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C. K. Paull

Publications and source records attributed to C. K. Paull.

At least 37 records · Page 2Linked to original sources
USGS2004

Drowning of the - 150 m reef off Hawaii: A casualty of global meltwater pulse 1A?

We present evidence that the drowning of the - 150 m coral reef around Hawaii was caused by rapid sea-level rise associated with meltwater pulse 1A (MWP-1A) during the last deglaciation. New U/Th and 14C accelerator mass spectrometry dates, combined with reinterpretation of existing radiometric dates, constrain the age of the coral reef to 15.2-14.7 ka (U/Th age), indicating that reef growth persisted for 4.3 k.y. following the end of the Last Glacial Maximum at 19 ka. The drowning age of the reef is roughly synchronous with the onset of MWP-1A between 14.7 and 14.2 ka. Dates from coralline algal material range from 14 to 10 cal ka (calibrated radiocarbon age), 1-4 k.y. younger than the coral ages. A paleoenvironmental reconstruction incorporating all available radiometric dates, high-resolution bathymetry, dive observations, and coralgal paleobathymetry data indicates a dramatic rise in sea level around Hawaii ca. 14.7 ka. Paleowater depths over the reef crest increased rapidly above a critical depth (30-40 m), drowning the shallow reef-building Porites corals and causing a shift to deepwater coralline algal growth, preserved as a crust on the drowned reef crest. ?? 2004 Geological Society of America.

Geology↗
USGS2002

Physiography of the Monterey Bay National Marine Sanctuary and implications about continental margin development

Combined EM-300 multibeam bathymetric data and satellite photography reveal the physiography of the continental margin between 35°50′ and 37°03′N and from the shoreline west of 122°40′ and 122°37′W, which includes Monterey Bay, in a previously unprecedented detail. Patterns in these images clearly reveal the processes that are actively influencing the current geomorphology of the Monterey Bay region, including the Monterey Bay National Marine Sanctuary (MBNMS). Our data indicates that seafloor physiography within the MBNMS results from plate margin tectonic deformation, including uplift and erosion along structural lineaments, and from fluid flow. Mass wasting is the dominant process active within the Ascension–Monterey and Sur–Partington submarine canyon systems and along the lower slopes. Meanders, slump dams, and constricted channels within the submarine canyons, especially within Monterey Canyon, slow and interrupt down-canyon sediment transport. We have identified for the first time thin sediment flows, rotational slumps, rills, depressions that may be associated with pipes, and other fluid-induced features we call ‘scallops’ off the Ascension slope, and suggest that fluid flow has sculptured the seafloor morphologies here. These unusual seafloor morphologies are similar to morphologies found in terrestrial areas modified by ground-water flow.

California↗
USGS2000

Comparisons of in situ and core gas measurements in ODP Leg 164 bore holes

During Ocean Drilling Program Leg 164, an unprecedented effort was made to determine the amounts of gas and gas hydrate in the sediments from Sites 994, 995, and 997. For the first time in the history of academic drilling, a pressure core sampler (PCS) worked well enough to generate an independent stratigraphy of in situ gas concentrations and compositions with depth. Here, gas concentrations and composition data produced by routine shipboard gas sampling techniques are compared with PCS data.

