Ronald R. West

Lower Permian (Wolfcampian) Paleosol-Bearing Cycles of the U.S. Midcontinent: Evidence of Climatic Cyclicity

Lower Permian sedimentary cycles of the North American Midcontinent consist predominantly of very shallow marine and paralic facies and well-developed stacked paleosol profiles. Although recording glacio-eustatic sea level fluctuations, these cycles also contain evidence of cyclic climate change. This evidence includes the repeated carbonate-to-clastic facies pattern observed for meter-scale cycles, and the regionally consistent change from calcic to vertic paleosols within the variegated mudstones of most cyclothems. Climates are interpreted to have fluctuated from arid or semiarid conditions to seasonally wet/dry conditions during the course of a single cyclothem. Furthermore, within the Midcontinent, drier conditions appear to have characterized times of sea-level rise and highstand, whereas wetter more seasonal conditions characterized times of sea-level fall and lowstand. This relationship is interpreted to have resulted from variations in the intensity of a Pangean monsoon generated by glacial-interglacial cycles.

Contrasting behavioral and feeding strategies recorded by tidal-flat bivalve trace fossils from the Upper Carboniferous of eastern Kansas

Upper Carboniferous tidal-flat deposits near Waverly, eastern Kansas (Stull Shale Member, Kanwaka Shale Formation), host abundant and very well-preserved trace fossils attributed to the activity of burrowing bivalves. Thin shell lenses with an abundant bivalve fauna are associated with the ichnofossil-bearing beds and afford an unusual opportunity to relate trace fossils to their makers. Two distinctive life and feeding strategies can be reconstructed on the basis of trace fossil analysis and functional morphology. Lockeia siliquaria hyporeliefs commonly are connected with vertical to inclined, truncated endichnial shafts in the absence of horizontal locomotion traces. These structures record vertical and oblique displacement through the sediment, and suggest relatively stable domiciles rather than temporary resting traces as typically considered. Crowded bedding surfaces displaying cross-cutting relationships between specimens of L. siliquaria and differential preservation at the top (concave versus convex epireliefs) record a complex history of successive events of colonization, erosion, deposition, and recolonization (time-averaged assemblages). Irregular contours of some large hypichnia indicate the cast of the foot, while other outlines closely match the anterior area of Wilkingia, its suggested tracemaker. Relatively stable, vertical to inclined life positions and dominant vertical mobility suggest a filter-feeding strategy. Moreover, the elongate shell and pallial sinus of Wilkingia provide a strong independent line of evidence for an opisthosiphonate, moderately deep-tier inhabitant. Wilkingia may represent a pioneer attempt at siphon-feeding in the late Paleozoic, preceding the outcome of the Mesozoic infaunal radiation. A second strategy is represented by Lockeia ornata and associated locomotion and locomotion/feeding structures. Lockeia ornata is commonly connected with chevron locomotion traces that record the bifurcated foot of a proto-branch bivalve. Lockeia ornata exhibits distinctive, fine, parallel lines that mimic the ornamentation of Phestia, a nuculanid protobranch bivalve. Rosary and radial structures give evidence of a patterned search for food. Lockeia ornata and associated Protovirgularia record dominant horizontal locomotion and suggest the activity of deposit-feeding bivalves. Morphologic variability of Protovirgularia was controlled by substrate fluidity, which was dependent on sediment heterogeneity and tidal-cycle dynamics. This study demonstrates that detailed analysis of bivalve traces provides valuable information on bivalve ethology and paleoecology, evolutionary innovations, environmental dynamics, and substrate fluidity.

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.

The role of climate in stratigraphic patterns exhibited by late Palaeozoic rocks exposed in Kansas

Abstract Late Palaeozoic “cyclothems” of the midcontinental U.S. cannot be represented by a single ideal facies sequence. Rather, they encompass a wide range of cycle types depending on their stratigraphic position. The exposed Late Palaeozoic (Pennsylvanian and Permian) rocks of Kansas, as compiled by Zeller (1968), can be divided into nine major lithofacies. These lithofacies were ordered based on their times of greatest abundance through the section. From oldest to youngest, they attain their peak abundance in the following order: (1) coal; (2) gray mudrocks and sandstones; (3) black mudrocks; (4) limestones; (5) cherty limestones; (6) fossiliferous mudrocks; (7) variegated mudrocks; (8) evaporites; and (9) variegated dolomitic siliciclastics. Climatically, these nine lithofacies suggest a change from generally wetter, at the base, to generally drier, at the top of the section. This climatic trend was probably generated by a complex interaction of factors primarily driven by global tectonics. Climatic changes can be used to explain the five generally recognized types of lithofacies “cyclothems” in Kansas, and thus are a potential explanation for the changing stratigraphic patterns of the entire Late Palaeozoic time interval of Kansas, and perhaps elsewhere.

