William P. Lanier

Ichnology of an Upper Carboniferous fluvio-estuarine paleovalley: The Tonganoxie Sandstone, Buildex Quarry, Eastern Kansas, USA

Tidal rhythmites of the Tonganoxie Sandstone Member (Stranger Formation, Douglas Group) at Buildex Quarry, eastern Kansas, contain a relatively diverse ichnofauna. The assemblage includes arthropod locomotion (Dendroidichnites irregulare, Diplichnites gouldi types A and B, Diplopodichnus biformis, Kouphichnium isp., Mirandaichnium famatinense, and Stiaria intermedia), resting (Tonganoxichnus buildexensis) and feeding traces (Stiallia pilosa, Tonganoxichnus ottawensis); grazing traces (Gordia indianaensis, Helminthoidichnites tenuis, Helminthopsis hieroglyphica); feeding structures (Circulichnis montanus, Treptichnus bifurcus, Treptichnus pollardi, irregular networks), fish traces (Undichna britannica, Undichna simplicitas), tetrapod trackways, and root traces. The taxonomy of some of these ichnotaxa is briefly reviewed and emended diagnoses for Gordia indianaensis and Helminthoidichnites tenuis are proposed. Additionally, the combined name Dendroidichnites irregulare is proposed for nested chevron trackways. Traces previously regarded as produced by isopods are reinterpreted as myriapod trackways (D. gouldi type B). Trackways formerly interpreted as limulid crawling and swimming traces are assigned herein to Kouphichnium isp and Dendroidichnites irregulare, respectively. Taphonomic analysis suggests that most grazing and feeding traces were formed before the arthropod trackways and resting traces. Grazing/feeding traces were formed in a soft, probably submerged substrate. Conversely, the majority of trackways and resting traces probably were produced subaerially in a firmer, dewatered and desiccated sediment. The Buildex Quarry ichnofauna records the activity of a terrestrial and freshwater biota. The presence of this assemblage in tidal rhythmites is consistent with deposition on tidal flats in the most proximal zone of the inner estuary, between the maximum landward limit of tidal currents and the salinity limit further towards the sea.

Tidal Sedimentation from a Fluvial to Estuarine Transition, Douglas Group, Missourian--Virgilian, Kansas

ABSTRACT The Tonganoxie Sandstone Member of the Stranger Formation (Douglas Group, Upper Pennsylvanian, Kansas) was deposited in a funnel-shaped, northeast-southwest-trending paleovalley that was incised during the uppermost Missourian sealevel lowstand and backfilled during the subsequent transgression. Quarry exposures of the Tonganoxie near Ottawa, Kansas, include 5 m of sheetlike, vertically accreted siltstones and sandy siltstones, bounded above and below by thin coals with upright plant fossils and paleosols. Strata range from submillimeter-thick, normally graded rhythmites to graded bedsets up to 12.5 cm thick with a vertical sedimentary structure sequence (VSS) consisting of the following intervals: (A) a basal massive to normally grad d interval; (B) a parallel-laminated interval; (C) a ripple-cross-laminated interval; and (D) an interval of draped lamination. The VSS-C intervals of thicker bedsets are characterized by climbing ripples that evolve from Type A (erosional-stoss) to Type B (depositional-stoss). Synsedimentary convolutions at the tops of many climbing-ripple sequences and a variety of water-escape structures indicate rapid deposition. The vertical sequence of sedimentary structures indicates each bedset was deposited by a waning current with significant suspended load. The Tonganoxie succession has many similarities to fluvial overbank/floodplain deposits: sheetlike geometry, upright plant fossils, lack of bioturbation and body fossils, dominance of silt, and a punctuated style of rapid sedimentation from suspension-laden waning currents. Missing, however, are thick clay drapes or evidence of prolonged exposure and desiccation, which generally characterize a floodplain sequence with seasonal overbanking. Physical and biogenic sedimentary structures--including tetrapod trackways, surface grazing traces, abundant raindrop impressions, wind ripples, runnel marks, runnel marks, and runoff washouts--indicate that subaerial exposure was periodic and brief, and may have followed each sedimentation event. Analysis of stratum-thickness variations through the succession suggests that tides significantly influenced sediment deposition. Strata ranging through three orders of magnitude systematically thicken and thin, recording the influence of an ebb-dominated, diurnal tidal system with a well developed semimonthly inequality. By conservative estimate of sedimentation rates based on neap-spring tidal cycles, the sequence aggraded at an average rate of approximately 3.8 m/yr. These unusually high rates appear to have prevailed for only a short time and were probably spatially restricted within the basin. A fluvial-to-estuarine transitional depositional setting is interpreted for the Tonganoxie by analogy with modern depositional settings that show similar physical and biogenic sedimentary s ructures, vertical sequences of sedimentary structures, and aggradation rates.

