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Big Cedar Ridge, Wyoming: a 73 million-year-old preserved landscape



Streamside Thicket

There is one part of the Big Cedar Ridge outcrop where fossil sites are dominated by broad-leaved flowering plants. Unlike the fern wetland and the palmetto wetland, the soil here had little organic matter. A local increase in sandy sediments below the tuff, and a channel-shaped lens of unusually thick tuff, suggest that a stream channel traversed the landscape in this area. In short, this area had been disturbed by channel erosion and fresh sediment deposition just before the tuff that preserved the landscape was deposited. The dominant plant in this area was probably related to living gooseberries (DN14 – Saxifragales). Quite a few other dicots occur in this area: DE8 (probably Laurales), DN12 (probably Austrobaileyales), and DN21 (family unknown). Apparently they grew well on bare mineral soils that had recently been deposited. Because of the nearby stream channel the soil here was probably wet, just as it was across the rest of the Big Cedar Ridge landscape.

Reconstruction of streamside vegetation at Big Cedar Ridge. This was the only part of the landscape with abundant broad-leaved flowering plants. The lobed and toothed leaves are DN14 (probably the order Saxifragales). The smooth-margined cordate leaves in the lower right of the painting are DE8 (probably the order Laurales), and the slender leaves at the top are DN12 (probably the order Austrobaileyales). (Mary Parrish reconstruction)

Fossils used in the reconstruction:

The flowering plant DN14 (Saxifragales).

The flowering plant DE8 (probably Laurales).

The flowering plant DN12 (probably Austrobaileyales).

The flowering plant DN21 (family unknown).

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