Conference Paper↗
USGS1997

Carbon isotopes in biological carbonates: Respiration and photosynthesis

Respired carbon dioxide is an important constituent in the carbonates of most air breathing animals but is much less important in the carbonates of most aquatic animals. This difference is illustrated using carbon isotope data from freshwater and terrestrial snails, ahermatypic corals, and chemoautotrophic and methanotrophic pelecypods. Literature data from fish otoliths and bird and mammal shell and bone carbonates are also considered. Environmental CO 2 /O 2 ratios appear to be the major controlling variable. Atmospheric CO 2 /O 2 ratios are about thirty times lower than in most natural waters, hence air breathing animals absorb less environmental CO 2 in the course of obtaining 0 2 . Tissue CO 2 therefore, does not isotopically equilibrate with environmental CO 2 as thoroughly in air breathers as in aquatic animals, and this is reflected in skeletal carbonates. Animals having efficient oxygen transport systems, such as vertebrates, also accumulate more respired CO 2 in their tissues. Photosynthetic corals calcify mainly during the daytime when photosynthetic CO 2 uptake is several times faster than respiratory CO 2 release. Photosynthesis, therefore, affects skeletal δ 13 C more strongly than does respiration. Corals also illustrate how “metabolic” effects on skeletal isotopic composition can be estimated, despite the presence of much larger “kinetic” isotope effects.

Nevada↗
USGS1993

Evidence for gas accumulation associated with diapirism and gas hydrates at the head of the Cape Fear Slide

Single-channel seismic reflection profiles show evidence for areas of significant gas accumulation at the head of the Cape Fear Slide on the continental rise oft North Carolina. Gas accumulation appears to occur beneath a gas hydrate seal in landward-dipping strata and in domed strata associated with diapirism. In addition, gas venting may have occurred near diapirs located at the head of the slide.

North Carolina↗
USGS1993

Sulfur isotope and porewater geochemistry of Florida escarpment seep sediments

Distributions of porewater constituents, SO 4 = , NH 4 + , Cl − , ∑CO 2 , and H 2 S, solid phase iron, and sulfur concentrations, and the sulfur isotopic composition of dissolved and solid phases were investigated in sediments from abyssal seeps at the base of the Florida escarpment. Despite the apparent similarity of seep sediment porewater chemistry to that of typical marine sediments undergoing early diagenesis, relationships between chemical distributions and isotopic measurements revealed that the distribution of pore fluid constituents was dominated by processes occurring within the platform rather than by in situ microbial processes. Ammonium and sulfate concentrations were linearly correlated with chloride concentrations, indicating that variations in porewater chemistry were controlled by the admixture of seawater and a sulfate depleted brine with a chlorinity of 27.5 ± 1.9%. and 2.2 ± 1.3 mM ammonium concentration. At sites dominated by seepage, dissolved sulfate isotopic composition remained near seawater values despite depletion in porewater concentrations. Porewater ∑CO 2 concentrations were found to be elevated relative to seawater, but not to the extent predicted from the observed sulfate depletion. Sediment solid phase sulfur was predominantly pyrite, at concentrations as high as 20% S by weight. In contrast to typical marine deposits, pyrite concentrations were not related to the quantity of sedimentary organic matter. Pyrite δ 34 S values ranged from −29%. to + 21%. (CDT). However, only positive δ 34 S values were observed at sites associated with high pyrite concentrations. Isotopically heavy pyrite was observed at sites with porewater sulfate of seawater-like isotopic composition. Isotopically light pyrite was associated with sites where porewater sulfate exhibited δ 34 S values greater than those in seawater, indicating the activity of in situ microbial sulfate reduction. Thus, dual sulfide sources are suggested to explain the range in sediment pyrite isotopic composition: a δ 34 S enriched (+10 to +20%.) source adverted from within the Florida platform, and a lighter 34 S depleted component generated in situ from microbial reduction of seawater sulfate. The degree of pyritization of seep sediments was as high as 0.9 and was controlled by pyrite concentrations, which varied over a wider range than did the non-pyrite solid phase iron concentrations. The highest non-sulfide solid phase iron concentrations were observed in sediments that are believed to be at the “front” of the advancing seep fluids (i.e., hemipelagic sediments newly exposed to the seep fluids), indicating that dissolution of hemipelagic background sediment may be the source of at least half of the iron to the highly pyritized seep sediments. Porewater sulfide concentrations were variable, reaching a maximum of 5.7 mM, and were not correlated with the degree of pyritization of the sediments, suggesting that iron was not particularly limiting to pyrite formation.

