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Hornsleasow Quarry (Jurassic of the United Kingdom)

Also known as Snowshill Quarry

Where: England, United Kingdom (52.0° N, 1.8° W: paleocoordinates 41.6° N, 8.6° E)

• coordinate estimated from map

• outcrop-level geographic resolution

When: Zigzagiceras zigzag zone, Chipping Norton Limestone Formation (Great Oolite Group), Early/Lower Bathonian (167.7 - 164.7 Ma)

• "Hornsleasow Clay Unit" placed between Chipping Norton Member (above) and Hook Norton Member (below). Upper part of unit is the "Green Clay" and lower part is the "Grey Clay". From the macrescens Subzone of the zigzag Zone

• bed-level stratigraphic resolution

Environment/lithology: karst; bioturbated, pebbly, carbonaceous claystone and claystone

• Clay units were deposited into the karstic surface of the Hook Norton Member. Clay deposition involved low paleocurrent activity and increasingly anoxic conditions. The unit "is interpreted as a paleosol. The depositional environment...is one of marshy, low-pH type. The partially decayed organic material within this deposit suggests relatively reducing conditions, and the presence of pyrolusite (MnO2)...is suggestive of bog or lake deposition...salinity was low to moderate...The Grey Clay is a waterlogged, boggy paleosol developing within a freshwater to brackish-water pond. The absence of dispersed kerogen indicates a low-energy depositional environment, with little fluvial influence...The Green Clay is also interpreted as a paleosol, deposited under more oxidizing, high-pH conditions.
• Primary (Grey Clay): "matrix-supported, but contains large, irregularu subrounded limestone cobbles (concentrated in the basal portion, which is interpreted as a regolith), with associated lime and lime-fraction silica sand. The clay is smectitic, with a high organic content, and it contains much partially lignitized wood...finely laminated. This lamination has been somewhat disrupted, possibly by bioturbation."

•Secondary (Green Clay): "more homogenous than the Grey Clay. Limestone clasts and sand make up only 3 percent of the composition by weight. The deposit has more silica and sand and is an illite/chlorite clay. Vertical rootlets pervade the layer, extending from the mud-cracked, upper surface...into the underlying Grey Clay...The plant material is somewhat oxidized."

Size classes: macrofossils, mesofossils, microfossils

Collected by K. Gardner in 1987

Collection methods: bulk, surface (in situ), sieve,

Primary reference: S. J. Metcalf and R. J. Walker. 1994. A new Bathonian microvertebrate locality in the English Midlands. In the Shadow of the Dinosaurs: Early Mesozoic Tetrapods, edited by N. C. Fraser and H.-D. Sues. Cambridge University Press, Cambridge 322-331 [M. Carrano/M. Carrano/J. Alroy] more details

Purpose of describing collection: general faunal/floral analysis

PaleoDB collection 31054: authorized by Matthew Carrano, entered by Matthew Carrano on 09.04.2003, edited by Kaitlin Maguire and Richard Butler

Creative Commons license: CC BY (attribution)