Comparison of drier- to wetter-interval estuarine roof facies in the Eastern and Western Interior coal basins, USA

Abstract Many of the Carboniferous coals in the eastern interior of the US are associated with siliciclastic roof facies that were deposited within a fluvio-estuarine transition. These facies include a variety of rhythmites, some of which exhibit tidal cycles. Drier-interval coals (Westphalian B-C, Stephanian) tend to be more laterally restricted and more commonly are associated with paleovalleys. Conversely, wetter-interval coals (Westphalian D) are very widespread and are not restricted to paleovalleys. Throughout the Lake Carboniferous, wet paleoclimates associated with these coals lead to valley incision during sea-level lowstand when large tropical rivers downcut older sediments deposited during previous sea-level highstands. During subsequent rise of sea level, these fluvial valleys were flooded and converted to estuaries where tidal ranges and sedimentation rates were significantly amplified. Based on modern analogs and interpretation of many examples of Carboniferous tidal rhythmites, the localized depositional rates in these settings are exceptionally high. The estuaries became sediment sinks, trapping sediment that is pumped in from both fluvial and marine sources. As a result, sedimentation readily keeps pace with rising baselevel. Extensive intertidal flats and shallow subtidal flats are created and prograde over the valley-confined mires. Thick tidal cycles and upright trees (some with attached foliage) record rapid burial of mires. This model is supported with examples of roof facies from the Westphalian B-C of the Eastern Interior Basin, and the Stephanian of the Western Interior Basin. In these areas facies within each cycle range from well-developed, extensive paleosols and coals, to widespread marine shales or limestones. Variations in both sea level and climate resulted in a complex history of valley fill during which coals could be developed at any time (except during widespread flooding). Minable, low-sulfur and low-ash coals occur, but the coals are relatively thin and discontinuous. Conversely, the Westphalian D coals are very widespread and significant peat accumulations were not confined to paleovalleys. Nonetheless, the lowest sulfur coals are related to rapid deposition of roof facies that occurred within the paleovalley whereas high-sulfur coals were formed in areas of lower sedimentation rate of roof facies that occurred beyond the confines of the paleovalley.

Taxonomic reassessment of the ichnogenus beaconichnus and additional examples from the Carboniferous of Kansas, U.S.A.

The ichnogenus Beaconichnus (Gevers 1973), an arthropod trace fossil, includes very different forms that comprise five ichnospecies, namely B. darwi‐nunt (Gevers 1971), B. gouldi (Gevers 1971), B. ahtarcticum (Gevers 1971), B. giganteum Gevers and Twomey 1982, and B. wrrighti Gevers and Twomey 1982. The original diagnosis of Beaconichnus is rather vague and potentially may accomodate virtually every arthropod trackway described from the fossil record. In view of these problems, the validity of Beaconichnus is reassessed and each of its ichnospecies is reviewed. We conclude that B. darwinum is a junior synonym of Diplopodichnus biformis Brady 1947; B. antarcticum should be regarded as Palmich‐niunt antarcticum; and B. wrighti is a nomen nudum. Additionally, we agree with previous proposals in considering B. gouldi as the senior synonym of B. giganteum, and including it in Diplichnites Dawson 1873. Therefore, we suggest that the ichnogenus Beaconichnus is best disregarded. Additionally, we describe specimen...

