L354 Limestone, shelly

L354_HS.jpg
L354_TS_ppl.jpg
L354_TS_xpl.jpg

Title

L354

Limestone, shelly

Subject

Age

Middle Jurassic

Location

Forest Marble
Near Weymouth

Description

Hand Specimen

This rock is made up of well cemented bioclasts. The bioclasts (mainly shell fragments) are poorly sorted, ranging from <1mm up to a few 10s of mm. 
Fine-grained cement fizzes with acid, indicating that it is carbonate. It has weathered to a pale yellow-grey.

Thin-section

Carbonate fossil fragment in a carbonate cement (sparite). The laminated structure of the shells is visible in places. 
Cement contains some hematite (brown regions). 
There are a few epidote grains and some opaque areas.
This is a rudstone (Dunham naming system) or biosparite (Folk naming system).

Rock History

The shells are not in life position – they have been transported. 
Deposited in moderate to high energy environment. 

Rock Name

shelly limestone

Citation

“L354
Limestone, shelly,” 1A Collections, accessed April 9, 2024, https://wserv3.esc.cam.ac.uk/p1acollections/items/show/33.