Glossary (F – K)

This page provides a glossary of geological terms to be found on the TVRIGS website and elsewhere. It is an evolving document and will grow as the site expands.


F

Fault
A fault is a dislocation of strata with an observable movement between opposite sides of the fracture. See also Joint.

Formation
A lithostratigraphic unit made up of one or more Members.


G

Ganister
Quartz-rich compact sandstone often underlying coal seams and used for making refractories.

Goaf
Mined area within which the pillars have been extracted and the roof allowed to collapse. Goafing is used to describe the second phase of working a seam of ironstone locally.

Group
A major lithostratigraphic unit. A grouping of Formations.


I

Igneous
One of the three main groups of rocks. Igneous rocks are crystalline and solidify from magma. They may be extruded at the Earth’s surface through volcanoes and fissures as lava, or intruded within existing beds beneath the surface to form dykes, sills and other features.

The Tees Valley’s single example of rock from the Tertiary Period is the igneous Cleveland Dyke emplaced about 58 million years before present..

Ironstone
General term for iron-bearing rocks containing more than around 15%wt iron. In Cleveland and North Yorkshire, several beds of ironstone have been exploited including the Main, Pecten, Two-foot, and Avicula Seams of the Cleveland Ironstone Formation, Top Seam (Dogger Formation) and within the Eller Beck Formation (Julian Band).


J

Joint
A fracture in rock which shows no observable movement on either side. See also Fault.

Jurassic
Named (by von Alberti, 1834) after the Jura Mountains of France. It covers an episode in Earth’s history between c.199million and 145 million years before present. The Jurassic is further subdivided into Lower, Middle and Upper episodes. These strata crop out extensively to the south of the River Tees.


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