Geochimica et Cosmochimica Acta↗
USGS1992

Anomalous abundances of deep-sea fauna on a rocky bottom exposed to strong currents

Unusually high abundances of sponges and gorgonian corals, covering as much as 25% of the bottom, occur at depths greater than 3.5 km on the Blake Spur, a rocky cliff-dominated feature on the western Atlantic continental margin. This is the first report of such high abundances of megafauna from a non-hydrothermal or otherwise chemosynthetically enriched site in abyssal depths. Animal densities at other steep rocky sites at similar depths are usually lower by more than an order of magnitude. The deep slope of the Blake Spur is exposed to the vigorous Western Boundary Undercurrent, with local flow speeds that may exceed 100 cm s-1. Currents can control this anomalous animal abundance by removing sediments and by enhancing fluxes, rather than concentrations, of food particles to the dominant suspension feeders. ?? 1992.

Deep Sea Research Part A, Oceanographic Research P↗
USGS1991

Seabed measurements of modern corrosion rates on the Florida escarpment

A mooring containing diverse carbonate and anhydrite substrates was exposed to bottom waters for 9 months at the base of the Florida Escarpment to determine the influence of dissolution on the development of this continental margin. Weight loss was measured on all samples. Etching, pitting, and loss of the original framework components were observed on substrates with known characteristics. Extrapolations of modern dissolution rates predict only about 1.6 meters of corrosion per million years. However, more rapid anhydrite dissolution, up to 1 km per million years, would cause exposed anhydrite beds to undercut and destabilize intercalated limestones.

Florida↗
USGS1991

Morphological development of the Florida Escarpment: Observations on the generation of time transgressive unconformities in carbonate terrains

An unconformity of 100 m.yr magnitude continues to form on the western edge of the Florida-Bahama Platform, near 26??N, where distal Mississippi Fan sediments are progressively burying the Florida Escarpment. Multiple perspectives of the developing unconformity's morphology are revealed using available technologies including GLORIA images of the entire platform's edge, Seabeam bathymetric contours, and Deep-Tow's high resolution side-scan data calibrated with bottom photographs. The structure and stratigraphy of the buried escarpment and the associated unconformity are resolved by airgun, sparker, and Deep-Tow's 4 kHz seismic reflection data; we summarize the morphological data on the exposed part of the unconformity and the sedimentary deposits accumulating in the basin above the unconformity. The exposed cliff face is composed of a staircase of bedding-plane terraces which are developed along joint planes. The terraces extend 100-1000 m along the escarpment's face, and the intervening vertical walls are up to 100 m high. The jointed morphology of this Mesozoic limestone cliff apparently reflects erosional exposure of its interior anatomy rather than its accretionary shape. The change in slope between the platform face and the abyssal plain is very abrupt. In places along the contact between the escarpment and fan sediments, reduced chemical-charged brine seeps occur, which locally cause carbonate dissolution and precipitation, sulfide mineralization, and the deposition of a fossiliferous and organic carbon-rich lens associated with chemosynthetic communities. These seep deposits and escarpment-derived megabreccias intercalate with basinal sediments that overlie the unconformity. Because surface seismic reflection data do not produce images of the escarpment's face that closely reflect the exposed escarpment's morphology, they must also be of limited value in characterizing the surface of similar steeply dipping buried escarpments. Thus, the downslope extent of the heavily eroded platform edge is unclear.

Florida↗
USGS1991

Terraces on the Florida escarpment: Implications for erosional processes

SeaBeam bathymetric data and GLORIA (Geologic LOng-Range Inclined Asdic) sidescan sonar images of a 175-km-long section of the Florida escarpment in the eastern Guff of Mexico show that this carbonate escarpment has been eroded since its initial formation, but its morphology suggests that erosional processes have not acted uniformly on the escarpment. Parts of the escarpment are notched by box canyons that have extremely steep headwalls and may be sites off active ground-water sapping. The intercanyon areas commonly have previously unrecognized terraces below 2600 m. Above 2600 m, the escarpment is steeper and has no terraces. The terraces may reflect differences in platform strata exposed at the escarpment that are responding differently to erosional processes.

