Two ignimbrite horizons are recognised in a Caradoc marine sequence. The uppermost, the Pandy Ash forms a single mappable unit, but is shown to consist of at least three separate flows, including both welded and non-welded tuffs. Locally lahars occur.
Structural arcuation in the Berwyn Hills, North Wales
β Scribed by M. A. Awan; N. H. Woodcock
- Book ID
- 102846319
- Publisher
- John Wiley and Sons
- Year
- 1993
- Tongue
- English
- Weight
- 697 KB
- Volume
- 28
- Category
- Article
- ISSN
- 0072-1050
No coin nor oath required. For personal study only.
β¦ Synopsis
Abstract
New mapping has better defined the well known arc in Acadian (late Caledonian) structures centred in the Berwyn Hills. This arc, convex to the northβwest and about 20 km across, is defined by the strikes of bedding and cleavage and the trends of fold hinges. In contrast, a mineral lineation within the cleavage has a northβnorthβwesterly plunge throughout the arc. It approximates to the long (X) axes of measured strain ellipsoids. A primary origin for the arcuation is implied by this consistency, by the absence of secondary cleavages and by opposing senses of fold transection across the arc. The new data favour the hypothesis of shortening of the Lower Palaeozoic cover against and over a preβexisting basement high inferred from geophysical data and from metamorphic and sedimentary facies.
π SIMILAR VOLUMES
## Abstract In the Rhoscolyn area of Anglesey, the late Precambrian interbedded psammites and pelites of the Monian Supergroup are folded into a kilometreβscale antiform, plunging about 25Β°NE and with an axial surface dipping about 40Β°NW. Numerous folds of up to a few tens of metres in wavelength a
To determine the pattern of geochemical variation within the Penmaenmawr intrusion, 41 rocks were analysed for major oxides and 15 minor elements. The results indicate pulsational emplacement of sheets of magma from a parental body at depth undergoing crystallization dierentiation. These sheets now
Refined biostratigraphy for the Arenig Series has permitted the use of the three stages recognized in South Wales, and hence the recognition of structurally-bounded areas of North Wales with substantially different depositional histories. During the Moridunian and Whitlandian, continuous subsidence