R.M. Joeckel

Mass-balance reconstruction of a modern Vertisol: implications for interpreting the geochemistry and burial alteration of paleo-Vertisols.

Abstract Utilizing identical sampling and analytical techniques, the morphological and chemical characteristics of a modern Vertisol (Houston Black series, central Texas) can be directly compared with an Upper Mississippian paleo-Vertisol from the Appalachian basin (Pennington Formation, east-central Tennessee). Mass-balance reconstructions suggest retention of primary pedochemical patterns in the paleo-Vertisol, including patterns of soil volume change (strain) and transport functions (translocations) of many major and trace elements. Retention of primary pedochemical patterns suggests that Vertisols constitute nearly closed systems during burial diagenesis. Chemical and mineralogical changes associated with burial diagenesis of the paleo-Vertisol include oxidation of organic carbon (OC), illitization of smectites, dehydration and recrystallization of Fe–Mn oxyhydroxides, and dolomitization of pedogenic calcite. Significant differences in the chemical behavior of gilgai microhigh and microlow pedons in modern Vertisols have implications for interpretation of geochemical data obtained from paleo-Vertisols. Overall wetter soil conditions and variable redox potential under gilgai microlows promote greater depths of leaching and mobility of redox-sensitive trace elements, including Co, Cr, Cu, Mn, Ni, and V. Gilgai microhighs behave as evaporative “wicks” that draw moisture and soluble phases towards the soil surface, resulting in precipitation of metal hydrosylate complexes and sulfates (gypsum) at the capillary fringe and shallower depths of leaching and fixation of trace elements. Paleoprecipitation estimates from paleosols, based on the depth to the top of the pedogenic carbonate horizon, should therefore utilize field, petrographic and geochemical data for characterizing maximum depths of leaching, loss or gain of exchangeable bases, and calcification, rather than relying solely upon field data.

Late Albian Kiowa-Skull Creek Marine Transgression, Lower Dakota Formation, Eastern Margin of Western Interior Seaway, U.S.A.

ABSTRACT An integrated geochemical-sedimentological project is studying the paleoclimatic and paleogeographic characteristics of the mid-Cretaceous greenhouse world of western North America. A critical part of this project, required to establish a temporal framework, is a stratigraphic study of depositional relationships between the Albian-Cenomanian Dakota and the Upper Albian Kiowa formations of the eastern margin of the Western Interior Seaway (WIS). Palynostratigraphic and sedimentologic analyses provide criteria for the Dakota Formation to be divided into three sedimentary sequences bounded by unconformities (D0, D1, and D2) that are recognized from western Iowa to westernmost Kansas. The lowest of these sequences, defined by unconformities D0 and D1, is entirely Upper Albian, and includes the largely nonmarine basal Dakota (lower part of the Nishnabotna Member) strata in western Iowa and eastern Nebraska and the marine Kiowa Formation to the southwest in Kansas. The gravel-rich fluvial deposits of the basal part of the Nishnabotna Member of the Dakota Formation correlate with transgressive marine shales of the Kiowa Formation. This is a critical relationship to establish because of the need to correlate between marine and nonmarine strata that contain both geochronologic and paleoclimatic proxy data. The basal gravel facies (up to 40 m thick in western Iowa) aggraded in incised valleys during the Late Albian Kiowa-Skull Creek marine transgression. In southeastern Nebraska, basal gravels intertongue with carbonaceous mudrocks that contain diverse assemblages of Late Albian palynomorphs, including marine dinoflagellates and acritarchs. This palynomorph assemblage is characterized by occurrences of palynomorph taxa not known to range above the Albian Kiowa-Skull Creek depositional cycle elsewhere in the Western Interior, and correlates to the lowest of four generalized palynostratographic units that are comparable to other palynological sequences elsewhere in North America. Tidal rhythmites in mudrocks at the Ash Grove Cement Quarry in Louisville (Cass County), Nebraska record well-developed diurnal and semimonthly tidal cycles, and moderately well developed semiannual cycles. These tidal rhythmites are interpreted to have accumulated during rising sea level at the head of a paleoestuary that experienced at least occasional mesotidal conditions. This scenario places the gravel-bearing lower part of the Nishnabotna Member of the Dakota Formation in the mouth of an incised valley of an Upper Albian transgressive systems tract deposited along a tidally influenced coast. Furthermore, it provides a depositional setting consistent with the biostratigraphic correlation of the lower part of the Nishnabotna Member of the Dakota Formation to the marine Kiowa Formation of Kansas.

