Mark Longman

• Denver Museum of Nature and Science

Castlewood Canyon is one of the most distinctive landforms on the Colorado plains—a geomorphology that developed as Cherry Creek and its precursors incised into the Eocene Wall Mountain Tuff and overlying Castle Rock Conglomerate (CRC). Outcrops of the CRC in Castlewood Canyon State Park (CCSP) contain boulders of the Wall Mountain Tuff that are up...

Hydrous amorphous silica (aka opal) is a common cement in the Upper Eocene Castle Rock Conglomerate (CRC) of the southwestern Denver Basin. Petrographic study of standard thin sections indicates that this opal forms from 5% to as much as 40% of any given sample. It also commonly occurs as a precursor to fibrous length-fast chalcedony, a crystalline...

Facies of the Permian Lyons Sandstone are described and interpreted based on analyses of 23 cores from Larimer and Weld counties, Colorado. Here, the Lyons Sandstone consists of very fine-to medium-grained sandstone with minor silt and mudstone interbeds. The unit has five recurrent siliciclastic facies that can be grouped into two facies associati...

We describe and interpret here a suite of eolian dunes and eolian-influenced facies that were deposited from the time of the (Virgilian-Wolfcampian?) Upper Fountain Formation through the (Wolfcampian) Ingleside and (Leonardian) Lyons formations at Lory State Park, Larimer County, Colorado. The eolian dunes were deposited mainly by northerly winds a...

Just as the world’s population, knowledge in general, and the Rocky Mountain Association of Geologists (RMAG) have changed in major ways during the past 100 years, so too has the study and interpretation of carbonate rocks and reservoirs. The RMAG, a century old in 2022, has evolved from just 50 original charter members who held the organization’s...

We report new LA-ICP-MS U–Pb detrital zircon ages and sedimentary petrology of silty to sandy limestones and dolostones, as well as calcareous to dolomitic sandstones of the Devonian–Carboniferous (Mississippian) Chaffee Group. We also report new detrital zircon ages from the late Cambrian Sawatch Quartzite, and a U–Pb zircon crystallization age on...

Paired chemostratigraphic and biostratigraphic data suggest that the Devonian–Carboniferous boundary and the Hangenberg extinction event are recorded in the Coffee Pot Member of the Dyer Formation of the White River uplift region of northwestern Colorado. The Hangenberg isotopic excursion interval occurs in biostratigraphically depauperate shallow...

We integrate new and previous stratigraphic and petrographic data for the mid-Turonian Codell Sandstone to interpret its provenance, depositional characteristics, and environments. Our focus is on sedimentologic, X-ray diffraction, and X-ray fluorescence analyses of cores and thin sections spread throughout the Denver Basin, augmented by interpreta...

Core data from five key wells spanning the Denver Basin were tied to wireline log data and used to interpret the distribution of the Middle Turonian Codell Sandstone Member of the Carlile Formation across the Denver Basin. The character of the Codell’s upper contact is sharp with a localized top-down truncation across the basin, which is consistent...

We formally assign, describe and interpret a principal reference section for the middle Turonian Codell Sandstone Member of the Carlile Shale near Codell, Kansas. This section, at the informally named Pumpjack Road, provides the thickest surface expression (9 m, ~30 ft) of the unit in Ellis County. The outcrop exposes features that typify the Codel...

Studies of Niobrara depositional environments done during the 1980s and 1990s relied on what was understood about the processes controlling deposition in ~300 ft (~100 m) water depth at that time. A common idea was that the chalkier beds formed as carbonate-rich marine “snow” settled slowly to the sea floor to form blanket-like deposits that could...

Big Sandy and Clinesmith oil fields are located about five miles apart along the boundary between Woodson and Wilson counties in southeast Kansas. They are located on the Pennsylvanian Cherokee Platform and were discovered almost 60 years apart in 1923 and 1982 respectively. Both fields produce from Desmoinesian lower Bartlesville sandstone reservo...

The Upper Devonian Woodford Shale is predominantly a black, organic-rich siliceous mudstone that has long been recognized as a prolific source rock in Oklahoma and in the Permian Basin of West Texas and New Mexico. In contrast to the basins of Oklahoma, however, an established liquids-rich horizontal play in the Woodford of the Permian Basin remain...

The Devonian Woodford Shale and Cretaceous Mowry Shale consist of relatively deep (below storm wave base) intracratonic basin deposits commonly referred to as “shales” because of their dark gray to nearly black color, very fine-grained nature, pelagic fossils such as radiolarians, and common amorphous marine kerogen. These shales typically contain...

A new interpretation of the subsurface geometries of the Ordovician Bighorn Dolomite and overlying Devonian strata across southwestern Wyoming arises from revising the stratigraphy in a core from the Mountain Fuel Supply UPRR #11–19–104–4 well drilled on the crest of the Rock Springs Uplift in 1962. One of only a few wells to penetrate all or part...

The thickest and most distal section of the Upper Devonian Woodford Shale in the Permian Basin was deposited near the axial depocenter of the early to mid-Paleozoic Tobosa Basin. Today, a >560 foot thick section of the Woodford is preserved in a subbasin on the Permian Basin's Central Basin Platform (CBP). Conventional core was cut from 11,468 to 1...

