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C. N. Threlkeld

Publications and source records attributed to C. N. Threlkeld.

9 recordsLinked to original sources
USGS2002

Ubiquitous tar balls with a California-source signature on the shorelines of Prince William Sound, Alaska

Although the shorelines of Prince William Sound still bear traces of the 1989 Exxon Valdez oil spill, most of the flattened tar balls that can be found today on these shorelines are not residues of Exxon Valdez oil. Instead, the carbon-isotopic and hydrocarbonbiomarker signatures of 61 tar ball samples, collected from shorelines throughout the northern and western parts of the sound, are all remarkably similar and have characteristics consistent with those of oil products that originated from the Monterey Formation source rocks of California. The carbonisotopic compositions of the tar balls are all closely grouped (<513Cpdb = -23.7 ± 0.2%o), within the range found in crude oils from those rocks, but are distinct from isotopic compositions of 28 samples of residues from the Exxon ValdezoW spill (<513Cpdb = -29.4 ± 0.1%o). Likewise, values for selected biomarker ratios in the tar balls are all similar but distinct from values of residues from the 1989 oil spill. Carbon-isotopic and biomarker signatures generally relate the tar balls to oil products used in Alaska before ~1970 for construction and pavements. How these tar balls with such similar geochemical characteristics became so widely dispersed throughout the northern and western parts of the sound is not known with certainty, but the great 1964 Alaska earthquake was undoubtedly an important trigger, causing spills from ruptured storage facilities of California-sourced asphalt and fuel oil into Prince William Sound.

Alaska↗
USGS1998

Carbon isotopic comparisons of oil products used in the developmental history of Alaska

Studies of the fate of oil released into Prince William Sound, AK, as a result of the 1989 Exxon Valdez oil spill, have led to an unexpected discovery. In addition to oil-like residues attributed to the spill, the ubiquitous presence of flattened tar balls, the carbon isotopic compositions of which fall within a surprisingly narrow range [??13C(PDB) = -23.7 ?? 0.3??? (n = 65)], were observed on the shorelines of the northern and western parts of the sound. These compositions are similar to those of some oil products [-23.7 ?? 0.7??? (n = 35)] that were shipped from California and used in Alaska for fuel, lubrication, construction, and paving before ~ 1970. These products include fuel oil, asphalt, and lubricants [-23.8 ?? 0.5??? (n = 11)], caulking, sealants, and roofing tar [-23.7 ?? 0.7??? (n = 16)], and road pavements and airport runways [-23.5 ?? 0.9??? (n = 8)]. Fuel oil and asphalt [-23.5 ?? 0.1??? (n = 3)], stored at the old Valdez town site and spilled during the 1964 Alaskan earthquake, appear to be the source of most of the beached tar balls. Oil products with lighter carbon isotopic compositions, between -25 and -30??? (n = 18), appear to have been used more recently in Alaska, that is, after ~ 1970. The source of some of the products used for modern pavement and runways [-29.3 ?? 0.2??? (n = 6)] is likely Alaskan North Slope crude oil, an example of which was spilled in the 1989 oil spill [-29.2??? (n = 1)].

Chemical Geology↗
USGS1993

Possible connection between two Alaskan catastrophes occurring 25 yr apart (1964 and 1989)

On March 24, 1989, the Exxon Valdez supertanker grounded on Bligh Reef, spilling North Slope crude oil into Prince William Sound, Alaska. Tracking the geochemical fate of this spilled oil has revealed, in addition to weathered products from the spill, minor oil residues on beaches from a distinctly different source. By using carbon isotopic compositions of whole-oil residues as a principal method of identification, we found that the δ 13 C values of Exxon Valdez oil (one sample) and its residues (eight samples from six islands) average -29.3 ±0.1‰. In contrast, the non- Exxon Valdez residues (15 samples from 12 localities) have an average δ 13 C value of -23.8 ±0.1‰. This tight distribution of carbon isotopic values suggests a single event to explain the non- Exxon Valdez residues. This event likely was the Great Alaska Earthquake of March 27, 1964. This quake and the subsequent tsunami destroyed asphalt storage facilities at the old Valdez town site, spilling asphalt (δ 13 C = -23.6‰) into Port Valdez fjord. From there the asphalt apparently advanced south into the sound. Thus, the possible connection between two Alaskan catastrophes, separated by 25 yr, is found in the minor oil- like residues that continue to mark the two events on the beaches of Prince William Sound.

Geology↗
USGS1988

Character, origin and occurrence of natural gases in the Anadarko basin, southwestern Kansas, western Oklahoma and Texas Panhandle, U.S.A.

Natural gas production in the Anadarko basin comes from three geographically separated areas that can be differentiated by age of reservoir and by inferred nature of organic, thermal origin of the gases. In the central basin, non-associated gases are produced mainly from Upper Mississippian and Pennsylvanian sandstones. Gas samples are from reservoirs as much as 6588 m deep. Gases become isotopically heavier (??13C1-values range from -49.8 to -33.2???) and chemically drier (C2+-values range from 1-33%) with increasing level of thermal maturity. Gases were generated mainly from interbedded shales with type-III kerogen during the mature and post-mature stages of hydrocarbon generation. Deviations from the trend are due to vertical migration and mixing of gases generated at different levels of thermal maturity over the past 250 Myr. In the giant Panhandle-Hugoton field, non-associated gases are generally produced from Permian carbonates at depths of <900 m. Gases display little compositional variation (mean ??13C1-value is -43.2???, mean C2+-value is 14%). Because organic-rich, mature source rocks are not present in the area, gases probably were generated in the central basin from Pennsylvanian or older source rocks during the mature stage of hydrocarbon generation. This interpretation implies migration over distances as much as several hundred kilometers. In the Sooner Trend, associated gases are produced from Silurian, Devonian and Mississippian carbonates at depths as great as 2950 m and were generated from type-II kerogen during the mature stage of hydrocarbon generation. Associated oil usually correlates with extracts of the Upper Devonian and Lower Mississippian Woodford Shale. Gases are isotopically lighter (mean ??13C1-value is -43.9???) and chemically wetter (mean C2+ value is 14%) than those derived from type-III kerogen at an equivalent level of thermal maturity. ?? 1988.

Chemical Geology↗
USGS1982

Geochemical analysis of potash mine seep oils, collapsed breccia pipe oil shows and selected crude oils, Eddy County, New Mexico

Oil shows, in the form of oil stains and bleeding oil, in core samples from two breccia pipes, Hills A and C, Eddy County, New Mexico, and seepage oils in a potash mine near Hill C breccia pipe are geochemically similar. The geochemical similarities strongly suggest that they belong to the same family of oils and were derived from similar sources. The oils are relatively high in sulfur (0.89 to 1.23 percent), rich in hydrocarbons (average 82 percent), relatively high in saturated hydrocarbon/aromatic hydrocarbon ratios (average 2.9), and based on analysis of seep oils alone, have a low API gravity (average 19.4?). The oils are for the most part severely biodegraded as attested by the loss of n-paraffin molecules. Geochemical comparison of seven crude oils collected in the vicinity of the breccia pipes indicates that the Yates oils are the likely source of the above family of oils. Six barrels of crude oil that were dumped into a potash exploration borehole near Hill C breccia pipe, to release stuck casing, are considered an unlikely source of the breccia pipe and mine seep oils. Volumetric and hydrodynamic constraints make it highly improbable that such a small volume of 'dumped' oil could migrate over distances ranging from about 600 feet to 2.5 miles to the sites of the oil shows.

Open-File Report↗