283,821 concretions, how do you measure the Mazon Creek? Assessing the paleoenvironmental and taphonomic nature of the Braidwood and Essex assemblages

The Mazon Creek Lagerstätte (late Carboniferous Period, Moscovian Stage; Illinois, USA) captures a diverse view of ecosystems in delta-influenced coastal settings through exceptional preservation of soft tissues in siderite concretions. The generally accepted paradigm of the Mazon Creek biota has been that of an inferred paleoenvironmental divide between what have been termed the Braidwood and Essex assemblages, wherein the former represents a freshwater ecosystem with terrestrial input and the latter a marine-influenced prodelta setting with abundant cnidarians, bivalves, worm phyla, and diverse arthropods. Here, we revisit the paleoecology of the Mazon Creek biota by analyzing data from nearly 300,000 concretions from 270 locations with complementary multivariate ordinations. Rather than a homogenization of ecological communities, our results show the Braidwood assemblage as a legitimate shoreward community and provide evidence for further subdivision of the Essex assemblage into two ..., , # 283,821 concretions, how do you measure the Mazon Creek? Assessing the paleoenvironmental and taphonomic nature of the Braidwood and Essex assemblages

Dataset DOI: [10.5061/dryad.z8w9ghxr2](10.5061/dryad.z8w9ghxr2)

## Description of the data and file structure

The raw dataset from Baird et al. (1985) comprises 286,953 concretions from 342 separate collections from the Mazon Creek Lagerstätte. These and other non-included samples and all available metadata are detailed in the Supplementary Online Materials (SOM), Appendix 1. Samples were collected from exposed mine dump surfaces in over 270 locations, including 25 strip mines and more than 80 shaft mines (Baird et al. 1985). The complete data set comprises 229 original identification groups (IDs), whether taxonomic or otherwise, including some subgroupings, taphomorphs, or other distinct characterizations (e.g., crushed bivalves vs. intact shells). IDs were originally coded by Baird as 4-character abbreviations, which have been incl...,