The Charnian Supergroup is a geologic supergroup in the

United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Northwestern Europe, off the coast of European mainland, the continental mainland. It comprises England, Scotlan ...

, and is a part of the wider Charnwood terrane. It preserves

fossils A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

dating back to the

Ediacaran The Ediacaran ( ) is a geological period of the Neoproterozoic geologic era, Era that spans 96 million years from the end of the Cryogenian Period at 635 Million years ago, Mya to the beginning of the Cambrian Period at 538.8 Mya. It is the last ...

and through into the

Cambrian The Cambrian ( ) is the first geological period of the Paleozoic Era, and the Phanerozoic Eon. The Cambrian lasted 51.95 million years from the end of the preceding Ediacaran period 538.8 Ma (million years ago) to the beginning of the Ordov ...

period Period may refer to: Common uses * Period (punctuation) * Era, a length or span of time *Menstruation, commonly referred to as a "period" Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (o ...

, with suggestions that the Brand Group and Maplewell Groups have a major hiatus in-between. It mainly contains

volcaniclastic Volcaniclastics are geologic materials composed of broken fragments (clasts) of volcanic rock. These encompass all clastic volcanic materials, regardless of what process fragmented the rock, how it was subsequently transported, what environment it ...

s, but is interrupted by and succeeded by

greywacke Greywacke or graywacke ( ) is a variety of sandstone generally characterized by its hardness (6–7 on Mohs scale), dark color, and Sorting (sediment), poorly sorted angular grains of quartz, feldspar, and small rock fragments or sand-size Lith ...

s, and is interbedded with

pelite A pelite () or metapelite is a metamorphism, metamorphosed fine-grained sedimentary rock, i.e. mudstone or siltstone. The term was earlier used by geologists to describe a clay-rich, fine-grained clastic sediment or sedimentary rock, i.e. mud or ...

tuff Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock co ...

s. Due to the thickness of the Supergroup, it spans over , with a possible lower date of and a maximum upper date of . This also means that it spans across two Ediacaran assemblages, with the Blackbrook Group and part of the lower

Maplewell Group The Maplewell Group is an Ediacaran lithostratigraphic group (a sequence of rock strata) present in Leicestershire in the English Midlands. The strata are exposed in Charnwood Forest, west of Leicester. Besides a variety of volcaniclastic sandsto ...

sitting within the

Avalon assemblage The Avalon assemblage was the first of the three Late Ediacaran biotic assemblages, spanning from 575 Ma to 560 Ma. It was followed by the White Sea assemblage, although temporal overlaps have been noted between the biotic assemblages. While ...

, whilst the rest of the Maplewell Group sits within the

White Sea assemblage The White Sea assemblage was the second of the three Late Ediacaran biotic assemblages, following the Avalon assemblage and preceding the Nama assemblage. It spanned from 560 Ma to 550 Ma. Showing an increase in genus diversity from the Aval ...

. The

Brand Group The Brand Group is a geologic group in Leicestershire. It preserves Ichnotaxon dating back to the Cambrian period. It mainly contains pelites, with greywacke and breccia. Formation units It is made up of two formations. Uppermost within the ...

was originally a part of the supergroup, until the discovery of several ichnogenera, like '' Teichichnus'', which helped to date it to the Lower Cambrian, and was subsequently taken out of the Charnian Supergroup.

Maplewell Group

The

is Ediacaran in age, and consists of three formations, and is the thickest group, coming in at 1768 m (5,800 ft). Topmost of the group, is the Hanging Rocks Formation, which consists of interbedded

s and lithic

. The middle Bradgate Formation is made up of tuffeceous

, dust tuffs and pelite, with thin horizons of medium-grained greywackes, and nearer to its base there is slump

breccia Breccia ( , ; ) is a rock composed of large angular broken fragments of minerals or Rock (geology), rocks cementation (geology), cemented together by a fine-grained matrix (geology), matrix. The word has its origins in the Italian language ...

s composed of

clast Clastic rocks are composed of fragments, or clasts, of pre-existing minerals and rock. A clast is a fragment of geological detritus,Essentials of Geology, 3rd Ed, Stephen Marshak, p. G-3 chunks, and smaller grains of rock broken off other rocks b ...

