Early investigators 1, 2 noticed that the isotope age curve for sedimentary carbon contains a neg... more Early investigators 1, 2 noticed that the isotope age curve for sedimentary carbon contains a negative displacement in δ 13 C at the Precambrian/Cambrian (PC/C) boundary, about 570 million years ago 3, which may have accompanied the profound biotic changes 4 from non-skeletal organisms to those with mineralized skeletons. Whereas the certainty of the δ 13 C shift across the elusive boundary has recently been confirmed from a number of localities 5–8, its interpretation remains largely controversial.
Description/Abstract Much attention has been given to Dorag-type dolomitization in recent years. ... more Description/Abstract Much attention has been given to Dorag-type dolomitization in recent years. Rodgers et al.(1982) used this model to explain dolomitization of the Niue Atoll, SW Pacific. The authors present here results of an ongoing isotope study of limestones and dolomites from a 170 foot core of the Niue Atoll and show that under present geochemical conditions mixing zone dolomitization (ie Dorag) is unlikely.
Abstract Hydrocarbon seeps on the Gulf of Mexico (GOM) seafloor are conventionally defined as" co... more Abstract Hydrocarbon seeps on the Gulf of Mexico (GOM) seafloor are conventionally defined as" cold", being characterized by hydrocarbon-rich fluid emissions at ambient sea floor temperature, mineralization of gas hydrates, precipitation of carbonates depleted in 13C, association with chemosynthetic fauna (mussel beds, tube worms etc.) and dominance of microbial processes fueled by venting hydrocarbons within the sediments.
The brevity of the historic coastal severe storm record (about 120 years) does not allow for stat... more The brevity of the historic coastal severe storm record (about 120 years) does not allow for statistically significant predictions of severe storm frequency and intensity caused by ongoing global climate changes. In this study we used shifts in C and N concentrations and d 13 C, d 15 N values from the sediment of Lake Shelby, AL, as multiple proxies for detecting severe storm-induced marine influxes.
Deep-sea mytilids (genus Bathymodiolus) harboring intracellular microbial symbionts are common in... more Deep-sea mytilids (genus Bathymodiolus) harboring intracellular microbial symbionts are common inhabitants of hydrothermal vents and hydrocarbon seeps. In general, growth rates of deep-sea biota are significantly slower than that of shallow water biota but whether or not the unique chemosymbiotic pathway of the bathymodiolids affects their growth rates is unknown. Here we present the results of a recent study whose objective is to determine the growth rates of bathymodiolids in their natural habitat.
ABSTRACT Radium activity and salinity have been determined in pore fluids from sediment cores tak... more ABSTRACT Radium activity and salinity have been determined in pore fluids from sediment cores taken during submersible dives in Garden Banks block# 382 and Mississippi Canyon block# 929 on the Gulf of Mexico slope. The 226 Ra activity and salinity of these pore fluids range from 0.43 x10 4 to 28.3 x10 4 dpm/100 L and 45 to 139^ pmil, respectively.
Hydrocarbon seepage in both liquid (crude oil) and gas (principally methane) forms has been amply... more Hydrocarbon seepage in both liquid (crude oil) and gas (principally methane) forms has been amply documented over the past decade from submersible dives on the northern Gulf of Mexico seafloor overlying salt diapirs. These seepage sites are inhabited by a remarkably diverse chemosynthetic fauna and are associated with massive carbonate buildups formed through bacterially-mediated processes of hydrocarbon oxidation coupled with sulfate reduction.
Description/Abstract Recent submersible research on the tops of salt diapirs at the shelf edge (/... more Description/Abstract Recent submersible research on the tops of salt diapirs at the shelf edge (/approximately/150 m) and upper slope (/approximately/300 m) confirms the occurrence of massive carbonate buildups (to/approximately/20 m relief) in these environmental settings.
Abstract: The world's largest insular phosphate deposit is found on Nauru, an uplifted coral atol... more Abstract: The world's largest insular phosphate deposit is found on Nauru, an uplifted coral atoll in the western equatorial Pacific. This deposit, which is draped over a dolomitized karstic surface, has an earthy pelletal texture; it is oolitic at its base and structureless in its upper part. The only phosphate mineral found is a carbonate fluorapatite with the stoichiometry Ca 10 (PO 4) 5.6 (CO 3) 0.6 F 1.6 (OH) 1-x. This mineral is slightly depleted in F-and CO 3 2-, relative to PO 4 3-, to be considered a true francolite.
