bluuebunny/crossref_metadata_2025 huggingface dataset:
Geology and Ground-Water Resources of Sumner County, Kansas
Authors: Walters Kenneth L.
Published: January 2025

This report describes the geography, geology, and ground-water resources of Sumner County in south-central Kansas. The hydrologic and geologic data upon which this report is based were obtained in the field during the summers of 1955 and 1956. Records of 300 wells and 2 springs, chemical analyses of 219 water samples from wells and test holes and of 15 from streams, and logs of 362 wells and test holes are included in tables.
Sumner County has an area of 1,183 square miles and lies in the Wellington Lowland and Arkansas River Lowlands of the Central Lowland physiographic province. It is drained by Arkansas River, Ninnescah River, and Chikaskia River and their tributaries. The land surface in general is a southeastward-sloping, gently rolling plain. The average annual precipitation at Wellington is about 31 inches. Wheat fanning is the principal industry of the county, and oil is the chief natural resource.
The Wellington Formation, of Permian age, crops out in the eastern two-thirds of the county except where it is covered by Pleistocene deposits. The Ninnescah Shale (Permian) overlies the Wellington Formation and crops out in parts of the western third of the county. The Permian rocks yield small quantities of hard water to wells. Pleistocene sand and gravel deposits of Nebraskan age are present in the northwestern corner of the county and yield moderate quantities of good water to wells. Discontinuous deposits of Kansan or Illinoisan age, locally mantled by colluvium, forms terraces in southern and eastern Sumner County, and may yield moderate quantities of water. Wisconsinan terrace deposits and Recent alluvium along the major streams yield large quantities of water. Colluvium and dune sand are unimportant as sources of water but may facilitate recharge.
Maps of Sumner County included in this report show the outcrop areas of the formations, geologic cross sections, the shape and slope of the water table, the locations of wells and test holes for which records are given, and the distribution of chloride in water samples.
The ground-water reservoir is recharged principally from rain and snow that fall within the county, by percolation from streams and other surface bodies of water, and by underflow from adjacent areas. Water is discharged from the ground-water reservoir by seepage into streams, by transpiration and evaporation, by movement into adjacent areas, and by wells. Water is pumped from wells for domestic, stock, municipal, industrial, and irrigation use. Irrigation from wells is most extensive in the valley of Arkansas River, in which area further development is most probable.
Chemical analyses of samples of water from Sumner County indicate that the quality varies greatly from place to place. Sulfate is common in water from the Wellington Formation and Ninnescah Shale. Water from Pleistocene deposits is generally suitable for most uses except in local areas where it contains excessive chloride.
Geology and Ground-Water Resources of Trego County, Kansas
Authors: Hodson Warren G.
Published: January 2025

Trego County is a 900-square-mile area in the High Plains section of west-central Kansas. The altitude ranges from about 2,000 to 2,600 feet above sea level. The climate is semiarid, and the mean annual rainfall is 21.40 inches. The population of the county in 1960 was 5,473. Farming and livestock raising are the chief occupations.
The Carlile Shale of late Cretaceous age is the oldest rock formation cropping out in the county. The Carlile is overlain by the Niobrara Chalk, the dominant bedrock formation in the county. The Ogallala Formation of Neogene (Pliocene) age unconformably overlies Cretaceous rocks in much of the county and consists principally of fluviatile deposits of sand, gravel, and silt. Terrace deposits of Pleistocene age occur along the principal valleys. Eolian silts that mantle the uplands and alluvium along stream valleys constitute the youngest deposits and are late Pleistocene in age.
The Ogallala Formation is the most widespread aquifer and yields water to many domestic and stock wells. Alluvium and terrace deposits yield moderate quantities of water, but these deposits are not of wide areal extent. In areas of Cretaceous outcrops, small quantities of ground water are obtained from the Dakota Formation of early (?) Cretaceous age and from the Codell Sandstone Member of the Carlile Shale of late Cretaceous age.
Hydrologic data are given in tables and include records of 280 wells, logs of 176 test holes and wells, and chemical analyses of 59 samples of water from wells.
Geology and Ground-Water Resources of Neosho County, Kansas
Authors: Jungmann William L.
Published: January 2025

Neosho County has an area of 576 square miles and is within the Osage Plains section of the Central Lowlands province of eastern Kansas. Sedimentary rocks of Cambrian, Ordovician, Devonian(?), Mississippian, Pennsylvanian, Tertiary, and Quaternary ages overlie the Precambrian basement complex, and they have a thickness of 2,100 feet. Rocks exposed in the county are of Pennsylvanian, Tertiary, and Quaternary ages that attain a thickness of 700 feet. Structure is controlled by the Prairie Plains Monocline in which the exposed Pennsylvanian rocks dip northwest at about 20 feet per mile.
Wells in consolidated rocks of Pennsylvanian age yield less than 1 gallon per minute of water from some limestone and shale aquifers to more than 30 gallons per minute from sandstone aquifers. The water from the consolidated aquifers is highly mineralized, but the sandstones tend to yield a softer, less mineralized water. Wells within unconsolidated Pleistocene alluvial deposits yield up to 30 gallons per minute.
The chief use of the ground water is for domestic and stock purposes, whereas all municipal systems use treated surface water. The estimated total use of ground water in 1961 was 109 million gallons (334 acre-feet).
Short Papers on Research in 1971
Authors: Kellogg Jo Anne
Published: January 2025

