) tothe d18O record of marine core DSDP 607 (Ruddiman and Raymo,1988) indicates that this is broadly equivalent to the total dura-tion of w185 ka for full interglacial conditions in the Middle andLate Pleistocene and w1 Ma in the Early Pleistocene.

3. Methods

3.1. Pit profiles

Pits were excavated in the Parkajoki area at sites that werechosen on the basis of previous excavations (Robert Lagerbäck, SGU,pers. comm.) and on understanding of the local geomorphology.Ten pits were dug by mechanical excavator to a maximum depth of

Fig. 3. Photo of Pit A1and stratigraphy of the10 excavated pits in the Parkajoki area (for location see Fig. 2).

K. Ebert et al. / Quaternary Geochronology 12 (2012) 11e2214

K. Ebert et al. / Quaternary Geochronology 12 (2012) 11e22 15

7.5 m and logged in the field (Fig. 3). Two pits (A1: Anakongas 1 andN3: Naakakarhakka 3) were sampled at close intervals for detailedanalysis of isotope geochemistry (Fig. 4).

3.2. X-ray fluorescence analyses

A total of 40 soil, till, saprolite, and bedrock samples wereselected for XRF analysis. These samples were crushed andpulverized to a powder and split down to 5 g sub-samples. Thepowdered samples were thenmixed with a borate glass and heatedto 1000 �C to form a glass pellet. These samples were measured atthe GFZ Potsdam on a PANalytical AXIOS Advanced machine todetermine their major and trace element concentrations and toallow elemental mass loss and thereby chemical weatheringintensities (Brimhall et al., 1991; White et al., 1998; Norton, 2008).

We characterize the geochemistry of the samples using threeweathering indices:

1. The chemical index of alteration (Nesbitt and Young, 1982):

CIA ¼ Al2O3

Al O þ CaOþ Na Oþ K O� 100 (1)

2 3 2 2

Note that here we have corrected the CaO concentrations due toapatite weathering (Price and Velbel, 2003). The CIA characterizesthe loss of major cations to weathering in granitic systems. Valuesabove w50 are characteristic of weathered material, depending onchemical composition (Nesbitt and Young, 1982).

2. The chemical depletion fraction (Riebe et al., 2001a,b):

CDF ¼ 1� Ci;pCi;w

(2)

Fig. 4. Profiles of A1 (top) and N3 (bottom). The chemical index of alteration (CIA) indicatesupper w20 cm shows that renewed soil formation is taking place on the tills. CDF and tarespectively (e.g. we do not assume that the tills are genetically related to the saprolites). CDFtau values in the saprolites (closed symbols) indicate weathering of the saprolite (positive CDThe CDF and tau values from A1 suggest that little weathering has taken place after deposi

where Ci,p is the concentration of an immobile element in the parentmaterial and Ci,w is the concentration of the same immobile elementin the weathered material (Fig. 4aec), are compatible with Ti loss.

3. The relative mass loss, s, of the mobile cations j, (Brimhall andDietrich, 1987, Fig. 4deh):

si;j ¼ Cj;wCj;p

Ci;pCi;w

� 1

!(3)

where we treat Zr as an immobile element to calculate loss.Negative s values indicate element loss and positive values elementgain. CDF and tau values for the till and saprolite are referenced tothe base of the till and saprolite respectively.

In equations (2) and (3), the immobile elements are often part ofa subset of the transition metals. Zirconium, titanium, and yttriumare most commonly used as tracers in weathering studies as theyform oxides which are typically stable under weathering (e.g.zircon, rutile, etc.). Previous work in Scandinavia has, however,shown considerable mobility of the rare earth elements and Tiassuming Zr is immobile (Öhlander et al., 1996). In particular, morethan 80% of the light rare earth elements were lost from tills duringweathering. Since both Zr and Y are near neighbours of the lightrare earth elements and also form low solubility oxides (Land et al.,1999; Railsback, 2003), we recognize the potential for the loss ofthe traditional immobile elements here. We plot Zr and Ti for tillsand saprolites to examine these trends (Fig. 5).

3.3. Meteoric 10Beryllium inventories

10Be is a natural, rare, and radioactive nuclide. It is found only inplaces where it has formed through interaction of cosmic radiationwith atmospheric gases, water, soil and rock minerals (Lal and

that both tills and saprolites are weathered while the increase in organic carbon in theu values for the till and saprolite are referenced to the base of the till and saprolitevalues from Ti (grey symbols) suggest significant loss of Ti during weathering. CDF andF and negative tau). The tills differ significantly in their depth profiles (open symbols).

tion. The inconsistent depth profile of N3 is likely due to loss of Zr during weathering.

Fig. 5. Concentrations of zirconium and titanium show considerable mobility of thetypically immobile transition metals. The low concentrations of Zr and Ti in the tills(open symbols) cannot be explained by in situ weathering of the underlying saprolite.

K. Ebert et al. / Quaternary Geochronology 12 (2012) 11e2216

Peters, 1967; Lal, 1991). The nuclide is produced both in theatmosphere (this production mechanism is often called ‘meteoric’)and within mineral lattices in material at the Earth’s surface (called‘in situ’). Meteoric 10Be falls to the ground attached to aerosols andin a soluble formwithin rain. The 10Be binds tightly to soil particlesonce it reaches the Earth’s surface (Fig. 6). 10Be produced in situ isformed in place in mineral lattices within soils and rocks. Both insitu-produced andmeteoric 10Be build-up in surficial materials overtime such that the concentration of the nuclide on and in rocks andsoil is related to the persistence of thematerial at or near the Earth’ssurface (Willenbring and von Blanckenburg, 2010). The high reac-tivity of 10Be at near-neutral pHs ensures that the vast majority ofmeteoric 10Be that reaches the ground is readily adsorbed to

Fig. 6. Schematic diagram of a Sweden-like landscape that incorporates 10Be. Thedownward movement of acidic leaching water carries the atmospheric flux of meteoric10Be from surface precipitation into the saprolite during saprolite formation. After thesaprolite is capped by till, the infiltration of 10Be ceases. The soil column is then treatedas a closed system, receiving no 10Be at the soil surface from rainfall after the depo-sition of the till cap. Any contamination will cause the maximum age of the saprolite toincrease. Adapted from Willenbring and von Blanckenburg (2010).

particles (Bourlès et al., 1989). In situ 10Be is however locked withinthe minerals (Lal, 1991). Because of this, the two varieties of 10Becan be separated through gentle chemical stripping of the outsideof the grain (for meteoric liberation) and dissolution of the crystallattice (for in situ liberation). The nuclide is found in highestconcentrations in the upper 1.5 m of the Earth’s surface (Graly et al.,2010). After the nuclide is produced or delivered to the Earth’ssurface, it decays with a half-life of w1.4 million years (Nishiizumiet al., 2007; Chmeleff et al., 2010; Korschinek et al., 2010). Becauseof the timescales of build-up and decay of 10Be in soils, it providesan attractive possibility to date saprolites (Pavich et al., 1985;Bouchard and Pavich, 1989).

