The Ives Head Formation is a geologic formation in Leicestershire, England. It forms part of the Blackbrook Group within the Charnwood Forest succession. The unit preserves rocks of Lower Ediacaran age and is named after the locality of Ives Head.
Geology The Ives Head Formation is the lowest formation within the Blackbrook Group, being overlain by the tuffaceous Blackbrook Reservoir Formation. The dominate rocks in this formation are also tuffaceous in nature. A borehole sample taken some below the formation itself, known as the "Morley Lane Borehole", showed that the formation is underlain by of greenish-gray tuffs, pelites and sandstone, which are inter-bedded in layers of porphyritic dacite lava-rock. This underlying rock would later be named the "Morley Lane Volcanic Formation".
Members There can be found three members in this formation, which are as follows, in ascending stratigraphic order (lowest to highest):
Morley Lane Tuffs Member: Coming in at , this member is primarily composed of coarse-grained tuffs, with moderate amounts of finely laminated dust-tuffs and tuffaceous pelites.
Lubcloud Greywackes Member: Coming in at , this member is dominated by medium to very fine-grained greywackes, with some layers of greywackes being tuffaceous in nature. There can also be found throughout the member moderate amounts of coarse-grained greywackes and finely laminated tuffaceous pelites.
South Quarry Slump Breccia Member: Only coming in at , this member is predominately composed of slump volcanic breccia, as well as coarse-grained tuffs and finely laminated dust-tuffs.
Dating The Ives Head Formation has been dated using U–pd dating on several zircon samples collected from the base, middle, and top of the formation. Samples collected from the top and middle of the formation yielded a date range of to , giving a maximum deposition age of . Samples from the base of the formation would yield a date range of to , with a minimum deposition age of used.
Paleobiota The Ives Head Formation contains the oldest known fossils within the Charnian Supergroup, occurring on the Lubcloud surface. Preliminary zircon ages suggest that these fossils may be older than the Gaskiers glaciation if the proposed dating is confirmed, with the base of the formation lying just below . This would place them among the oldest currently recognised Ediacaran assemblages; however, comparisons with units such as the Rocky Harbour Formation in Newfoundland and Labrador and the Lantian Formation in China remain tentative, as the dating of the Charnian succession requires further refinement.
Ivesheadiomorph
GenusSpeciesLocalityNotesImagesBlackbrookiaB. oaksiLubcloud Greywackes MemberPoorly preserved organism, possibly of a petalonamid.IvesheadiaI. lobataLubcloud Greywackes MemberPoorly preserved organism.ShepshediaS. palmataLubcloud Greywackes MemberPoorly preserved organism.
See also
List of fossiliferous stratigraphic units in the United Kingdom
References