Gravity measurements support the hypothesis that an abandoned lead and zinc mine near Pleasanton, Kansas, is associated with a slump pipe. A negative gravity anomaly closure of ≈ 0.4 mgal is consistent with a brecciated zone extending at least 600 feet through basal Pennsylvanian strata and into those of the Mississippian. A second negative gravity anomaly of the same magnitude occurs several hundred feet north of the first and may correspond to a similar slump structure. This second anomaly remains unexplored to date. Magnetic field measurements show no apparent correlation with slumps in this area.
Suitability of high-resolution seismic method to identifying petroleum reservoirs in Kansas--a geological perspective
Authors: Newell K. David , Watney W. Lynn , Steeples Don W. , Knapp Ralph W. , Cheng Stephen W. L.
Published: January 2025

Kansas has been a part of a stable craton since at least the beginning of the Paleozoic some 550 m. y. ago. The majority of the sedimentary rocks deposited during the last 550 m. y. are products of numerous inundations by shallow seas. Interspersed with these transgressions were periods of erosion, many coinciding with widespread uplift. The distribution of reservoir-quality rocks has been controlled by the varying structural and depositional settings in both time and space. The identification of these reservoirs begins with a knowledge of the geologic history as detailed by the vast subsurface information base, mainly wire line logs and completion records, that is available for Kansas. Seismic profiling has been and will continue to be used effectively to resolve structural traps. The trend in exploration in the midcontinent has been to strengthen the search for reservoirs associated with more subtle structures and difficult-to-find stratigraphic traps. Stratigraphic traps will become increasingly important, particularly within established production trends. The many unconformities in the midcontinent stratigraphic column afford numerous types of trapping geometry such as truncation beneath an unconformity, traps associated with buried valleys, discontinuous onlap onto erosion surfaces, and porosity pinchouts due to changes in original depositional conditions and diagenetic alteration. The most widespread petroleum accumulations in Kansas occur in structural and stratigraphic traps associated with the pre-Pennsylvanian unconformity. Production associated with the unconformity includes numerous lower Paleozoic pay zones which subcrop directly beneath the unconformity in the Sedgwick, Salina, and Anadarko basins; the Arbuckle production on the Central Kansas uplift; and numerous fields which payout from either conglomerates or weathered zones along the unconformity. Considerable production also occurs farther up-section with the Cherokee and Lansing-Kansas City groups, and down-section in the Viola Formation and Simpson Group. In order to demonstrate the potential use of the seismic method in defining subtle traps, synthetic seismograms were produced for selected strata in central Kansas. Critical attributes of reservoir rock and associated strata conducive to seismic stratigraphic processing include the thickness of a potential reservoir bed and its velocity and density contrast with adjacent strata. Thicker strata such as the Morrow and most lower Paleozoic formations may be more easily defined by seismic-stratigraphic methods. In contrast, the stratigraphy of the Pennsylvanian and Permian cyclothems may not be amenable to definition by seismic methods because these units contain heterogenous reservoirs interbedded with other thin strata of similar composition.
Seismic exploration for the Morrow trend
Authors: Rummerfield Benjamin F. , Rummerfield Larry J.
Published: January 2025

The Southwest Kansas basin, encompassing the southwest one-third of Kansas, southeast Colorado, and northwest Oklahoma, was the major structural feature influencing the deposition of the Pennsylvanian rock units in this area. Morrow production here currently is attracting attention. Multiple oil- and gas-producing zones are found in these Pennsylvanian clastics. They were eroded, in part, from the ancestral Rocky Mountain uplift for the upper sequence and from the Amarillo uplift for the basal sequence. The Central Kansas uplift also contributed its share of sediments. Deformation and subsequent erosional processes during Late Mississippian time had a profound effect, especially on Morrowan deposition, in this vicinity. Therefore, paleostructure and stratigraphic studies are essential for delineation of hydrocarbon reservoirs in this region. The use of a datumized Pennsylvanian reflecting horizon helps to correct the effects caused by the variations of the Permian salt beds. This provides the means of defining the erosional channels of the Mississippian surface and the associated deposition of the Morrow sands. The regional seismic program shown is designed to provide high-quality structural and stratigraphic information through the use of innovative near-surface static corrections. The seismic-refraction breaks (first arrivals) of existing 100% data are used in conjunction with uphole velocity surveys to obtain more exact corrections. This near-surface velocity control produces a final seismic section of superior quality.
Seismic-reflection study in Rice County, Kansas
Authors: Roehl Nelda L. , Knapp Ralph W. , Newell K. David
Published: January 2025