Gulf of Mexico↗
USGS1990

Variations in the styles of erosion along the Florida Escarpment, eastern Gulf of Mexico

GLORIA sidescan sonographs and Seabeam bathymetric data show morphological differences along the Florida Escarpment which reflect that different erosional styles have been active along different parts of this carbonate platform edge. The northern half of the escarpment is cut by numerous small ravines spaced 1-5 km apart. Its southern half is deeply incised by large box canyons that have flat floors and steep headwalls. The northern half of the escarpment is covered by Cenozoic-aged sediments, and erosion appears to be limited to this Cenozoic cover. An apron of this eroded material is accumulating along the base of this half of the escarpment, extending as much as 30 km from its base. South of 27??N, active erosion of older strata of the escarpment is shown by talus deposits of Lower Cretaceous limestone that occur at the heads of box canyons. The box canyons are not evenly distributed, but instead are most abundant where two basins that underlie the Florida Platform intersect the escarpment. Pleistocene-aged sediments eroded from the slope above the escarpment are funnelled through small valleys into the heads of the box canyons. The smooth headwalls of the box canyons suggest that downslope transport of the material from the slope above the escarpment does little to erode the escarpment. Instead, erosion triggered by dissolution of the carbonate rocks by acidic brines that seep out of the escarpment is the proposed mechanism of escarpment retreat. The concentration of the erosion at the heads of the box canyons may indicate sites where the platform rocks are more intensely fractured, thus enhancing permeability and flow of brines. The concentration of box canyons in the escarpment sections adjacent to sedimentary basins beneath the platform may reflect regional differences in the geology and hydrology of the platform. ?? 1990.

Florida Escarpment, Gulf of Mexico↗
USGS1987

Chemistry and mineralogy of pyrite-enriched sediments at a passive margin sulfide brine seep: Abyssal Gulf of Mexico

Pyrite is rapidly accumulating at the contact between the Cretaceous limestones of the Florida Platform and the hemipelagic sediments of the abyssal Gulf of Mexico. Sediments sampled with the submersible “Alvin” in 3266 m of water are associated with a dense community of organisms that depend on chemosynthetic primary production as a food source. Analysis of the chemistry, mineralogy, and textural composition of these sediments indicate that iron sulfide mineralization is occurring at the seafloor within an anoxic micro-habitat sustained by the advection of hydrogen sulfide-charged saline brines from the adjacent platform. The chemosynthetic bacteria that directly overlie the sediments oxidize hydrogen sulfide for energy and provide elemental sulfur that reacts with iron monosulfide to form some of the pyrite. The sediments are mixtures of pyrite (∼ 30 wt.%), Ba Sr sulfates (∼ 4 wt.%), clays, and locally derived biogenic carbonates and are progressively being cemented by iron sulfides. Oxidation of hydrogen sulfide produces locally acidic conditions that corrode the adjacent limestones. Potential sources of S, H 2 S, Fe, Ba, and Sr are discussed.