High Na-HCO3 water in the stacked sand and clay aquifer system of Southeastern Louisiana was foun... more High Na-HCO3 water in the stacked sand and clay aquifer system of Southeastern Louisiana was found to be caused by a combination of bacterial oxidation of organic matter, ion exchange, and calcite dissolution. Dissolution of feldspar had little impact on water chemistry. Na and alkalinity are highly correlated as a result of calcite dissolution and subsequent exchange by clays of 2 Na ions for each Ca ion. Na content is a good indicator of the amount of calcite dissolved.
Abstract Carbon isotope equilibrium fractionations in the system CH 4-CO 2-HCO 3-CaCO 3 predict t... more Abstract Carbon isotope equilibrium fractionations in the system CH 4-CO 2-HCO 3-CaCO 3 predict that a solid carbonate phase whose carbon is derived from methane oxidation should yield a delta 13 C value which is about 50/00 more negative than the methane source. Methane is highly depleted in the 13 C isotope and therefore methane-derived carbonates are expected to yield delta 13 C values which are at least as negative as the methane source.
Niue Island is a large uplifted former atoll in the tropical South Pacific Ocean where karst is p... more Niue Island is a large uplifted former atoll in the tropical South Pacific Ocean where karst is pervasive in the carbonate cap. The elemental chemistry and stable isotopes of dripwaters from which speleothems are actively forming in two adjacent coastal caves were determined in order to identify their sources. This study also examined the differences and similarities between vadose (cave dripwaters) and phreatic groundwaters on the island.
Abstract Improved understanding of ocean-atmosphere interactions that control interdecadal ENSO v... more Abstract Improved understanding of ocean-atmosphere interactions that control interdecadal ENSO variability prompted recently a renewed interest in the acquisition of highly resolved proxy ENSO records. Corals possessing annual growth increments have extended the ENSO archive several centuries beyond the existing instrumental data but much longer records are needed to constrain the interdecadal periodicities and unravel their underlying causes.
Early investigators 1, 2 noticed that the isotope age curve for sedimentary carbon contains a neg... more Early investigators 1, 2 noticed that the isotope age curve for sedimentary carbon contains a negative displacement in δ 13 C at the Precambrian/Cambrian (PC/C) boundary, about 570 million years ago 3, which may have accompanied the profound biotic changes 4 from non-skeletal organisms to those with mineralized skeletons. Whereas the certainty of the δ 13 C shift across the elusive boundary has recently been confirmed from a number of localities 5–8, its interpretation remains largely controversial.
Description/Abstract Much attention has been given to Dorag-type dolomitization in recent years. ... more Description/Abstract Much attention has been given to Dorag-type dolomitization in recent years. Rodgers et al.(1982) used this model to explain dolomitization of the Niue Atoll, SW Pacific. The authors present here results of an ongoing isotope study of limestones and dolomites from a 170 foot core of the Niue Atoll and show that under present geochemical conditions mixing zone dolomitization (ie Dorag) is unlikely.
Abstract Hydrocarbon seeps on the Gulf of Mexico (GOM) seafloor are conventionally defined as" co... more Abstract Hydrocarbon seeps on the Gulf of Mexico (GOM) seafloor are conventionally defined as" cold", being characterized by hydrocarbon-rich fluid emissions at ambient sea floor temperature, mineralization of gas hydrates, precipitation of carbonates depleted in 13C, association with chemosynthetic fauna (mussel beds, tube worms etc.) and dominance of microbial processes fueled by venting hydrocarbons within the sediments.
The brevity of the historic coastal severe storm record (about 120 years) does not allow for stat... more The brevity of the historic coastal severe storm record (about 120 years) does not allow for statistically significant predictions of severe storm frequency and intensity caused by ongoing global climate changes. In this study we used shifts in C and N concentrations and d 13 C, d 15 N values from the sediment of Lake Shelby, AL, as multiple proxies for detecting severe storm-induced marine influxes.
