Project with Richard Lisle on ‘Structural Techniques’ - Introduction

Overview of Project

The East-West trending Bristol Channel basin experienced a series of sedimentation and regional tectonics movement from Carboniferous until Neogene. The carbonaceous shelf-limestone was largely deposited in early Carboniferous period. Later, the Variscan orogeny uplifted the area which formed the unconformity throughout the Permian. Crustal extension and lithospheric thinning throughout the Permian until the Early Cretaceous led to a synextensional deposition of Triassic Sheerwood sandstone, Mercia mudstone and the Penarth Group in the basin. During the Cretaceous period, extensional tectonics continued, which laid down other formations such as the Chalk, Wealdon and Greensand facies. Eustatic sea-level fall at the end of the Cretaceous period which led to tectonic uplift of the basin and erosion took place.

Extensional events during the Triassic and Permian trapped a certain amount of stresses within the plane of weakness. Up until it reached its maximum stress capacity, the stresses were released causing for movement parallel to the deformation direction. This movement will leave a strain marker, of which could be studied using palaeostress and strain analysis.

Observation from geology maps and visits to the study area have shown that there are presence of faults trending N-S on the Triassic formations. The underlying tilted beds of Carboniferous limestone is thought to be a controlling factor for the fault displacements in the Triassic formations during the extensional period between Triassic and Permian.

Findings of this project may provide the answer whether faults growth and fault movement may be controlled by the underlying beds. Investigation will take place in 3 study areas within the Bristol Channel basin:

Tom Point     - 51° 23’ N, 3° 17’W
Barry Island     - 51° 23’ N, 3° 16’ W
Sully Island     - 51° 23’, 3° 11’ W

Research question / Hypothesis

Did the Triassic-Permian extensional stresses took advantage on the Carboniferous Limestone bedding planes as plane of weakness in forming the faults in the Triassic Sandstone?

2 Responses to “Project with Richard Lisle on ‘Structural Techniques’ - Introduction”

1. Rafie says:

   November 26, 2008 at 8:19 pm

   Nice thumbnail!
2. admin says:

   November 26, 2008 at 11:59 pm

   got the idea whilst praying Zuhr the other day (not khusyu’??!). thanks Rafie!