Earth and Planetary Science Letters↗
USGS1987

Recent geologic history of lake Atitlán, a caldera lake in western Guatemala

Lake Atitlán, a caldera lake in western Guatemala, was investigated for evidence of recent volcanic and tectonic activity. No vents, faults, or folds are apparent on high-resolution seismic reflection profiles of lake sediment, representing at least 17,500 years and probably more than 35,000 years of deposition. Three post-caldera stratovolcanoes (San Pedro, Tolimán, and Atitlán) have grown in southern parts of the caldera and two deltas have grown from the north shore of the lake. Elsewhere, the caldera is occupied by Lake Atitlán, which is more than 300 m deep and has a relatively flat floor. Refraction profiles suggest that the original floor of the caldera lies ca. 300 m below the current lake floor, but prodigious amounts of methane gas in the lake sediment attenuated seismic signals and prevented any detailed view of the original caldera floor or faults along which the floor is presumed to have collapsed. Piston cores from deep basins of Lake Atitlán record ca. 2,000 years of unusually rapid sedimentation (ca. 0.5 cm/yr). Only one thin silicic ash layer was penetrated, and it is probably from a distant source. Cores contain evidence of Mayan disturbance of the environment around the lake and, to a lesser degree, of the lake itself; they might also record episodes of increased thermal activity, each lasting several decades. Heat-flow measurements inside and just outside the caldera are high (290 and 230 mW m −2 ), suggesting hydrothermal convection and a shallow heat source. High heat flow, a geological record of post-caldera silicic eruptions, and unexplained fluctuations of lake level (episodic tumescence ofthe lake floor?) suggest that magma remains beneath Lake Atitlán and that future eruptions are possible.

Journal of Volcanology and Geothermal Research↗
USGS1985

A geophysical and geological study of Laguna de Ayarza, a Guatemalan caldera lake

Geologic and geophysical data from Laguna de Ayarza, a figure-8-shaped doublecaldera lake in the Guatemalan highlands, show no evidence of postcaldera eruptive tectonic activity. The bathymetry of the lake has evolved as a result of sedimentary infilling. The western caldera is steep-sided and contains a large flat-floored central basin 240 m deep. The smaller, older, eastern caldera is mostly filled by coalescing delta fans and is connected with the larger caldera by means of a deep channel. Seismicreflection data indicate that at least 170 m of flat-lying unfaulted sediments partly fill the central basin and that the strata of the pre-eruption edifice have collapsed partly along inward-dipping ring faults and partly by more chaotic collapses. These sediments have accumulated in the last 23,000 years at a minimum average sedimentation rate of 7 m/103 yr. The upper 9 m of these sediments is composed of > 50% turbidites, interbedded with laminated clayey silts containing separate diatom and ash layers. The bottom sediments have >1% organic material, an average of 4% pyrite, and abundant biogenic gas, all of which demonstrate that the bottom sediments are anoxic. Although thin (<0.5 cm) ash horizons are common, only one thick (7-16 cm) primary ash horizon could be identified in piston cores. Alterations in the mineralogy and variations in the diatom assemblage suggest magnesium-rich hydrothermal activity. ?? 1985.

Journal of Volcanology and Geothermal Research↗
USGS1984

Biological communities at the Florida Escarpment resemble hydrothermal vent taxa

Dense biological communities of large epifaunal taxa similar to those found along ridge crest vents at the East Pacific Rise were discovered in the abyssal Gulf of Mexico. These assemblages occur on a passive continental margin at the base of the Florida Escarpment, the interface between the relatively impermeable hemipelagic clays of the distal Mississippi Fan and the jointed Cretaceous limestone of the Florida Platform. The fauna apparently is nourished by sulfide rich hypersaline waters seeping out at near ambient temperatures onto the sea floor.

Florida↗
USGS1981

Patterns of groundwater salinity changes in a deep continental-oceanic transect off the southeastern Atlantic coast of the U.S.A.

Investigations of formation-fluid salinities in a transect from western Georgia to the edge of the Blake Plateau off the coast of Georgia show surprisingly similar hydrochemical features offshore and onshore. A fresh-brackish wedge of groundwater (<25 g/kg total dissolved solids) lies beneath the shelf to a depth of ∼ 900 m. On land, brackish waters extend to a maximum depth of ∼ 1.2 km below sea level in Lowndes County, Georgia. In deeper horizons, hypersaline brines (> 100 g/kg) occur in Lower Cretaceous (?) strata. These strata have a pronounced evaporitic (anhydritic) character in the offshore segment. Strong salinity gradients in interstitial waters signify buried evaporite deposits at drill sites beneath the Blake Plateau.

Florida, Georgia, South Carolina↗