A tidal model of Carboniferous Konservat-Lagerstaetten formation

Rapid deposition of laminated sediments in tidally influenced estuaries can explain many characteristics of some Carboniferous Konservat-Lagerstatten. In modern environments each tide can potentially deposit a layer of normally graded mud. Localized depositional rates as high as 1 cm or more of sediment per week can occur in tidal estuarine settings. Characteristic periodicities in lamination thicknesses reflect neapspring cycles and other earth-moon orbital parameters; these periodicities can be used to identify tidal deposits in Carboniferous rocks. Commonly preserved in tidal sedimentary rocks are neap/spring cycles and the semi-diurnal tidal inequality. Such deposits are widespread in the midcontinental USA

Construction versus accumulation in phylloid algal mounds: an example of a small constructed mound in the Pennsylvanian of Kansas, USA

Abstract Most phylloid algal mounds are currently interpreted as no more than accumulations of leaf-like thalli supported by mud. We report here phylloid algae from the Upper Pennsylvanian (Late Carboniferous) Frisbie Limestone Member in Kansas, USA, which built small mounds with recognizable primary topographic relief. Cup-shaped algal thalli, growing closely packed and juxtaposed near and above one another, produced a framework in the shapes of topographically conspicuous mounds from smaller, centimeter-scale to meter-scale features. Meter-scale mounds are composites of smaller, juxtaposed, centimeter-scale mounds and intramound areas contain crinoid debris, sponges, bryozoans, brachiopods, and skeletal grains. The intercup voids enclosed in the framework fabrics of individual thalli are filled with a variety of matrix and cements: (1) peloidal grains, both in clotted wackestone and grainstone; (2) early marine cement; (3) microbial encrustations, often oriented against gravity; and (4) mudstone. Bedded limestones equivalent to and overlying the mounds are bioclastic wackestone and differ fundamentally from the mound limestone in facies, biotic components, absence of both frameworks and of peloidal clotted grains. Topographic relief above the sea floor, the growth fabrics with a framework including primary intramound and intercup voids and their complex infillings, and the lithic and biotic differences between mound and off-mound intervals fulfil the stratigraphic and biological criteria characterizing reefs. The model proposed here interprets these mounds as the result of active constructional algal growth, in contrast to published hypotheses that most phylloid algal mounds were passive accumulations of algal thalli within a mud matrix and/or early diagenetic marine cements.

A NEW ICHNOSPECIES OF NEREITES FROM CARBONIFEROUS TIDAL-FLAT FACIES OF EASTERN KANSAS, USA: IMPLICATIONS FOR THE NEREITES–NEONEREITES DEBATE

Abstract Predominantly horizontal, gently curved to slightly sinuous traces constituting uniserial rows of imbricated, subspherical sediment pads occur in Pennsylvanian tidal-flat facies of eastern Kansas. These traces exhibit a complex, actively filled internal structure. The presence of a median tunnel enveloped by overlapping pads of reworked sediment indicates that these biogenic structures should be included in the ichnogenus Nereites MacLeay in Murchison, 1839. A new ichnospecies, N. imbricata, is erected. Externally, Nereites imbricata differs from the other Nereites ichnospecies by the large, tightly packed, imbricated pads that commonly result in an annulated appearance on bedding-planes. Internally, obliquely arranged, arcuate laminae envelope the median tunnel and tend to follow the outline of the external semispherical pads. Additionally, the behavioral pattern reflected by N. imbricata is less specialized than that of the other Nereites ichnospecies. Eione monoliformis Tate, 1859 resembles N. imbricata in general appearence, but lack the diagnostic Nereites internal structure, and is invariably preserved as positive epireliefs. Occurrence of Nereites imbricata as both median tunnels surrounded by reworked sediment (Nereites preservation) and uniserial rows of imbricated sediment pads (Neonereites preservation) supports the notion that Neonereites Seilacher, 1960 is a preservational variant of Nereites. The ichnogenus Nereites is an eurybathic form and is a common component of Paleozoic shallow-marine facies.

