Geological Sites | Leeds
| Bradford | Calderdale
| Kirklees | Wakefield
 STATUS:
Local Geological Site
OTHER DESIGNATIONS:
COUNTY: West Yorkshire
DISTRICT: Bradford
OS GRID REF. SE 038 468
OS SHEET 1:50,000 Landranger 104 Leeds and Bradford
OS SHEET: 1:25,000 Outdoor Leisure 21 South Pennines
BGS Sheet 1:50,000 Geological Sheet 60 Bradford (Solid and Drift Edition)
FIRST DESIGNATED by West Yorkshire LGS Group in 1996
DATE OF MOST RECENT SURVEY January 2009
SCIENTIFIC INFORMATION produced by Neil Aitkenhead
DESIGNATION SHEET UPDATED August 2009
SITE DESCRIPTION:
The site runs along the Bracken Hill Gill in a wooded valley, exposing
Upper
Carboniferous (Namurian) mudstones, clays and sandstone beds which
give important
information about the environment of deposition of the rocks.
HISTORICAL ASSOCIATIONS:
Green and Russell recorded in 1878 that the brook between Silsden and
Throstle Nest
contained fossiliferous shales with earthy limestones (p70). The
site contains the original
exposure of the Marchup Marine Beds where Anthracoceras glabrum and
Cravenoceratoides bisati were collected. Specimens collected from
this site in the 1920s
enabled W. S.Bisat to describe the goniatite succession in the Arnsbergian
(E2) Stage of
the Namurian Epoch.
 EDUCATIONAL
VALUE:
The data provided above may enable the visiting student to see
for themselves the
evidence for a changing
palaeoenvironment from the abandonment of a river delta with
consequent soil
development and plant colonisation and growth followed by marine
flooding with mud
deposition containing marine organisms. A 'K (potassium)-bentonite' clay
band provides evidence of distant volcanic activity and
consequent
ashfall into this marine environment.
The site also illustrates how the rapidly evolving ammonoids (formerly
goniatites) found
in marine bands are used in the zoning and correlation of Namurian
and Westphalian rock
successions.
AESTHETIC CHARACTERISTICS:
In the last 10 years the lower section of the LGS has been affected
by tipping from a
small, family-run waste-recycling plant which runs along the
west side of the valley
above the stream. There is much litter in the stream bed.
ACCESS AND SAFETY:
Although footpaths pass nearby the site is located on private
land. This is an important
scientific site and unauthorised collecting is prohibited.
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