Do marine faunas track lithofacies? Faunal dynamics in the Upper Cretaceous Pierre Shale, Western Interior, USA

https://doi.org/10.1016/j.palaeo.2018.01.038Get rights and content

Highlights

  • We recognize five biofacies.

  • Biofacies reflect benthic oxygenation and substrate firmness.

  • Oxygenation and substrate firmness were both controlled by water depth.

  • Changes in benthic diversity can arise in response to variations in depth with no apparent change in lithofacies.

  • Fossil taxa are more sensitive to environmental change than lithofacies.

Abstract

Most studies examining faunal assemblages use their sedimentary context as a critical element in constraining and reconstructing their underlying environmental controls. This has resulted in the assumption that an absence of lithofacies change in a section should be reflected in a lack of environmental variation. This inference, however, has been placed into question by evidence that marine species are influenced by a broader range of environmental dynamics than just change in lithofacies. In this study, we examine the sensitivity of marine faunas to broadly defined environmental change within lithologically homogenous strata by examining concretionary fossil assemblages of the Baculites eliasi through B. clinolobatus biozones in monotonous, clay-rich strata of the Campanian-Maastrichtian Pierre Shale in Wyoming. We recognize five biofacies, which reflect different environmental conditions related to benthic oxygenation, substrate firmness, and water depth. Analyses of abundance patterns, raw species richness trends, and life-habit patterns display recurrent switching, upsection, between low- and high-diversity intervals. Our data reveal that samples with lower diversity show a strong relationship with intervals when water conditions were deepest, whereas higher diversity samples are associated with periods when shallow-water conditions prevailed in the study area. The distribution of taxa and diversity of the assemblages most likely reflect migrating oxygen- and substrate-controlled biofacies that were responding to changes in depth. This study shows that substantial changes in biofacies, diversity, and life habits can arise in response to variations in water depth with limited to no apparent change in lithofacies supporting the hypothesis that fossil taxa are much more sensitive indicators of environmental change than lithofacies.

Introduction

The distributions of marine faunas in both time and space are known to be correlated with changes in environmental conditions, including water depth, substrate, oxygen levels, and temperature (Thorson, 1966; Patzkowsky and Holland, 2012). However, until recently, most paleontological studies have linked marine faunal distributions to lithofacies control based on analyses of faunal and biofacies change in conjunction with varying lithologies (e.g., Kauffman, 1967; Fürsich, 1976; Patzkowsky, 1995). This has resulted in the assumption that an absence of lithofacies change in a stratigraphic section should be reflected in a lack of environmental influence on faunal distributions. This inference has led many studies of mass extinctions and evolutionary patterns (e.g., Hansen et al., 1993; Elder, 1987; Sheldon, 1996; Jin et al., 2000) to prefer to utilize stratigraphic sections with limited lithofacies change under the assumption that these settings will reflect change over time within a single environment rather than those influenced by shifting environments, which could influence faunal patterns and an organisms' phenotype. However, this has been questioned by evidence that marine species are even more highly sensitive to environmental dynamics than that captured in lithofacies change (Brett, 1998; Holland et al., 2001).

Numerous studies linking variation in faunal distribution to lithofacies come from the Upper Cretaceous of the Western Interior. For example, Kauffman (1967) linked faunal distributions in the Upper Cretaceous of Colorado to changing lithofacies patterns in his cyclothem model of sea-level change. Similarly, Waage (1967) documented the relationship between lithofacies and biofacies in a prograding nearshore system represented by the Fox Hills Formation of South Dakota (see also Fürsich and Kauffman, 1984; Kauffman, 2008). However, despite these studies, changes in faunal distributions and biofacies in monotonous lithofacies in the Western Interior have been almost completely ignored (for exceptions see: Sageman, 1989; Elder, 1990, Elder, 1991). This is significant as much of the Upper Cretaceous strata in the Western Interior are represented by extensive monotonous successions of shale, siltstone, and marls that were deposited in offshore settings hundreds of kilometers from the shoreline (e.g., Fig. 1). These offshore successions can extend up to hundreds of meters in thickness and cover thousands of square kilometers. Studies that have examined faunal change in these monotonous lithofacies in the Western Interior have usually attributed them to change over time within a single environment rather than sampling different environments (e.g., Elder, 1987; Ozanne and Harries, 2002).

The primary aim of this study is to examine the sensitivity of marine species to broadly defined environmental change within a monotonous, clay-rich succession. To assess the interplay between lithofacies and faunal sensitivity to environmental change, faunal distributions, as determined by an investigation of fossiliferous concretionary horizons, are examined through four ammonite zones in an offshore setting. These assemblages provide the context from which to investigate the paleoecological, paleobiological, and paleoenvironmental dynamics associated with ocean/climate changes within an epeiric seaway.

