Akademik Veri Yönetim Sistemi
Gallois A. B. C., Burgess P., Yilmaz I. Ö., Isamaila A., Özyurt M., Hollis C.
Diğer Uluslararası Fon Programları, 2025 - 2027
Solution collapse breccias can
result from the dissolution of sulphate beds (gypsum and/or anhydrite), leading
to the brecciation of the overlying carbonate beds. Such breccias are increasingly
recognised and relevant to subsurface energy and storage (e.g. Geothermal or Carbon
Capture and Storage; CCS). Injecting CO2-rich brines into the
subsurface may lead to further dissolution to collapse brecciation. This is why
it is crucial to characterise the mechanisms involved in forming such collapse
breccias.
One of the best examples of a solution breccia is exposed along the Jurassic Coast in the southern Dorset coast of the UK, in the lower beds of the Purbeck Limestone Group (Upper Jurassic to Lower Cretaceous), the so-called Broken Beds. The origin of the Broken Beds has been debated for more than 200 years, yet no process has been accepted. Four hypotheses exist for the possible origin of formation of this breccia: (1) the decay of plant remains interbeds; (2) a tectonic breccia within asymmetric folds during formation of Purbeck Anticline in Cenozoic Alpine inversion; (3) a collapse breccia due to the dissolution of gypsum and anhydrite beds of the Cypris Freestone unit; and/or (4) an overpressure within the Cypris Freestone due to the volume decrease associated with dehydration of gypsum layers into anhydrite. The most recent published study on the Broken Beds (Gallois et al., 2018) used a multi-hypothesis to suggest that the most likely timing of brecciation was during a tectonic event related to the Cenozoic Alpine inversion and compression that affected Western Europe. However, they acknowledged that the lack of data was a limitation to concluding the formation process.
The primary aim of this project
is to improve our understanding of the mechanisms involved in collapse breccias
formation.
The secondary aim is to provide
an answer to the debated origin of the specific breccia of the Broken Beds in
particular.
The tertiary aim is to improve
our overall knowledge of the effect of the Alpine compression in northern
Europe.
The
following objectives will be achieved to reach the aims:
- Determine the composition and variation of the clasts and the matrix,
as well as the clast shape and size from a sedimentological analysis in the
field and petrography.
- Determine the diagenetic
history of this unit to decipher the processes at the origin of the breccia
formation by identifying cements and cement hierarchy from petrography and
cathodoluminescence coupled with geochemistry stable isotope (C, O and Sr) and
Rare Earth Elements (REE) analyses.
- Determine the main tectonic
force direction(s) that led to the formation of the folds observed with
a structural analysis in the field by measuring the dip and strike of strata, fractures,
faults, and joints.
- Determine stratal
relationships to decipher when the collapse breccia was formed and preserved by
integrating sedimentology and diagenetic analyses and structural measurements
to unravel the timing of formation, i.e. single, dual, or multiple events.