Deep-sea mytilids (genus Bathymodiolus) harboring intracellular microbial symbionts are common in... more Deep-sea mytilids (genus Bathymodiolus) harboring intracellular microbial symbionts are common inhabitants of hydrothermal vents and hydrocarbon seeps. In general, growth rates of deep-sea biota are significantly slower than that of shallow water biota but whether or not the unique chemosymbiotic pathway of the bathymodiolids affects their growth rates is unknown. Here we present the results of a recent study whose objective is to determine the growth rates of bathymodiolids in their natural habitat.
ABSTRACT Radium activity and salinity have been determined in pore fluids from sediment cores tak... more ABSTRACT Radium activity and salinity have been determined in pore fluids from sediment cores taken during submersible dives in Garden Banks block# 382 and Mississippi Canyon block# 929 on the Gulf of Mexico slope. The 226 Ra activity and salinity of these pore fluids range from 0.43 x10 4 to 28.3 x10 4 dpm/100 L and 45 to 139^ pmil, respectively.
Hydrocarbon seepage in both liquid (crude oil) and gas (principally methane) forms has been amply... more Hydrocarbon seepage in both liquid (crude oil) and gas (principally methane) forms has been amply documented over the past decade from submersible dives on the northern Gulf of Mexico seafloor overlying salt diapirs. These seepage sites are inhabited by a remarkably diverse chemosynthetic fauna and are associated with massive carbonate buildups formed through bacterially-mediated processes of hydrocarbon oxidation coupled with sulfate reduction.
Description/Abstract Recent submersible research on the tops of salt diapirs at the shelf edge (/... more Description/Abstract Recent submersible research on the tops of salt diapirs at the shelf edge (/approximately/150 m) and upper slope (/approximately/300 m) confirms the occurrence of massive carbonate buildups (to/approximately/20 m relief) in these environmental settings.
Abstract: The world's largest insular phosphate deposit is found on Nauru, an uplifted coral atol... more Abstract: The world's largest insular phosphate deposit is found on Nauru, an uplifted coral atoll in the western equatorial Pacific. This deposit, which is draped over a dolomitized karstic surface, has an earthy pelletal texture; it is oolitic at its base and structureless in its upper part. The only phosphate mineral found is a carbonate fluorapatite with the stoichiometry Ca 10 (PO 4) 5.6 (CO 3) 0.6 F 1.6 (OH) 1-x. This mineral is slightly depleted in F-and CO 3 2-, relative to PO 4 3-, to be considered a true francolite.
High Na-HCO3 water in the stacked sand and clay aquifer system of Southeastern Louisiana was foun... more High Na-HCO3 water in the stacked sand and clay aquifer system of Southeastern Louisiana was found to be caused by a combination of bacterial oxidation of organic matter, ion exchange, and calcite dissolution. Dissolution of feldspar had little impact on water chemistry. Na and alkalinity are highly correlated as a result of calcite dissolution and subsequent exchange by clays of 2 Na ions for each Ca ion. Na content is a good indicator of the amount of calcite dissolved.
Abstract Carbon isotope equilibrium fractionations in the system CH 4-CO 2-HCO 3-CaCO 3 predict t... more Abstract Carbon isotope equilibrium fractionations in the system CH 4-CO 2-HCO 3-CaCO 3 predict that a solid carbonate phase whose carbon is derived from methane oxidation should yield a delta 13 C value which is about 50/00 more negative than the methane source. Methane is highly depleted in the 13 C isotope and therefore methane-derived carbonates are expected to yield delta 13 C values which are at least as negative as the methane source.
Niue Island is a large uplifted former atoll in the tropical South Pacific Ocean where karst is p... more Niue Island is a large uplifted former atoll in the tropical South Pacific Ocean where karst is pervasive in the carbonate cap. The elemental chemistry and stable isotopes of dripwaters from which speleothems are actively forming in two adjacent coastal caves were determined in order to identify their sources. This study also examined the differences and similarities between vadose (cave dripwaters) and phreatic groundwaters on the island.
Abstract Improved understanding of ocean-atmosphere interactions that control interdecadal ENSO v... more Abstract Improved understanding of ocean-atmosphere interactions that control interdecadal ENSO variability prompted recently a renewed interest in the acquisition of highly resolved proxy ENSO records. Corals possessing annual growth increments have extended the ENSO archive several centuries beyond the existing instrumental data but much longer records are needed to constrain the interdecadal periodicities and unravel their underlying causes.
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Papers by Paul Aharon