Geology topics
Publications and source records attributed to John W. Counts.
Using a geology-based assessment methodology, the U.S. Geological Survey estimated undiscovered, technically recoverable mean conventional resources of 96 trillion cubic feet of gas in the Northern Alaska Province.
The Upper Jurassic Norphlet Formation is a stratigraphic unit located in the subsurface of the United States Gulf coastal plain and offshore Gulf of America (Gulf of Mexico). The Norphlet consists of clastic sediments derived from the southern Appalachian highlands, and was deposited in a continental dryland setting on the margins of the early Gulf of America rift basin. The formation contains a variety of sedimentary facies, including facies representing updip alluvial fans, wadis, red beds, and a widespread erg, or eolian sand sea. The erg facies form the primary reservoirs from which hydrocarbons sourced from the overlying Smackover Formation are produced. Development of the Norphlet began in earnest in the late 1960s, with new discoveries, including large fields at Flomaton, Hatters Pond, and Mobile Bay, continuing through the 2000s–2010s with the discovery of major oil fields in the offshore Desoto Canyon area. Onshore, Norphlet hydrocarbon traps typically are faulted salt anticlines, although many fields also have a stratigraphic trapping component because of the preservation of dune-scale bedforms. Thermal maturity across the Norphlet play varies significantly with depth, resulting in oil production transitioning downdip to natural gas liquids production, then dry gas production; production depths reach to greater than 21,000 feet. A 2024 U.S. Geological Survey assessment divided the Norphlet into four conventional assessment units defined by the type and frequency of trapping mechanisms, sedimentology, and thermal maturity of each area, with little potential for hydrocarbon development observed west of the Mississippi River. Although petroleum resources in the Norphlet were revised downward, it is probable that significant resources remain to be discovered.
Using a geology-based assessment methodology, the U.S. Geological Survey estimated undiscovered, technically recoverable mean resources of 3 million barrels of oil and 343.5 trillion cubic feet of gas in reservoirs of the Bossier Formation within the onshore United States and State waters of the Gulf Coast region.
Using a geology-based assessment methodology, the U.S. Geological Survey estimated undiscovered, technically recoverable mean resources of 5 million barrels of oil and 25 billion cubic feet of gas in conventional reservoirs and 361 million barrels of oil and 10,978 billion cubic feet of gas in continuous reservoirs in the Western Gulf Basin Province of the U.S. Gulf Coast region.
Using a geology-based assessment methodology, the U.S. Geological Survey (USGS) estimated undiscovered, technically recoverable mean resources of 16 million barrels of oil and 348 billion cubic feet of gas in conventional reservoirs of the Norphlet Formation in the U.S. Gulf Coast region.
The type locality for the upper Oligocene Nuwok Member of the Sagavanirktok Formation (Carter Creek, North Slope, Alaska, USA) contains abundant occurrence of glendonite, a pseudomorph after the calcium carbonate mineral ikaite, which typically forms in the shallow subsurface of cold marine sediments. The region during the time of Nuwok Member deposition was located at a high latitude, similar to today, and the study site is characterized by sands and silty muds interpreted here to have been deposited in coastal and shelfal marine environments. Isotopic (Sr) and biostratigraphic (foraminifera) evidence presented here refine the depositional age of the outcrop to approximately 24 Ma. Glendonites occur in two basic forms: radial clusters, commonly centered around a single larger primary crystal ( approx. 10 cm; Type A) and larger single blades generally without accessory crystals (approx. 15–25 cm; Type B). Microscopic examination revealed a sequence of multiple types of replacive calcite that formed as a direct result of ikaite transformation: Type 1 rhombohedral crystals characterized by microporous and inclusion-rich cores and concentric zones, Type 2A, composed of clear calcite that overgrew and augmented Type 1 crystals, and inclusion-rich, microcrystalline Type 2B, which formed a matrix surrounding the rhombs and commonly dominates the outer rims of glendonite specimens. Type 3 calcite precipitated as fibrous, botryoidal epitaxial cement atop previous phases and is not ikaite-derived. These phases are distributed in similar ways in all examined specimens and are consistent with several previously described glendonite occurrences around the world, despite differing diagenetic and geologic histories. Stable isotope evidence (δ13C and δ18O) suggests sourcing of glendonite carbon from both organic and methanogenic sources. Glendonites of the Nuwok Member can therefore assist in the determination of a more comprehensive ikaite transformation model, improving our understanding of glendonite formation and the sedimentological and environmental context of their occurrence. Oligocene glendonites are uncommon globally; the well-preserved occurrence described here can allow future studies to better reconstruct Arctic environmental conditions and paleoclimates during this time.