Section snippets

Stratigraphic and geographic setting

This study examined the Campanian to Maastrichtian (Upper Cretaceous) Pierre Shale, which is under- and overlain by the Coniacian-Santonian Niobrara and Maastrichtian Fox Hills formations, respectively (Robinson et al., 1964; Waage, 1967; Landman and Waage, 1993). These lithostratigraphic units and their lateral equivalents are well exposed across the Western Interior and vary from non-marine to offshore lithofacies (Gill and Cobban, 1966; Lynds and Slattery, 2017).

This study investigated the

Data

To examine the faunal trends through this monotonous succession, a total of 19 whole or portions of fossiliferous carbonate-cemented concretion (i.e., samples) were collected from separate horizons. Concretions were bulk sampled from two concretionary horizons from the upper 40 m of the lower shale member, from two concretionary horizons within the 10 m Kara Bentonitic Member, and from 15 concretionary horizons spanning the 210 m upper shale member (Fig. 5). To standardize sample volumes for

Occurrence of concretions and fossils

Fossils from the study interval are primarily concentrated in carbonate-cemented concretions, which occur as laterally persistent horizons, surrounded by poorly lithified shale or silty shale (Fig. 5, Fig. 6; also see Gill and Cobban, 1966). These surrounding sediments are typically unfossiliferous (or barren) to poorly fossiliferous. Poorly fossiliferous and barren concretion beds are also found throughout the Pierre Shale, although most of these horizons occasionally preserve mature Baculites

Taphonomy and fidelity of fossil assemblages

All the fossil assemblages display taphonomic features that relate to their composition, mode(s) of death, exposure time on the sea floor prior to final burial, depositional setting, and post-burial diagenetic processes that ultimately resulted in concretion formation. The taphonomic characteristics of the various samples reveal that those analyzed represent time-averaged, within-habitat assemblages.

Paleobiological implications

Our results suggest that substantial temporal variation in biofacies, diversity, and life habits can arise in response to variations in water-depth-correlated environmental factors with limited to no apparent change in lithofacies. This provides empirical support for the hypothesis that fossil taxa are much more sensitive indicators of environmental change than lithofacies. Several studies have documented the sensitivity of marine faunas to environmental change (e.g., Springer and Bambach, 1985

Conclusions

  • 1.

    The concretionary faunas at Red Bird represent “within-habitat, time-averaged assemblages” (sensu Kidwell, 1998). The parallel alignment of the shells of Baculites and the inclusion of abundant, disarticulated epifaunal shells and articulated infaunal shells indicate that the assemblages were partially reworked and concentrated by storms or currents on the sea floor. The random orientation of the specimens in the shell concentrations is likely the product of both the current winnowing and the

Acknowledgments

We would like to thank the various Niobrara County ranchers and ranches that made this project possible. We especially want to acknowledge and thank the Williams, the Four Three Ranch, the Mengs, as well as one anonymous land owner for granting permission to carry out field work on their land for this project. We would also like to thank I. Montanez, S. Holland, C. Myers, T. Algeo, N. Landman, N. Larson, G. Herbert, and two anonymous reviewers for their helpful comments and suggestions on

References (111)

  • G. Thorson

    Some factors influencing the recruitment and establishment of marine benthic communities

    Neth. J. Sea Res.

    (1966)
  • C.J. Tsujita et al.

    Ammonoid habitats and habits in the Western Interior Seaway: a case study from the Upper Cretaceous Bearpaw Formation of southern Alberta, Canada

    Palaeogeogr. Palaeoclimatol. Palaeoecol.

    (1998)
  • R.C. Baron-Szabo

    Corals of the K/T-Boundary: Scleractinian Corals of the Suborders Dendrophylliina, Caryophylliina, Fungiina, Microsolenina, and Stylinina

    (2008)
  • T.J. Bergstresser

    Foraminiferal biostratigraphy and paleobathymetry of the Pierre Shale, Colorado, Kansas, and Wyoming

  • C.E. Brett

    Sequence stratigraphy, paleoecology, and evolution: biotic clues and responses to sea-level fluctuations

    PALAIOS

    (1998)
  • C.E. Brett et al.

    Response of shallow marine biotas to sea-level fluctuations: a review of faunal replacement and the process of habitat tracking

    PALAIOS

    (2007)
  • S.J. Carpenter et al.

    Diagenesis of fossiliferous concretions from the Upper Cretaceous Fox Hills Formation, North Dakota

    J. Sediment. Petrol.

    (1988)
  • C. Carvajal et al.

    Source-to-sink sediment volumes within a tectonostratigraphic model for a Laramide shelf-to-deep-water basin: Methods and results

  • W.A. Cobban et al.

    A USGS zonal table for the upper cretaceous middle Cenomanian-Maastrichtian of the western interior of the United States based on ammonites, inoceramids, and radiometric ages

  • J.S. Crampton

    Inoceramid bivalves from the Late Cretaceous of New Zealand

  • P.G. DeCelles

    Late Jurassic to Eocene evolution of the Cordilleran thrust belt and foreland basin system, Western United States of America

    Am. J. Sci.