s. The Beacon Hill Formation is the basal unit of the Maplewell Groupk, and consists of tuffeceous pelite, with coarse-grained tuffs and greywackes, as well as slump and pull-apart breccias. The Hanging Rocks Formation was once a part of the Brand Hills Formation as a Member, but was then split out to be its own formation within this group, although it is occasionally referred to the Brand Group. In

stratigraphical Stratigraphy is a branch of geology concerned with the study of rock layers (strata) and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks. Stratigraphy has three related subfields: lithostrati ...

order, i.e. uppermost/youngest first: *Hanging Rocks Formation *Bradgate Formation **Hallgate Member **Sliding Stone Slump Breccia Member *Beacon Hill Formation **Old John Member **Outwoods Member **Buck Hills Member **Sandhills Lodge Member **Beacon Tuffs Member **Charnwood Lodge Member **Benscliffe Member

Blackbrook Group

The Blackbrook Group is Ediacaran in age, and consists of two formations, and is the basal-most unit of the Charnian Supergroup, with its thickest point sitting at 1,430 m (4,691 ft), possibly more. The upper layers of the group are a part of the Blackbrook Reservoir Formation, and is made up of tuffeceous pelite, tuffs and coarse-grained tuffs. The lower layers of the group are a part of the Ives Head Formation, which is also the basal-most formation in the entire supergroup, and consists of slump breccia, coarse-grained tuffs and dust tuffs, with fine-grained and tuffeceous greywackes in the middle part of the formation, and nearer to its base are

sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...

s and

dacite Dacite () is a volcanic rock formed by rapid solidification of lava that is high in silica and low in alkali metal oxides. It has a fine-grained (aphanitic) to porphyritic texture and is intermediate in composition between andesite and rhyolite. ...

lavas. In

order, i.e. uppermost/youngest first: *Blackbrook Formation *Ives Head Formation **South Quarry Slump Breccia Member **Lubcloud Greywackes Member **Morley Lane Tuffs Member

Dating

Within the strata is clasts of

diorite Diorite ( ) is an intrusive rock, intrusive igneous rock formed by the slow cooling underground of magma (molten rock) that has a moderate content of silica and a relatively low content of alkali metals. It is Intermediate composition, inter ...

s horizons that allow for zircon U-Pb dating and, noted within the South Charnwood Diorites found in the hiatus between the Brand and Maplewell Groups, a date is returned of , suggesting the intrusion is Lower Ediacaran in age, which led to the research and discovery that the Brand Group was Cambrian in age, and is no longer assigned to the Charnian Supergroup. Zircon has also been found within tuff in the Beacon Hill Formation, and another tuff at

Brandon Hill Brandon Hill () is the highest mountain in County Kilkenny, Ireland, with an elevation of and prominence at . The South Leinster Way, a long-distance trail, meandering through the Barrow Valley and traverses Brandon Hill. The village of Gra ...

(Also within the Beacon Hill Formation. The dates recovered for both of these samples were and respectively, meaning the Beacon Hill Formation temporally correlates with the Trepassey Formation in

Newfoundland and Labrador Newfoundland and Labrador is the easternmost province of Canada, in the country's Atlantic region. The province comprises the island of Newfoundland and the continental region of Labrador, having a total size of . As of 2025 the populatio ...

. Alongside this, a more recent study within the supergroup found more zircon samples, from the oldest and youngest known parts of the Maplewell Group and the lower parts of the Blackbrook Group, with the dates recovered from the Maplewell Group samples being and , showing that the uppermost part of the Charnian Supergroup overlaps the Trepassey Formation, and the preliminary dates recovered from the Blackbrook Group at around , although it has been noted that a more refined dating is required to confirm this.

References

* {{cite web, title= Fossilworks: Gateway to the Paleobiology Database, author= ((Various Contributors to the Paleobiology Database)), url= https://www.fossilworks.org, access-date= 8 July 2014 Ediacaran Europe Cambrian Europe Geology of Leicestershire Geologic supergroups of the United Kingdom

Maplewell Group

Blackbrook Group

Dating

See also

References