Cramer B.D.,University of Kansas |
Cramer B.D.,University of Iowa |
Condon D.J.,British Geological Survey |
Soderlund U.,Lund University |
And 10 more authors.
Bulletin of the Geological Society of America | Year: 2012
High-precision isotope-dilution U-Pb (zircon) dating was conducted on three volcanic ash fall (bentonite) samples from the Swedish island of Gotland, and on a fourth ben tonite from the West Midlands, England. Zircons from the Ireviken, Grötlingbo, Djupvik (Gotland), and Wren's Nest Hill-15 (West Midlands) bentonites yielded weighted mean 206Pb/238U ages of 431.83 ± 0.23/0.67 Ma, 428.45 ± 0.35/0.73 Ma, 428.06 ± 0.21/0.66 Ma, and 427.86 ± 0.32/0.71 Ma, respectively (analytical/ total uncertainties). These biostratigraphically well-controlled age dates effectively bracket the Wenlock Epoch of the Silurian Period and provide control for the duration of one of the major Paleozoic biotic events and associated perturbations to the global carbon cycle (the "Big Crisis" or lundgreni event-graptolites; the Mulde Event-conodonts; the Mulde excursion-carbon isotopes). These new data suggest an older and shorter duration for the recalibration of the Wenlock Series and demonstrate that the cascade of biological and chemical events that took place during the Big Crisis happened on time scales of tens to hundreds of thousands of years. © 2012 Geological Society of America.
Worton G.J.,Dudley Museum and Art Gallery |
Gillard R.,University of Birmingham
Proceedings of the Geologists' Association | Year: 2013
The UK has weakening development controls, limited earth science teaching and reducing financial resources which directly impact the geological community's ability to sustain the conservation of local geodiversity. Geoconservation is becoming a function of interested local people's desire to do something rather than having a formal mandate and paradoxically it is non-geologists who are often best placed to do the practical conservation. Fewer younger people are getting involved in geoconservation which is particularly worrying for the future. Local geology needs to be meaningful and personal to a much wider range of people if we are to achieve a sustained geoconservation outcome. There is a fantastic array of local geodiversity assets to engage new people but perhaps we need to use them in exciting new ways in order to succeed. This paper focuses on some inspirational projects that have engaged local communities and younger people in the Black Country, England, UK. © 2013.
Ray D.C.,University of Portsmouth |
Ray D.C.,Neftex Petroleum Consultants Ltd. |
Collings A.V.J.,Arup |
Worton G.J.,Dudley Museum and Art Gallery |
Jones G.,248 The Broadway
Geological Magazine | Year: 2011
The upper Wenlock Series (Homerian Stage) of the northern Midland Platform, England, contains numerous volcanic bentonite clay layers.AtWren'sNestHill, Dudley, 15 bentonites have been investigated and comparisons with the type-Wenlock have been made by means of two key sections alongWenlock Edge, Shropshire. In total 22 bentonites have been investigated and their clay and sandgrade mineralogies determined. Rare earth element (REE) and yttrium concentrations of apatite grains contained within ten of the bentonites have been established allowing geochemical fingerprinting as an indication of provenance of source magmas and identification of geochemical marker beds. Based on the analysis of REE and yttrium concentrations it seems likely that the majority of these bentonites originated from a granodiorite magmatic source. Comparisons with published Llandovery and lower Wenlock age bentonites indicate generally more enrichment in light REEs relative to heavy REEs. In addition, close geochemical similarities between bentonites along Wenlock Edge and at Wren's Nest Hill strongly argue for their presence as precise stratigraphic equivalents within the upper Much Wenlock Limestone Formation. These correlations are further supported by geophysical data from borehole wire-line logs across the West Midlands. Finally, a chemically distinct mid-Homerian episode of volcanism is identified and represents a potentially important marker interval between the study area and other similarly aged bentonites reported from the Island of Gotland, Sweden. © 2010 Cambridge University Press.
Passler J.-F.,Friedrich - Alexander - University, Erlangen - Nuremberg |
Jarochowska E.,Friedrich - Alexander - University, Erlangen - Nuremberg |
Ray D.C.,Neftex |
Munnecke A.,Friedrich - Alexander - University, Erlangen - Nuremberg |
Worton G.,Dudley Museum and Art Gallery
Estonian Journal of Earth Sciences | Year: 2014
A microbial origin has been proposed for matrix-supported, low-diversity buildups reported from different palaeocontinents during the onset of the Mulde positive carbon isotope excursion. We have investigated a small aphanitic buildup from the Lower Quarried Limestone Member of the Much Wenlock Limestone Formation, exposed at Whitman’s Hill (Herefordshire), corresponding to the central part of the Midland Platform (UK). Up to 50% of the rock volume in this buildup consists of mottled micrite. The SEM studies revealed that the micrite is largely detrital and does not show features characteristic of calcareous cyanobacteria or leiolites. The aphanitic character of the buildup is suggested to be controlled by the depositional rate, and the widespread occurrence of matrix-supported reefs in this interval to be driven by a mid-Homerian rapid eustatic transgression. © 2014, Estonian Academy Publishers. All rights reserved.