Uranium concentrations and isotope ratios Bahamas seawater and ODP holes pore-water
The geometry, timing, and rate of fluid-flow through carbonate margins and platforms is not well constrained. In this study, we use U concentrations and isotope ratios measured on small volumes of pore-water from Bahamas slope sediment, coupled with existing chlorinity data, to place constraints on...
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ftpangaea:oai:pangaea.de:doi:10.1594/PANGAEA.711398 2024-09-15T18:24:30+00:00 Uranium concentrations and isotope ratios Bahamas seawater and ODP holes pore-water Henderson, Gideon M Slowey, Niall C Haddad, Geoffrey A MEDIAN LATITUDE: 23.987300 * MEDIAN LONGITUDE: -78.123000 * SOUTH-BOUND LATITUDE: 23.614000 * WEST-BOUND LONGITUDE: -79.235700 * NORTH-BOUND LATITUDE: 24.562900 * EAST-BOUND LONGITUDE: -76.083300 * DATE/TIME START: 1996-03-12T15:02:00 * DATE/TIME END: 1996-04-10T10:10:00 1999 application/zip, 3 datasets https://doi.pangaea.de/10.1594/PANGAEA.711398 https://doi.org/10.1594/PANGAEA.711398 en eng PANGAEA https://doi.pangaea.de/10.1594/PANGAEA.711398 https://doi.org/10.1594/PANGAEA.711398 CC-BY-3.0: Creative Commons Attribution 3.0 Unported Access constraints: unrestricted info:eu-repo/semantics/openAccess Supplement to: Henderson, Gideon M; Slowey, Niall C; Haddad, Geoffrey A (1999): Fluid flow through carbonate platforms: constraints from 234U/238U and Cl[-] in Bahamas pore-waters. Earth and Planetary Science Letters, 169(1-2), 99-111, https://doi.org/10.1016/S0012-821X(99)00065-5 166-1005A 166-1009A DRILL Drilling/drill rig Joides Resolution Leg166 North Atlantic Ocean Ocean Drilling Program ODP dataset publication series 1999 ftpangaea https://doi.org/10.1594/PANGAEA.71139810.1016/S0012-821X(99)00065-5 2024-08-21T00:02:25Z The geometry, timing, and rate of fluid-flow through carbonate margins and platforms is not well constrained. In this study, we use U concentrations and isotope ratios measured on small volumes of pore-water from Bahamas slope sediment, coupled with existing chlorinity data, to place constraints on the fluid-flow in this region and, by implication, other carbonate platforms. These data also allow an assessment of the behaviour of U isotopes in an unusually well constrained water-rock system. We report pore-water U concentrations which are controlled by dissolution of high-U organic material at shallow depths in the sediment and by reduction of U to its insoluble 4+ state at greater depths. The dominant process influencing pore-water (234U/238U) is alpha recoil. In Holocene sediments, the increase of pore-water (234U/238U) due to recoil provides an estimate of the horizontal flow rate of 11 cm/year, but with considerable uncertainty. At depths in the sediment where conditions are reducing, features in the U concentration and (234U/238U) profiles are offset from one another which constrains the effective diffusivity for U in these sediments to be c. 1-2 * 10**-8 cm**2/s. At depths between the Holocene and these reducing sediments, pore-water (234U/238U) values are unusually low due to a recent increase in the dissolution rate of grain surfaces. This suggests a strengthening of fluid flow, probably due to the flooding of the banks at the last deglaciation and the re-initiation of thermally-driven venting of fluid on the bank top and accompanying recharge on the slopes. Interpretation of existing chlorinity data, in the light of this change in flow rate, constrain the recent horizontal flow rate to be 10.6 ( 3.4) cm/year. Estimates of flow rate from (234U/238U) and Cl[-] are therefore in agreement and suggest flow rates close to those predicted by thermally-driven models of fluid flow. This agreement supports the idea that flow within the Bahamas Banks is mostly thermally driven and suggests that flow rates on the ... Other/Unknown Material North Atlantic PANGAEA - Data Publisher for Earth & Environmental Science ENVELOPE(-79.235700,-76.083300,24.562900,23.614000) |
institution |
Open Polar |
collection |
PANGAEA - Data Publisher for Earth & Environmental Science |
op_collection_id |
ftpangaea |
language |
English |
topic |
166-1005A 166-1009A DRILL Drilling/drill rig Joides Resolution Leg166 North Atlantic Ocean Ocean Drilling Program ODP |
spellingShingle |