The middle Cretaceous greenhouse period experienced profound environmental change including episodes of enhanced global burial of organic carbon marked by carbon isotopic excursions (CIEs). However, the role and response of polar regions like the newly formed, partially enclosed Arctic Ocean Basin during middle Cretaceous carbon burial remains enigmatic. We present the first Arctic deepwater CIE record that characterizes conditions offshore of the Alaska margin north of 75°N paleolatitude. Organic carbon isotopes (δ 13 C org ) and 103–82 Ma ash zircon U-Pb dates from the distal Hue Shale record multiple Albian–Campanian CIEs during slow ∼3–15 m/Myr sediment accumulation rates. Average total organic carbon (TOC) increased substantially during large 2–3 ‰ CIEs of the ∼101 Ma Albian-Cenomanian boundary event (from 7 to 18 % TOC) and ∼94 Ma Cenomanian-Turonian boundary event (5 to 10 % TOC). Turonian TOC remained elevated (8–13 %) during high global sea levels and temperatures of the Cretaceous Thermal Maximum, followed by an increase from 7 to 11 % TOC during the ∼90 Ma late Turonian event 1.5 ‰ CIE. Average TOC subsequently decreased in the Coniacian–Campanian, but relative maxima occurred during subtle 0.5–1 ‰ CIEs interpreted as the ∼87 Ma late Coniacian event (increase from 4 to 7 % TOC), ∼85 Ma Horseshoe Bay event (3.5 to 4.5 % TOC), and ∼84 Ma Santonian-Campanian boundary event (3.5 to 5 % TOC). Increases in hydrogen index and productivity proxies (P, Ba, Nd) that accompanied each CIE episode with enhanced TOC suggest a strong link between marine productivity and organic carbon burial at short-term CIE timescales. However, long-term (>5–8 Myr) changes in trace metal redox (Mo, Fe, V) and salinity (B/Ga) proxies suggest shifts in prevailing environmental conditions at timescales longer than the CIEs. Late Albian–middle Turonian marine salinity occurred during euxinic (103–98 Ma) and suboxic (98–90 Ma) conditions with deposition interpreted to have occurred within and beneath an oxygen minimum zone, respectively. In contrast, late Turonian–early Campanian (90–82 Ma) freshening and restricted euxinic basin conditions may signal the start of widespread restriction known to characterize the Paleogene Arctic. Overall, these results highlight that middle Cretaceous Arctic deepwater remained a productive marine carbon sink coupled to the global carbon cycle despite evolving Arctic greenhouse conditions.
Detrital zircon data from modern barrier island and estuarine environments in the Outer Banks (Atlantic Coast, USA) were statistically compared to sands from nearby rivers to assist in determining source-to-sink pathways. Fluvial samples, collected from near the Fall Line contact between the Appalachian Orogen and sediments of the coastal plain, all have age unique distributions, making them ideal for tracing provenance. Three samples from the Atlantic foreshore showed high similarities to one another, as well as to three samples from the estuarine (back-barrier) Pamlico and Albemarle Sounds. Mixture modeling with multiple data reduction methods and three different statistical tests for similarity consistently indicated that the nearby Potomac River was the primary source for all Atlantic foreshore and estuarine zircons, followed by minor contributions from the James River in some models. The models indicate little or no sediment contribution from the Susquehanna, Roanoke, Tar, Neuse, Cape Fear, and Peedee Rivers. Both Atlantic foreshore and estuarine sands are therefore interpreted to have initially originated from Appalachian bedrock to the north of their present-day location, and subsequently to have been transported southward through the Chesapeake Bay watershed before deposition in Virginia and North Carolina. Prior to barrier island formation in the last several thousand years, differing geomorphology of the Chesapeake Bay facilitated southward movement of sediments from its constituent rivers via longshore drift, where they were deposited in coastal settings on the mainland. The modern barrier islands, formed during the most recent post-glacial transgression, may be reworked from these deposits, but may also include a contribution from sediments that were derived more recently from relict deposits on the shelf. Oceanographic and sedimentological evidence suggests that movement of sand-sized grains from southern rivers across the back-barrier sounds is unlikely. These findings can assist with coastal resilience planning and resource management in a region under severe threat from climate change and rising sea levels.
