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

Iron mineral structure, reactivity, and isotopic composition in a South Pacific Gyre ferromanganese nodule over 4 Ma

“…Although many processes contribute to the ultimate concentrations and ratios of 9 Be and 10 Be in ocean waters, two important general principles apply: (1) the delivery of 9 Be to oceans is primarily from terrestrial sediments and 10 Be was extracted from the nodule material through a series of acidification steps and cation column chromatography prior to being oxidized and analyzed by AMS. The methodology used here is modified from Ebert et al (2012). Approximately 0.25 g of ground nodule material was extracted in Teflon vessels with 6 M HCl and 250 lg of spiked 9 Be carrier at 110 C for 3 h. 4 ml of HF was added to the cation solution in two steps to bind excess Ca and Mg. After each HF addition step, 2 mL of ultrapure H2O2 was added to remove organics.…”

Late Cenozoic deep weathering patterns on the Fennoscandian shield in northern Finland: A window on ice sheet bed conditions at the onset of Northern Hemisphere glaciation

“…Postglacial weathering of till has affected only the most mobile minerals (Öhlander et al, 1996;Land et al, 1999), and till clasts remain largely fresh. Grussification of boulders occurs however in pre-Weichselian tills in northern Sweden (Ebert et al, 2012b) and western Finland (Pitkäranta, 2009a) and in interglacial palaeosols in northern Norway (Olsen, 1998) and indicates that limited gruss development may have continued in bedrock in the warm intervals of the middle Pleistocene in northern Fennoscandia. Gruss-type saprolites truncated by glacial erosion occur beneath preElsterian tills in northern Norway (Olsen, 1998), Saalian tills in northern Finland (Helmens et al, 2000), and early Pleistocene deposits in western Finland (Pitkäranta, 2009a) indicating that deeper grussification is of early Pleistocene or older age.…”

“…The youngest likely time period for the development of thick, gruss-type saprolites is during the Early Pleistocene, when ice-and largely permafrost-free conditions may have existed for a total of 1 Myr. First attempts to date grusses in northern Sweden using meteoric cosmogenic isotopes indicate formation in the time frame of 1-5 Ma (Ebert et al, 2012b). Sandy, gruss-type deep weathering in Finland and northwest Russia has been attributed to Neogene humid temperate climates because of the low degree of chemical alteration in these saprolites (Afanas'ev, 1968(Afanas'ev, , 1977Söderman, 1985).…”

“…Where ice sheets were warm-based and erosive and transport distances were consequently long, any saprolite materials were probably evacuated in early glacial phases to distant depocentres as indicated by progressive changes in clay and heavy mineralogy (Roy et al, 2004b) and cosmogenic nuclide inventories (Balco et al, 2003) in stacked till sequences that span the Pleistocene period in midwest USA. In contrast, where ice sheets were mainly cold-based and unerosive and transport distances were short (Sarala and Peuraniemi, 2007;Ebert et al, 2012b), material eroded from saprolite remained on the shield surface as an important component of glacial tills (Feininger, 1971;Bédard, 1993;Peuraniemi et al, 1997;Refsnider and Miller, 2010).…”

“…Isotope geochemistry of clay minerals may yield direct estimates of palaeotemperatures during weathering and indirect indications of the age of the weathered material (Gilg et al, 2013;Hall et al, 2015). Cosmogenic isotopes from weathering profiles and tills can constrain weathering age and depths of shield erosion (Matmon et al, 2003;Ebert et al, 2012b;Refsnider and Miller, 2013). The penetration in fracture zones of supergene mineralisation to depths of N100 m in shield rocks (Drake et al, 2009) also provides opportunities to date weathering episodes and to better constrain denudation rates over 1-10 My time frames (Dill et al, 2010a(Dill et al, , 2010b.…”