GCR block - Aalenian - Bajocian (AAL-BAJ)

Aalenian - Bajocian

Block Description

UK map showing distribution of GCR sites of GCR block AAL-BAJ
Distribution of GCR sites of GCR block Aalenian - Bajocian

The GCR sites selected for this GCR Block represent the British geological record of Earth history from about 178 to 166 million years ago (Ma). This interval is the first part of the Mid Jurassic Epoch, which spans from 178 to 157 Ma. Rocks that formed during the Mid Jurassic Epoch (part of the Jurassic Period) constitute the Middle Jurassic Series (part of the Jurassic System).

The Aalenian (178–174 Ma) and Bajocian (174–166 Ma) strata are included in one GCR Block together because they are commonly closely associated in general lithology – over much of southern England they approximately equate with the old stratal term, ‘Inferior Oolite’.

Outcrop pattern

On maps showing the solid geology of England, Middle Jurassic rocks crop out in an almost continuous strip from the Dorset coast to the North Yorkshire coast. In Scotland, Middle Jurassic rocks crop out in scattered patches in the islands to the north-west as well as in northern Scotland.

Palaeoenvironment and palaeogeography

During Early Jurassic times Britain was largely covered by shelf sea, however towards the end of the Epoch there was a significant fall in sea level accompanied by crustal upwarping and vulcanicity in the central North Sea Basin. Consequently, Middle Jurassic rocks reflect a variety of depositional environments including shallow marine, fluvial, deltaic, saltmarsh and coastal lagoon. In addition, limestone and clastic sedimentation (mudstone, siltstone and sandstone) was often widespread.

Palaeontology, fauna and flora

The traditional means of subdividing the Jurassic System is by means of ammonites, abundant and diverse nektonic cephalopod molluscs that, because of their rapid evolution, prove to be almost ideal ‘zone fossils’, enabling the correlation and division of the rocks into relative ages by way of a distinct fossil ‘signature’.

The many different depositional environments that developed in Britain during Mid Jurassic times mean that the fossil record is rich and varied. Invertebrate faunas included simple and compound corals, calcareous sponges and bryozoa, abundant bivalve molluscs, such as oysters, smooth terebratulid and ribbed rhynchonellid brachiopods, gastropods (snails), asteroids (starfish), echinoids (sea urchins) and crinoids (sea lilies). The brachiopods occurred in an abundance that was never repeated on such a scale in later geological times. Microscopic organisms included foraminifera, ostracods and phytoplankton (dinoflagellates and coccolithophorid algae).

Lobster- and shrimp-like crustaceans often produced burrows within sediments, preserved as trace fossils.

Belemnites, relatives of the ammonites, were abundant and along with fish were probably the main food of the aquatic reptiles, which were the largest vertebrate animals in the sea. These included ichthyosaurs, plesiosaurs, pliosaurs, crocodiles and turtles. The fish included both holostean and teleostean bony fishes, and sharks and rays.

On land, dinosaurs had already become established in Mid Jurassic times; primitive mammals formed a minor but important part of the fauna. Land plants of particular prominence were the gymnosperms, notably conifers, cycads, ginkgoes, ferns and horsetails. Insect life included dragonflies.

In contrast to the manner in which most invertebrate fossils are represented in the GCR, fossils of vertebrates, arthropods (except trilobites) and terrestrial plants do have their own dedicated selection categories, owing to the relative rarity of the fossil material. See APD; JUR-CRE-RP; MES-MAM; MES-PALBOT; MZ-TR-FI-A; PALENT.

GCR site selection

For the purposes of site evaluation and selection, the GCR sites can be grouped into five themes or ‘networks’, reflecting depositional setting, which was largely controlled by deep-seated structural features. The networks are:

• Wessex Basin

• Cleveland Basin (North Yorkshire sites)

• East Midlands shelf

• Worcester Basin and Shelf (Cotswolds sites)

• Moray Firth and Hebrides basins.

Although the relatively common invertebrate fossils do not have a separate selection category in the GCR in their own right, the scientific importance of many stratigraphy sites lies in their fossil content. Therefore, some of the GCR sites are selected specifically for their fossil fauna, which facilitates stratal correlation and enables the interpretation of the environments in which the animals lived. Moreover, some sites have international significance because they have yielded fossils that are the ‘type’ material for a taxonomic group.

