Forensic Geology
(tutor - Mike Horne)
Jargon Buster
Every science use “scientific terminology” to convey information in a concise way to fellow scientists. This jargon is also a good way of excluding the public form our world!
Here is a glossary of some of the jargon words used in the Forensic Geology course in laymen’s terms :-
age - a defined relative period of geological time smaller than a Period - click here for stratigraphy
Boulder Clay - a mixed, poorly consolidated sediment deposited by a glacier, containing clasts from clay to boulder size [see grain size] . Also know as Till. Sometimes described as diamict (though not all diamicts are glacial in origin).
clast - a piece of sediment - may be a mineral grain or piece of rock.
clastic - sediment or rock that is made up of clasts.
clay - A family of silicate minerals, similar to the mica family, characterised by very small, plate-like crystals.
clay - any sediment grains that have a diameter of 4 micrometres (microns) or less
clay - (loosely) a very fine grained clastic sediment rich in clay minerals, that absorbs water; an unconsolidated mudrock.
Clay - a fine grained soft sedimentary rock unit (as in Speeton Clay).
derived - 'recycled' - sediment, rocks, minerals or fossils are older than the deposit that they are now in; but they need not have travelled very far, as with an Erratic.
erratic - a rock, mineral or fossil that has come from somewhere else. Glacial Erratics have been transported by a glacier.
grain size - the size of clasts or crystals in a rock or sediment - there is a standard scale used by sedimentologists (click here).
fossil - solid remains of a plant or animal.
maturity - used to describe the overall characteristics of a clastic sediment - mature sediments are well-sorted, the garins are well-rounded and less-stable minerals are missing; immature sediments are porrly-sorted, contain many angular clasts and minerals that are prone to weathering.
microfossil - very small fossil that you look at down a microscope, about 50um to 2mm. (Click here for microfossils web pages)
nanofossil - very, very small fossil that you look at down a powerful microscope or SEM.
Quartz - pretty hard variety of silica that is resistant to weathering.
Recent - to a geologist this means the last few hundreds of thousands of years.
sand - clasts between 63um and 2mm in size.
sand - term loosely used for an unconsolidated deposit found on a beach, desert, sand dune; often made of grains of quartz but may be broken shells (as in "shell sand") or other materials.
sand - even more loosely used to mean an unconsolidated sandstone
Sand - part of a formal name for stratigraphic unit (e.g. Kellaways Sands).
sandstone - a consolidated sedimentary rock made from sand grains.
sediment - unconsolidated deposit of clasts, not yet turned into a solid rock.
sedimentary rock - sediment that has been cemented together to form a solid rock, or just very old sediment (click here for Rock Cycle).
sorting - have the clasts in a sediment or sedimentary rock been sorted by size or density? Or are they poorly sorted - a mixture of different sizes?
If there are other words in these notes that you don't understand please e-mail me with a request and I will add them.