To extract the amorphous oxide-bound beryllium, a 10 mLsolution of 0.5 M HCl was added and placed on a roller for agitatingat room temperature for 24 h. To extract the crystalline oxide-bound beryllium, 10 mL of 1 M hydroxylaminehydrochloridesolution was added to the centrifuge tubes with the sediment andplaced into the ultrasonic bath at 80 �C for 4 h with manual over-head shaking every 10 min. We transferred this leachate to a Tef-lon� digestion vessel and used strong oxidizers and distilled acidsin an MLS microwave digestion system under pressure and at180 �C for 2 h to quickly destroy recalcitrant organic compoundsthat can affect the cation column chromatography (see below). Weused 2 mL 20% H2O2, 2 mL 50% HF acid and 2 mL Aqua Regia forcomplete leachate dissolution. This protocol was adapted fromBourlés (1988), Barg et al. (1997) and Guelke-Stelling and vonBlanckenburg (2012).

After taking the aliquot for elemental analysis, we spiked oursample with w200 mg 9Be carrier. The liquid sample was homog-enized with the 9Be spike and 2 mL HF was added to the acidsample solution. This solution was nearly completely dried downand then dissolved in 1 additional mL of 50% HF acid and drieddown completely. We added 1 additional mL of 50% HF acid anddried down completely again. We then added 10 mL ultrapure(18 MU) water to the warm Fluoride residue and leached it for 1 hon awarm hotplate. Be is very soluble inwater but large amounts ofCa, Al and Mg and other fluorides are left behind in the insolubleresidue. The water containing the Be is gently removed via pipetteand dried down separately.

The Be in the water leach solutionwas extracted and purified bya form of the ion exchange chromatography procedure from vonBlanckenburg et al. (2004) that was adapted for meteoric 10Bepurification. Sediments have substantial amounts of a number ofunwanted, contaminant elements. First, Fe was removed from thesolution by a rapid anion exchange column. The anion resin wasconditionedwith 6MHCl. 2 mL 6MHCl was added to the sample todissolve the residue so that the cations take chloride form. Thischloride solution containing the Be sample was loaded to a columncontaining 2 mL of Biorad AG1-X8 100e200 mesh anion resinpacked in a 7.5 mL polypropylene column. Be passes through thecolumn but Fe is retained. Remnant Be is collected with an addi-tional 5 mL of 6 M HCl. The sample was dried down over severalhours and is dissolvedwith 1mL of 0.4M oxalic acid overnight. Thissample in an oxalic acid solution was centrifuged in case ofincomplete dissolution and loaded to a separate 1 mL Biorad AG50-X8 (200e400 mesh, conditioned with 0.4 M oxalic acid) cationresin that was stored in a 7.5 mL polypropylene column. Oxalic acidcomplexes all trivalent cations including Al, which pass throughcation resin with 9 mL of 0.4 M oxalic acid. The oxalic acid isremoved from the column with 2 mL of water. Be is then elutedwith 9 mL of 1 M HCl. Hydroxides of Be were precipitated from thesolution that had been eluted from the cation exchange column byadding ammonia drop-wise until pH ¼ 9. During this step, anyremaining K, Na, Ca, and Mg were left in solution. After precipita-tion, we separated the supernate and the sample precipitate by

K. Ebert et al. / Quaternary Geochronology 12 (2012) 11e22 17

centrifugation and washed it with distilled water and re-precipitated to remove any remaining Boron, which is, unfortu-nately, an isobar of 10Be. The BeOH precipitate was then dried for2 h at 70 �C, then overnight at 200 �C and then oxidized by flame at>850 �C to form BeO. We then pressed the BeO powder intocathodes for AMS analyses at PRIME Lab, Purdue University, USA.

The 10Be concentration in saprolite in glaciated terrain dependson the pre-glacial 10Be inventory, the depth of glacial erosion; theice cover history, the radioactive decay of the various 10Be inven-tories since burial by till and the rate of downward translocation of10Be (Balco, 2004). Although 10Be systematics for saprolite in thiscontext are clearly highly complex, age estimation has to start fromthe 10Be inventory in the saprolite (Bouchard and Pavich, 1989). Forsaprolites, age can be thought of as the time since the initiation ofchemical weathering, which produces secondary clays onto whichmeteoric 10Be can adsorb. Its age can be determined by measuringthe total meteoric 10Be inventory that has accumulated over time, I[in atoms cm�2], where Ni is the number of 10Be atoms in a layer i,Dzi is the layer thickness, and r the soil density [g cm�3] (fromWillenbring and von Blanckenburg, 2010).

I ¼Xi

Ni � r� Dzi (4)

The atmospheric flux of 10Be, Q [in atoms cm�2 y�1] dictates themaximum 10Be that enters the system, The saprolite’s inventorythen relates to the saprolite soil age, t, by the following equation(Brown et al., 1987), where l is equal to 0.5 � 10�7 y�1 the radio-active decay constant of 10Be.

I ¼Q�1� e�lt

�l

(5)

The 10Be concentration in till also depends on the factors listedabove, plus the degree to which 10Be-enriched regolith might bediluted with 10Be-free sediment, the 10Be inventory depositedduring ice-free periods and the degree of mixing betweena particular till and the stock of older glacial sediment thatmight beoverrun and entrained (Balco, 2004). Again, the 10Be inventory inthe till is a starting point for understanding the provenance of thetill and estimation of the timescale over which till material hasbeen close to the landsurface and available for meteoric 10Beaccumulation (Bouchard and Pavich, 1989).

A major problem with applying the above approach in sucha setting is the uncertainty in the atmospheric flux through time.This arises mainly as a result of repeated cover of unknown dura-tion by glacier ice. Because of this, we compare the measuredsaprolite concentrations here with minimum and maximum pub-lished values to provide an estimate of saprolite age. Our approachassumes an exponential decrease of meteoric 10Be with depth.

NðzÞ ¼ Nsurf e�zk (6)

As noted by Graly et al. (2010), not all meteoric 10Be profiles havea purely exponential decrease with depth. Most reach a maximum10Be concentration within the top 2 m, with the subsequentdecrease in concentration being described by an exponential curve.As our data point to glacial profile truncation by up to 2.5 m (seediscussion below), the use of the exponential function is warranted.

