ICE FT 06 | Syn-Rift Lacustrine Carbonates; Cycles, Microbial Mounds, Brackish-Hypersaline Facies, Wessex Basin, United Kingdom
Amercian Assocation of Petroleum Geologists (AAPG)
Friday, 13 October – Sunday, 15 October 2017, 7:30 a.m.–4:00 p.m. | Weymouth, England
Who Should Attend
Geologists, geophysicists and anyone interested in learning about the Purbeck microbial limestones of Dorset.
Objectives
To study Upper Jurassic microbial carbonates and to compare the lower part of the Purbeck Limestone Group with the South-Atlantic pre-salt carbonates.
Course Content
The lacustrine limestones of the Purbeck Group were deposited in a shallow lake on the western margin of the Wessex Basin during its late syn-rift phase of basin evolution. This field trip will demonstrate the palaeoenvironmental setting of these limestones in the latest Jurassic and show how this lake was firstly brackish water and later hypersaline. The lower, brackish phase, of the Purbeck limestones are characterised by in-situ, highly porous, thrombolitic microbial mounds that reveal complex and irregular shapes. These microbial mounds are surrounded by, and interdigitate with, an intermound
packstone-grainstone facies and together are arranged in high-frequency lacustrine cycles capped by paleosols.
This fieldtrip will demonstrate these complex and highly variable carbonate facies and compare them with the pre-salt carbonates of the South Atlantic. This new work on the Dorset Purbecks represents the results of a four year industry funded research project at Royal Holloway, University of London.
Itinerary Roster
Day 1, Friday, 13 October
07:30 — Coach departs from the ExCeL London
12:00 — Lunch at the local pub, the Cove House Inn
13:00 — Introduction to trip with view stop of West Weare cliffs from Cove Hotel.
13:30–15:30 — Field study of Kimmeridge Clay to Portland Group transition, West Weare cliffs.
16:00–16:30 — Field study overview of Purbeck Limestone Group, Tout Quarry.
17:00 — Arrive at hotels at Weymouth
Accommodations
Edenhurst Guesthouse, DT4 7ER
Langham Hotel, DT4 7EX
Gresham Hotel, DT4 7EW
Day 2, Saturday, 14 October
09:00 — Coach departs for Lulworth Cove.
10:00–11:00 — Lulworth Cove for overview of Jurassic to Cretaceous stratigraphy and Stair Hole to demonstrate tectonic setting of Purbeck Group.
11:00–13:00 — Detailed examination of Purbeck Group, Fossil Forest with microbial mounds around in situ tree stumps and the change in the depositional environment from brackish to hypersaline water lake.
13:00–13:30 — Picnic lunch.
13:30–14:30 — Walk to Mupe Bay, examination of oil seep.
14:30–16:30 — Mupe Bay to Bacon Hole examination of Purbeck Group facies, freshwater to brackish to marginal marine palaeoenvironments. These are organised as a succession of clays, oolitic and shelly grainstones and fresh to brackish water mollusc-rich beds (coquinas of the Unio
Member, Corbula Member, Broken Shell Limestone and Viviparus limestones).
17:00 — Coach returns to Weymouth.
Day 3, Sunday, 15 October
09:00 — Coach departs hotel.
9:30–10:30 — Portland Bill, to study the transition between marine deposits of the Portland Limestone Group (oolitic grainstone with oyster shells) organised in massive beds to the lacustrine deposits of the Purbeck Limestone Group (wackestone-packstone with peloids and some ostracods) organised in thin laminated beds with paleosol intercalations.
10:30–12:00 — God Nore, to see the basal part of the Purbeck Group where two sequences illustrating the development of in-situ microbial mounds (some around tree trunks and branches) in a brackish water lake environment and capped by paleosols.
12:00–12:30 — Discussion on value as an analogue for south Atlantic pre-salt carbonates.
12:30 — Return to London.
ExCeL London. Arrive approximately 16:00.
Fees
Professionals: US $600 + 20% VAT
Students: US $400 + 20% VAT
Includes: Transportation by coach, breakfast (Friday, Saturday, Sunday), accommodation in Weymouth and guidebook.
Limit: 20 People
Note: Temperatures can range from 5-20 degrees Celsius during this time period. Be prepared for wet and windy weather. Field boots, hard hats and high visibility vests are required for this trip and must be provided by each participant.
Venue
Weymouth, Dorset, United Kingdom
Weymouth,
Dorset
United Kingdom