Bradgate Formation


The Bradgate Formation is a geologic formation in Leicestershire, and lies within the wider Bradgate Park area. It also preserves fossils dating back to the late Ediacaran period.

Geology

The formation is composed of various volcaniclastic rocks, like tuff, and is broken up into two members. It is overlain by the Hanging Rocks Formation, whilst it is underlain by the Beacon Hill Formation.

Members

The Bradgate Formation is formally split up into two members, which are as follows, in ascending age:
  • Sliding Stone Slump Breccia Member: This member, also sometimes referred to as "Park Breccia Member", is the thinnest of the two, only getting up to thick. The lower of this member is primarily composed of slump breccias as the name suggests, which contain clasts that are composed of dust tuff, alongside tuffaceous pelites, set into a matrix of coarse-grained tuffs and medium-grained graywackes. Meanwhile the upper of this member sees the breccias fade away, only being composed of coarse-grained tuffs that are andesitic in nature, and slowly turn into medium-grained tuffaceous graywackes.
  • Hallgate Member: This member is the thickest of the two, getting up to thick. It is predominated by tuffaceous pelites, as well as pelites and dust tuffs. Through-out, there are also thin layers coarse-grained tuffs and medium-grained graywackes.

    Dating

At the base of the Bradgate Formation, zircon samples were collected to take U-Pb dating on them and determine the overall age of the formation and fossils. The zircon sample JNC 912, from the base of the formation, returned a date of. Meanwhile a zircon sample, JNC 846, collected from near the base of the overlying Hanging Rocks Formation returned an age of, which would constrain the Bradgate Formation entirely within the Avalon assemblage, and correlating it roughly with the Trepassey Formation.

Paleobiota

The Bradgate Formation contains the richest fossil beds within the Charnian Supergroup, from frondose organisms like Bradgatia and Charnia, which when the latter was discovered, showed definitive proof that macroscopic life did indeed exist before the Cambrian, to discoid forms like Aspidella.

Petalonamae

GenusSpeciesNotesImages
Bradgatia
  • B. linfordensis
Sessile frondose organism.
Charnia
  • C. masoni
    		• Sessile frondose organism, and first organism found within this formation.
    Charniodiscus
  • C. concentricus
    		• Sessile frondose organism.
    Hylaecullulus
  • H. fordi
    		• Sessile frondose organism.
    Primocandelabrum
  • P. aelfwynnia
  • P. aethelflaedia
  • P. boyntoni
    		• Sessile frondose organism.
    Vinlandia
  • V. antecedens
    		• Sessile frondose organism.

    Cnidaria

    GenusSpeciesNotesImages
    Auroralumina
    • A. attenboroughii
    		Early sessile crown-group medusozoan cnidarian.

    ''incertae sedis''

    GenusSpeciesNotesImages
    Aspidella
    • Aspidella sp.
    		Enigmatic discoidal fossil.
    Thectardis
  • T. avalonensis
    		• Discoid organism, possibly holdfasts of petalonamids.

    Undescribed forms

    GenusSpeciesNotesImages
    Gladius form
    • ???
    		Enigmatic fossil, described to be in the shape of a gladius sword.
    Hemispherical form
  • ???
    		• Enigmatic fossil, described to be hemispherical in shape, with bifurcating radial ribs.
    Lanceolate frond
  • ???
    		• Enigmatic frondose fossil, described to be in the shape of a lance head, which has collapsed in onto itself.