The Upper Devonian Woodford "Shale" on the Central Basin Platform of the Permian Basin was cored from 11,468 to 11,515 ft (TVD) at the Hentz Family A56-0407 N 02WS in Winkler County, Texas. Core analyses show that this is a very siliceous mudstone with 55 to 75 weight percent silica (average 65%) and just 15 to 30% total clay (average 24%, includin...

The Three Forks Formation, which is about 230 ft thick along the southern Nesson Anticline (McKenzie County, ND), has four “benches” with distinct petrographic and petrophysical characteristics that impact reservoir quality. These relatively clean benches are separated by slightly more illitic (higher gamma-ray) intervals that range in thickness fr...

The Baxter Shale, stratigraphically equivalent to the Cody, Steele, and Mancos shales of Wyoming, was deposited in the Western Interior Seaway about 90 to 85 million years ago. In Canyon Creek Field, it consists of about 2700 ft of dominantly carbonate-rich, siliceous and illitic marine siltstones and shales. Siltstone beds range in thickness from...

Eland Field, the most prolific Lower Mississippian Lodgepole mound complex found to date in the Williston Basin, covers an area of about 6 mi2 and has produced more than 29 MMBO from 16 wells in the 20 years since the field was discovered. Three of the field’s updip wells have each produced more than 4 MMBO from mounds more than 250 ft thick althou...

The Yuma Arch is herein proposed as a major structural element forming the northeast margin of the Denver Basin. This previously little-recognized regional geological feature has significance in exploration for oil in this area of the basin. It was initially uplifted during the Paleozoic, but is largely masked by late Cretaceous - early Tertiary te...

Glen Bench Field was discovered in 1982 by a well drilled to test the gas potential of the Upper Cretaceous Mesaverde Sandstone. The field produces oil from a thin (3 to 6 ft), elongate (4 mi by 0.5 mi), oolitic, quartzarenite (>95% quartz grains) deposited along what was then the eastern shore of Eocene Lake Uinta. The sandstone is part of a shall...

From a brief overview of Tertiary carbonate reservoirs in Southeast Asia, it is clear that the productive buildups vary widely in terms of their distribution, overall size, facies geometry, and hydrocarbon reserves. Understanding the relationship between tectonic setting, basin type, and relative fluctuations in sea level can provide information us...

The contiguous Horse Creek and South Horse Creek fields produce oil from the Ordovician Red River Formation's "D" zone (equal to the "C" Burrowed Member). These fields produce from dolomite reservoirs at depths of about 9000 ft (3000 m) in the southern Williston basin on the northeastern flank of the southern end of the Cedar Creek anticline. Gentl...

Micrite-rich skeletal wackestones and packstones with common branching corals and benthonic foraminifera form the reservoirs in the Ramba and Rawa oil and gas fields. These limestones are part of the lower Miocene Batu Raja Formation, a widespread carbonate unit deposited over much of southern Sumatra and the Sunda Shelf on a relatively stable carb...

Ordovician oils in Mohawkian and Cincinnatian reservoirs of the United States Mid-Continent retain the biochemical imprint of Middle and Upper Ordovician oceanic life before the evolution of land plants and most vertebrates. Thus, these oils have some geochemical features that distinguish them from younger oils. These features include (1) a predomi...

Depositional facies indicate that the Charles 'C' interval represents a generally shallowing-upward depositional sequence. The major shallowing upward cycle can be subdivided into 5 smaller cycles separated by minor periods of transgression. The depositional facies can be traced far beyond the field's productive limits, but the degree of dolomitiza...

Remarkably uniform distribution of limestone, laminated dolomite, and anhydrite as determined from compensated neutron-density logs suggests that the entire Ordovician Red River Formation of the central Williston Basin was deposited in subtidal ''brining-upward'' sequences. Study of cores and thin sections verifies this locally dolomitized fossilif...

A paraconformity representing at most several thousand years separates vadose-cemented eolianites from modern uncemented dune sands on the S part of Isla Cancun, Yucatan Peninsula. Both eolian sands are carbonate grainstones composed of thinly coated skeletal fragments. Comparable (in terms of time) paraconformities are probably common in the rock...

Remarkably uniform distribution of limestone, laminated dolomite, and anhydrite as determined from compensated neutron-density logs suggests that the entire Ordovician Red River Formation of the central Williston basin was deposited in subtidal "brining-upward" sequences. Study of cores and thin sections verifies this interpretation and reveals tha...

Understanding the processes and products of carbonate diagenesis is essential to exploration for, and optimum development of, hydrocarbon reservoirs in carbonate rocks. Major diagenetic environments of the shallow subsurface are defined in this paper. Characteristic diagenetic textures produced in each environment are described and related to the p...

The first commercial oil production in the Philippines is from the Nido “B” field located about 30 miles northwest of Palawan. Oil is being produced from a Lower Miocene atoll-like carbonate buildup at a depth of approximately 6,800 feet. During development drilling, a 30-foot core was taken in the Nido B-3A well drilled near the margin of the buil...

Thesis--University of Texas at Austin. Vita. Includes bibliographical references (leaves 295-311). Photocopy of typescript.