166-1005A 166-1009A DRILL Drilling/drill rig Joides Resolution Leg166 North Atlantic Ocean Ocean Drilling Program ODP Henderson, Gideon M Slowey, Niall C Haddad, Geoffrey A Uranium concentrations and isotope ratios Bahamas seawater and ODP holes pore-water |
topic_facet |
166-1005A 166-1009A DRILL Drilling/drill rig Joides Resolution Leg166 North Atlantic Ocean Ocean Drilling Program ODP |
description |
The geometry, timing, and rate of fluid-flow through carbonate margins and platforms is not well constrained. In this study, we use U concentrations and isotope ratios measured on small volumes of pore-water from Bahamas slope sediment, coupled with existing chlorinity data, to place constraints on the fluid-flow in this region and, by implication, other carbonate platforms. These data also allow an assessment of the behaviour of U isotopes in an unusually well constrained water-rock system. We report pore-water U concentrations which are controlled by dissolution of high-U organic material at shallow depths in the sediment and by reduction of U to its insoluble 4+ state at greater depths. The dominant process influencing pore-water (234U/238U) is alpha recoil. In Holocene sediments, the increase of pore-water (234U/238U) due to recoil provides an estimate of the horizontal flow rate of 11 cm/year, but with considerable uncertainty. At depths in the sediment where conditions are reducing, features in the U concentration and (234U/238U) profiles are offset from one another which constrains the effective diffusivity for U in these sediments to be c. 1-2 * 10**-8 cm**2/s. At depths between the Holocene and these reducing sediments, pore-water (234U/238U) values are unusually low due to a recent increase in the dissolution rate of grain surfaces. This suggests a strengthening of fluid flow, probably due to the flooding of the banks at the last deglaciation and the re-initiation of thermally-driven venting of fluid on the bank top and accompanying recharge on the slopes. Interpretation of existing chlorinity data, in the light of this change in flow rate, constrain the recent horizontal flow rate to be 10.6 ( 3.4) cm/year. Estimates of flow rate from (234U/238U) and Cl[-] are therefore in agreement and suggest flow rates close to those predicted by thermally-driven models of fluid flow. This agreement supports the idea that flow within the Bahamas Banks is mostly thermally driven and suggests that flow rates on the ... |
format |
Other/Unknown Material |
author |
Henderson, Gideon M Slowey, Niall C Haddad, Geoffrey A |
author_facet |
Henderson, Gideon M Slowey, Niall C Haddad, Geoffrey A |
author_sort |
Henderson, Gideon M |
title |
Uranium concentrations and isotope ratios Bahamas seawater and ODP holes pore-water |
title_short |
Uranium concentrations and isotope ratios Bahamas seawater and ODP holes pore-water |
title_full |
Uranium concentrations and isotope ratios Bahamas seawater and ODP holes pore-water |
title_fullStr |
Uranium concentrations and isotope ratios Bahamas seawater and ODP holes pore-water |
title_full_unstemmed |
Uranium concentrations and isotope ratios Bahamas seawater and ODP holes pore-water |
title_sort |
uranium concentrations and isotope ratios bahamas seawater and odp holes pore-water |
publisher |
PANGAEA |
publishDate |
1999 |
url |
https://doi.pangaea.de/10.1594/PANGAEA.711398 https://doi.org/10.1594/PANGAEA.711398 |
op_coverage |
MEDIAN LATITUDE: 23.987300 * MEDIAN LONGITUDE: -78.123000 * SOUTH-BOUND LATITUDE: 23.614000 * WEST-BOUND LONGITUDE: -79.235700 * NORTH-BOUND LATITUDE: 24.562900 * EAST-BOUND LONGITUDE: -76.083300 * DATE/TIME START: 1996-03-12T15:02:00 * DATE/TIME END: 1996-04-10T10:10:00 |
long_lat |
ENVELOPE(-79.235700,-76.083300,24.562900,23.614000) |
genre |
North Atlantic |
genre_facet |
North Atlantic |
op_source |
Supplement to: Henderson, Gideon M; Slowey, Niall C; Haddad, Geoffrey A (1999): Fluid flow through carbonate platforms: constraints from 234U/238U and Cl[-] in Bahamas pore-waters. Earth and Planetary Science Letters, 169(1-2), 99-111, https://doi.org/10.1016/S0012-821X(99)00065-5 |
op_relation |
https://doi.pangaea.de/10.1594/PANGAEA.711398 https://doi.org/10.1594/PANGAEA.711398 |
op_rights |
CC-BY-3.0: Creative Commons Attribution 3.0 Unported Access constraints: unrestricted info:eu-repo/semantics/openAccess |
op_doi |
https://doi.org/10.1594/PANGAEA.71139810.1016/S0012-821X(99)00065-5 |
_version_ |
1810464868065607680 |