1. Introduction
2. Dogger Formation
3. Saltwick Formation
4. Eller Beck Formation
5. Cloughton Formation
6. Scarborough Formation
7. Scalby Formation
8. Cornbrash and Osgodby Formations

Introduction

Column showing Formations making up the Middle Jurassic of the Tees Valley.

Following the marine conditions of the Lower Jurassic, transition to the Middle Jurassic is marked by extensive uplift and erosion of the local land surface producing a patchwork of different environments. During this episode the upper parts of the Lower Jurassic succession were eroded and the Dogger Formation deposited.
 
Next, a river delta encroached upon the area from the north and west laying down thick sandstone with occasional mudstone lenses. The sea intermittently transgressed this delta, and associated marsh, resulting in cycles of deltaic followed by marine regime. During times of delta-marsh sedimentation a diverse flora occupied the delta which has left a legacy of plant and reptile footprint beds.
 
The resulting succession of rocks are collectively referred to as the Ravenscar Group. They cap the outliers of Eston Hills, Errington and Airy Hill near the coast and underlie the uplands of the North York Moors.

Dogger Formation

At the base of the Middle Jurassic, the area was gently folded into a series of low domes and basins, producing a mosaic of depositional environments. Parts of the former sea floor emerged above the water to be weathered and eroded. The sediment became generally coarser due to the closer proximity of land, and was inhabited by a diverse fauna of invertebrates and other marine creatures. Accordingly, the Dogger Formation displays a number of different rock types (sandstone, mudstone, siltstone, sandstone, and ironstone) which vary across the area. These are often packed with fossilised burrows. The formation rarely attains a thickness in excess of a few metres and in places is absent altogether.

Saltwick Formation

As uplift progressed, so the deposits change to thickly bedded yellow sandstones, grey siltstones, and some minor mudstones. This change occurred as a great river delta advanced across the former sea floor. Within the Saltwick Formation can be found beds of fossil wood, some of which form seams of jet, indicating that the delta was well vegetated. In fact, the earliest fossil of a flowering plant (Weltrechsia whitbiensis) was recovered from beds in this formation near Whitby. Perhaps the most sought after, and least found fossils, are those of dinosaur footprints. These tell us that land-dwelling reptiles of many species once browsed and hunted on the delta-marsh.

Eller Beck Formation

This is a thin sequence deposited when the sea briefly covered the delta from the southeast. It laid down a basal bed of mudstone with marine fossils, which is replaced higher up (in places) by a thin or nodular ironstone, and lastly a sandstone. The presence of Ooids within some of the iron nodules indicate a shallow tropical environment.

Cloughton Formation

Renewed uplift of the crust once again banished the sea and the area returned to a deltaic regime. The Cloughton Formation is much more variable than the Saltwick, though it retains a very similar set of fossils. The imprints of delicate ferns and horsetails can be found amongst the beds of sandstone, siltstone, and mudstone. It also bears the imprints of reptilian feet at various levels.

Scarborough Formation

A second incursion of the sea deposited sandy limestone packed with marine fossils. This is generally a blue-grey rock containing the fossils of belemnites, shellfish, scattered wood fragments, and sea-lily stems. The formation attains a thickness of around 5 metres locally, though is seldom well exposed at the surface.

Scalby Formation

A return to deltaic conditions is marked by the Scalby Formation. The lower 10 metres consists of high-grade sandstone known as the Moor Grit with a quartz content as high as ninety-eight percent. It contains few fossils except for the occasional wood fragment. Above it lays the Long Nab Member marking a return to the delta-marsh conditions of the Saltwick and Cloughton Formations. Further south are extensive plant beds, but in the Tees Valley, it comprises flaggy sandstones with intermittent mudstones deposited during periods of flood.

Cornbrash and Osgodby Formations

The deltaic regime ended with deposition of the Osgodby Formation at the top of the Middle Jurassic. Marine deposits above it are assigned to the Upper Jurassic and are non-existent in the Tees Valley. Only on the southern parts of the North York Moors (Tabular Hills) can these rocks be found. Here, the Upper Jurassic Formations, all marine, are in ascending order: Oxford Clay, Lower Calcareous Grit, Coralline Oolite, Upper Calcareous Grit and Kimmeridge Clay.

« Lower Jurassic                               Tertiary »

©2011 Tees Valley RIGS Group.

