Logging of the bottom section of the borehole by the Robertson Geo folk starts today. So does the first snowfall of the year. Photo credit: Dominika Sz?cs
The team look on as the core-catcher is unscrewed for the last core at the Prees-2 drill site. Only nine years waiting to get to this point.. Photo credit: Dominika Sz?cs
Exquisite laminated carbonate bed developed within the red playa lake sediments of the Brooks Mill Mudstone Formation, in the Upper Triassic. These beds show very well developed lithological rhythms that are likely forced by Milankovitch cycles in the same manner as the marine Lias rocks that are the primary focus of our project. Photo credit: Dominika Sz?cs
Christmas Day at the drill site – many thanks to our neighbours the Holy Farm Garden Centre and Nursery for the donation of the Christmas Tree and all at Platt Farm for their hospitality during the project. The Christmas cake went down particularly well in the mess room. Photo credit: Dominika Sz?cs
Curated cores stacking up in the core container waiting to be transported to the National Core Repository at the British Geological Survey in Nottingham. Each1-metre-long core section is carefully marked to show the order and the right way up using a variety of different signs (a “belt-and-braces” approach). Photo credit: Domi Szucs.
Another day, another core (or two). Here the full 6-m long core barrel is being lowered to the catwalk where the core catcher (the device that holds the core in place) is loosened. The cores are then transported around the site to the core core lab where they are cut into sections of a manageable length. Photo credit: Jim Riding.
As hoped for we have new core! More lovely grey mudstone which is just what we want. Ammonites suggest we are in the upper Hettangian now, approaching 500 m before midnight, and well on the way towards the Triassic.
A new dawn at the Prees drill site. The Top Drive is now fixed, and we are looking forward to renewed coring at about lunchtime today. Our hope is that the open hole is still in good condition and we can proceed without further issues.
A quiet day at Prees whilst we wait for repairs to be completed. We expect this to take just over a week and look forward to coring the last part of the hole over the following couple of weeks. Time to unpack the Christmas lights.
During the night we had an issue with the Top Drive, which is the motor that turns the drill string and the bit. The problem has not been solved yet. We have pulled the string back up inside the metal-cased hole whilst the problem is investigated. This could be a little while.....
Coring rate has improved dramatically over the last couple of days, and the rocks recovered continue to be exactly what we hoped for, dark grey mudstones with many fossils, and apparently rhythmical changes in colour and grainsize. Shown here is one of the many layers of the oyster-like bivalve Gryphaea that we are passing through as we go back in time.
Ammonites in cross section at about 300 m depth. Ammonite identifications provide one of the most important ways to give these rocks a relative geological age. Ultimately, the team aims to tie together all major methods in stratigraphy to come up with a really detailed and accurate numerical timescale for the Early Jurassic. The fact that the core contains abundant ammonite fossils augurs well for the follow-up science.
Coring ahead, but slow going. The rocks are similar to the age-equivalent strata in North Yorkshire – the Siliceous Shale – and so a clue to the tough coring may be in the name. Next set of strata in Yorkshire going down is the Calcareous Shale, so fingers crossed that the stratigraphy is similar in Shropshire.
Coring resumes for the deep section of the hole. We successfully recovered cement from the bottom of the hole, followed by intact previously uncored formation. A ‘leak off test’ was also successfully completed, and we are now coring ahead again. The recovered cement will make a nice paperweight.
The drill site at sunrise seen from the hill on which much of Prees village sits (the hill is capped by upper Pliensbachian ‘Marlstone Rock’). Coring is still paused while we sort out some technical issues.......
The Blowout Preventer now installed and ready for testing. After this operation is completed, a short core will be taken before the formation is pressure-tested. Following that, coring will commence again in earnest.
The next pair of scientists arrive on site ready to start their nightshift when we begin coring again. The scientists offices are the two stacked containers on the right. Photo credit: Jim Riding.
JET scientists with Prees core in the BGS core scanning facility (CSF) working on core scanning in parallel with ongoing coring activity at Prees. The first results from the multi-sensor core logger are beginning to be compiled and look very promising. X-ray flourecence scans, giving elemental abundances, will probably be started on Monday.
Core scanning of the first Prees core has started at the Core scanning Facility (CSF) at the BGS. Geophysical measurements including gamma density, magnetic susceptibility and natural gamma as well as radiographic images are compiled for each core section. Geophysical core scanning data will be compared with geophysical downhole logging data obtained on-site in order to inform core-log-integration.
Geophysical logging was completed successfully this morning. Shown here are an array of the slim-line tools used for making measurements in the borehole. Tools used included caliper, temperature, acoustic televiewer, sonic, resistivity, spectral gamma ray, magnetic susceptibility, density and neutron porosity. There was a little doubt that the caliper was working at first, but this turned out to due to very good hole condition.
Overnight, the rig crew pulled up the casing for the top of the borehole, and now the borehole is being logged by Robertson Geo who are undertaking this work in place of the Leibniz Institute of Applied Geophysics (LIAG). The LIAG scientists were unfortunately unable to travel because of the pandemic. Downhole logging – whereby the geophysical and geochemical properties of the borehole wall are measured by various instruments on a long wire – is estimated to take 24 hours to complete. Coring is due to resume in about seven days’ time.
Star of the Sinemurian? This crinoid ossicle (part of a ‘sea lily’) occurs in strata with ammonites that are probably of Sinemurian age. Just below this level we cored a ~15 m thick siltstone with wonderful trace fossil assemblages.