Stratigraphic Architecture of the Tonganoxie Paleovalley Fill (Lower Virgilian) in Northeastern Kansas

Lower Pennsylvanian paleovalley-confined sandstones are important petroleum reservoirs in the Midwest. In Kansas, such reservoirs have produced approximately 220 million bbl of oil and 1.7 tcf of gas. Valley-fill successions tend to become muddy upward, but there can be considerable local heterogeneity in which reservoir sandstones pass laterally into muddy sandstones or nonreservoir shales. The lack of understanding of this reservoir heterogeneity can lead to low drilling success rates. The Tonganoxie paleovalley (Upper Pennsylvanian, northeastern Kansas) contains facies very similar to Lower Pennsylvanian (Morrowan) valley fills, and can provide an outcrop- and subsurface-based model of sandstone deposition. The Tonganoxie paleovalley was incised during lowered sea level and filled during the subsequent transgression. The main paleovalley is approximately 41 m deep, 11 km wide, and 240 km long, and was fed by 1-km-wide tributary valleys oriented roughly normal to the trunk valley. Sandstones occur in four distinct architectural elements that were deposited during different phases of transgression. Type I sandstone consists of a belt of sandstone and conglomerate 3-18 m thick and confined to the trunk valley and wider portions of tributary valleys. Type I sandstone consists of amalgamated channel fills, has little or no mud, and has the highest porosity and permeability. The type I sandstone is overlain by estuarine deposits of sandstone (type II sandstones), rippled argillaceous sandstone to sandy mudstone, and coal. Most of the paleovalley was filled during this stage. The type II sandstones are narrow (1.5 km wide) arcuate bodies up to 8 km long and were likely deposited in tidal point bars near the fluvial to tidal transition, are either isolated sandstone bodies or are incised into type I sandstone. The higher mud content is expected to reduce porosity and permeability compared to fluvial facies. Type III sandstone bodies occur at the upstream limits of narrow tributaries and are probably bay-head deltas. Well logs indicate a range of mud content. Type IV sandstone is a thin (3 m) discontinuous sheet of marine sandstone deposited after most of the paleovalley had been filled.

Interstitial and peloid microfossils from the 2.0 Ga Gunflint formation: implications for the paleoecology of the Gunflint Stromatolites

Abstract Silicified peloidal arenite sediments from the 2.0 Ga Gunflint Formation contain morphologically diverse and exceptionally well-preserved microfossil assemblages. Peloids are current-deposited, sand-sized and larger intraclasts of organic-rich siliceous sediment which were derived from low- to high-energy sedimentary environments within the Gunflint depositional basin. Two distinct occurrences can be differentiated: (1) an interstitial assemblage dominated by well-preserved autochthonous Gunflintia minuta filamentous microfossils, but also containing larger filaments, spheroidal to elongated vesicles and other unusual microfossil-like structures, and (2) intragranular/peloid assemblages containing essentially all previously described Gunflint stromatolite taxa including clonal groupings of Huroniospora (Type E cells) showing over 12% dividing cells, and two undescribed filamentous morphotypes which resemble “actinomycetes” eubacteria. The size distribution of clonal Type E populations is almost identical to a major modal population of Huroniospora from exceptionally well-preserved Gunflint stromatolite materials. Both assemblages show a range of textures reflecting post-mortem degradation, but locally the interstitial communities show better preservation. Interstitial filaments differ from stromatolitic G. minuta insofar as they show (1) occasional cross-walls; (2) a size-frequency distribution which seems to reflect post-mortem/pre-permineralization shrinkage; (3) preferred growth orientations; and (4) lengths of up to 2.5 millimeters. The interstitial microbiota is also permineralized by early-diagenetic silica cement. The recognition of this new habitat contributes substantially to our understanding of Gunflint microbial ecosystems by providing new information concerning the ecology, growth and reproductive patterns of Huroniospora and Gunflintia . Detailed comparisons of interstitial Gunflintia with its stromatolitic counterpart collectively suggest that it was a photoautotrophic microorganism with the capacity to form dense (but very thin) microbial mats and of having directly influenced stromatolite morphogenesis. Similar comparisons suggest the Type E Huroniospora did not contribute directly to stromatolite growth.