Paleoecology of Echinoderms in Cold Seep Environments Revealed by Isotope Analysis in the Late Cretaceous Western Interior Seaway

<strong>Crinoids lived around the Cretaceous seeps: the second example from cold-seep deposit in the Yezo Group in Hokkaido, Japan</strong>

“…Fossil crinoids, which can be assigned to the suborder Isocrinina, have been found in the Upper Cretaceous cold seep deposits of the Yezo Group, Hokkaido, Japan. This is the second occurrence of fossil crinoids from cold seep deposits, following the previous occurrence (Lakotacrinus brezinai) from the Pierre Shale Formation of the U.S. Western Interior (Landman et al 2012;Hunter et al 2016;Kato et al 2017).…”

“…3). The stereom structure suggests that the crinoid fossil is in a good state of preservation and it is expected to keep original isotope status in its skeleton (for further discussion see Kato et al 2017). Thus, it is considered that the fossil crinoids used in this study were not suffered severe diagenesis, and are expected to keep initial stable isotope ratios.…”

“…Thus, the seep crinoid from Hokkaido should have utilized organic matter produced through chemosynthesis in cold seep environments for their metabolism including secreting their skeleton. It is the second example of fossil crinoids that used chemosynthetic products, next to Lakotacrinus brezinai (Hunter et al 2016;Kato et al 2017).…”

“…The seep carbonates are characterized by "brecciated" carbonate rocks with low δ 13 C values, and fossil assemblages such as vestimentiferan tubeworms and some characteristic molluscan species. Although echinoderms were not regarded as a member of chemosynthetic community, Kato et al (2017) showed an example that the morphologically peculiar stalked crinoid, Lakotacrinus brezinai, from Upper Cretaceous Pierre Shale Formation (Campanian) of South Dakota, USA used carbon derived from methane for their skeletal formation. Considering that the crinoid stalks are endoskeleton, Lakotacrinus brezinai also used carbon derived from the methane for their soft body.…”

Brittle-star mass occurrence on a Late Cretaceous methane seep from South Dakota, USA

“…Around the Black Hills, these deposits were formed from methane enriched fluids escaping from underlying layers of the Pierre, Niobrara, Belle Fourche, Mowery and Greenhorn Formations 35 , 37 . The presence of methane was confirmed through isotopic analyses of the carbonate cements 35 , 37 – 39 . Methane gas probably migrated along faults and fractures that developed in the Late Cretaceous prior to the uplift of the Black Hills during the Laramide Orogeny 34 , 35 .…”