Paul Aharon
University of Alabama - Tuscaloosa, Geological Sciences, Faculty Member
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... 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. Rodgers et al.(1982) used this model to explain dolomitization of the Niue Atoll, SW Pacific. The authors present here results of an ongoing... 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" cold", being characterized by hydrocarbon-rich fluid emissions at ambient sea floor temperature, mineralization of gas hydrates, precipitation... 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 statistically significant predictions of severe storm frequency and intensity caused by ongoing global climate changes. In this study we used... 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 inhabitants of hydrothermal vents and hydrocarbon seeps. In general, growth rates of deep-sea biota are significantly slower than that of... 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 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... 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 documented over the past decade from submersible dives on the northern Gulf of Mexico seafloor overlying salt diapirs. These seepage sites... 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 (/approximately/150 m) and upper slope (/approximately/300 m) confirms the occurrence of massive carbonate buildups (to/approximately/20 m... 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 atoll in the western equatorial Pacific. This deposit, which is draped over a dolomitized karstic surface, has an earthy pelletal texture; it is... 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 found to be caused by a combination of bacterial oxidation of organic matter, ion exchange, and calcite dissolution. Dissolution of feldspar had... 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.
59 BASIC BIOLOGICAL SCIENCES; SULFATE-REDUCING BACTERIA; POPULATION DYNAMICS; THICKNESS; GULF OF MEXICO; PETROLEUM; SEEPS; ATLANTIC OCEAN; BACTERIA; CARIBBEAN SEA; DIMENSIONS; ENERGY SOURCES; FOSSIL FUELS; FUELS; MICROORGANISMS; SEAS;... more
59 BASIC BIOLOGICAL SCIENCES; SULFATE-REDUCING BACTERIA; POPULATION DYNAMICS; THICKNESS; GULF OF MEXICO; PETROLEUM; SEEPS; ATLANTIC OCEAN; BACTERIA; CARIBBEAN SEA; DIMENSIONS; ENERGY SOURCES; FOSSIL FUELS; FUELS; MICROORGANISMS; SEAS; SURFACE WATERS
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... 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 pervasive in the carbonate cap. The elemental chemistry and stable isotopes of dripwaters from which speleothems are actively forming in two... 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 variability prompted recently a renewed interest in the acquisition of highly resolved proxy ENSO records. Corals possessing annual growth... 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.
Abstract Niue Island (19 00'S, 169 50'W), a large carbonate platform located at the edge of Pacific Warm Water Pool offers an ideal opportunity to reconstruct El Nino Southern Oscillation (ENSO) history by means of speleothems. Rainfall... more
Abstract Niue Island (19 00'S, 169 50'W), a large carbonate platform located at the edge of Pacific Warm Water Pool offers an ideal opportunity to reconstruct El Nino Southern Oscillation (ENSO) history by means of speleothems. Rainfall on Niue is primarily controlled by ENSO. Previously employed layer thickness proxy revealed that ENSO phenomenon is archived in stalagmites from Niue (Rasbury et al., 2006).
Abstract Carbonate speleothems are useful archives of land-based paleoclimate studies. Trace elements (eg, Mg, Sr, Ba) and stable isotopes of carbon and oxygen that are incorporated into the carbonate minerals are used to infer changes in... more
Abstract Carbonate speleothems are useful archives of land-based paleoclimate studies. Trace elements (eg, Mg, Sr, Ba) and stable isotopes of carbon and oxygen that are incorporated into the carbonate minerals are used to infer changes in air temperature, vegetation, rainfall amount and short-lived events such as hurricanes. Most speleothems exhibit stable calcite mineralogy but a growing number of studied archives display aragonite mineralogy that tends to convert to calcite with time.
The Carribbean karst model indicates that mixing of freshwater with seawater in carbonate coastal areas leads to karst development and cave formations because dissolution of carbonates is significantly enhanced in the mixing zone. Here we... more
The Carribbean karst model indicates that mixing of freshwater with seawater in carbonate coastal areas leads to karst development and cave formations because dissolution of carbonates is significantly enhanced in the mixing zone. Here we extend the Caribbean karst model to the Pacific carbonate islands in order to explain the occurrence of coastal caves there.
Sediment evacuation scars, gullies, shattered and deformed sediment masses, vent-like dewatering structures, stress fractures/cracks associated with incipient failures, and exaggerated slopes linked to recent episodes of mass movement... more
Sediment evacuation scars, gullies, shattered and deformed sediment masses, vent-like dewatering structures, stress fractures/cracks associated with incipient failures, and exaggerated slopes linked to recent episodes of mass movement were all common features of the dome flank and crest. This family of features emphasizes the importance of mass movement processes to the current configuration of the dome. Hydrocarbon seeps and commonly associated chemosynthetic communities plus authigenic carbonates were not found on top or upper flanks of the dome.
