Field Visit to Scunthorpe and Crosby Warren Quarry - Saturday 25th March 2006

For the first trip of the 2006 season, our Field Trip Secretary Jane expressed the hope we would experience ‘Sunny Scunny’ but also reminded us that the wind, rain and snow on the east coast can be more severe than us softies living west of the Pennines are used to. Happily her wish came true and it was warm, dry and just a little sunny for the twelve of us who assembled outside the museum at Scunthorpe. We were met by Steve Thomas, Keeper of Earth Sciences who spoke to us about the geology of the area and how it has influenced the history and economy of the area.

Scunthorpe is situated in the middle of the Lower Jurassic which strikes north/south through Lincolnshire with Triassic to the west running through to Upper Cretaceous to the east at Grimsby. The strata are generally undeformed and flat lying and are predominantly limestones and mudstones deposited in a shallow sea with a land mass to the south east. The local stratigraphy is summarised below and is interpreted as representing deposition with varying amounts of clastic inputs from that landmass.

The iron is present as the carbonate Siderite and the clay mineral Chamosite in ooids and matrix material, not as nodules. Ironstones are not being deposited anywhere today and although it is generally accepted that a reducing environment is required to produce them, the mechanism of formation remains enigmatic. Total iron content is between 20-30% which might sound a lot but is at the lower end of what would be economically viable.

Lower Jurassic under Scunthorpe





U. Lias



absent in N. Lincs


Shales & mudstones

M. Lias



Marlstone above an unconformity


Shales and mudstones

L. Lias


Pecten Ironstone


Marine silty mudstones




Frodingham Ironstone c. 60’ thick


Shales & mudstones





Limestones within mudstones

Although there is evidence of Roman and Saxon iron workings abstraction had died out until the 1850s when an entrepreneurial local landowner and a geologically literate pastor became aware of the economic potential. Commercial abstraction began in 1864 and continued until 1987 and alongside this mining grew up one of the largest steel manufacturing sites in the country. The modern day Corus plant, on the site of what was up to seven independent foundries, is a world leader in steel manufacturing with the longest steel rolling mill in the world working imported material.

The Four Queens of Scunthorpe in 1954

Employing 5,000 people today, at its peak the industry employed 23,000 in a town with a population of just 80,000. We saw dramatic photographs of men working in the most precarious of positions tens of feet above the ground pushing wheel barrows of overburden on wooden boards only 14” wide. Equally dramatic were the mechanical devises subsequently developed to remove overburden to reveal the ironstones which, as the mining developed, became deeper and deeper. By the time mining ceased up to 200’ of overburden was being stripped off. The enormous holes left behind are now used a depository for the domestic refuse of Manchester.

After the talk we were allowed to handle specimens from the museum store some dating form the nineteenth century collectors who discovered the ironstone and unravelled the local geology. The public displays are also well worth a look at.

After lunch we assembled on the Frodingham Ironstone at the Crosby Warren quarry on the steel works site where belemnites, ammonite fragments (e.g. Asteroceras) and the bivalve Pecten, which gives its name to one of the ironstones, were almost jumping out of the rocks. The shelly deposits were in discrete band as opposed to evenly deposited through the formation and some bedding planes resembled the walls of shell covered grottos.

The final stop was at a rock store the museum have established with some 25,000 tonnes of the most fossiliferous parts of the Frodingham Ironstone rescued when the mining ceased and dumped on waste ground. They hope to develop it as an outdoor education centre and allow groups such as ours to fossil hunt under supervision which we did with almost indecent enthusiasm for the rest of the afternoon.

Notes by Niall Clarke