A reassessment of Arundian¿Holkerian (Viséan) carbonates in South Cumbria, UK
Despite the importance of south Cumbrian sections for the Arundian¿Holkerian (mid Viséan) boundary, beyond the stratotype proposed at Barker Scar in 1976, little else is known regionally about this boundary and its relationship to adjacent formations. We re-evaluate the Dalton Formation, making its...
| Published in: | Proceedings of the Geologists' Association |
|---|---|
| Main Authors: | , , , , |
| Other Authors: | , |
| Format: | Article in Journal/Newspaper |
| Language: | unknown |
| Published: |
Geologists' Association
2022
|
| Subjects: | |
| Online Access: | http://hdl.handle.net/10261/305334 https://doi.org/10.1016/j.pgeola.2022.04.005 |
| Summary: | Despite the importance of south Cumbrian sections for the Arundian¿Holkerian (mid Viséan) boundary, beyond the stratotype proposed at Barker Scar in 1976, little else is known regionally about this boundary and its relationship to adjacent formations. We re-evaluate the Dalton Formation, making its upper and lower boundaries regionally more consistent and precisely-defined, in good quality outcrops with associated biostratigraphy. The Dalton Formation is formally divided into the Blackstone Member and overlying Raven's Member. Rich foraminiferal assemblages of the Cf4¿ subzone are recognized in the BlackstoneMember and the lower to mid Raven's Member in nine sections. The Cf4¿¿Cf4¿ boundary is recognized in the underlying Red Hill Limestone Formation in 3 sections. The upper part of the Raven'sMember shows the first appearance of taxa assigned to the Cf5¿ and Cf5ß subzones of the Holkerian in three of the sections. Bentonitic shales in the mid and upper-most part of the Raven's Member were evaluated for zircon and apatite geochronology, although only 4 out of 504 analyses yielded Carboniferous ages, indicating an almost entirely detrital source. This detritus was northerly or northeasterly-derived and predominantly from the Southern Uplands Terrane with subsidiary input from the Lewisian Complex or eastern Greenland sources. Petrographic analysis identified 13 microfacies indicating that the Dalton Formation represents the inner to outer part of a southward inclined shelf, in which east¿west changes inmicrofacies were generated by synsedimentary faulting inherited from northwest¿southeast aligned basement structures. Wearegrateful to the comments by E. Kulagina and an anonymous reviewer. MWHwasinpartfundedbyNERC(grant NE/P00170X/1).PC is grateful to the financial support by the project CGL2016-78738 of the Spanish Ministry ofScienceandInnovation.DC issupportedinpartbya research grant from Science Foundation Ireland (SFI) under Grant Number 13/RC/2092_P2 (iCRAG, the SFI Research Centre in Applied ... |
|---|