BSRG - 12th PG Fieldtrip: Fluvio-deltaic to deep-marine systems in the South Pyrenean Foreland Basin (2014)

The 12th Annual BSRG Postgraduate fieldtrip was sponsored by VNG Norge, British Geological Survey, BG Group and Badley Ashton. We were led by the enthused Miquel Poyatos (University of Manchester) and Marco Fonnesu (University College Dublin) to the beautiful Spanish South-Pyrenean Foreland Basin to see the story of fluvial-deltaic systems through to deep marine systems. We were a group of 22, including postdocs, an industry representative and postgrad students from a variety of universities within Europe.

Our leaders, Miquel Poyatos (University of Manchester) and Marco Fonnesu (University College Dublin).

We met in Barcelona on the morning of the 13th of November and set off by coach to the first locality where we overlooked the Tremp-Graus Basin, where we were to spend the next couple of days. Moving into the basin we observed the thickening of deltaic parasequences caused by the syn-tectonic activity and many of us were newly introduced to the elementary depositional sequence (EDS) concenpt: a different type of parasequence based on unconformities instead of flooding surfaces which was the topic of many discussions throughout the remaining days. Through the afternoon we got to know the Tremp Basin a little better from structural to sedimentary features before heading back to the hotel in La Pobla and having a relatively early night after a quick introduction by everyone about their research and some fancy field work photos.

Our first view of the Tremp-Graus Basin.

Day two: we headed further south and began to understand the structure of the Ager syncline and the deformation of the Figols Group in the Ager Basin including looking at the onlap geometry with the continental red beds and alveolina limestones of the underlying Tremp – Ager Group. Next we visited the ‘geology museum’ where preservation of the tidal bundles and sigmoidal bedding is truly amazing, and later we walked to see the progradation of tidal bars with abundant glauconite and bioturbation. That evening we heard from James Churchill, an industry representative from BG group who gave a talk about the complications faced with understanding heterogeneity of sedimentary architecture in hydrocarbon reservoirs and the importance of fieldwork within the industry to help understand the 3D nature of such deposits. Later, as it was Friday night, we of course wasted no time in hitting the bars in the surprisingly sleepy village of La Pobla de Segur.

Well preserved root structures and palaeosols on the floodplain of a fluvial system.

Subtidal sigmoids at La Regola.

The next morning was business as normal with no holding back, despite some sleepy heads at the breakfast table. We headed west, further into the depths of the Tremp Basin, again looking at the stratigraphic sub-units of the Figols Group. We saw the impressive mouth bars and delta plain deposits in the Montllobar Pass and discussed the 3D architecture of dunes and ripples at the Mas De Faro outcrop where we also saw an impressive fluvial sandstone succession. Later we headed further north to the see the Roda sandstone and the Sis conglomerate palaeovalley, before heading to our accommodation just south of Ainsa. That evening we headed to the town of Ainsa and enjoyed the historic village and various types of gin which came in all colours and exotic flavours. Ten it was back to the hotel for dinner and a quiz where the spectacular knowledge of American geography helped the ‘Biacote’ team steal the show.

The group sheltering from the rain before looking at tidal bars.

Enjoying the sights of the historic town of Anisa.

Day 4, the final day, was an early start and off to the first panorama view of what we expected to be stratigraphy of the Ainsa Basin, but instead we were covered by thick cloud, but don’t fear, our trusty guides came well prepared for such events and we all gathered around a pre-printed photograph and discussed the formation of the lateral ramp thrust-and-fold complex. Next we headed to the deep water deposits and saw some truly spectacular mass flow units, channelized sand in slope fans and shelf edge deposits. Then it was time for us to hit the road and head back to Barcelona, say our goodbyes and head home.

Impressive deep-water turbidites complete with an impressive view.

I think it is fair to say that many of the outcrops seen over then 4 days were some of the best field examples many of us have seen, and we were really spoilt by numerous world class outcrops and of course leaders whose enthusiasm was never doubted, even when the fog distorted their greatly anticipated panoramas. Another huge thank you to the sponsors and, of courses, all participants for their engagement and willingness to face the elements.

The group at the last outcrop.

Your postgraduate reps,
Leah Nolan (University of Leicester), Hazel Beaumont (Keele University), Luz Gomis (University of Manchester) and Hannah Brooks (University of Leeds)