During the summer of 1983, a MiniSOSIE seismic-reflection study was conducted in Rice County in which an 11.2-km (7-mi) 12-fold common depth point (CDP) profile was shot to investigate several local structural and stratigraphic features. The seismic line was oriented east-west, perpendicular to the local structural grain. Several units, ranging from the Arbuckle through the Mississippian limestones, subcrop beneath the basal Pennsylvanian angular unconformity in this area. The subcrop pattern is dominantly north-south and is related to the eastward dip of these units off the Central Kansas uplift. Reflectors in excess of 1,070-m (3,500-ft) depth are detectable on the seismic profile. The deepest reflectors (0.850 secs) correspond to the Precambrian Rice Formation. Good reflectors occur in the lower Paleozoic section corresponding to a local limestone in the Chattanooga Shale and the subjacent Maquoketa-Viola formations. Several limestones in the Upper Pennsylvanian and Permian section also are good reflectors of seismic energy. Stratigraphic features such as local thinning or thickening and channel cuts can be detected in this part of the stratigraphic section. The Lyons anticline, a local north-south-trending structure currently used for gas storage, also is expressed on the seismic line. The seismic profile shows the structural history of this anticline to be long and complex. Initially, the anticline was a broad, symmetric feature possibly related to the formation of the Precambrian Keweenawan rift. Minor growth may have occurred prior to the deposition of the Chattanooga Shale. A third major period of movement occurred during Late Mississippian to Early Pennsylvanian time when a reverse fault developed on the west flank of the structure, thereby making the structure an asymmetric anticline. Minor structural movement occurred again subsequent to the development of the basal Pennsylvanian angular unconformity.
Geophysical model of the Midcontinent Geophysical Anomaly in northeastern Kansas
Authors: Somanas Chaturong , Knapp Ralph W. , Yarger Harold L. , Steeples Don W.
Published: January 2025

A geophysical model of the Midcontinent Geophysical Anomaly (MGA) in northeastern Kansas was derived to fit gravity and magnetic data using an initial model suggested from COCORP seismic sections, along with available drill data. An asymmetric basin filled with interbedded basaltic and clastic rocks in the shallow crust, interpreted by Serpa et al. (1984), appears to be mainly responsible for the primary positive magnetic anomaly of the MGA. The favorable magnetization of 60° inclination and 320° declination indicates that the remanent magnetization is an important factor. Reprocessing part of COCORP seismic data reveals a possible mafic intrusion in the shallow crust beneath a secondary magnetic high. Its favorable net magnetization of 30° inclination and 80° declination suggests it occurred in a different ambient earth's magnetic field than that in which the basaltic rift basin was formed. In addition, the nonmagnetic source of high density at midcrustal levels extending to deep crust and the nonmagnetic Rice Formation basins of low density at shallow crust on both sides of the MGA were proposed to fit the gravity anomaly. The final derived model infers the mafic intrusion in the shallow crust beneath the secondary magnetic high to be of younger age than the Rice Formation.
Proposed Repositioning of the Pennsylvanian-Permian Boundary in Kansas
Authors: Baars D. L. , Ross Charles A. , Ritter Scott M. , Maples C. G.
Published: January 2025

The Pennsylvanian-Permian boundary in North America has not corresponded with the Carboniferous-Permian boundary in Europe for decades. To facilitate global correlations, an attempt is here made to suggest a possible solution to the dilemma by making the best possible correlation of the Kansas stratigraphic section with the recently proposed boundary location in the Russian type section.
The Virgilian Stage (Upper Pennsylvanian) was defined nearly 60 years ago to include those rocks lying between the Missourian Stage and the base of the Permian System. In the type area in east-central Kansas, the Virgilian Stage comprised the Douglas, Shawnee, and Wabaunsee Groups. In Kansas, the Pennsylvanian-Permian boundary was placed eventually at the top of the Brownville Limestone Member on the basis of what was then believed to be a regional disconformity rather than on paleontological criteria. Recent advances in fusulinid and conodont biostratigraphy provide tentative criteria upon which to suggest a change in the placement of the Virgilian-Permian boundary.
A Russian delegation formally proposed at the International Congress on the Permian System of the World held in Perm, U.S.S.R. (Russia) in August 1991 that the base of the Permian System be established at the base of the Asselian Stage at the approximate stratigraphic position of the first inflated fusulinids (Sphaeroschwagerina vulgaris-S. fusiformis). Inflated schwagerinids (Paraschwagerina kansasensis) first occur, along with evolutionary changes in conodonts, in the Neva Limestone Member of the Grenola Limestone (Council Grove Group). Thus, if we assume that inflated schwagerinids arose globally at about the same time, the Neva Limestone Member is the oldest definitive Permian in the United States midcontinent, as related to the newly proposed boundary in Russia and Kazakhstan. Consequently, we propose that the Virgilian Stage in Kansas include rocks between the top of the Missourian Stage and the base of the Neva Limestone Member.
Redefinition of the Upper Pennsylvanian Virgilian Series in Kansas
Authors: Baars D. L. , Ritter Scott M. , Maples C. G. , Ross Charles A.
Published: January 2025