Anomalously negative d 13 C excursions in fossil benthic foraminifera tests coinciding with rapid climate changes were used as the smoking gun of hydrate-sourced methane released into the atmosphere. Although highly desirable, the effects... more
Anomalously negative d 13 C excursions in fossil benthic foraminifera tests coinciding with rapid climate changes were used as the smoking gun of hydrate-sourced methane released into the atmosphere. Although highly desirable, the effects of methane hydrate dissociation on stable isotopes of recent benthic foraminifera have not yet been tested. Here we present carbon and oxygen isotope records of benthic foraminifera species Bolivina ordinaria and B.
Description/Abstract Early Organic Evolution is the proceedings of the ninth Alfred Wegener Conference, the final meeting of IGCP Project 157 held in Germany in 1988. Over the past 15 years, Project 157 has promoted the blending of... more
Description/Abstract Early Organic Evolution is the proceedings of the ninth Alfred Wegener Conference, the final meeting of IGCP Project 157 held in Germany in 1988. Over the past 15 years, Project 157 has promoted the blending of organic geochemistry, economic geology, and evolutionary biology. This IGCP publication covers a diverse set of topics and truly reflects the interdisciplinary nature of the field of early organic evolution.
ABSTRACT Seismic and echo-sounder profiles across Louisiana's continental slope have historically suggested the presence of abundant hydrocarbons in shallow subsurface sediments and in the water column. Various mineralogical types of... more
ABSTRACT Seismic and echo-sounder profiles across Louisiana's continental slope have historically suggested the presence of abundant hydrocarbons in shallow subsurface sediments and in the water column. Various mineralogical types of authigenic carbonates are common in hydrocarbon seep areas. Significance of a substantial carbonate component to the sedimentary architecture of the Mississippi delta complex has never been seriously evaluated.
Cenozoic carbonate platforms are a potential rich source of information concerning eustasy but their prerequisite dating is fraught with difficulties. Paleomagnetism has long been established as a highly successful tool for dating... more
Cenozoic carbonate platforms are a potential rich source of information concerning eustasy but their prerequisite dating is fraught with difficulties. Paleomagnetism has long been established as a highly successful tool for dating deep-sea sediments but its applicability to shallow-water reef carbonates has only recently been explored. Here we derive a detailed magnetostratigraphy of the carbonate platform at Niue on the basis of cores drilled into lagoonal facies to a maximum depth of 303 m below surface.
ABSTRACT Although most salt dome-related oil production in the Gulf Coast is from clastic reservoirs, oil has been produced from Tertiary carbonate reservoir facies within (1) carbonate cap rocks over salt domes, and (2) the Heterostegina... more
ABSTRACT Although most salt dome-related oil production in the Gulf Coast is from clastic reservoirs, oil has been produced from Tertiary carbonate reservoir facies within (1) carbonate cap rocks over salt domes, and (2) the Heterostegina zone coral reef facies of the Anahuac Formation. The only known surface exposure of both carbonates occurs over the Damon Mound salt dome, near Houston, where oil and thermogenic gas have been produced from early Oligocene to early Miocene reservoirs flanking the dome crest.
ABSTRACT Hydrocarbon exploration and production on the Louisiana continental slope have produced data derived from high-resolution geohazards surveys which indicate that enormous volumes of authigenic carbonates are present. Geochemical... more
ABSTRACT Hydrocarbon exploration and production on the Louisiana continental slope have produced data derived from high-resolution geohazards surveys which indicate that enormous volumes of authigenic carbonates are present. Geochemical analyses of these carbonates show a wide range of mineralogies as well as 6 13C values (--25 to-55•/•• PDB) indicating an origin from microbial oxidation of hydrocarbons.
ABSTRACT Pore fluids associated with hydrocarbon seeps in deepwater Gulf of Mexico were sampled and analyzed for chemical and isotope compositions in order to determine their nature and origin. Three types of fluids have been discerned.... more
ABSTRACT Pore fluids associated with hydrocarbon seeps in deepwater Gulf of Mexico were sampled and analyzed for chemical and isotope compositions in order to determine their nature and origin. Three types of fluids have been discerned. Fluids pertaining to type I have normal Gulf of Mexico deepwater salinities (about 38^ pmil) and their 87 Sr/86 Sr ratios (0.70916, n= 3) are identical to the overlying seawater (0.70917).
