Early Cambrian origin of the shelf sediment mixed layer

Romain C Gougeon,Luis A Buatois,Brittany A Laing,Guy M Narbonne,M Gabriela Mángano

doi:10.1038/s41467-018-04311-8

Romain C Gougeon, Luis A Buatois + Show 3 more

Open Access

https://doi.org/10.1038/s41467-018-04311-8

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Abstract

The mixed layer of modern oceans is a zone of fully homogenized sediment resulting from bioturbation. The mixed layer is host to complex biogeochemical cycles that directly impact ecosystem functioning, affecting ocean productivity and marine biodiversity. The timing of origin of the mixed layer has been controversial, with estimates ranging from Cambrian to Silurian, hindering our understanding of biogeochemical cycling and ecosystem dynamics in deep time. Here we report evidence from the Global Stratotype Section and Point (GSSP) of the basal Cambrian in the Burin Peninsula of Newfoundland, Canada, showing that a well-developed mixed layer of similar structure to that of modern marine sediments was established in shallow marine settings by the early Cambrian (approximately 529 million years ago). These findings imply that the benthos significantly contributed to establishing new biogeochemical cycles during the Cambrian explosion.

Highlights

The mixed layer of modern oceans is a zone of fully homogenized sediment resulting from bioturbation
In contrast with modern seafloors, Ediacaran marine sediment surfaces were pervasively coated with resistant microbial mats that acted as a geochemical filter between the underlying sediment and overlying seawater[15,16]
Fortune Head is the one that has captured the most attention because it contains the Cambrian Global Stratotype Section and Point (GSSP), which is located 2.4 m above the base of member 2 at the last occurrence of Ediacaran megafossils and the base of the Treptichnus pedum ichnofossil Zone[26,27,33,34,35] (Fig. 1)

Summary

Introduction

The mixed layer of modern oceans is a zone of fully homogenized sediment resulting from bioturbation. We report evidence from the Global Stratotype Section and Point (GSSP) of the basal Cambrian in the Burin Peninsula of Newfoundland, Canada, showing that a welldeveloped mixed layer of similar structure to that of modern marine sediments was established in shallow marine settings by the early Cambrian (approximately 529 million years ago). These findings imply that the benthos significantly contributed to establishing new biogeochemical cycles during the Cambrian explosion.

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Conclusion