Where N is the meteoric 10Be concentration at depth z and thesurface, and k ¼ 0.022 cm�1 is an empirically derived e-foldingdepth (Balco, 2004). Such a decrease is often observed in in situweathering systems (e.g. Balco, 2004). We estimate the saproliteage with a closed system approach. We assume that the saproliteaccumulated meteoric 10Be during weathering and has beenremoved from the surface system by deep burial by till since. Balco

(2004) analysed samples of profiles in Minnesota and SouthDakota, where tills overlie glacially truncated pre-glacial regolith.Minimum saprolite age in our paper is determined using theminimum published weathered material 10Be concentration (seecompilation in Graly et al., 2011) from Balco (2004) of 1 � 108

atoms/g, and model the best fit based on a 10Be half-life of 1.39 Ma(Chmeleff et al., 2010; Korschinek et al., 2010). The maximumsaprolite age is also estimated assuming a closed system, but withthe maximum recorded 10Be surface concentration as an input(w2.5 � 109: Pavich et al., 1985). This maximum age can also becomplicated by erosion of the top of the saprolite. We assumea closed system (to 10Be movement) in our implementation oferosion, assuming simple profile truncation. We therefore deter-mine profiles assuming different combinations of erosion depthsand time since burial. While this approach cannot provide a highprecision age of the saprolite, based on existing data, it canreasonably discriminate between modern and ancient saprolite.

4. Results

4.1. Pit profiles

Pit excavations revealed a complex local Pleistocene stratig-raphy, with at least 4 till units interlayered with sand and gravelbeds beneath thin Holocene soils. Near-surface tills up to 5 m deepof typical Late and Middle Weichselian aspect (Robertsson et al.,2005) were encountered widely (Fig. 3). These tills are dominatedby locally-derived clasts that are angular, unweathered and onlyrarely striated. Additionally, however, two lower till units wereexposed in 4 pits in which granite and diorite clasts up to bouldersize showed well developed weathering rinds or were partly orwholly disintegrated. Such weathered till units have not been re-ported previously in northern Sweden. Typically, the lowermostpart of the till sequence incorporates large amounts of weatheredmaterial reworked from saprolite.

Pit excavations also confirmed the findings of the NordkalottProject (1986) that saprolites occur widely away from hillsummits in the Parkajoki area and its surroundings. The saprolitesare locally >3 m deep but fresh bedrock was also encountered inthree pits. The saprolites are of gruss-type (Hall et al., 1989; Migo�nand Lidmar-Bergström, 2001), with incipient weathering of feld-spar and mica and only low fines contents. No palaeosol featureswere observed beneath the saproliteetill contact, except perhaps inPit A3, where a 15-cm thick Fe-stained zone occurs (Fig. 3). Themost common bedrock type encountered was coarse-grained redgranite, with muscovite and biotite mica and minor pyrite, andpervasive haematite staining. Additionally, coarse-grained biotitegneiss of dioritic composition occurs locally at Naakakarhakka andAnokangas.

4.2. X-ray fluorescence analyses

Geochemical analysis suggests limited weathering of tills andsaprolites in northern Sweden. Within the soils (Fig. 4), the CIAincreases only slightly towards the surface before decreasing in theupper organic layer. Incipient weathering is also apparent in thenear surface increase in organic carbon (Fig. 4b). Similar limitedlosses of major elements to weathering during post-glacial soildevelopment have been observed in granitic tills in neighbouringparts of northern Sweden (Land et al., 1999).

CIA values in the tills are moderate (>60%). However, as theseWeichselian tills contain only fresh clasts of the subjacent bedrock,these values are mainly a result of the incorporation of pre-weathered material into the tills. The tills differ significantly intheir depth profiles (Fig. 4). In A1, CIA values are higher than in the

K. Ebert et al. / Quaternary Geochronology 12 (2012) 11e2218

till than in the subjacent saprolite, whereas in N3 the CIA values areslightly lower. The CDF and tau values from A1 (Fig. 4) suggest thatlittle weathering of the till has taken place after deposition. Theimmobile elements Ti and Zr show diverging trends, with Tidepletion and Zr enrichment in the till relative to the subjacentsaprolite. Zr concentrations conform with an assumption ofimmobility, suggesting that Ti may be mobile in this setting. Thehigh Zr concentrations in the tills potentially confirm the incor-poration of more highly weathered material than is represented bythe saprolite at its current level of erosion. The regularity of the CIAand organic carbon values in N3 tills suggests that the large vari-ability of CDF and s values (Fig. 6) and Ti and Zr concentrations(Fig. 5) might be due to incomplete mixing of till layers fromdifferent sources during deposition.

Within the saprolites, the CIA values for both A1 and N3 (Fig. 4a)are above 50%, confirming that some weathering has occurred. Thehigher CIA values for N3 saprolites are due to its more maficlithology, as opposed tomore intenseweathering, asmajor elementlosses remain modest. Positive CDF and negative tau values in thesaprolites also indicate weathering, with both saprolites showingloss of Si, Al, Fe, and Na (Fig. 4deh), and A1 being slightly moreintensely weathered.

4.3. 10Be inventories

10Be concentrations in the saprolite range from 1 to 47 � 106

atoms g�1 and decrease exponentially with depth below the tillcontact (Table 1). The 10Be concentrations in the Parkajoki sapro-lites are low in comparison to saprolites of Pleistocene age in theAppalachians, Virginia USA (Pavich et al., 1984; 3� 1012 atoms g�1),the Massif Central (Guillaume, 1997; 15 � 106 atoms g�1) and theGaspé Peninsula, Quebec, Canada (Bouchard and Pavich, 1989;w100 � 106 10Be atoms g�1). The total inventory of 10Be in thesaprolite with an estimated density of 1.8 g/cm2, in relation todelivery rate and radioactive decay, may have accumulated in aslittle as 3 ka at the ground surface. However the low 10Be concen-trations in the saprolite, together the widespread evidence ofreworking of saprolite into till mean that it is very likely that theoriginal weathering profile has been truncated by glacial erosion.The only till-covered, gruss-type saprolite available for comparison

Table 110Be inventories for Pit A1 (Anokangas) and Pit N3 (Naakakarhakka).

