Daniel F. Merriam

Paleolimulus, an early limuline (Xiphosurida), from Pennsylvanian‐Permian Lagerst tten of Kansas and taphonomic comparison with modern Limulus

The Pennsylvanian-Permian horseshoe crab Paleolimulus signatus (Beecher), incorporating as a junior synonym P. avitus Dunbar, is one of the earliest species of the Limulina (Xiphosurida). Some specimens from Kansas, USA, are exceptionally well preserved, retaining intact book gills and appendages. Indistinct, bilobed burrowing traces of variable width occur in association with some examples of P. signatus and may have been produced by that animal. Based on actualistic taphonomic experiments on Limulus polyphemus, ancient horseshoe crabs and other arthropods having non-mineralized exoskeletons are inferred to have become pliable soon after death or moulting, and to have disarticulated slowly prior to burial. Extreme compression, wrinkling, and loose folding of sclerites are attributed to burial of a pliable exoskeleton. Slow preburial disarticulation partly accounts for the exceptional preservation of Paleolimulus remains. Also relevant for the exceptional preservation of these arthropods was burial in estuarine, tidal flat, or lacustrine environments. Because of fluctuating salinity and possibly dessicating conditions, these settings were limiting to scavengers, burrowers, and some microbes that could potentially disarticulate or decompose xiphosurid remains.

Application of optical-fiber temperature logging - An example in a sedimentary environment

Continuous‐temperature depth logs, especially when recorded in boreholes under thermal equilibrium conditions, provide detailed information of the subsurface thermal structure, which is necessary for the determination of reliable heat‐flow and rock thermal properties. In conjunction with independent thermal‐conductivity determinations, thermal logging data also allow the separation of heat conduction effects from thermal convection effects by fluid flow driven by various pressure differences such as pore fluid pressure. The Earths thermal field is related intimately to geothermal resources and hydrocarbon resources. Therefore, the characterization of temperature in the subsurface and its relationship to lithology is of critical importance.

Use of relational databases to evaluate regional petroleum accumulation, groundwater flow, and CO2 sequestration in Kansas

Large-scale relational databases and geographic information system tools are used to integrate temperature, pressure, and water geochemistry data from numerous wells to better understand regional-scale geothermal and hydrogeological regimes of the lower Paleozoic aquifer systems in the mid-continent and to evaluate their potential for geologic CO2 sequestration. The lower Paleozoic (Cambrian to Mississippian) aquifer systems in Kansas, Missouri, and Oklahoma comprise one of the largest regional-scale saline aquifer systems in North America. Understanding hydrologic conditions and processes of these regional-scale aquifer systems provides insight to the evolution of the various sedimentary basins, migration of hydrocarbons out of the Anadarko and Arkoma basins, and the distribution of Arbuckle petroleum reservoirs across Kansas and provides a basis to evaluate CO2 sequestration potential. The Cambrian and Ordovician stratigraphic units form a saline aquifer that is in hydrologic continuity with the freshwater recharge from the Ozark plateau and along the Nemaha anticline. The hydrologic continuity with areas of freshwater recharge provides an explanation for the apparent underpressure in the Arbuckle Group.

Geohistory and Thermal Maturation in the Cherokee Basin (Mid-Continent, U.S.A.): Results from Modeling