The Virgilian Series was defined nearly 60 years ago to include those rocks lying between the Missourian Series and the base of the Permian System. In the type area in east-central Kansas, the Virgilian Series comprised the Douglas, Shawnee, and Wabaunsee Groups. In Kansas, the upper boundary of the Virgilian (Pennsylvanian-Permian boundary) was placed at the top of the Brownville Limestone Member on the basis of what was then believed to be a regional disconformity rather than on paleontological criteria. Recent advances in fusulinid and conodont biostratigraphy provide tentative criteria upon which to effect a change in the placement of the Virgilian-Permian boundary. It is now generally agreed that the base of the Permian System is approximated by the first occurrence of Pseudoschwagerina, an inflated schwagerinid. Furthermore, the Subcommission on Permian Stratigraphy has informally agreed that the base of the Permian should coincide with the first occurrence of the conodont species Streptognathodus barskovi. Inflated schwagerinids (Paraschwagerina kansasensis) first occur along with evolutionary changes in the Conodonta in the Neva Limestone of the Council Grove Group. Consequently, the Virgilian Series is herein redefined to include rocks present between the top of the Missourian Series and the base of the Neva Limestone.
To increase compatibility between chronostratigraphic and lithostratigraphic nomenclature, the following changes are made: I) the Admire Group is redefined to include rocks between the base of the Onaga Shale and the base of the Neva Limestone; 2) the Admire is reassigned to the upper Virgilian Series; 3) the Neva Limestone is elevated to formational status; 4) the Grenola Limestone is redefined to include strata between the top of the Roca Shale and the base of the Neva Limestone; 5) the overlying Council Grove Group is redefined to include strata lying between the base of the Neva Limestone and the base of the Chase Group; and 6) regionally the base of the emended Council Grove Group marks the base of the Permian System. The emended Council Grove Group is lower Wolfcampian in age and is time equivalent with the Neal Ranch Formation of the west Texas type Wolfcampian.
Lithostratigraphy of the Hugoton and Stevens Members of the St. Louis Limestone and the Ste. Genevieve Limestone (Upper Mississippian), Southwestern Kansas
Authors: Abegg F. E.
Published: January 2025

The Hugoton and Stevens Members are new lithostratigraphic units of the St. Louis Limestone in the Hugoton embayment, southwestern Kansas. A core from the Mobil #1 Foster (sec. 5, T. 34 S., R. 36 W.) is proposed as the type section for both members.
The Hugoton is the lower member and at the type section contains primarily dolomitic peloidal grainstone/packstone, dolomite, and anhydrite. Breccia, algal boundstone, and dolomitic lime mudstone are common facies elsewhere in southwestern Kansas. The Hugoton Member is easily differentiated from skeletal and oolitic limestones of the uppermost Salem Limestone. Abundant peloids, anhydrite, and paucity of stenohaline marine organisms in the Hugoton Member indicate deposition in a restricted lagoon. Restricted conditions probably resulted from oolite-skeletal shoals in the underlying Salem.
Strata of the Stevens Member contain dominantly skeletal packstone/wackestone. Periodic winnowing, intercalated oolites, and a diverse and abundant assemblage of stenohaline echinoderms, brachiopods, and bryozoans indicate Stevens skeletal packstone/wackestone was deposited in a normal-marine shelf environment at or near fair-weather wave base. Stevens Member oolitic grainstone/packstone, the reservoir facies, accumulated in a highly agitated, marine-shoal environment, probably at depths less than 15 ft (5 m). A quartzose grainstone 3.8 ft (1.2 m) thick in the Stevens Member contains abundant rhizoliths and ubiquitous climbing translatent strata with dips less than T, indicating deposition in a vegetated eolian sand sheet.
Ste. Genevieve strata are recognized by the lowest prominent quartz-rich grainstone. In the Mobil #1 Foster, the basal quartzose grainstone is 9.4 ft (2.9 m) thick, lacks rhizoliths, and consists of abundant climbing translatent, common grainfall, and minor grainflow stratification in crossbed sets up to 1.5 ft (0.5 m) thick with dips as high as 24°. This crossbedding, climbing trans latent strata, and the apparent absence of vegetation indicate deposition by eolian dunes. The overlying Shore Airport Formation typically contains argillaceous limestone and intercalated calcareous shale.
Cyclic stratigraphy, sequence stratigraphy, and stratigraphic modeling from 1964 to 1989: Twenty-five years of progress?
Authors: Ross W. C.
Published: January 2025

The evolution of concept development in stratigraphy between 1964 and 1989 is reviewed by comparing and contrasting the contents of the golden book volume on cyclic stratigraphy (Merriam, 1964) with the present volume. Although separated by more than 25 years, both volumes treat strikingly similar subject material with an emphasis on cyclic stratigraphy, time stratigraphy, and the genetics of basin fill. The collection of papers found in the earlier volume reflects the culmination of work from the most prominent stratigraphers of the 1940's through the early 1960's, a period strongly affected by the principles of sequence stratigraphy. Workers from this generation established many of the fundamental stratigraphic concepts that we view as modem. During the mid-1960's and 1970's emphasis shifted to research on facies models, and with few exceptions stratigraphic cyclicity, sequence stratigraphy, and the genetics of basin fill processes were scarcely considered. With the advent of seismic stratigraphy, in the late 1970's, sequence stratigraphy was reborn, and with it a new generation of researchers focusing on the genetics of basin fill. The earlier book and the present volume reflect two distinct episodes of stratigraphic concept development related to two separate episodes in the history of sequence stratigraphy. In contrast to the authors of the golden book, genetic stratigraphers in the present volume have the advantage of computer-based stratigraphic modeling tools. Armed with these tools and the body of knowledge about facies models accumulated in the past 25 years, the geologic community is poised to make great strides in the development of powerful predictive models for sedimentary basin evolution.
Nonlinear dynamic systems in the geosciences
Authors: Nicolis G. , Nicolis C.
Published: January 2025