PRIME Lab# Sample# 10Be concentration,106 atoms g�1

AMS uncerta

201001533 A1-0 49 4201001534 A1-10 274 1201001535 A1-25 547 1201001536 A1-85 263 1201001537 A1-105 306 3201001538 A1-125 258 3201001539 A1-200 24 3201001540 A1-280 5.4 4201001541 A1-325 0.7 11201001542 A1-365 2.8 7

201001553 N3-315 200 3201001552 N3-310 604 2201001551 N3-300 151 3201001550 N3-285 339 3201001549 N3-245 217 2201001548 N3-200 268 3201001547 N3-180 252 4201001546 N3-150 47 4201001545 N3-110 14 4201001544 N3-50 6.8 4201001543 N3-0 3.8 3

to Parkajoki is fromQuebec, where comparable 10Be concentrationsoccur at depths of 4e5 m in saprolite below till (Bouchard andPavich, 1989).

10Be concentrations in the till are much higher and range from24 to 604� 106 atoms g�1. The highest 10Be concentrations occur innear-surface units, but without clear decreases down profile(Table 1). In comparison to tills in other areas (Fig. 7), the 10Beconcentrations in the Parkajoki tills are much higher than thosederived from fresh bedrock sources during the last glacial cycle.Concentrations are instead comparable to tills of Pliocene and EarlyPleistocene age in Minnesota, USA (Balco, 2004). The total inven-tory of 10Be in a till layer with an estimated density of 1.8 g/cm2

would require accumulation for>50 ka at the ground surface basedon delivery rates 1.3 � 106 atom/cm2 (Bouchard and Pavich, 1989).Lower modelled delivery rate of 0.8 � 106 atom/cm2 for Swedenwould require even longer accumulation of >80 ka (Willenbringand von Blanckenburg, 2010). 10Be concentrations found in the tillgreatly exceed the levels of 10Be that can have accumulated sincedeglaciation at w11 ka BP and during the w20 ka of the lastinterglacial (Forsström, L. and Punkari, M., 1997). Granite torsummits in the Parkajoki area have yielded comparable cosmogenic10Be exposure ages of 64e79 � 16 ka, which when matched to 26Alconcentration ratios and ice cover models indicate first exposure oftor summits at >485e765 ka (Stroeven et al., 2002). Tor exposurebefore the Middle Pleistocene is likely (Hättestrand and Stroeven,2002). The 10Be exposure ages and the common ice cover andpermafrost history for the Parkajoki tills indicate a similar age.Indeed, the dilution of 10Be concentrations in the till by the intro-duction of fresh material as clasts and granules requires that thepresent 10Be inventory includes material of Early Pleistocene andpossibly greater age. As meteoric 10Be is largely concentrated insoils, glacial erosion at these sites has failed to evacuate old soilmaterial and instead reworked this material into till.

5. Discussion

Information on the genesis and age of the tills and saprolitesin the Parkajoki area is provided by the stratigraphy andthe geochemistry of near-surface materials, including 10Beconcentrations.

inty, % Depth below surface Unit

0e10 Middle Weichselian till10e20 Middle Weichselian till25e35 Middle Weichselian till85e95 Middle Weichselian till

105e115 Middle Weichselian till125e130 Middle Weichselian till200e210 Diorite Saprolite280e290 Diorite Saprolite325e335 Diorite Saprolite365e375 Weathered diorite passing

down into fractured, fresh rock0e5 Soil5e10 Middle Weichselian till

15e20 Middle Weichselian till30e35 Middle Weichselian till70e75 Middle Weichselian till

110e120 Middle Weichselian till135e140 Middle Weichselian till165e170 Intermediate igneous saprolite205e210 Intermediate igneous saprolite255e260 Intermediate igneous saprolite310e320 Intermediate igneous saprolite

Fig. 7. Published records of meteoric 10Be concentrations compared to this work.

K. Ebert et al. / Quaternary Geochronology 12 (2012) 11e22 19

Pit excavations have shown that old tills and saprolites existbeneath Weichselian tills in the Parkajoki area. Contrasts in clastweathering between the Weichselian and lower tills indicatea considerably greater age for the latter, especially as potentialweathering intervals without ice cover or permafrost were of shortduration in the Middle and Late Pleistocene in this area. Correla-tions with weathered tills in neighbouring parts of Finland (Hirvas,1991) indicate that the lower tills are Middle Pleistocene in age orolder. Similar associations of old tills and saprolite have been notedin the neighbouring Kittilä area in northern Finland (Peuraniemi,1989; Peuraniemi et al., 1997) and in north-east Scotland (Merritet al., 2003), other crystalline terrains where glacial erosion hasbeen very limited. The Parkajoki finds also provide further evidencethat an important record of Weichselian (Helmens et al., 2000) andpre-Weichselian glaciation (Hirvas, 1991) exists in the ice dividezone of northern Fennoscandia.

The Weichselian tills in Pits A1 and N3 visibly incorporate attheir base much debris reworked from the subjacent saprolite.However, there are significant differences between the sampled tilland saprolite in Ti and Zr concentrations, CIA values and 10Beconcentrations. We conclude that the main body of the till matrix isnot derived from erosion of the immediately subjacent saprolite.Instead, 10Be has been cannibalized from former soils that repre-sented the main stores of 10Be in the landscape before glacialerosion (Graly et al., 2010; Pavich et al., 1985). This situation is notcomparable to that where old tills have been buried and subject toradioactive decay in the post-burial period (Nishiizumi et al., 1989;Balco, 2004). Hence the 10Be concentrations in Parkajoki tills cannotbe used to date the tills directly. Nonetheless, our results show thatthe 10Be inventory in the till is very likely to include near-surfacematerial that was exposed before the Middle Pleistocene. Thisfinding is supported by the survival of weathered tills of MiddlePleistocene or older age at nearby sites. The retention of 10Bethrough multiple glacial cycles requires very weak glacial erosion(Staiger et al., 2006) and supports previous work that has identifiedParkajoki as an area of minimal glacial erosion (Hättestrand andStroeven, 2002). High 10Be concentrations in tills remote from icemargins can be regarded as a useful indicator of repeated, cold-based, non-erosive ice covers (Staiger et al., 2006).

The Parkajoki saprolites are of gruss-type. CIA values lie belowthe 60e70% values reported for grusses from further south inEurope and North America (Migo�n and Thomas, 2002) and so these

saprolites remain in the early stages of chemical weathering.Limited alteration may reflect a young age or truncation of theoriginal weathering profile. The first alterative is unlikely due to thecover of till which itself has experienced only limited weathering inthe post-glacial period. A very young age for the saprolite is alsoinconsistent with erosion and incorporation of saprolite materialinto the bases of Middle Pleistocene or older tills. The secondalternative is consistent with the presence of reworked saprolitematerial in the till. The original thickness of saprolite is difficult toestimate due to a lack of borehole data in the Parkajoki area, butthicknesses for gruss-type saprolites of >10 m have been reportedin numerous localities across Lapland (Elvhage and Lidmar-Bergström, 1987; Peuraniemi, 1989; Islam et al., 2002). Clay-richand highly kaolinitic weathering is confined to a small number ofsites in northern Finland (Lintinen and Al-Ani, 2005) and saprolitesare predominantly of gruss-type (Islam et al., 2002). Availablegeochemical evidence indicates that the Parkajoki saprolitesrepresent the lower parts of gruss weathering profiles.