The first Prees core has arrived at the British Geological Survey ready to be curated by the professional BGS Core Store team at the National Geological Repository (NGR). Nineteen core runs with approximately 90-100 m of core will be labelled, databased, and stacked onto pallets ready to be delivered to the Core Scanning Facility (CSF) for geophysical and geochemical core scanning.
Today the core drilled so far was loaded up and taken to the British Geological Survey ready for scanning and splitting. Drilling is progressing well, and we are past 150 metres. (Photo: Amy Elson.)
Jet scientists preparing for geochemical and geophysical scanning of core from Prees using archive material from the Llanbedr (Mochras Farm) drill core in Wales. Thanks to the help of the Core Scanning Facility (CSF) team, effective workflow procedures and scanning parameters were established. The aim is to start scanning Prees core next week.
An example of the long intact cores recovered from about 50 m down to 100 m. The lithology here is shelly dark grey mudstone, likely of Early Pliensbachian age, and the core recovery for the last 50 m has been 99.6% of the drilled section. The common belemnite, bivalve, and brachiopods fossils will be analysed as archives of past seawater geochemistry.
Coring has reached about 60 m, and on the end of the cut core seen here are Jurassic marine fossils. So far the core recovery has been good, and is improving as we core deeper.
We have our first (short) core. We only advanced 0.8 m (intentionally, we’re still getting used to the rig) and recovered about 0.6 m of Jurassic mudstone. This is essentially what we expect to recover throughout. Pictured: Dr. Kara Bogus (University of Exeter).
Science team in (and around) the core lab container. We are now working 24 h, which means two shifts of scientists, each working 12 h. Communication at the cross-over is going to be more challenging in light of the pandemic, but we are still able to go over some important core handling procedures to ensure consistency across the 24 h workday. Right to left: Professor Stephen Hesselbo (Project PI; University of Exeter), Ailsa Roper (PhD student; University of Leeds) and Prof. Robert Newton (Project Co-I; University of Leeds).
The science team is housed in offices on site. These are basically stacked containers that include desks, chairs and heating. We’re busy getting our procedures finalized to receive core imminently.
ig 18 set amongst the cabbages. Our rig is located at Platt Farm, and we are incredibly appreciative to the landowner Mr. Beddoes and his family for their support of this project.
Our posters are prominently displayed on the entrance gate to the Prees site. We’ve had a lot of local interest thus far and hope this provides a good introduction of what we attempting to recover and why
Even though we cannot host large groups of people on site, you can always stop by the drill site and see where we are currently coring. We will be updating the poster each day with coring progress, lithology and any other features (concretions, fossils), and comparing what we see to what was drilled at nearby Prees-1 and our predicted stratigraphy.
How do we recover the Jurassic rocks from Prees that JET project scientists will use for study? Here is a basic explanation of the scientific coring process, and is the second (of three) posters to be featured at the Prees site entrance.
As we are unable to host a visitor’s station on site at Prees, we have been busy generating some posters to attach to the site gates to allow passersby (and we have enthusiastic local interest so far!) to read a bit about what we are doing here, what we anticipate recovering, and how. The post today depicts what material we anticipate recovering from Prees, based on regional geology and previous drilling in the area.
Want to know more about the JET project in general and the Prees borehole in particular? We’re arranging to have some information available at the site entrance for members of the general public (in lieu of a visitors’ station within the site), as we’ve had enthusiatic local interest in the Jurassic sediment records of the area.
The main drilling rig, Rig 18, arrived at the drill site for the JET project at Prees (UK) and is rigged up ready to go next week. The first scientists and PI Steve Hesselbo will be at the site by the end of the week.
This week our first rig is undertaking the installation of the conductor, which will support the upper portion of the borehole where the formation is unconsolidated so that we do not have any wash outs or cave in of material when we start drilling deeper. After these operations, we will be ready to mobilize the larger, main drilling rig!
Yesterday, we received delivery of Rig 14 at the Prees drill site. This rig will be used for the conductor installation operations, scheduled to begin on Monday (12 October)
Construction of the drill pad at Prees finished yesterday, with the completion of the drilling cellar. We are now awaiting mobilisation of the first rig that will install the conductor casing.
On site, perimeter containment ditches have been dug and different linings are being installed to support operations at the drill site, including the main drilling rig. We are currently expecting that construction will be completed next week!
Site construction for the Early Jurassic Earth System and Timescale (JET) project begins at Prees, Cheshire Basin, UK. The principal aim for Prees is to core an expanded 850 m thick Late Triassic to Early Jurassic mudstone succession for integrated astrochronology, biostratgraphy, chemostratigraphy and magnetostratigraphy. The new record will complement ongoing studies of the historic Llanbedr (Mochras Farm) borehole, UK, and the project will lead to a greatly enhanced understanding of major environmental changes and Earth System transitions that took place over this time interval.
Jet project team members at the new British Geological Survey core scanning laboratory, January 28th 2020. Site investigation cores yielded several metres of Jurassic mudstone, which were used to develop a scanning protocol and define core work flows. Core scanning will be critical to the project success for core-log integration and to provide data for cyclostratigraphic analysis.
Site investigation at Prees, December 2019. Two cores were drilled that recovered core down to 37 m and established the unconformity between Quaternary diamict and Jurassic mudstone. The top of the Lower Jurassic is strongly fractured, likely as a result of glacial loading. Photo credit: SM Associates