Volume Introduction

Aalenian - Bajocian

Site List

Your selection found 50 GCR sites. Sites are sorted alphabetically by country, local authority and then by site name -
CodeNameCountryLocal AuthorityGrid RefGCR Site Account
53Bradford Abbas Railway CuttingEnglandDorset CCST592145Not available
51Burton Cliff and Cliff Hill Road SectionEnglandDorset CCSY492887Not available
164Conegar HillEnglandDorset CCST439028Not available
55Frogden QuarryEnglandDorset CCST649183Not available
56Halfway House Cutting and QuarryEnglandDorset CCST601164Not available
54Holway Hill QuarryEnglandDorset CCST638211Not available
57Horn Park QuarryEnglandDorset CCST457021Not available
2826Louse Hill QuarryEnglandDorset CCST610161Not available
2729Peashill QuarryEnglandDorset CCSY495916Not available
52Sandford Lane QuarryEnglandDorset CCST628178Not available
255Eastfield QuarryEnglandEast Riding of YorkshireSE916323Not available
138Crickley HillEnglandGloucestershireSO924161Not available
139First cutting west of NotgroveEnglandGloucestershireSP083208Not available
140Fort QuarryEnglandGloucestershireSO850040Not available
141Frith QuarryEnglandGloucestershireSO867082Not available
165Haresfield HillEnglandGloucestershireSO819088Not available
166Harford CuttingEnglandGloucestershireSP135218Not available
167Jackdaw QuarryEnglandGloucestershireSP077309Not available
142Knap House QuarryEnglandGloucestershireSO925147Not available
168Leckhampton HillEnglandGloucestershireSO946183Not available
169Leigh's QuarryEnglandGloucestershireSO826026Not available
170Nibley KnollEnglandGloucestershireST744956Not available
171Rolling Bank QuarryEnglandGloucestershireSO987115Not available
143Swift's HillEnglandGloucestershireSO877067Not available
248Clipsham QuarryEnglandLeicestershire CC and RutlandSK977150Not available
254Ketton QuarryEnglandLeicestershire CC and RutlandSK978058Not available
299Sproxton QuarryEnglandLeicestershire CC and RutlandSK864253Not available
246Castle BythamEnglandLincolnshireSK990180Not available
245Copper HillEnglandLincolnshireSK978427Not available
244Greetwell QuarryEnglandLincolnshireTF002724Not available
247MetheringhamEnglandLincolnshireTF054615Not available
301Cliff Farm PitEnglandNorth and North East LincolnshireSE942009Not available
256Manton Stone QuarryEnglandNorth and North East LincolnshireSE940025Not available
88Barns Batch SpinneyEnglandNorth and North East Somerset, South GloucestershireST557659Not available
163Hawkesbury QuarryEnglandNorth and North East Somerset, South GloucestershireST771873Not available
89South Main Road QuarryEnglandNorth and North East Somerset, South GloucestershireST566654Not available
264Blea WykeEnglandNorth Yorkshire CCNZ990013Not available
265Gristhorpe BayEnglandNorth Yorkshire CCTA079841Not available
267Hawsker BottomsEnglandNorth Yorkshire CCNZ937080Not available
266Iron Scar - HundaleEnglandNorth Yorkshire CCTA017964Not available
300Whitwell QuarryEnglandNorth Yorkshire CCSE734679Not available
269CollywestonEnglandNorthamptonshireTF000030Not available
146Doulting Railway CuttingEnglandSomersetST645424Not available
147Godminster Lane Quarry and Railway CuttingEnglandSomersetST681345Not available
148Milborne Wick SectionEnglandSomersetST662205Not available
149Seavington St Mary QuarryEnglandSomersetST400144Not available
150Vallis ValeEnglandSomersetST760495Not available
144Cross Hands QuarryEnglandWarwickshireSP269290Not available
268Bearreraig Bay, Isle of SkyeScotlandLochaber, Skye and Lochalsh and Argyll and the IslandsNG520545Not available
305Beinn na Leac, Isle of RaasayScotlandLochaber, Skye and Lochalsh and Argyll and the IslandsNG592389Not available
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