The main unknowns when considering the age of the Parkajokisaprolites in terms of 10Be concentrations are the pre-glacial 10Beinventory, the rate of downward translocation of 10Be (Balco, 2004),and the depth of glacial erosion. The pre-glacial 10Be inventories ofsaprolites in former glaciated regions have received very limitedattention (Bouchard and Pavich, 1989). Indeed, studies of weath-ering profiles of gruss-type weathering profiles remain few evenbeyond glacial limits (Fifield et al., 2010; Graly et al., 2010;Bouchard and Pavich, 1989; Pavich et al., 1985; Stanford et al.,2002). 10Be is known to be mobile in soils (Jungers et al., 2009;Pavich et al., 1985). The existence of meteoric 10Be at depths of 15min saprolites in the temperate zone (Pavich et al., 1985) and to evengreater depths in the tropical zone (Graly et al., 2010) impliestranslocation to greater depths, although transfer across thesoilesaprolite boundary is limited where clayey horizons capsaprolite (Jungers et al., 2009). It is unlikely, however, that the low10Be concentrations in the Parkajoki saprolites represent trans-location. Lateral translocation is unlikely at these flat sites. Down-ward translocation from the 1.5e2.0 m thick till is possible, butthere are reasons why the unconformity between the till andsaprolite probably represents a division between two separate 10Besystems. Firstly, weathering in the till and transfer of mobile basiccations from the till into the saprolite has been very limited in the11 ka of the present interglacial period. Similarly limited weath-ering is likely during earlier interglacials in the Middle Pleistocene.Secondly, the sharp differences in 10Be concentration between thetill and the saprolite are matched by differences in CIA, CDF and svalues, both indicating that different weathering systems exist inthe till and saprolite. Hence we suggest that the 10Be within thesaprolites mainly represents accumulation prior to glacial erosion.Comparison with grusses in Quebec (Bouchard and Pavich, 1989)indicates that such glacial erosion has been no more than a fewmetres, a finding that is in agreement with the recycling andretention of 10Be from former soils, near-surface sediments andsaprolite in the overlying till.

A lower limit to the age of the Parkajoki saprolite is provided byoverlying tills. There is no evidence for weathering occurringbeneath till covers and incorporation of saprolite material indicatesinstead that weathering occurred before glacial erosion. The oldestoverlying tills are Early to earlyMiddle Pleistocene in age and so thesaprolites must be of this age or older. However, the 10Be content ofthe saprolite is very low and the CIA index also indicates limitedweathering. Available evidence for substantial geochemical fluxesproduced by chemical weathering in the Arctic during the Holocene(Allen et al., 2001; Zakharova et al., 2007) implies that chemicalweathering was significant during earlier interglacials. Withw1 Ma available for weathering under conditions similar to those

K. Ebert et al. / Quaternary Geochronology 12 (2012) 11e2220

of today during the Early Pleistocene, formation of saprolites1e10 m deep can be accommodated within this timeframe. AnEarly Pleistocene age for saprolite weathering would be consistentwith the similar style of grussification observed in boulders in oldtills at Parkajoki.

An upper limit can be derived by modelling the meteoric 10Beconcentration depth profiles for different scenarios. One possi-bility is that that the Parkajoki saprolite originally had concen-trations equivalent to those reported for saprolites beyond glaciallimits (Pavich et al., 1985) but that when saprolite formationended due to burial by till the 10Be has substantially decayed. Weassess the potential upper limiting age and erosion history of thesaprolite in this case. The minimum age of the saprolite (Fig. 8) canbe estimated by assuming that the modern tillesaprolite boundarywas the saprolite surface while meteoric 10Be was accumulating,and that the surface concentration was equivalent to theminimum surface value recorded in other saprolites (w1 � 108).Based on these assumptions, the Parkajoki saprolites are bestmodelled by an age of 2 Ma. The sedimentological and chemicalevidence suggest that at least some erosion of the saprolite hasoccurred. In order to account for this, and to estimate themaximum potential depth of saprolite stripping, we apply the

Fig. 8. Concentrations of 10Be with depth below the till in the saprolites of the 2sampled excavations. (A) The black and grey lines show the 10Be concentration profilesafter 1, 2, and 3 Ma of decay based on the assumptions of no erosion and an initialconcentration that is equal to the lowest concentration (hence these are likelyminimum ages) measured in other saprolites. (B). The solid lines show the concen-tration profiles assuming 50, 100, 150, and 250 cm erosion from the surface of thesaprolites after 5 Ma decay assuming an initial concentration equal to the maximumconcentration (hence maximum erosion depths) measured in other saprolites. Thedashed lines are the ranges assuming 1 and 10 Ma decay. Note that in the case of morethan 250 cm of erosion, the 10Be concentrations are significantly lower than themeasured values, even assuming no decay.

same approach with the exception that we use the maximumvalue recorded in other saprolites (w1 � 1010). The best fit in thiscase would suggest that about 1.5 m of saprolite have been erodedfrom a w5 Ma saprolite. The measured 10Be concentrations for thetwo saprolites would not be compatible with erosion depths ofgreater than 2.5 m, given the assumptions above. However, as theoriginal meteoric 10Be inventories of the Parkajoki saprolitesremain unknown and may have been much less than those usedhere, the modelling merely indicates plausible upper age limits forthe Parkajoki saprolites.

In order to use meteoric 10Be to more closely date saprolites informer glaciated areas, it is probably necessary to extend the closedsystemmethod used for soils (Barg et al., 1997; Schiller et al., 2009).Firstly it is necessary to identify sites where saprolites retain tracesof soils formed at the time of rock weathering, thereby demon-strating negligible glacial erosion. The saprolite also should besealed from the translocation of 10Be by thick glacial deposits. Thatsuch sites exist is implied by the preservation of interglacial andinterstadial soils and organic deposits within glacial sequences.Secondly, existing studies of meteoric 10Be in soils are almostexclusively confined to the extra-glacial zone and there is a pressingneed to examine more till sequences, gruss-type saprolites andsoils in formerly glaciated areas to better understand 10Besystematics in low temperature chemical weathering environ-ments over long time periods. This, together with improvedunderstanding of long-term delivery rates of meteoric 10Be (Gralyet al., 2011) should in turn allow estimation of original 10Beinventories in saprolites and so lead to determinations of age using10Be decay in closed systems.