Marker on the Cleveland Way east of Saltburn. Huntcliff can be seen in the background.

Stretching along the coast between Redcar and Filey can be found a sequence of rocks that have been highly acclaimed by generations of geologists:

“In no part of England is the relation of the surface topography to the nature of the underlying rocks more instructively displayed than in this district; nor can the succession of a considerable part of the Jurassic series of formation be anywhere more advantageously examined than along the coast-sections…”
[Archibald Geikie, Director of the Geological Survey. (1888)]

Jurassic deposits locally total around 560 metres of strata which were deposited between c.199 million and 161 million years ago in environments which varied between deep sea, populated by a variety of distinctive marine creatures, to well-vegetated river delta upon which reptiles once roamed.

An example of the locally abundant ammonite Dactylioceras commune which has been split and polished to show crystals of calcite filling the internal chambers.

Geologists long-ago realised that similar rocks in diverse areas could be correlated by examining their fossil content. One of the earliest to realise this was Lewis Hunton (1814-1838), son of a Loftus alum-worker who studied remains of long extinct sea creatures in Jurassic rocks at Hummersea and Boulby. As far as correlation of different rock units is concerned, the most useful fossils turned out to be the coiled shells of many species of ammonite. Ammonites are now-extinct creatures related to modern day squid and octopuses (Cephalopods). Modern geologists can identify over sixty ammonite zones in the Lower Jurassic alone, which finely subdivide the various strata and make relationships between them much easier to understand.

Table showing the various sub-divisions of the Jurassic along with ammonite zones able to be seen within the Tees Valley and North Yorkshire.
Adapted from The Yorkshire Coast by P.F. Rawson & J.K. Wright (1992).

Lower Jurassic »

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©2011 Tees Valley RIGS Group.

1. Site Description
2. Site Map
3. Site Assessment
4. Surveyors

Grid Reference NZ 690 127
BGS Sheet 34
OS Sheet 94
Forwarded as RIGS 30/09/2003

View of Freebrough Hill from the lay-by on the A171.

Site Description

Site Status


Description of Geodiversity: An outlier of nearby Moorsholm Rigg to the south with its summit reaching to 250m above sea level and 50m above the surrounding moorland. Freebrough Hill is a natural landform sculpted by glacial ice between c.120,000 and 20,000 years ago during the last (Devensian) glaciation. The outlier comprises Middle Jurassic (Bathonian) Scalby Formation deltaic deposits at its base, around c. 5m of the (Callovian) Cornbrash intervenes, and is succeeded by up to 7m of Osgodby Formation sandstones which cap the hill. The country rock is obscured by glacial deposits in the form of both till (boulder clay) and sand. The locality also has a wealth of well-marked glacial meltwater chanels running W-E across and around Moorsholm Rigg which together constitute evidence of glacial retreat at a point close to Devensian ice’s maximum extent.

PLEASE NOTE: There is NO access to this site without landowner permission.

This said, the hill can be viewed from several points in the locality including the lay-by at NZ 68355 13182 (see image above). The moorland around Moorsholm Rigg south of the hill is open access and good views can be had from here.


Literature References


Wishart, D. Date Unknown; An Interpretation of the Geomorphology of Freebrough Hill. University of Durham.


Barrow, G. 1888; The Geology of North Cleveland: Memoirs of the Geological Survey. HMSO, London. 101p


Ord, J.W. 1846; The History & Antiquities of Cleveland: Comprising The Wapentake Of East And West Langbargh, North Riding, County York. Publisher Unknown.


Smith Fletcher, J. 1901; Picturesque history of Yorkshire: Being an account of the history, topography, antiquities, industries, and modern life of the cities, towns, and villages of the county of York, founded on personal observations made during many journeys through the three ridings, Volume 3. Caxton.


Murray, J. 1882; Handbook for travellers in Yorkshire. J. Murray.


Atkinson, Rev. J.C. Date Unknown; The Last of the Giant Killers: Or, the Exploits of Sir Jack of Danby Dale. Publisher Unknown.


Knox, R. 2009; Descriptions, geological, topographical, and antiquarian in Eastern Yorkshire, Between the Rivers Humber and Tees. Publisher Unknown.

Site Map

Site Assessment

Surveyors

2003: Andrew Carter, John Waring, Andy Cooper.

2010: Andy Cooper, Alan Simkins, Beth Andrews.