Late Palaeozoic corals of Tibet (Xizang) and West Yunnan, Southwest China: successions and palaeobiogeography

Abstract A dynamic pattern of coral faunal provincialism in the Carboniferous to Permian sequence is preserved in Tibet–West Yunnan. During the Early Carboniferous, an undifferentiated Eurasian province was present, containing the Kueichouphyllum , Keyserlingophyllum - Siphonophyllia , and Cyathaxonia faunas, that reflect major environmental differences relative to previous interpretations. During the Late Carboniferous–Early Permian, the Indoralian province and the Cathaysian province can be distinguished. The former is recognised by an absence of Late Carboniferous–Asselian corals and by the presence of the Sakmarian–Artinskian Cyathaxonia fauna. The latter contains the Late Carboniferous and Early Permian compound corals Nephelophyllum and Kepingophyllum . As many blocks drifted northward beginning in the late Early Permian, the Indoralian province had evolved into two discrete provinces: the Himalayan and Cimmerian provinces. The Himalayan province as a relic of the Indoralian province was in the northern margin of Gondwanaland. The Cimmerian province between the Himalayan and the Cathaysian provinces consists of the present tectonic blocks: Lhasa, Qiangtang, Tengchong, and Baoshan in Tibet and West Yunnan. It is characterised by Roadian non-dissepimental solitary corals and Wordian–Capitanian compound Waagenophyllidae, as well as some endemic Cimmerian taxa such as Thomasiphyllum and Wentzellophyllum persicum . The Cathaysian province is dominated by Szechuanophyllum and Ipciphyllum . During the Late Permian, the Himalayan province and the Cathaysian province can be recognised. The former contains only small solitary corals, referred to as the Lytvolasma fauna, and the latter is identified by Liangshanophyllum , a fasciculate waagenophyllid.

Spatial competition among clonal organisms in extant and selected paleozoic reef communities

SummaryOccurrences of densely packed benthic organisms in extant reefs are of two types: 1) live-live interactions, where two living organisms interact, and 2) live-dead associations, where only one is alive and uses the other as a substrate. The latter are common in reef deposits due to biostratinomic feedback, i.e. dense skeletal accumulations provide hard substrates for clonal recruitment, thus facilitating greater frequency of live-dead encounters than in lower biomass level-bottom communities dominated by solitary organisms. Differentiating between these two types in ancient reefs is difficult, often impossible.Most live-live interactions among clones in extant reef communities involve competition for space. Clonal spatial competition is divisible into four types: 1) direct-aggressive: encrusting overgrowth; 2) indirect-passive: depriving neighbors of resources, chiefly sunlight, by growth above them; 3) stand-off: avoidance of competition by organisms adopting positions that avoid or minimize direct polyp/zooid contact; and 4) overwhelming: one clone/ species volumetrically or numerically overwhelms the other, meeting minimal resistance. Despite class-order level differences in taxa, our results indicate that extant analogs, based on the arrangement and distortion of skeletons, are valuable for recognizing live-live interactions in Silurian and Carboniferous reefs and interpreting the types of spatial competition represented.Comparison of overhead (plan) views of live-live coral competition in Polynesian reefs with vertical sections of Silurian and Carboniferous sponge-dominated reefs and biostromes suggests that direct-aggressive competition is more common among extant than among Paleozoic reef-builders. Stand-offs showing clone margin distortion and overwhelming with minor skeletal distortion are most common in our fossil examples and probably relate to the dominance of these reefs by sponges. Success by extant sponges in spatial competition is largely due to allelochemical deterrence which may explain the predominance of stand-off and overwhelming confrontations in fossil sponges rather than tentacle-mesentery based direct aggression among extant corals and bryozoans.

LOCKEIA, NOT PELECYPODICHNUS

The nomenclatorial history of the ichnogenera Lockeia and Pelecypodichnus has been confused by duality during the past 20 years. Many authors presume Pelecypodichnus is correct because Lockeia is a nomen oblitum. This presumption is rejected on both objective and subjective grounds. First, Lockeia is not a nomen oblitum. Two major gaps in the citational history of Lockeia exist, the first one of 35 years duration and the second of 43 years duration. Thus, no 50-year gap exists in the valid use of the name Lockeia. Second, the Committee on Zoological Nomenclature was not petitioned to declare Lockeia a nomen oblitum during the period of time that the nomen oblitum concept was in effect. Third, the name Pelecypodichnus implies a specific trace-maker for the trace-a practice we, and others, judge should be avoided. Fourth, topotype specimens and the lectotype of Lockeia are available for study. Fifth, even many of those authors who use Pelecypodichnus instead of Lockeia commonly note the existence of Lockeia as a synonymous generic name. Thus, use of Lockeia by numerous authors in the past 20 years results in no confusion or destabilization of the generic-level taxonomy. Lockeia, the senior synonym of Pelecypodichnus, has been used by numerous authors, is well understood, and therefore should be used instead of Pelecypodichnus.