6. Conclusion

The Parkajoki area retains a till stratigraphy that provides animportant record of Middle Pleistocene or earlier glaciation by theFennoscandian ice sheet. Despite multiple glaciation, glacialerosion has been very limited due to cold-based ice covers. Previouswork has demonstrated negligible glacial erosion of Parkajoki torsummits in the Middle and Late Pleistocene. We find that tilldeposited in the last glacial cycle in this area has concentrations ofmeteoric 10Be equal to those of Early Pleistocene and Pliocene tillsin North America. The high 10Be concentrations in near-surface tillsat Parkajoki amount to >52 ka of surface accumulation and havebeen derived from glacial reworking of soils that predate theMiddle Pleistocene. The retention of 10Be in the till layer and inunderlying saprolite indicates the removal of only a few metres ofsurface material by glacial erosion. Parkajoki is confirmed as a typearea for minimal glacial erosion on the northern Fennoscandianshield.

The precise age of saprolite in the study area remains uncertain.The gruss-type weathering profiles have been truncated by glacialerosion and must predate overlying Middle Pleistocene or oldertills. The weathering however need not be of great age asgeochemistry indicates only limited alteration and the grussifica-tion of boulders in old tills is of similar character to that of thebedrock. The Parkajoki saprolites have lower concentrations ofmeteoric 10Be than all other saprolites measured to date in theliterature. Modelling of saprolite age based on meteoric 10Beinventories from extra-glacial saprolites and decay of 10Be ina closed system beneath till indicates an upper age limit of 5 Ma butit is likely that the true ages of the saprolites are considerablyyounger and the Early Pleistocene interglacials provided perhaps1 Ma for deep weathering of bedrock. There is a pressing need forfurther studies of meteoric 10Be inventories in soils, tills andsaprolites in formerly glaciated areas to allow dating using 10Bedecay to be extended to high latitudes.

K. Ebert et al. / Quaternary Geochronology 12 (2012) 11e22 21

Acknowledgements

We thank the Geological Survey of Sweden for funding thisstudy. JKW thanks the Humboldt Foundation for postdoctoralfunding, Marc Caffee for AMS measurements and Friedhelm vonBlanckenburg for help designing the Beryllium leaching strategy.AMH thanks the Carnegie Trust for the Universities of Scotland forits support of fieldwork. This paper has benefitted considerablyfrom the careful criticism of referees J Graly and R Grün.

Editorial handling by: D. Bourlés

References

Allen, C.E., Darmody, R.G., Thorn, C.E., Dixon, J.C., Schlyter, P., 2001. Clay mineralogy,chemical weathering and landscape evolution in Arctic-Alpine Sweden. Geo-derma 99 (3e4), 277e294.

André, M.-F., 2002. Rates of postglacial rock weathering on glaciallyscoured outcrops (AbiskoeRiksgränsen area, 68�N). Geografiska Annaler 84A,139e150.

Balco, G., Rovey, C.W., 2010. Absolute chronology for major Pleistocene advances ofthe Laurentide ice sheet. Geology 38, 795e798.

Balco, G., Stone, J.O.H., Jennings, C., 2005. Dating Plio-Pleistocene glacial sedimentsusing the cosmic-ray-produced radionuclides Be-10 and Al-26. AmericanJournal of Science 305, 1e41.

Balco, G.A., 2004. The sedimentary record of subglacial erosion beneath the Lau-rentide Ice Sheet, Ph.D. thesis, University of Washington.

Barg, E., Lal, D., Pavich, M., Caffee, M., Southon, J., 1997. Beryllium geochemistry insoils: evaluation of 10Be/9Be ratios in authigenic minerals as a basis for agemodels. Chemical Geology 140 (3e4), 237e258.

von Blanckenburg, F., Hewawasam, T., Kubik, P.W., 2004. Cosmogenic nuclideevidence for low weathering and denudation in the wet, tropical highlands ofSri Lanka. Journal of Geophysical Research 109 (F03008), 1e22.

Bouchard, M., Pavich, M.J., 1989. Characteristics and significance of pre-Wisconsinansaprolites in the northern Appalachians. Zeitschrift für Geomorphologie Sup-plementbände 72, 125e138.

Bourlès, D., Raisbeck, G.M., Yiou, F., 1989. 10Be and 9Be in marine sediments andtheir potential for dating. Geochimica et Cosmochimica Acta 53, 443e452.

Bourlés, D., 1988. Etude de la géochimie de l’isotope cosmogénique 10Be et de sonisotope stable 9Be en milieu oceanique. Application à la datation des sédimentsmarins. Ph.D. thesis, Univ. Paris XI.

Brimhall, G.H., Dietrich, W.E., 1987. Constitutive mass balance relations betweenchemical composition, volume, density, porosity, and strain in metasomatichydrochemical systems: results on weathering and pedogenesis. Geochimica etCosmochimica Acta 51, 567e587.

Brimhall, G.H., Christopher, L.J., Ford, C., Bratt, J., Taylor, G., Warin, O., 1991. Quan-titative geochemical approach to pedogenesis: importance of parent materialreduction, volumetric expansion, and eolian influx in lateritization. Geoderma51, 51e91. doi:10.1016/0016-7061(91)90066-3.

Brown, T.A., Nelson, D.E., Southon, J.R., Vogel, J.S., 1987. 10Be production rate vari-ations as recorded in a mid-latitude lake sediment. Nuclear Instruments andMethods in Physics Research B29, 232e237.

Chmeleff, J., von Blanckenburg, F., Kossert, K., Jackob, D., 2010. Determination of the10Be half-life by multicollector ICP-MS and liquid scintillation counting. NuclearInstruments and Methods in Physics Research Section B 268, 192e199.

Ebert, K., Hättestrand, C., 2010. The impact of Quaternary glaciations on inselbergsin northern Sweden. Geomorphology 115, 56e66.

Ebert, K., Hättestrand, C., Hall, A.M., Alm, G., 2011. DEM identification of macroscalestepped relief in arctic northern Sweden. Geomorphology 132, 339e350.

Ebert, K., Hall, A.M., Hättestrand, C., in press. Pre-glacial landforms on a glaciatedshield: the inselberg plains of northern Sweden. Norwegian Journal of Geology.

Elvhage, C., Lidmar-Bergström, K., 1987. Some working hypotheses on thegeomorphology of Sweden in the light of a new relief map. Annals of Geography69, 343e358.

Feininger, T., 1971. Chemical Weathering and Glacial Erosion and the Origin of Till,United States Geological Survey Professional Paper So-CC, pp. 65e81.