Geophysical phenomena are often characterized by complex, random-looking deviations of the relevant variables from their average values. Typical examples of such aperiodicity are the intermittent succession of Quaternary glaciations as revealed by the oxygen isotope record of deep-sea cores of the last 106 years or the pronounced spatial disorder characterizing geologic materials. A major task of the geoscientist is to reconstitute from this type of record the principal mechanisms responsible for the observed behavior. Traditional approaches attribute the complexity encountered in the record of a natural variable to external uncontrollable factors and to poorly known parameters whose presence tends to blur fundamental underlying regularities. Here, we consider that complexity might be an intrinsic property generated by the nonlinear character of the system's dynamics. We review bifurcations, chaos, and fractals, three important mechanisms leading to complex behavior in nonlinear dynamic systems, and stress the role of the theory of nonlinear dynamic systems as a major tool of interdisciplinary research in the geosciences. The general ideas are illustrated on the dynamics of Quaternary glaciations and the dynamics of tracer transport in a sediment.
Observational foundation for sequence modeling
Authors: Wanless Harold R.
Published: January 2025

The design of useful models for predicting sequences and facies patterns of sedimentary cycles depends on an observational foundation that includes the recognition and adequate understanding of fundamental depositional sequences. Six facets must be met. The modeler must have (1) adequate documentation of sequence character; (2) adequate characterization of spatial and directional variability and continuity of facies; (3) an adequate database on the influence of primary and secondary controls on sedimentation; (4) an understanding of interaction of controls on sedimentation; (5) an understanding of limits of physical, biologic, and chemical influences; and (6) an understanding of diagenetic modifications to sequence nature and thickness. In addition, the models should work from the fundamental depositional sequence. The modeler should use caution in applying models designed for one scale of sedimentary sequence to another scale. Examples illustrate the necessity for meeting each facet.
Lithofacies and geochemical facies profiles from nuclear wire-line logs: New subsurface templates for sedimentary modeling
Authors: Doveton John H.
Published: January 2025

The use of wire-line logs in subsurface studies is all too often restricted to the correlation of selected stratigraphic horizons. There is an increasing content of valuable geologic information in modern wire-line logs that can be extracted by simple computer processing. The resulting log transformations provide lengthy and continuous records of sections of interest. Examples of these methods, as applied to Cretaceous and Permian stratigraphic case studies, are described here. The log data can be incorporated in either forward- or reverse-modeling modes in the simulation and analysis of sedimentary sequences. In addition to their geologic information content, wire-line logs are quantitative, and so their data can be entered easily into numerical modeling programs. Analysis can be made in either the stratigraphic time or frequency domain. The power spectra of logs give key insights into the nature and scale of sedimentary depositional mechanisms.
Genetic stratigraphy of the Fort Scott Limestone (Pennsylvanian, Desmoinesian), southeastern Kansas
Authors: Suchy D. R. , West R. R.
Published: January 2025

The punctuated aggradational cycle (PAC) approach of Anderson and Goodwin (1980) and transgressive-regressive units of Busch and Rollins (1984) were used to differentiate small-scale [1-3 m (3.3-10 ft) thick] genetic units in strata of the 9+-m-thick (30+-ft-thick) Fort Scott Limestone (Marmaton Group, Desmoinesian Stage, Middle Pennsylvanian Series) of southeastern Kansas, northeastern Oklahoma, and west-central Missouri. Nine outcrop exposures were observed directly, and information from 20 stratigraphic sections was taken from the literature. The lithologic sequence of the Marmaton Group is similar to cyclothems of the Illinois basin, and thus the genesis of coal is important. Many recent studies have interpreted midcontinent sedimentary strata using Heckel's (1977) model of the basic Kansas cyclothem, which emphasizes a lithostratigraphic approach. The PAC hypothesis is a genetic approach that provides a chronostratigraphic framework for interpreting the strata, reveals a more detailed sea-level history compared to the cyclothem approach, and provides more details for inferring the paleotopography, structural controls, paleogeography and paleoclimatology of the interval. We have identified four (possibly five) sixth-order cycles (Brett et al., 1990) or PACs (Goodwin and Anderson, 1985), which include as many flooding surfaces, in an interval previously interpreted as one cyclothem [the upper Fort Scott cyclothem of Knight (1985)]. These PACs can be traced and correlated throughout the outcrop area, a distance of over 300 km (190 mi), and are similar to small-scale cycles recognized by others in the Triassic of Italy and in the Silurian-Devonian sequence of New York. Recognition and correlation of sixth-order cycles (Brett et al., 1990) or PACs is of value to sedimentary modelers because the more detailed relative sea-level curves and finer scale stratigraphic details will result in better defined parameters, such as sedimentation rates, magnitudes of sea-level changes, and climatic perturbations.
High-frequency carbonate cycles and stacking patterns: Interplay of orbital forcing and subsidence on Lower Jurassic rift platforms, High Atlas, Morocco
Authors: Crevello Paul D.
Published: January 2025