Fluvial sediments are the product of erosion, weathering, and transport of bedrock within a well-defined catchment area, and their constituent grains may therefore record valuable information about the lithological and geochemical properties of geologic units within the upstream drainage. Analysis of U-Pb ages and Lu/Hf isotopic values in detrital zircon grains from major rivers in the eastern USA characterizes these parameters within broad areas of the Appalachian orogen. In this study, five modern fluvial sediment samples, collected across ~1500 km and representing 216,000 km2 of total catchment area, reveal that the relative proportions of Mesoproterozoic to Paleozoic U-Pb crystallization ages vary widely across the former Laurentian margin. However, εHft values in the same samples are largely consistent regardless of their geographic location. Mesoproterozoic (Grenville orogen) zircons display a more limited range of εHft values (approximately 0 to +10 εHft units) compared to the more negative, more variable values (-15 to +10) found in grains from the Paleozoic orogenies. When compared to other published modern detrital samples from the Gulf Coastal Plain, Appalachian samples show more similarity to each other and to the Pleistocene of Florida than to those from the Mississippi River mouth, likely because the latter also sources sediments from the Cordillera of western North America. More negative εHft values in Paleozoic zircons may be genetically related to older Mesoproterozoic grains, as they are compatible with the continued isotopic evolution of Lu/Hf derived from the mantle between 1.2 and 2.0 Ga. Hafnium geochemistry in detrital grains may therefore have some utility in discerning sediment provenance between the Appalachians and other regions, and may also provide useful information regarding the nature of crustal generation through time.
Using a geology-based assessment methodology, the U.S. Geological Survey estimated a mean of 1,407 billion (1.4 trillion) cubic feet of gas in conventional accumulations in Upper Devonian to Lower Cretaceous strata of the western North Slope, Alaska.
Isolated, detached sands provide opportunities for large-volume stratigraphic traps in many deepwater petroleum systems. Here we provide a review of the different types of sandbody detachments based on published data from the modern-day seafloor and recent (generally Quaternary-present), shallow-buried strata. Detachment mechanisms can be classified based on their timing of formation relative to deposition of the detached sandbody as well as their process of formation. Syndepositional detachment mechanisms include flow transformation associated with slope failure (Class 1), turbidity current erosion (Class 2), and contourite deposition (Class 3). Post-depositional detachment is related to subsequent erosive processes and truncation of the pre-existing sandbody, either by submarine channels (Class 4), mass-transport events (Class 5), post-depositional sliding or faulting (Class 6) or bottom currents (Class 7). Examples of each of these mechanisms are identified on the modern seafloor, and show that detached sandbodies can form at different locations along the continental slope and rise (from upper slope to basin floor), and between or within different architectural elements (i.e., canyon, channels and lobes). This variation in formation style results in detached sands of highly variable sizes (tens to hundreds of kilometres) and geometries across and along the depositional profile, which are dependent upon the erosive and/or depositional processes involved, as well as the seafloor topography of the area in question. Whilst modern seafloor systems may not always represent the final stratigraphic architecture in the subsurface, they provide important insights into the development of detached sandbodies and therefore serve as potential analogues for subsurface stratigraphic traps.