Recognizing the Albian-Cenomanian (OAE1d) sequence boundary using plant carbon isotopes : Dakota Formation, Western Interior Basin, USA.

Analysis of bulk sedimentary organic matter and charcoal from an Albian-Cenomanian fluvial-estuarine succession (Dakota Formation) at Rose Creek Pit (RCP), Nebraska, reveals a negative excursion of ∼3‰ in late Albian strata. Overlying Cenomanian strata have δ13C values of −24‰ to −23‰ that are similar to pre-excursion values. The absence of an intervening positive excursion (as exists in marine records of the Albian-Cenomanian boundary) likely results from a depositional hiatus. The corresponding positive δ13C event and proposed depositional hiatus are concordant with a regionally identified sequence boundary in the Dakota Formation (D2), as well as a major regressive phase throughout the globe at the Albian-Cenomanian boundary. Data from RCP confirm suggestions that some positive carbon-isotope excursions in the geologic record are coincident with regressive sea-level phases. We estimate using isotopic correlation that the D2 sequence boundary at RCP was on the order of 0.5 m.y. in duration. Therefore, interpretations of isotopic events and associated environmental phenomena, such as oceanic anoxic events, in the shallow-marine and terrestrial record may be influenced by stratigraphic incompleteness. Further investigation of terrestrial δ13C records may be useful in recognizing and constraining sea-level changes in the geologic record.

Paleosols Below the Ames Marine Unit (Upper Pennsylvanian, Conemaugh Group) in the Appalachian Basin, U.S.A.: Variability on an Ancient Depositional Landscape

ABSTRACT A Vertisol-like paleosol complex, ranging from 3 to > 10 m thick, is developed below the Ames marine interval (Conemaugh Group, Upper Pennsylvanian) in the Appalachian Basin (eastern Ohio, western Pennsylvania, West Virginia, and adjacent parts of Maryland and Kentucky). Sub-Ames mudstones contain the following pedogenic features: very large slickensides, microsparitic calcite nodules, nodules or coatings of radial calcite spar, preserved soil microstructure, soil-compatible birefringence fabrics, and prominent mottling (commonly restricted to the lower part of the paleosolum). Soil formation comprised: (1) long-term pedogenesis in alluvial (and probably lacustrine) sediments, and (2) rapid development of Histosols (Harlem Coal) as much as 8 m thick encouraged by the approaching Am s transgression. Pedogenic carbonates in the sub-Ames interval at three localities yielded 18O values ranging from -6.18 to -1.21 PDB (average = - 4.02 PDB; s.d. = 1.42) and 13C values ranging -9.17 to -6.72 PDB (average = -8.12 PDB; s.d. = 0.59). A inary plot of these values suggests mixing (probably seasonal) of evaporative and meteoric effects on isotope partitioning. The stratigraphy of the Ames-Harlem Coal interval, the regional distribution and thickness of the Harlem Coal, and features of the sub-Ames paleosol show that the pre-Ames landscape had significant local relief (in the form of shallow paleovalleys with broad interfluves) along the western to northern margin of the Appalachian Basin (Ohio, southwestern Pennsylvania). The stratigraphic relationships of sub-Ames paleosols, the Harlem Coal-Ames marine unit interval, and the Ames marine unit itself are compatible with a significant effect of eustatic sea-level rise in this area. Greater regional tectonic subsidence was probably the strongest control on sub-Ames sedimenta ion and pedogenesis along the eastern to southern margin (south-central Pennsylvania, West Virginia, northeasternmost Kentucky), where there appears to have been very little relief. The morphology and stable-isotope geochemistry of sub-Ames paleosols are compatible with seasonally wet-dry climates, probably with moderate ( 500-1000 mm) annual rainfall.

