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

Recent studies of eurypterid paleoecology suggest that formation of
eurypterid Lagerstätten in the mid-Paleozoic of Laurentia was 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, and stratigraphic survey and quantitative analysis of all
Silurian–Lower Devonian eurypterid-bearing intervals in the Appalachian
basin, the most prolific region for eurypterid remains in the world.
Canonical correspondence analysis of sedimentological and faunal
associations revealed a strong lithologic gradient between groupings of
eurypterid genera and associated taxa across the 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 subaerial 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 microbialite sediment
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 promoted inhabitation and eventual preservation within the
same setting. This study provides the first quantitative 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.