Résumé/Abstract Dissolved inorganic carbon (DIC), δ 13 C DIC and δ 18 O HO2 are traditionally measured using three different analytical techniques. Herein is described a precise, accurate and relatively simple technique for analyzing all... more
Résumé/Abstract Dissolved inorganic carbon (DIC), δ 13 C DIC and δ 18 O HO2 are traditionally measured using three different analytical techniques. Herein is described a precise, accurate and relatively simple technique for analyzing all three parameters from a single≤ 2-ml water sample. Water samples are injected through a septum into a temperature-controlled, water-jacketed, evacuated vessel containing∼ 0.3 ml of orthophosphoric acid and a magnetic spinbar.
Abstract The contrast between the scanty magnesite deposition in modern sedimentary environments and the large strata-bound magnesites of the past constitutes a “magnesite problem” which, unlike the “dolomite problem”, has so far... more
Abstract The contrast between the scanty magnesite deposition in modern sedimentary environments and the large strata-bound magnesites of the past constitutes a “magnesite problem” which, unlike the “dolomite problem”, has so far attracted little attention from the geologists.
The core of the former atoll on Niue island, South Pacific, is extensively dolomitized. A detailed stable isotope study reveals that the dolomites are uniformly enriched in and) relative to their carbonate precursor. The Sr isotope ratios... more
The core of the former atoll on Niue island, South Pacific, is extensively dolomitized. A detailed stable isotope study reveals that the dolomites are uniformly enriched in and) relative to their carbonate precursor. The Sr isotope ratios are equally constant with depth yielding values between 0.70912 and 0.70916. The observed isotopic compositions point to sea water as the dominant dolomitizing fluid.
Time-series d 18 O and d 13 C records from cohabiting massive coralPorites australiensis and giant clamTridacna gigas from the Great Barrier Reed of Australia, and from calcareous green algae in a core through modernHalimeda bioherm... more
Time-series d 18 O and d 13 C records from cohabiting massive coralPorites australiensis and giant clamTridacna gigas from the Great Barrier Reed of Australia, and from calcareous green algae in a core through modernHalimeda bioherm accreting in the eastern Java Sea, provide insights into the complex links between environmental factors and stable isotopes imprinted in these reef skeletal materials. The aragonitic coral and giant clam offer 20 years and 15 years of growth history, respectively.
Hydrocarbon-derived and microbially mediated authigenic carbonates occur over the entire depth range of the northern Gulf of Mexico slope. These carbonates consist of nodules and incipient nodules in surface sediments, hardgrounds and... more
Hydrocarbon-derived and microbially mediated authigenic carbonates occur over the entire depth range of the northern Gulf of Mexico slope. These carbonates consist of nodules and incipient nodules in surface sediments, hardgrounds and isolated slabs, and moundlike buildups of up to 10–20 m relief above the surrounding seafloor.
Abstract White and pigmented filamentous bacterial mats dominated by several undescribed species of Beggiatoa were sampled during research submersible dives to cold hydrocarbon seep sites on the upper continental slope off Louisiana... more
Abstract White and pigmented filamentous bacterial mats dominated by several undescribed species of Beggiatoa were sampled during research submersible dives to cold hydrocarbon seep sites on the upper continental slope off Louisiana (130–550 m). Mats occur at the interface between reducing sediments and the oxygenated water column. They are localized at sea floor features related to seepage of biogenic methane and crude oil, but there is little evidence that the organisms utilize the hydrocarbons directly.
The Solar Lake is a hypersaline monomictic, seasonally mesothermal pond on the Gulf of Elat coast. Bottom water temperatures reach 57° C, compared with about 20° C at the surface. Dolomite has formed recently in the sediment of the pond.... more
The Solar Lake is a hypersaline monomictic, seasonally mesothermal pond on the Gulf of Elat coast. Bottom water temperatures reach 57° C, compared with about 20° C at the surface. Dolomite has formed recently in the sediment of the pond. The dolomite has a 6-7% mole excess of and is poorly ordered. of the dolomite averages (PDB), its has an average of. Coexisting aragonite is depleted by is close to that of the dolomite.
Abstract Observations and samples from research submersible dives confirm that brines, crude oil, fluid mud, and gases are common seep products. Through this mechanism a unique interplay of geochemical, geologic, and biological processes... more
Abstract Observations and samples from research submersible dives confirm that brines, crude oil, fluid mud, and gases are common seep products. Through this mechanism a unique interplay of geochemical, geologic, and biological processes resulting in unusual sea floor features ranging from carbonate-rich nodular sediments to mounds with tens of meters relief.