Virgilian (Upper Pennsylvanian) Paleosols in the upper Lawrence Formation (Douglas Group) and its Snyderville Shale Member (Oread Formation, Shawnee Group) of the northern Midcontinent, USA; pedologic contrasts in a cyclothem sequence

ABSTRACT Paleosols in the upper Lawrence Formation and in the Snyderville Shale Member (Virgilian) extend over an estimated area of over 14,000 km2 in Nebraska, Iowa, Missouri, and Kansas. These paleosols, both within cyclothems, are: (1) critical indicators of nearly basin wide emergence (peak regression of the Midcontinent seaway) and geomorphic stability, and (2) useful stratigraphic markers. Both paleosols appear to be analogous to modern Vertisols: they have nested, synformal-antiformal sets ( 4-10 m wide) of very large, intersecting slickensides. Also, some profiles of the upper Lawrence paleosol also have filled cracks extending to depths of 100+ cm. There are, however, significant differences between the paleosols: high-chrom coloration, strong preserved soil structure, and small iron oxide nodules (upper Lawrence) versus dominantly low-chroma coloration, weak to very weak preserved soil structure, and pyrite segregations (Snyderville). After a period of widespread subaerial exposure, each paleosol was drowned and slightly eroded by a marine transgression. The upper Lawrence shows a single paleosol across the study area. The paleosol is thickest and best-developed shelfward (northward) and shows topohydrosequence variation at two basinward localities in northeastern Kansas. Stratigraphic trends suggest an appreciable time differential in the south-to-north migration of the Toronto transgression. The Snyderville shows two welded paleosols in southeastern Nebraska and a single one elsewhere in the study area. Elsewhere in the Snyderville, there is local evidence for lowstand incision of streams and small lows that underwent little or no subaerial exposure. Snyderville paleogeography and pedogenesis, however, were markedly different from upper Lawrence paleogeography and pedogenesis. Contrasts between the two paleosols are likely to be rel ted to intercycle changes in geomorphic conditions (driven by patterns of sedimentation, eustasy, and tectonics) and climate.

UNIQUE FRONTAL SINUSES IN FOSSIL AND LIVING HYAENIDAE (MAMMALIA, CARNIVORA): DESCRIPTION AND INTERPRETATION

ABSTRACT Unique, caudally elongated frontal sinuses 2′ (terminology of Paulli, 1900c) are present in the living hyaenine hyaenids (Crocuta crocuta, Parahyaena brunnea, Hyaena hyaena) and in at least four fossil hyaenids (Adcrocuta eximia, Hyaenotherium wongii, Palinhyaena reperta, and Ictitherium viverrinum). In Crocuta crocuta, Parahyaena brunnea, Hyaena hyaena, and Adcrocuta eximia, the elongated frontal sinuses completely overlie the brain cavity, a condition apparently unique in the history of the Carnivora. Elongated frontal sinuses are conspicuously absent in the extant aardwolf (Proteles cristatus), however. The cladogenetic distribution of these fossil and living hyaenid species is broad enough to indicate a persistent difference in skull architecture between proteline and hyaenine hyaenids through time. The elongated frontal sinuses in all hyaenids examined in this study except for Proteles is an impressive pattern, and its potential function is unlikely to be related to shock dissipation, brain ...

A functional interpretation of the masticatory system and paleoecology of entelodonts

Entelodonts are medium to large (perhaps 150–750 kg) Oligocene–Miocene bunodont artiodactyls with unique crania but typical artiodactyl postcrania. Functional and ecological interpretations are difficult because there is no clear modern analog to an entelodont in size, dentition, and cranial morphology. Entelodont crania combine primitive and derived features, including laterally expanded zygomatic arch/large temporal fossa (suggesting a large temporalis muscle), unreduced dental formula, long premolar row, fused mandibular symphysis, isognathy, and subcylindrical dentary condyles. Furthermore, the cranium has unique architectural and ontogenetic aspects unparalleled in extant mammals. Canines show heavy, carnivoran-like, apical wear in old individuals, suggesting regular contact with food. Conical premolars and associated diastemata dominate the tooth row. Premolars are often apically worn, in a fashion somewhat like those of carnivorans (e.g., Crocuta, Borophagus ). Molars are low-cusped crushing teeth. Wide gape, indicated by the form of the coronoid process and temporal fossa, facilitated canine and premolar use, probably both in feeding and in social behavior. Jaw mechanics, tooth morphology, and tooth wear are compatible with omnivory and probable scavenging, an intriguing proposition for the huge Dinohyus hollandi .

