Petroleum Geology & Geochemistry Field Courses in Dorset
IGI have led a large number of field excursions to the petroleum system that is well exposed on Dorset's "Jurassic Coast". Most of our staff have field experience in this area, and several have conducted research studies on aspects of this petroleum system. In addition to visits to the various field localities listed below, our field courses have often included review and analysis of relevant geochemical data in after-
The Chapman’s Pool section lies to the east of Kimmeridge Bay and on the eastern flank of the ‘Kimmeridge Anticline’.The total Kimmeridge Clay in the east Dorset area is some 508m thick (Cox and Gallois, 1981), and the Chapman’s Pool section allows inspection of the Upper Kimmeridge Clay and its boundary with the Purbeckian.The east side of Chapman’s Pool baya slumped and vegetated Kimmeridge Clay outcrop capped by vertical cliffs of the Portland limestones.
Kimmeridge Bay: The Upper Jurassic Kimmeridge Clay is seen in an anticline with minor faults.The cliff outcrop displays laminated organic-
Lulworth Cove is a geo-
At Mupe Bay we see the Lower Cretaceous in "Wealden" facies -
The outcrop lies within a military training area, and permission is required to visit. Allow 45 minutes to walk to Mupe Bay from the car park at Lulworth Cove. Access is via steep steps.
Osmington Mills: Here we see the breached oil reservoir in Upper Jurassic (Oxfordian, Corallian) fluvial & shallow marine (oil-
Portland Bill: The fossiliferous Portland Stone has been quarried since Roman times and is found in some of the most prestigious of the nation’s buildings (e.g. the rebuilt St Paul’s Cathedral in the 1680s).The stone was normally quarried, but, at the turn of the Century (2000) demand was such that a completely new mine was being trialled (Albion Stone’s Portland Stone Mine).The accessible quarries on the western side of the tip of Portland show the most prized stone to be a shallow marine oolitic micrite. Its fine grain and absence of lamination makes it a ‘freestone’ capable of being worked (carved) in all planes. The shallow water & lagoonal Purbeck beds above and the deeper water Cherty Series and Portland Sand below the freestone contain abundant fossils, ranging from turritellid gastropods, via brachipods and the areas signature giant ammonites, to dinosaur footprints and fossilized tree stumps.
Travel to West Bay or Burton Bradstock to see the Bridport Sands, a reservoir of clean shallow marine sand with carbonate-
Further west (and lower in the stratigraphic column) at Lyme Regis, the Liassic source rock of the Wessex Basin petroleum system is well exposed in cliffs in Chippel Bay (Monmouth Beach). Comparisons can be made with the Kimmeridge Clay Formation at Kimmeridge Bay, and distinct differences are observed. Cyclic interbedding of black shales, claystones and limestones characterize the Blue Lias, whilst the overlying "Shales with Beef" and Black Ven Marls are more homogeneous and still contain very good source potential.
Budleigh Salterton has a good cliff exposure of the Middle Triassic Sherwood Sandstone and the underlying Pebble Beds. The Sherwood Sandstone is the main reservoir of the Wytch Farm oilfield much further east in the basin, where the facies may show some interesting differences. This locality also offers a useful comparison with the Bridport Sands exposed at West Bay.