The Cherokee basin in southeastern Kansas contains a stratigraphic section consisting mostly of Permian-Pennsylvanian alternating clastics and thin carbonates overlying carbonates of Mississippian and Cambrian-Ordovician age on a Precambrian crystalline basement. Based on a conceptual model of events of deposition, nondeposition, and erosion, a burial history model for (1) noncompaction, and a series of models for (2) compaction are computed for a borehole location in the south-central part of the basin. The models are coupled with the calculation of nonsteady-state geothermal conditions. Maximum temperatures during basin evolution of about 70°C at the base of the organic-rich Pennsylvanian are predicted by our models, assuming pure heat conduction and a heat flow from the basement of 60 mW/m2. The maturation of organic matter as indicated by three different vitrinite reflectance (Ro) models is on the order of 0.3-0.5% Ro for Pennsylvanian rocks and 0.6% Ro for the Devonian-Mississippian Chattanooga Shale. Vitrinite reflectance was measured on subsurface samples from three wells. The measured values correlate in the upper part of the sequence with modeled data, but diverge slightly in the Lower Pennsylvanian and Chattanooga Shale. The differences in maturation may be a result of differing local geological conditions within the basin. The relatively high Ro-depth gradient observed in one borehole may be explained by conditions in the Teeter oil field, which is a typical plains-type anticline that has been affected by fluid flow through vertical faults. Higher Ro values correlate positively with the grade of sulfide mineralization in the sediment, which may be a hint of fluid impact. The high Ro values relative to the shallow depth of the Mississippian and the Chattanooga Shale in the Brown well are on the order of Ro values modeled for the same stratigraphic units at present-day greater depths and may reflect uplift of the Ozark dome, located farther east, affecting the eastern side of the Cherokee basin.

Precambrian Basement Control on ‘Plains-Type Folds’ (Compacttonal Features) in the Midcontinent Region, USA

‘Plains-type folds’ were described in the early 1930s by petroleum geologists working in the Midcontinent, USA. The folds are characterized by small size, increased sharpness with depth, asymmetry, and association with faulting. These folds are ascribed to the compaction of sediments over crystalline, rigid basement, in this instance tilted Precambrian fault blocks. Initially, the ‘plains-type folds’ were formed when the present major structural features of the region were formed and adjustments continue today as recognized by neotectonics in the region. Development of these features in sediment veneers over the basement in the many cratonic environments of the world is of interest because locally they serve as traps for petroleum. Timing of development of the ‘plains-type folds’ determined when and if they were available for entrapment of petroleum as fluids moved through the system. This study indicates that there are two types of ‘plains-type folds’ in the Midcontinent: (1) the normal type developed mainly in the early Middle Pennsylvanian as a result of intraplate stresses caused by collision of the North and South American plates; and (2) those formed later as a result of other influences. By using a structural-depth gradient, which expresses the change in thickness of stratigraphic units on and off structure, it is possible to determine at which time(s) these features were affected by local or regional structural adjustments in the basement. By plotting the structural gradient, which is the change in structural closure with depth, the nature of the ‘plains-type fold’ can be recognized as being either (1) or (2). We propose that features exhibiting a low or no structural gradient (2), that is a similar structural closure with depth, and that are small and nearly circular in nature can be attributed to the emplacement of late Mesozoic or early Tertiary intrusive igneous plugs.

Problems and Potential of Industrial Temperature Data from a Cratonic Basin Environment

A thin veneer of clastic and carbonate sediments 460–1,375 m (1,500–4,500 ft) thick overlies a Precambrian crystalline basement complex in southeastern Kansas (Midcontinent, USA). Well-log temperatures were analyzed and related to modeled temperatures for different-size areas in a relatively simple structural setting of the shallow, cratonic Cherokee Basin. A statistical analysis of bottom-hole temperatures (BHTs) confirmed that (1) there is no significant change of temperature with season or through the 40 years of drilling and logging the wells in the area; and (2) the distribution of values is normal indicating they were recorded correctly on the rig within the instrumental precision of about 1 K. It was obvious from the large data set of nonequilibrium BHTs analyzed by depth and stratigraphic unit that they differed from drillstem test temperatures (DSTs) and modeled temperature- depth distributions based on heat conduction. At shallow depth (less than 500 m), BHT values as read from the logs are higher than ‘true’ formation temperature; in a depth range of 500–700 m, values scatter around a ‘true’ formation temperature; and at greater depths (up to 1,100 m), the uncorrected BHTs slightly underestimate the formation temperature. Different amounts of data scatter in the composite BHT-depth plots occur in different size areas, which also impacts the calculated geothermal gradients and empirical correction methods developed on the basis of these data. Although the BHTs in the 60×75 km area of Elk and Chautauqua counties scatter ±5–9°C around some mean value, seemingly the scatter can be reduced slightly when working with smaller areas, for example 10×10 km. A mapping approach made to investigate the variability of the 60×75-km BHT cluster in more detail showed part of the BHT scatter to be related to regional geology. Temperature residuals of the trend are on the order of ±2.5°C with some values as large as ±7.5°C. This provides an indication of variability of BHTs resulting from other influences, which might be different perturbations as a result of drilling practices and different shut-in times of the wells. In addition, some of the temperature highs are shown to be related to local, subtle anticlines developed in the sedimentary cover over faulted basement blocks and therefore contain signal. The separation of different effects on BHTs has implications on the reliability of geothermal gradient and heat-flow density estimations.