The stratigraphy of carbonate cycles and cycle-stacking patterns in Lower Jurassic shallow-water platforms from the High Atlas rift are related to base-level changes driven by orbital forcing and subsidence. Multifold platform stratigraphic hierarchy, originally recognized from field observations, yields cycle ratios approximating 20:5:1 with time-thickness (Fischer plots) and time-series analyses. The cycle ratios are similar to orbital cycles of long and short eccentricity and precession. A depositional sequence model for cycle-stacking patterns, which is governed by a threefold superimposed sea-level curve that yields a 20:5:1 cycle ratio, is compared with the stratigraphic field data. Divergence of Jurassic cycle distribution and stacking patterns from the ideal model suggest that subsidence and variation in long-term eccentricity controlled the development of progradational, aggradational, or retrogradational stacking patterns and thus dictated the resulting distribution of systems tracts within depositional sequences. The lithofacies character and cycle symmetry of individual carbonate cycles are controlled by local environmental conditions in addition to eustasy and subsidence. Cycles are considered the fundamental stratigraphic element constructing the platforms. However, the contribution of complete cycles to the overall stratigraphic record of the platform is varied. Outer-platform cyclic strata make up nearly 75% of the stratigraphic interval. In contrast, platform-margin or inner-platform strata contain less than 50% complete cycles. The balance at the outer platform between subsidence and the interplay of high-frequency and low-amplitude sea-level fluctuations of 1-5 m (3-16 ft) accounts for the higher percentage of cycles in shallow-water settings. Inner-platform strata were limited by creation of accommodation space, and platform-margin strata were too deep on the distally steepened margin to be influenced by every base-level shift that affected shallow-water sedimentation. Only infrequently did high-amplitude sea-level falls, of the order of 30 m (100 ft), expose sediments at the platform margin.
Controls on carbonate and siliciclastic sediment deposition on a mixed carbonate-siliciclastic shelf (Pennsylvanian Eastern Shelf of north Texas)
Authors: Yancey Thomas E.
Published: January 2025

Patterns and trends of carbonate and siliciclastic lithologies in late Paleozoic cyclothems are used as the basis for identifying the factors controlling deposition in mixed carbonate-siliciclastic systems. The cyclothems examined in detail occur on the Eastern Shelf of the Midland basin in north Texas. Cyclothems are products of deposition in shelfwide mixed carbonate-siliciclastic systems and contain an intermediate water depth carbonate zone positioned between a shallow nearshore zone of siliciclastic deposition and a deep-water outer shelf zone of siliciclastic deposition. Carbonate sedimentation was largely depth controlled, because carbonate sediment production was primarily from microbes, multicellular algae, or other light-controlled benthic organisms. Siliciclastic sedimentation in the noncarbonate outer shelf environments resulted from pulses of fine-grained siliciclastic sediment traversing the carbonate zone in storm-generated suspension clouds. Increased siliciclastic sediment input narrowed the carbonate zone on the shelf but did not greatly shift its central position. Cyclothem deposition corresponds to a limited range of conditions covered in a general model of mixed carbonate-siliciclastic deposition on shelf surfaces. The major variables in this model are the quantity and composition of siliciclastic sediment delivered to the shoreline and carried onto the shelf, the depth of the lower limit of the photic zone as it intersects the shelf surface, the gradient of the depositional surface, and the proportion of benthic production to planktic production of carbonate sediment. In systems where carbonate sediment is predominantly benthic in origin (Paleozoic and Triassic oceans), the first three variables are dominant and result in outer shelf siliciclastic deposition beyond a carbonate zone. In systems where planktic production of carbonate occurs (Jurassic to modern warm-water oceans), planktic production of carbonate tends to overwhelm benthic production and produces carbonate deposition on outer shelf surfaces. General patterns of sedimentation are set by the benthic/planktic production ratio and the gradient of the depositional surface, whereas specific patterns are produced by the amounts of siliciclastic sediment transported onto the shelf and the manner in which the photic zone intersects the shelf.
Evidence for orbital forcing of Middle Cambrian peritidal cycles: Wah Wah range, south-central Utah
Authors: Bond Gerard C. , Kominz Michelle A. , Beavan John
Published: January 2025

We have applied a new method (gamma method) for constructing high-resolution age models to peritidal cycles in the Middle Cambrian Pierson Cove Formation (13 cycles) and the Trippe Limestone (40 cycles) exposed in the Wah Wah range, south-central Utah. Spectral analyses of the time series for the gamma age model indicate the presence of significant spectral peaks (relative to a null model) in both data sets. After experimenting with different assumptions for the duration of the mean primary or measured cycle, we found that for the Trippe data set assigning the mean duration of precession to the mean primary cycle produced a reasonably good correlation between the spectrum and the early Paleozoic estimate of insolation forcing. In particular, the periods of the three significant spectral peaks in the Trippe record correspond to estimated line periods for eccentricity and precession and a combination tone of precession. A spectrum for the Trippe cycles based on the conventional assumption that time is proportional to thickness contained only one significant peak, and reasonable estimates of the duration of the mean primary cycle produced a poor fit to the insolation model. Spectral results from the Pierson Cove cycles were less compelling, possibly because of the short length of the record. The presence in the Trippe spectrum of significant peaks with periods corresponding to high-frequency orbital variations suggests that preservation of high-frequency Milankovitch signals is more common than implied by models of shallow marine cyclicity based on Pleistocene sea-level records. The results of these spectral analyses suggest that the gamma method can be used to construct age models for peritidal carbonate cycles that are accurate enough to test for periodicity and deterministic mechanisms, even in rocks as old as the Cambrian.
Hierarchy of stratigraphic forcing: Example from Middle Pennsylvanian shelf carbonates of the Paradox basin
Authors: Goldhammer R. K. , Oswald E. J. , Dunn P. A.
Published: January 2025