    (2004)
  • W.P. Elder

    The Paleoecology of the Cenomanian-Turonian (Cretaceous) Stage Boundary extinctions at Black Mesa, Arizona

    PALAIOS

    (1987)
  • W.P. Elder

    Soft-bottom paleocommunity dynamics in the Cenomanian-Turonian boundary extinction interval of the Western Interior, United States

  • W.P. Elder

    Molluscan paleoecology and sedimentation patterns of the Cenomanian-Turonian extinction interval in the southern Colorado plateau region

    Geol. Soc. Am. Spec. Pap.

    (1991)
  • W.P. Elder et al.

    Correlation of basinal carbonate cycles to nearshore parasequences in the Late Cretaceous Greenhorn seaway, Western Interior, USA

    Geol. Soc. Am. Bull.

    (1994)
  • J.M. Erickson

    Revision of the Gastropoda of the Fox Hills Formation, Upper Cretaceous (Maestrichtian) of North Dakota. Bulletin of American

    Paléo

    (1974)
  • J.W. Fatherree et al.

    Oxygen and carbon isotopic “dissection” of Baculites compressus (Mollusca: Cephalopoda) from the Pierre Shale (upper Campanian) of South Dakota; implications for paleoenvironmental reconstructions

    PALAIOS

    (1998)
  • R.M. Feldmann

    Bivalvia and paleoecology of the Fox Hills Formation (Upper Cretaceous) of North Dakota

  • R.M. Feldmann

    Stratigraphy and paleoecology of the Fox Hills Formation (Upper Cretaceous) of North Dakota

  • R.M. Feldmann et al.

    Formation of lobster-bearing concretions in the Late Cretaceous Bearpaw Shale, Montana, United States, in a complex geochemical environment

    PALAIOS

    (2012)
  • F. Fuentes et al.

    Jurassic onset of foreland basin deposition in northwestern Montana, USA: implications for along-strike synchroneity of Cordilleran orogenic activity

    Geol. Soc. Am. Bull.

    (2009)
  • F. Fuentes et al.

    Evolution of the cordilleran foreland basin system in northwestern Montana. USA

    Geol. Soc. Am. Bull

    (2011)
  • F.T. Fürsich

    Fauna-substrate relationships in the Corallian of England and Normandy

    Lethaia

    (1976)
  • F.T. Fürsich et al.

    Paleoecology of marginal marine sedimentary cycles in the Albian Bear River Formation of south-western Wyoming

    Paléo

    (1984)
  • D.L. Gautier

    Siderite concretions: indicators of early diagenesis in the Gammon Shale (Cretaceous)

    J. Sediment. Petrol.

    (1982)
  • J.R. Gill et al.

    The Red Bird Section of the Upper Cretaceous Pierre Shale in Wyoming

  • J.R. Gill et al.

    Stratigraphy and geological history of the Montana Group and equivalent rocks, Montana, Wyoming, and North and South Dakota

  • O. Hammer et al.

    Paleontological Data Analysis

    (2006)
  • P.J. Harries et al.

    The inoceramids

  • J.H. Hartman et al.

    Brackish and Marine mollusks of the Hell Creek Formation of North Dakota: evidence for a persisting Cretaceous Seaway

  • E.D. Hattin

    Widespread, synchronously deposited beds in Greenhorn Limestone (Upper Cretaceous) of Kansas and southeastern Colorado

    Am. Assoc. Pet. Geol. Bull.

    (1971)
  • M.O. Hill et al.

    Detrended correspondence analysis: an improved ordination technique

    Vegetatio

    (1980)
  • J.W. Hoganson et al.

    Marine Breien Member (Maastrichtian) of the Hell Creek Formation in North Dakota: stratigraphy, vertebrate fossil record, and age

  • S.M. Holland et al.

    The stratigraphic distribution of fossils in a tropical carbonate succession: Ordovician Bighorn Dolomite, Wyoming, USA

    PALAIOS

    (2009)
  • S.M. Holland et al.

    The detection and importance of subtle biofacies within a single lithofacies: the Upper Ordovician Kope Formation of the Cincinnati, Ohio Region

    PALAIOS

    (2001)
  • D.K. Jacobs et al.

    Oxygen and evolutionary patterns in the sea: onshore/offshore trends and recent recruitment of deep-sea faunas

    Proc. Natl. Acad. Sci.

    (1998)
  • Y.G. Jin et al.

    Pattern of marine mass extinction near the Permian-Triassic boundary in South China

    Science

    (2000)
  • A. Kaim et al.

    Faunal dynamics of bivalves and scaphopods in the Bathonian (Middle Jurassic) ore-bearing clays at Gnaszyn, Kraków-Silesia Homocline, Poland

    Acta Geol. Pol.

    (2012)
  • E.G. Kauffman

    Coloradoan macroinvertebrate assemblages, central Western Interior, United States

  • E.G. Kauffman

    Geological and biological overview: western interior cretaceous basin

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