This four-day field course in the Wessex Basin of Southern England provides graduate students in the energy industry with hands-on experience in sedimentology and stratigraphy. The Wessex Basin offers a unique opportunity to explore a variety of depositional environments from the Triassic, Jurassic, and Cretaceous periods, providing valuable analogues for subsurface reservoirs. The course focuses on interpreting sedimentary structures, facies transitions, and tectonic influences, all of which are critical for understanding reservoir quality, stratigraphic traps, and source rocks in hydrocarbon exploration.

Through guided visits to world-class outcrops, students will refine their observational skills, learn how to interpret sedimentary processes from rock records, and gain a deeper understanding of the stratigraphic framework and tectonic history of the basin. The field course emphasizes practical skills in describing outcrops, interpreting depositional environments, and recognizing key stratigraphic surfaces that are relevant to georesources.

Learning Objectives

The overarching goals of this field course are to:

• Identify and describe key sedimentary structures and facies in outcrops.
• Interpret depositional environments and reconstruct paleo-environmental settings.
• Understand the stratigraphic framework of the Wessex Basin and its relevance to hydrocarbon exploration.
• Recognize tectonic influences on sedimentation, including fault movement and salt withdrawal.
• Apply field-based observations to subsurface reservoir characterization.

Itinerary and Key Outcrops

Day 1 – Triassic Depositional Systems

The first day focuses on Triassic fluvial and lacustrine deposits. Students will observe coarse-grained fluvial deposits, overbank facies, and lacustrine sediments, gaining insights into continental depositional environments.

• Stop 1: Budleigh Salterton
  • Description: Coarse pebble beds of braided rivers with clearly visible paleo-river channels.
  • Learning Focus: Understanding braided river systems, channel migration, and sediment transport processes.
  • Key Features: Impressive cross-bedding, paleo-channels, and evidence of high-energy fluvial processes.
• Stop 2: Sidmouth
  • Description: Lacustrine facies transitioning to overbank deposits containing rizocretion (root structures).
  • Learning Focus: Interpreting lacustrine and floodplain environments and recognizing paleosols and root traces as indicators of subaerial exposure.
  • Key Features: Alternating mudstones and sandstones, root casts, and desiccation cracks.
• Stop 3: Dawlish
  • Description: Fluvial sandstone with well-preserved cross-stratification.
  • Learning Focus: Recognizing cross-bedding as an indicator of sediment transport direction and interpreting fluvial processes.
  • Key Features: Large-scale cross-stratification, channel structures, and evidence of changing flow regimes.

Day 2 – Jurassic Shoreface and Marine Deposits

The second day explores Jurassic coastal and shallow marine deposits, focusing on paleo-shoreline environments, storm influence, and fossil-rich sequences.

• Stop 4: Bridport
  • Description: Paleo-shoreface sandstone with impressive storm scour surfaces cemented by limestone.
  • Learning Focus: Interpreting storm-dominated shoreface environments and understanding the impact of storm events on sedimentation.
  • Key Features: Scoured surfaces, ripple marks, and bioturbation.
• Stop 5: Lyme Regis
  • Description: Beautiful alternation of siliciclastic shales and limestones containing world-class ammonite records.
  • Learning Focus: Interpreting marine depositional cycles, fossil assemblages, and sequence stratigraphy.
  • Key Features: Ammonite fossils, laminated shales, and limestone interbeds.

Day 3 – Jurassic Organic-Rich Clays and Cretaceous Tectonic Features

The third day highlights Jurassic source rocks and Cretaceous tectonically-influenced deposits, providing key insights into petroleum systems.

• Stop 6: Kimmeridge Bay
  • Description: Organic-rich, laminated clays of Jurassic age, known as the Kimmeridge Clay Formation.
  • Learning Focus: Understanding source rocks, their formation, and their significance in hydrocarbon systems.
  • Key Features: Dark laminated shales, evidence of anoxic conditions, and bituminous layers.
• Stop 7: Durdle Door
  • Description: Evidence of syn-tectonic fault movement and salt withdrawal within Cretaceous shallow-water limestone and chalk deposits.
  • Learning Focus: Recognizing the impact of tectonics on sedimentation and interpreting syn-sedimentary deformation features.

Key Geological Concepts Explored

• Sedimentology: Understanding fluvial, lacustrine, shoreface, and marine depositional environments through outcrop observations.
• Stratigraphy: Recognizing key stratigraphic surfaces and interpreting sequence stratigraphy in the field.
• Tectonics: Observing the influence of syn-tectonic processes on sedimentation, including faulting and salt withdrawal.
• Fossil Records: Using ammonite assemblages and other fossils to date and correlate rock sequences.
• Source Rocks and Reservoirs: Understanding the formation of source rocks (Kimmeridge Clay) and the development of potential reservoir facies.

Why the Wessex Basin?

The Wessex Basin in Southern England is a classic geological region with well-preserved outcrops spanning the Triassic, Jurassic, and Cretaceous periods. The basin’s diverse depositional environments provide excellent analogues for subsurface hydrocarbon systems, making it a valuable location for graduate students in the energy industry to study stratigraphy and sedimentology.

The field course highlights critical geological concepts relevant to petroleum exploration, including depositional environments, stratigraphic surfaces, source rocks, and tectonic controls. The outcrops visited during this course showcase a range of facies and depositional processes that are directly applicable to reservoir characterization, stratigraphic trapping, and source rock analysis..