Examination of surface exposure age of Antarctic moraines using in situ produced [sup 10]Be and [sup 26]Al

Journal Article · Thu Aug 01 00:00:00 EDT 1991 · Geochimica et Cosmochimica Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(91)90103-C· OSTI ID:6967766

Brown, E T; Edmond, J M ^[1]; Raisbeck, G M; Yiou, F ^[2]; Kurz, M D; Brook, E J ^[3]

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1. Massachusetts Institute of Technology, Cambridge (United States)
2. Centre de Spectrometric Nucleaire et de Spectrometric de Masse, Campus Orsay (France)
3. Woods Hole Oceanographic Institution, MA (United States)

Concentrations of [sup 10]Be (t[sub 1/2] = 1.5 [times] 10[sup 6]y) and [sup 26]Al (t[sub 1/2] = 0.72 [times] 10[sup 6]y) have been determined by accelerator mass spectrometry (AMS) in a suite of quartz samples taken from sandstone boulders in several moraines in Arena Valley, a dry valley adjacent to the Taylor Glacier in the Quatermain Mountains, Southern Victoria Land, East Antarctica. These isotopes are produced in surficial quartz by cosmic ray spallation of O and Si. The concentrations in these samples ranged from 6.1 [times] 10[sup 5] to 3.0 [times] 10[sup 7] at g[sup [minus]1] for [sup 10]Be and from 9.4 [times] 10[sup 6] to 1.2 [times] 10[sup 8] at g[sup [minus]1] for [sup 26]Al, depending upon the extent of exposure at the surface. Production rates of 17[sub [minus]4][sup +16] at g[sup [minus]1]y[sup [minus]1] for [sup 10]Be and 113[sub [minus]16][sup +54] at g[sup [minus]1]y[sup [minus]1] for [sup 26]Al at 1300 m and 87[degree]S and a [sup 26]Al:[sup 10]Be production ratio of 6.5[sub [minus]1.3][sup +1.3] were calculated from the data. These values correspond to sea-level production rates at high geomagnetic latitude of 6.4 at g[sup [minus]1]y[sup [minus]1] and 41.7 at g[sup [minus]1]y[sup [minus]1] for [sup 10]Be and [sup 26]Al, respectively, consistent with determinations based on [approximately]11 Ky glacially polished surfaces in the Sierra Nevada in California. These production rates imply exposure ages for the various moraines ranging from 50 Ky to 2.5 My, in accordance with other geological evidence. The [sup 10]Be and [sup 26]Al ages of these rocks compare favorably with those found using a similar dating method based on in situ production of [sup 3]He.

• OSTI ID: 6967766
• Journal Information: Geochimica et Cosmochimica Acta; (United States), Vol. 55:8; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
ANTARCTICA
MORAINES
ISOTOPE DATING
ALUMINIUM 26
ANTARCTIC REGIONS
BERYLLIUM 10
COMPARATIVE EVALUATIONS
HELIUM 3
MASS SPECTROSCOPY
QUARTZ
SANDSTONES
AGE ESTIMATION
ALKALINE EARTH ISOTOPES
ALUMINIUM ISOTOPES
BERYLLIUM ISOTOPES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BETA-PLUS DECAY RADIOISOTOPES
EVALUATION
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
GEOLOGIC DEPOSITS
HELIUM ISOTOPES
ISOTOPES
LIGHT NUCLEI
MINERALS
NUCLEI
ODD-ODD NUCLEI
OXIDE MINERALS
POLAR REGIONS
RADIOISOTOPES
ROCKS
SECONDS LIVING RADIOISOTOPES
SEDIMENTARY ROCKS
SPECTROSCOPY
STABLE ISOTOPES
YEARS LIVING RADIOISOTOPES
580000* - Geosciences