Surface expression of buried geologic features in Kansas

Abstract Now they knew that she was a real princess [geologist] because she had felt [mapped] the pea [structure] right through the twenty mattresses [two thousand feet of sediment] and the twenty … beds [limestones]. Nobody but a real princess [geologist] could be as sensitive as that. Apologies to Hans Christian Andersen, The Princess and the Pea, 1835. Topographic features, under certain circumstances, may reveal information about what is hidden beneath. By studying the configuration of the surface, information can be gained as to what might be below, and visa versa the configuration of subsurface features can give insight as to what may be expected on the surface. Thus, surficial topographic features may be indicators of buried folds, faults, igneous intrusives, and other subsurface geologic features. The Big Springs (Shawnee/Douglas counties) and Beagle (Miami County) anomalies in eastern Kansas are given as examples.

Comparison of British and American Carboniferous cyclic rock sequences

Classification is of interest to geologists as a convenient means of expressing ideas and concepts. Most classification schemes categorize a continuum into discrete classes or states based on some prominent character of the objects being classified. Unknowns then are identified as to their position within the classification scheme. Until recently most geologic classification schemes have been qualitative. With advent of the computer, applications of many quantitative statistical techniques have become practical. These techniques offer the advantages of repeatability and objectivity. This report gives results of the applications of several techniques for classifying Carboniferous cyclic rock sequences. Twenty sections were measured in detail in Great Britain and the United States. Particular importance was placed on noting transition from one lithology to another. Seven lithologic types were distinguished: (a) sandstone, (b) siltsone, (c) nonfossiliferous shale, (d) seatearth or underclay, (e) coal, (f) fossiliferous shale, and (g) limestone. It was noted also which part of the sequence was marine and which nonmarine. From the original data, the number of changes per 100 ft were calculated as well as an entropy index indicating the “orderliness” of the sequence and a matching index obtained by comparing the similarity in sequences of lithology between pairs of sections. The matching index is based on qualitative characters and in this regard belongs to a type of sequential analysis of scaleless nonnumeric data. The matching coefficients were clustered and displayed as dendrograms. A cluster analysis also was performed using nine variables (number of changes per 100 ft, entropy index, percentage thickness of sandstone, siltstone, nonfossiliferous shale, seatearth and coal, fossiliferous shale, and limestone, and percentage of nonmarine units) and the results displayed as dendrograms. In addition principal components analysis utilized the nine variables to determine if groups were present in the data. The first three principal components were interpreted geologically and a three-dimensional model constructed. Three loosely grouped clusters could be recognized in this display: (1) cyclic sequences associated with deltaic complexes, (2) sequences characteristic of deposition farther offshore, and (3) those composed mainly of marine sequences formed in an offshore open-marine environment.

Computerized basin analysis : the prognosis of energy and mineral resources

A selection of 19 papers from an international conference in Gnstow, (then) East Germany, June 1990. They discuss the application of computer methods to the exploration and exploitation of oil and gas, coal, and other energy and mineral resources. Among the topics are differential compaction and str

Seismite Indicates Pleistocene Earthquake Activity in Ellis County, Kansas

The post-Precambrian stratigraphic record is incomplete with one estimate that 80 percent of time is not represented (Merriam, 1963). Even so, there is ample evidence that the craton has remained active through time as recorded by the soft-sediment deformation that occurs in the record. Soft-sediment deformation or convolute features occur when the sediment is yet in a semi-liquid state and a trigger (earthquake) causes the sediment to deform by dewatering (Fig. 1). The soft-sediment deformation which forms convolute features has been adequately described in the geological literature and are referred to as seismites.