Data from: Paleoecological and stratigraphic controls on eurypterid Lagerstätten: a model for preservation in the mid-Paleozoic

The results of recent studies intimate that formation of eurypterid Lagerstätten in the mid-Paleozoic of Laurentia may have been controlled by the presence of an ecological-taphonomic window that recurred predictably in nearshore, marginal environments during transgressions. We tested this hypothesis by performing a high-resolution taxonomic, environmental, stratigraphic survey and quantitative analysis of all Silurian–Early Devonian eurypterid-bearing intervals in the Appalachian basin, the most prolific region for eurypterid remains in the world. Canonical correspondence analysis (CCA) of sedimentological and faunal associations revealed a strong lithological gradient between groupings of eurypterid genera and associated taxa across basin, and a significant association of eurypterids with microbialites (thrombolites, stromatolites) and evaporitic structures. Field observations confirmed that, stratigraphically, eurypterids in the basin frequently occur above the microbialite structures and beneath evaporites and other indicators of increased salinity or sub-aerial exposure. Following interpretation of these features within a sequence stratigraphic framework, we present a preservational model in which 1) eurypterids inhabited nearshore settings following freshening conditions concomitant with minor transgressions, 2) their remains were subsequently buried by storms or baffling, and 3) subsequent long-term preservation of tissues was facilitated by regression and cyclical shallowing-up successions that promoted hypersalinity and anoxia. In the central and southern region of the basin, where microbial structures and evidence for hypersalinity are less common, a similar pattern of cyclical shallowing-upward deposition within eurypterid-bearing units holds. Thus, eurypterid preservation appears to reflect a combination of ecological preferences and abiotic conditions that promote inhabitation and eventual preservation within the same setting. This study provides the first stratigraphic support for a sea-level-based control on preservation of eurypterids, and adds to the growing body of evidence that suggests that analysis of exceptional preservation in the fossil record benefits from interpretation within a sequence stratigraphic framework.