Middle Pennsylvanian (Desmoinesian) shelf carbonates in the southwestern Paradox basin display three superimposed orders of stratigraphic cyclicity with a systematic vertical succession of facies, cycle, and sequence stacking patterns. Fifth-order cycles [34 cycles in a 645-ft (197-m) section; average 20 ft (6.1 m) thick; mean period 29,000 years] are grouped into fourth-order sequences [average 100 ft (30 m) thick; mean period 257,000 years], which in turn stack vertically to define a third-order sequence [650+ ft (200+ m) thick; 2-3 m.y. duration]. Fifth-order cycles are composed of shallow ing-upward packages of predominantly subtidal shelf carbonates with sharp cycle boundaries (either exposure or flooding surfaces). Fifth-order cycles are packaged into fourth-order sequences bounded by regionally correlative subaerial exposure surfaces. These type 1 sequences contain a downdip, restricted lowstand wedge of evaporites and quartz clastics in topographic lows on the Paradox shelf (intrashelf depressions). The lowstand systems tract is overlain by a regionally correlative transgressive shaly mudstone (condensed section) and a highstand systems tract composed of thinning-upward, aggradational fifth-order cycles. Systematic variation in the thickness of fourth-order sequences (thinning upward followed by thickening upward) and systematic variations in the number of fifth-order cycles and fourth-order sequences (decreasing followed by increasing number) defines a third-order accommodation trend that is also regionally correlative. High-frequency cycles and sequences are interpreted as predominantly aggradational allocycles generated in response to composite fourth- and fifth-order glacio-eustatic sea-level fluctuations. Two different orbital forcing (Milankovitch) scenarios are evaluated to explain the composite stratigraphic cyclicity of the Paradox sequences, each of which is plausible given Desmoinesian age estimates. The cycle, sequence, and facies stacking patterns have been replicated by means of computer modeling by superimposing composite high-frequency glacio-eustasy atop regional subsidence using depth-dependent, sedimentation.
STRATA-VARIOUS: A flexible Fortran program for dynamic forward modeling of stratigraphy
Authors: Frohlich Cliff , Matthews R. K.
Published: January 2025

STRATA-VARIOUS version 1.3 is a computer program written in Fortran 77 to perform two-dimensional forward modeling of stratigraphic processes. We designed specific features of the program to investigate orbital forcing of high-frequency glacioeustasy. This requires forward modeling of many hundreds of sea-level stillstands and the graphic display of relatively precise spatial details. To use this program, the user constructs files that specify the times and elevations of sea-level stillstands, the initial basement topography, numerous parameters that control the geometry and physical properties of stratigraphic beds, the isostatic response of the lithosphere, the pattern of tectonic subsidence and uplift, the number and scale of desired output cross sections, etc. Two features of this program are especially novel. Whereas many forward-modeling programs store information about stratigraphic beds in fixed-size horizontal bins, our program retains in memory the precise locations of all horizontal locations where any stratigraphic bed undergoes any distinct change. This allows us to obtain regional cross sections and magnified sections that preserve information about the geometry and lithology of individual beds. Second, for clastic sediments we have developed a realistic parametric scheme for describing how sea-level variation affects the sediment discharge rate. The parameters that control this scheme have simple physical interpretations in terms of the dimensions, erosion rates, etc. for the alluvial valley responsible for the sediment supply. In this article we give various examples of STRATA-VARIOUS graphic output to illustrate model sensitivity and to demonstrate some of the options available.
Depth-dependent diffusion algorithm for simulation of sedimentation in shallow marine depositional systems
Authors: Kaufman P. , Grotzinger J. P. , McCormick D. S.
Published: January 2025

An algorithm has been developed to simulate sediment dispersal on shallow marine siliciclastic, carbonate, and mixed siliciclastic-carbonate shelves. The algorithm is based on a diffusion scheme in which the diffusion coefficient decays exponentially with water depth. The rationale for using a varying diffusion coefficient lies in the observation that on marine shelves wave energy and therefore bed shear stress decay exponentially with water depth. Thus sediment flux cannot be modeled by a diffusive process based on a linear dependence on slope alone. This approach is probably most appropriate for wave-dominated shelves. The model simulates deposition in two dimensions. Siliciclastic shelf sedimentation occurs solely by lateral transport in the plane of section by diffusion; carbonate sedimentation occurs by depth-dependent in situ sediment production with subsequent lateral dispersal of sediment by diffusion. The effects of early cementation can be modeled by varying the transport coefficient that governs the efficiency of diffusion.
Carbonate progradation geometry and significance of sediment accumulation patterns and syndepositional relief: Comparison of modeling results with outcrop data
Authors: Harris Mark T.
Published: January 2025