Fifield, L.K., Wasson, R.J., Pillans, B., Stone, J.O.H., 2010. The longevity of hillslope soilin SE and NW Australia. Catena 81, 32e42.

Forsström, L., Punkari, M., 1997. Initiation of the last glaciation in northern Europe.Quaternary Science Reviews 16 (10), 1197e1215.

Geological Survey of Sweden, 2011. http://maps2.sgu.se/kartgenerator/en/maporder.html (accessed 04.06.11.).

Glasser, N.F., Hall, A.M., 1997. Calculating Quaternary erosion rates in North EastScotland. Geomorphology 20, 29e48.

Graly, J.A., Bierman, P.R., Reusser, L.J., Pavich,M.J., 2010.Meteoric 10Be in soil profilesea global meta-analysis. Geochimica et Cosmochimica Acta 74 (23), 6814e6829.

Graly, J.A., Reusser, L.J., Bierman, P.R., 2011. Short and long-term delivery rates ofmeteoric 10Be to terrestrial soils. Earth and Planetary Science Letters 302 (3e4),329e336.

Guelke-Stelling, M., von Blanckenburg, F., 2012. Fe isotope fractionation caused bytranslocation of iron during growth of bean and oat as models of strategy I andII plants. Plant and Soil 352 (1e2), 217e231. Pre-publication version.

Guillaume, P., 1997. Bilan altération-ablation en moyenne montagne de socle:apport de la datation par le 10Be (Monts Dore, Massif central français). Géo-morphologie 3, 227e236.

Hall, A.M., Sugden, D.E., 1987. Limited modification of mid-latitude landscapes byice sheets: the case of north-east Scotland. Earth Surface Processes and Land-forms 12, 531e542.

Hall, A.M., Mellor, T., Wilson, M.J., 1989. The clay mineralogy and age of deeplyweathered rock in north-east Scotland. Zeitschrift für GeomorphologieSupplement Band 72, 97e108.

Hall, A.M., 1985. Cenozoic weathering covers in Buchan, Scotland, and theirsignificance. Nature 315, 392e395.

Hall, A.M., 1986. Deep weathering patterns in north-east Scotland and theirgeomorphological significance. Zeitschrift für Geomorphologie 30, 407e422.

Hättestrand, C., Stroeven, A., 2002. A relict landscape in the centre of Fennoscandianglaciation: geomorphological evidence of minimal Quaternary glacial erosion.Geomorphology 44, 127e143.

Hättestrand, C., 1998. The glacial geomorphology of Central and Northern Sweden.Sveriges Geologiska Undersökning Ca 85, 1e47.

Helmens, K.F., Räsänen, M.E., Johansson, P., Jungner, H., Korjonen, K., 2000. The lastInterglacialeGlacial cycle in NE Fennoscandia: a nearly continuous record fromSokli (Finnish Lapland). Quaternary Science Reviews 19, 1605e1623.

Hirvas, H., 1991. Pleistocene stratigraphy of Finnish Lapland. Bulletin of theGeological Society of Finland 354, 1e123.

Islam, M.R., Peuraniemi, V., Aario, R., Rojstaczer, S., 2002. Geochemistry andmineralogy of saprolite in Finnish Lapland. Applied Geochemistry 17, 885e902.

Jungers, M.C., Bierman, P.R., Matmon, A., Nichols, K., Larsen, J., Finkel, R., 2009.Tracing hillslope sediment production and transport with in situ and meteoric10Be. Journal of Geophysical Research 114 (F4), F04020.

Kleman, J., Stroeven, A.P., 1997. Preglacial surface remnants and Quaternary glacialregimes in northwestern Sweden. Geomorphology 19, 35e54.

Kleman, J., Hättestrand, C., Borgström, I., Stroeven, A.P., 1997. Fennoscandianpalaeoglaciology reconstructed using a glacial geological inversion model.Journal of Glaciology 43, 283e299.

Kleman, J., Stroeven, A.P., Lundqvist, J., 2008. Patterns of Quaternary ice sheeterosion and deposition in Fennoscandia and a theoretical framework forexplanation. Geomorphology 97, 73e90.

Kleman, J., 1994. Preservation of landforms under ice sheets and ice caps.Geomorphology 9, 19e32.

Korschinek, G., Bergmaier, A., Faestermann, T., Gertmann, U.C., Knie, K., Rugel, G.,Wallner, A., Dillmann, I., Dollinger, G., Lierse von Gosstomski, Ch, Kossert, K.,Maiti, M., Poutivtsev, M., Remmert, A., 2010. A new value for the 10Be half-life byheavy-ion elastic recoil detection and liquid scintillation counting. NuclearInstruments and Methods in Physics Research Section B 268, 187e191.

Lal, D., Peters, B., 1967. Cosmic ray produced radioactivity on earth. Handbuch derPhysik XLVI (2), 551e612.

Lal, D., 1991. Cosmic ray labelling of erosion surfaces: in situ nuclide productionrates and erosion models. Earth and Planetary Science Letters 104, 424e439.

Land, M., Ingri, J., Öhlander, B., 1999. Past and present weathering rates in northernSweden. Applied Geochemistry 14, 761e774.

Lidmar-Bergström, K., Olsson, S., Olvmo, M., 1997. Palaeosurfaces and associatedsaprolites in southern Sweden. In: Widdowson, M. (Ed.), Palaeosurfaces:Recognition, Reconstruction and Palaeoenvironmental Interpretation. TheGeological Society, London, pp. 95e124.

Lidmar-Berström, K., 1996. Long term morphotectonic evolution in Sweden.Geomorphology 16, 33e59.

Lintinen, P., Al-Ani, T., 2005. The Vittajänkä kaolin deposit, Salla, Finnish Lapland.Geological Survey of Finland, Special Paper 38, 41e47.

Lundqvist, J., 1985. Deep weathering in Sweden. Fennia 163, 287e292.Merrit, J., Auton, C.A., Connell, E.R., Hall, A.M., Peacock, J.D., 2003. Quaternary

Geology and Landscape Evolution of North-east Scotland. In: Memoir of theBritish Geological Survey. NERC.

Migo�n, P., Lidmar-Bergström, K., 2001. Weathering mantles and their significancefor geomorphological evolution of central and northern Europe since theMesozoic. Earth Science Reviews 56, 285e324.

Migo�n, P., Thomas, M.F., 2002. Grus weathering mantles e problems of interpre-tation. Catena 49, 5e24.

Mokma, D.L., Yli-Halla, M., Lindqvist, K., 2004. Podzol formation in sandy soils ofFinland. Geoderma 120, 259e272.

