Anatomy of a Concretion: Life, Death, and Burial in the Western Interior Seaway

Landman, Neil H.; Klofak, Susan M.

doi:10.2110/palo.2011.p11-105r

Cited by 40 publications

(55 citation statements)

References 56 publications

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“…Because the density of calcium carbonate is similar to that of terrigenous sediments, the volume of calcium carbonate in the concretion can be estimated by determining the percent mass or weight of calcium carbonate. The weight of calcium carbonate in our concretion, as well as that of the concretion documented by Landman and Klofak (2012), is *80 %. Thus, all of the pore volume of the sediments in our concretion was replaced by calcium carbonate.…”

Section: Post-depositional Historysupporting

confidence: 59%

“…One of the most common modes of preservation of ammonites in the Upper Cretaceous US Western Interior is in concretions (Waage 1964;Kauffman and Caldwell 1993;Tsujita 1995;Tsujita and Westermann 1998;Larson et al 1997;Landman and Klofak 2012). Because such concretions form early in diagenesis, the ammonites are preserved in three dimensions.…”

Section: Introductionmentioning

confidence: 99%

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3-D orientation and distribution of ammonites in a concretion from the Upper Cretaceous Pierre Shale of Montana

Landman

Grier²,

Grier

et al. 2015

Swiss J Palaeontol

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One of the most common modes of preservation of ammonites in the Upper Cretaceous US Western Interior is in concretions. We examine an accumulation of ammonites from a single concretion in the lower Maastrichtian Pierre Shale of eastern Montana. The concretion is an oblate spheroid 50 cm in length and 26 cm in diameter, with its long axis parallel to the substrate. It contains approximately 90 ammonite specimens representing three species of Hoploscaphites including adults and juveniles. The concretion also contains other fauna, primarily bivalves and gastropods. A total of 33 ammonites, mostly adults, are concentrated in a cluster that spans 71 % of the length of the concretion (called the ''sculpture''). 3-D measurements of the ammonites in the sculpture reveal that (1) the shells dip at all angles, with a significant trend toward more horizontal from west to east; (2) the shells dip with a highly significant bias toward the east, suggesting a current from that direction; and (3) a highly significant number of the shells that are non-vertical face with their left side up. Most of the shells show lethal damage as indicated by missing pieces of body chamber. After settling to the bottom, the shells may have piled up against each other, creating a sediment trap. Other organisms such as scavenging gastropods may have been attracted to the site to feed on the stranded ammonite carcasses. The chambers of the ammonite phragmocones and even some of the body chambers are empty, suggesting relatively rapid burial. Oxygen and carbon isotopic analyses of the ammonite shells reveal that they preserve their original isotopic signature. The values of d 13 C of the carbonate cement in the concretionary matrix are much lighter than those in the ammonite shells and imply that cementation of the concretion occurred in association with the decomposition of organic matter.

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Section: Post-depositional Historysupporting

confidence: 59%

Section: Introductionmentioning

confidence: 99%

3-D orientation and distribution of ammonites in a concretion from the Upper Cretaceous Pierre Shale of Montana

Landman

Grier²,

Grier

et al. 2015

Swiss J Palaeontol

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show abstract

“…This inference is based on several lines of evidence, including incidence and kinds of injuries on the shells, facies and faunal associations, and isotopic analyses Landman and Klofak, 2012). For example, in the Campanian Pierre Shale of the U.S. Western Interior, scaphites are associated with a rich benthic and nektic fauna (Tsujita and Westermann, 1998;Landman et al, 2010).…”

Section: Paleoecologymentioning

confidence: 99%

Allostratigraphy and Biostratigraphy of the Upper Cretaceous (Coniacian-Santonian) Western Canada Foreland Basin

Landman

Plint²,

Walaszczyk

2017

Bulletin of the American Museum of Natural History

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“…A similar hypothesis has been proposed to explain the abundance of ammonite jaws in a concretion from the upper Campanian Pierre Shale of South Dakota. Many of the jaws in this concretion are fragmentary and several of them are even perforated by holes (Landman and Klofak 2012, fig. 6J).…”

Section: Baculites Sp (Smooth)mentioning

confidence: 99%

Description of the lower jaws of Baculites from the Upper Cretaceous U.S. Western Interior

Larson

Landman

2017

Acta Geologica Polonica

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We report the discovery of lower jaws of Baculites (Ammonoidea) from the Upper Cretaceous U.S. Western Interior. In the lower Campanian Smoky Hill Chalk Member of the Niobrara Chalk of Kansas, most of the jaws occur as isolated elements. Based on their age, they probably belong to Baculites sp. (smooth). They conform to the description of rugaptychus, and are ornamented with coarse rugae on their ventral side. One specimen is preserved inside a small fecal pellet that was probably produced by a fish. Another specimen occurs inside in a crushed body chamber near the aperture and is probably in situ. Three small structures are present immediately behind the jaw and may represent the remains of the gills. In the lower Maastrichtian Pierre Shale of Wyoming, two specimens of Baculites grandis contain lower jaws inside their body chambers, and are probably in situ. In both specimens, the jaws are oriented at an acute angle to the long axis of the shell, with their anterior ends pointing toward the dorsum. One of the jaws is folded into a U-shape, which probably approximates the shape of the jaw during life. Based on the measurements of the jaws and the shape of the shell, the jaws could not have touched the sides of the shell even if they were splayed out, implying that they could not have effectively served as opercula. Instead, in combination with the upper jaws and radula, they constituted the buccal apparatus that collected and conveyed food to the esophagus.

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Anatomy of a Concretion: Life, Death, and Burial in the Western Interior Seaway

Cited by 40 publications

References 56 publications

3-D orientation and distribution of ammonites in a concretion from the Upper Cretaceous Pierre Shale of Montana

3-D orientation and distribution of ammonites in a concretion from the Upper Cretaceous Pierre Shale of Montana

Allostratigraphy and Biostratigraphy of the Upper Cretaceous (Coniacian-Santonian) Western Canada Foreland Basin

Description of the lower jaws of Baculites from the Upper Cretaceous U.S. Western Interior

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