The relatively simple geometries of carbonate buildup margins are amenable to quantitative computer modeling. Margin geometries (progradational, vertical, or backstepping) are the consequences of sediment accumulation patterns across the depositional profile during the evolution of the buildup. Modeling allows comparisons of how different margin geometries and sediment accumulation patterns can influence progradation geometry and provides a range of geometric responses for comparison to actual outcrop examples. MARGIN is a sediment accumulation model of a carbonate buildup written in Pascal for an IBM PC. The model uses a generalized three-dimensional buildup geometry with a circular or linear margin, a foreslope with a constant dip, and a flat-lying basin. The subsidence history, sediment production rate, and basinal sediment accumulation rate control the addition of sediment during a series of iterations. The simulation ends when the basin fills, the platform drowns, or a preselected platform thickness is reached. The model calculates the buildup's geometric dimensions and relative rates of sediment accumulation and outputs a scaled cross section. Variations in sediment accumulation parameters or initial buildup geometry result in quite different progradation geometries. Enhanced progradation results from low buildup relief, steeper foreslope dip, slow subsidence, high sediment production, linear margin geometry, and/or high rates of basinal deposition. For buildups of several hundred meters in thickness, the extent of progradation depends on the basin fill rate. In all simulations starved basins ultimately become too deep for foreslope infilling. This geometric relation suggests that the thickness and timing of basinal sedimentation is a controlling factor on carbonate buildup progradation. The results provide insights for interpretation of ancient buildup geometries (Triassic of the Dolomites, Permian of the Guadalupe Mountains, Devonian of the Canning basin). In all these examples the extent of buildup progradation depends to some degree on the rate of basinal deposition.
Forward Seismic Modeling--Applications and Utility
Authors: Anderson Neil L. , Hedke Dennis E. , Knapp Ralph W.
Published: January 2025

Geological bodies such as reefs, horst blocks, channel sandstones, faults, salt diapirs, deltaic complexes, etc., typically generate recognizable seismic signatures (or distinguishing seismo-geological features). The seismic signature of a geological body (a reef, for example) is composed of any and all features on the seismic data that can be confidently attributed to the presence of the reef.
Seismic signatures have two basic components: time-structure variations and character variations. The time-structure variation component is created by structural relief in the subsurface and velocity-generated, time-structural relief (pull-up/push-down effects). The character variation component consists of lateral changes in the amplitude and/or phase of specific events and lateral variations in the seismic image of specified units (typically corresponding to stratigraphic groups). The seismic image of a specified layer is the pattern of the sequence of events from the top to the base of that layer, inclusive.
Forward seismic modeling is the process through which a geologic section (subsurface depth! density/acoustic-velocity model) is transformed into a synthetic seismogram, thereby enabling the relationships between the subsurface and the corresponding synthetic seismogram to be deduced. Such modeling can elucidate the potential utility of the seismic technique prior to the acquisition of field seismic data and facilitate the interpretation of acquired data. Seismic modeling is typically done both before and after the acquisition of seismic field data. It aids the planning of an acquisition program and it is essential in interpretation, making correlation of the observed reflections with geologic interfaces possible, and verifying the seismic responses of deduced anomalies.
Comparison of High-resolution and Conventional-resolution Seismic Data--Application to Cyclothems
Authors: Knapp Ralph W. , Anderson Neil L.
Published: January 2025

The interpreter who is used to conventional-resolution seismic data may be perplexed when confronted with high-resolution seismic data because conventional- and high-resolution data respond differently to the acoustic properties of the earth. For example, a high-amplitude, tuned, thin-bed reflection on a conventional seismic section may correspond to a low-amplitude, thick-bed event on a high-resolution section. Conversely, beds too thin to be effectively imaged by conventional data may be represented as high-amplitude, tuned reflections on high-resolution data. This may result in misidentification if the interpreter bases his stratigraphic correlations on amplitude response. Amplitude contrasts may also result from acoustic impedance gradients which generate high-amplitude reflections on conventional data but correspond to severely dimmed events on a high-resolution section. Lateral rugosity of the reflector surface and interference from adjacent thin layers can have a similar effect. As evidenced by models and seismic data incorporated into this paper, these factors result from the fact that conventional-resolution data and high-resolution data image different properties of the geologic strata.
Use of minimum-phase wavelets will cause time-correlation differences when data of different frequency content are compared and peaks or troughs rather than true wavelet onsets are picked. For this reason it is very important to ensure that data are processed to have zero-phase wavelets. Zero-phase wavelets also have the greatest resolving power; this is particularly important on high-resolution data. Because data of different frequency bands show different features of the earth, it may be advantageous in some situations to display each broad-band high-resolution section at a few different pass bands. Thus, features best imaged by conventional resolution are displayed and features best imaged by higher resolution are displayed.
Comparison of high-resolution data with conventional-resolution data and synthetic seismograms leads to inferences of vertical acoustic-impedance gradient and lateral surface rugosity. Vertical gradients on limestone surfaces, for example, may be related to porosity, and thus, recognition of their seismic signature may be an important interpretation tool.