Nesbitt, H., Young, G., 1982. Early Proterozoic climates and plate motions inferredfrom major element chemistry of lutites. Nature 299, 715e717.

Nishiizumi, K., Imamura, M., Caffee, M., Southon, J.R., Finkel, R.C., McAninch, J., 2007.Absolute calibration of 10Be AMS standards. Nuclear Instruments and Methodsin Physics Research Section B 258, 403e413. http://www.sciencedirect.com/science?_ob¼PublicationURL&_tockey¼%23TOC%235315%232007%23997419997%23651312%23FLA%23&_cdi¼5315&_pubType¼J&view¼c&_auth¼y&_acct¼C000050221&_version¼1&_urlVersion¼0&_userid¼10&md5¼79004f97a0c3cafa5d69c271fb2bae15.

Nordkalott Project, 1986. Map of Quaternary Geology, Sheet 4: Quaternary Stra-tigraphy, Northern Fennoscandia, 1:1 Mill. Geological Surveys of Finland,Norway and Sweden.

Norton, K., 2008. Response of the landscape in the Swiss Alps to the late Glacial toHolocene climate transition. Ph.D thesis, University of Hannover.

Öhlander, B., Land, M., Ingri, J., Widerlund, A., 1996. Mobility of rare earthelements during weathering of till in northern Sweden. Applied Geochemistry11, 93e99.

K. Ebert et al. / Quaternary Geochronology 12 (2012) 11e2222

Paasche, Ø., Strømsøe, J.R., Dahl, S.O., Linge, H., 2006. Weathering characteristics ofarctic islands in northern Norway. Geomorphology 82 (3e4), 430e452.

Pavich, M.J., Brown, L., Klein, J., Middleton, R., 1984. 10Be accumulation in a soilchronosequence. Earth and Planetary Science Letters 68, 198e204.

Pavich,M.J., Brown, L., Valette-Silver, J.N., Klein, J., Middleton, R.,1985. 10Be analysis ofa Quaternary weathering profile in the Virginia Piedmont. Geology 13, 39e41.

Peuraniemi, V., Aario, R., Pulkkinen, P., 1997. Mineralogy and geochemistry of theclay fraction of till in northern Finland. Sedimentary Geology 111, 313e327.

Peuraniemi, V., 1989. Till stratigraphy and ice movement directions in the Kittiläarea, Finnish Lapland. Boreas 18, 145e157.

Pitkäranta, R., 2009. Pre-late Weichselian podzol soil, permafrost features andlithostratigraphy at Penttilänkangas, western Finland. Bulletin of the GeologicalSociety of Finland 81, 53e74.

Price, J.R., Velbel, M.A., 2003. Chemical weathering indices applied to weatheringprofiles developed on heterogeneous felsic metamorphic parent rocks. Chem-ical Geology 202, 397e416.

Railsback, L.B., 2003. An earth scientist’s periodic table of the elements and theirions. Geology 31, 737e740.

Rapp, A., 1982. Zonation of permafrost indicators in Swedish Lappland. GeografiskTidsskrift 82, 37e38.

Riebe, C.S., Kirchner, J.W., Granger, D.E., Finkel, R., 2001a. Minimal climatic controlon erosion rates in the Sierra Nevada, California. Geology 29, 447e450.

Riebe, C.S., Kirchner, J.W., Granger, D.E., Finkel, R., 2001b. Strong tectonic and weakclimatic control of long-term chemical weathering rates. Geology 29, 511e514.

Robertsson, A.-M., Lundqvist, J., Brunnberg, L., 2005. Dark clayey till in central andnorthern Sweden e microfossil content and stratigraphical importance. 127,169e178.

Robertsson, A.-M., 1997. Reinvestigation of the interglacial pollen flora at Leveä-niemi, Swedish Lapland. Boreas 26, 81e89.

Roy, M., Clark, P.U., Barendregt, R.W., Glasmann, J.R., Enkin, R.J., 2004. Glacial stra-tigraphy and paleomagnetism of late Cenozoic deposits of the north-centralUnited States. Geological Society of America Bulletin 116 (1), 30e41.

Ruddiman, W.F., Raymo, M., 1988. Northern hemisphere climate regimes during thelast 3 Ma. Philosophical Transactions of the Royal Society of London B318,411e430.

Schiller, M., Dickinson, W., Ditchburn, R., Graham, I., Zondervan, A., 2009. Atmo-spheric 10Be in an Antarctic soil: Implications for climate change. Journal ofGeophysical Research 114 (F1), F01033.

Staiger, J.K.W., Gosse, J.C., Johnson, J.V., Fastook, J., Gray, J.T., Stockli, D.F., Stockli, L.,2005. Quaternary relief generation by polythermal glacier ice. Earth SurfaceProcesses and Landforms 30 (9), 1145e1159.

Staiger, J.W., Gosse, J., Little, E.C., Utting, D.J., Finkel, R., Johnson, J.V., Fastook, J.,2006. Glacial erosion and sediment dispersion from detrital cosmogenic nuclideanalyses of till. Quaternary Geochronology 1, 29e42.

Stanford, S.D., Ashley, G.M., Russell, E.W.B., Brenner, G.J., 2002. Rates andpatterns of late Cenozoic denudation in the northernmost Atlantic CoastalPlain and Piedmont. Geological Society of America Bulletin 114 (11),1422e1437.

Stroeven, A., Fabel, D., Hättestrand, C., Harbor, J., 2002. A relict landscape in thecentre of Fennoscandian glaciation: cosmogenic radionuclide evidence of torspreserved through multiple glacial cycles. Geomorphology 44, 145e154.

White, A.F., Blum, A.E., Schulz, M.S., Vivit, D.V., Stonestrom, D.A., Larsen, Matthew,Murphy, S.F., Eberl, D., 1998. Chemical weathering in a tropical watershed,Luquillo Mountains, Puerto Rico: I. Long-term versus short-term weatheringfluxes. Geochimica et Cosmochimica Acta 62, 209e226.

Willenbring, J.K., von Blanckenburg, F., 2010. Meteoric cosmogenic beryllium-10adsorbed to river sediment and soil: applications for earth-surface dynamics.Earth-Science Reviews 98, 105e122.

Wråk, W., 1908. Bidrag till Skandinaviens reliefkronologi. Ymer 28 (141e191),254e300.

Zakharova, E.A., Pokrovsky, O.S., Dupré, B., Gaillardet, J., Efimova, L.E., 2007.Chemical weathering of silicate rocks in Karelia region and Kola peninsula, NWRussia: assessing the effect of rock composition, wetlands and vegetation.Chemical Geology 242 (1e2), 255e277.