TY - JOUR
T1 - Al, Be and U-Th isotopes in blake outer ridge sediments
T2 - Implications for past changes in boundary scavenging
AU - Luo, Shangde
AU - Ku, Teh Lung
AU - Wang, Lei
AU - Southon, John R.
AU - Lund, Steve P.
AU - Schwartz, Martha
N1 - Funding Information:
We thank T.C. Johnson of Duke University for letting us sample core CH88-11P. Comments made by EPSL reviewers and editor greatly helped improve our presentation. This work was supported by the NSF Chemical Oceanography Program under grant OCE-9633469. [EB]
PY - 2001
Y1 - 2001
N2 - We have investigated the distributions of 26Al, 10Be, U-Th isotopes, and stable 27Al and 9Be in core CH88-11P (30°40′N, 74°41′W; 3337 m) from the Blake Outer Ridge (BOR) in the western North Atlantic, an area that is characterized by high terrigenous input. Results show authigenic 26Al/27Al of < 2-8 × 10-14 (atom/atom), authigenic 10Be/9Be of 0.5-2.6 × 10-8 (atom/atom), < 0.2-1.8 × 106 atoms/g of 26Al, and 5.3-15.1 × 108 atoms/g of 10Be in the core over the last glacial/interglacial cycle. These values, as well as total 230Thex/232Th and 10Be/9Be ratios, were all at their minima during the last glacial maximum (LGM), reflecting intensified terrestrial influx to the area. Aluminosilicate material (clays) in this influx preferentially scavenged 230Th over the two other particle-reactive nuclides, 26Al and 10Be, such that their boundary scavenging during LGM followed the order 230Th > 10Be > 26Al, as opposed to 10Be ≥ 230Th > 26Al in the Holocene. They appear at variance with the order 10Be > 26Al ≈ 230Th as would be predicted from the relative particle reactivities of the three species. These scavenging characteristics point to 10Be/26Al as a potentially more suitable proxy for paleoproductivity than 10Be/230Thex. Mass-balance considerations for 26Al and 10Be show a five-fold LGM-to-Holocene increase in deep-water circulation in the study area, with little change in ocean productivity except during the deglaciation when it increased noticeably.
AB - We have investigated the distributions of 26Al, 10Be, U-Th isotopes, and stable 27Al and 9Be in core CH88-11P (30°40′N, 74°41′W; 3337 m) from the Blake Outer Ridge (BOR) in the western North Atlantic, an area that is characterized by high terrigenous input. Results show authigenic 26Al/27Al of < 2-8 × 10-14 (atom/atom), authigenic 10Be/9Be of 0.5-2.6 × 10-8 (atom/atom), < 0.2-1.8 × 106 atoms/g of 26Al, and 5.3-15.1 × 108 atoms/g of 10Be in the core over the last glacial/interglacial cycle. These values, as well as total 230Thex/232Th and 10Be/9Be ratios, were all at their minima during the last glacial maximum (LGM), reflecting intensified terrestrial influx to the area. Aluminosilicate material (clays) in this influx preferentially scavenged 230Th over the two other particle-reactive nuclides, 26Al and 10Be, such that their boundary scavenging during LGM followed the order 230Th > 10Be > 26Al, as opposed to 10Be ≥ 230Th > 26Al in the Holocene. They appear at variance with the order 10Be > 26Al ≈ 230Th as would be predicted from the relative particle reactivities of the three species. These scavenging characteristics point to 10Be/26Al as a potentially more suitable proxy for paleoproductivity than 10Be/230Thex. Mass-balance considerations for 26Al and 10Be show a five-fold LGM-to-Holocene increase in deep-water circulation in the study area, with little change in ocean productivity except during the deglaciation when it increased noticeably.
UR - http://www.scopus.com/inward/record.url?scp=0035052184&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0035052184&partnerID=8YFLogxK
U2 - 10.1016/S0012-821X(00)00372-1
DO - 10.1016/S0012-821X(00)00372-1
M3 - Article
AN - SCOPUS:0035052184
SN - 0012-821X
VL - 185
SP - 135
EP - 147
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
IS - 1-2
ER -