THE AUDITORY REGION AND NASAL CAVITY OF OLIGOCENE NIMRAVIDAE (MAMMALIA: CARNIVORA)

Abstract Highly detailed microscopic preparation of both newly discovered and previously undescribed nimravine crania from the White River Group of North America reveals hitherto unreported morphological features of the basicranium and auditory region, particularly the composition of the auditory bulla and form of the petrosal. The monophyly of Dinictis, Hoplophoneus, and Nimravus is supported by a remarkably uniform configuration of the auditory bulla: (1) the form and placement of the entotympanics; (2) a near-vertical ectotympanic with elaborate styliform process partially enclosing the Eustachian tube; and (3) an anterior bulla wall formed by a unique overlap of the anterior entotympanic lamina by the elongate styliform process. Although an intact auditory bulla is unknown in an Eurasian nimravine, the auditory regions of the species represented by crania (Eusmilus bidentatus and Nimravus cf. intermedius from Quercy) demonstrate a definite affinity with New World genera, affirming the Holarctic distribution of the Nimravinae. In addition to identifying basicranial similarities among nimravines, we describe the first largely intact turbinate bones within the nasal cavity of a nimravid. CT (computed tomography) scanning of nimravid rostra reveals differing configurations of the maxilloturbinate in Dinictis and Hoplophoneus, the former more derived than the latter. Compared to other Carnivora, nimravid maxilloturbinates are most similar to those of living aeluroids, which are confined to the ventral part of the anterior nasal cavity. Nimravids lack the elaborately branching (dendrolamellar) maxilloturbinates of arctoid and cynoid carnivorans.

Surface features of the Salt Basin of Lancaster County, Nebraska

Abstract The Salt Basin of Lancaster County, Nebraska is distinguished by the presence of ephemeral to semi-permanent saline wetlands, salt flats, surface accumulations of salt, zones of bacterial sulfate reduction in wetland soils and stream sediments, and soil cryptogam layers. Salt flat soils are unique in the region and have laminated surface horizons, which probably result from a combination of soil crusting, salt crusting, and microbial binding of grains, with vesicular horizons characteristic of desert soils directly underneath. Soil-surface salt accumulations are dominated by halite (NaCl) and contain minor amounts of thenardite (Na 2 SO 4 ); they range in morphology from thin, powdery, and very transient efflorescences to thicker, more persistent, soil-cementing crusts. The salt crusts form by the upward wicking of Na + - and Cl − -dominated groundwaters and their subsequent surface evaporation. Although it has been largely ignored by geologists for over a century, the Salt Basin can now be viewed as an unusual occurrence of inland sebkhas.

Basicranial anatomy of Syndyoceras cooki (Artiodactyla, Protoceratidae) and the need for a reappraisal of tylopod relationships

ABSTRACT Observations of the holotype of Syndyoceras cooki and comparative material indicate that protoceratid basicrania share no striking resemblances to those of camelids, a group purported to be closely related to the protoceratids. The protoceratid petrosal has a massive posterodorsal (canalicular) part with a strong dorsal crest separating the cerebral and cerebellar surfaces, like the petrosals of ruminants, and its endocranial surface lacks a fossa mastoidea, a feature of uncertain polarity found in camelid petrosals dating back at least as far as the Oligocene genus Poebrotherium. Furthermore, the subarcuate fossa of the petrosal is reduced in protoceratids (a derived condition found in pecoran ruminants). These results, while they cannot be analyzed completely with currently available data, indicate: 1) a pressing need for the reappraisal of interrelationships of “tylopod” artiodactyl taxa and their relationships with the ruminants, and 2) the potential that protoceratids themselves may be more ...