Tuesday 19 February 2019

Here by the sea and sand

Greetings readers!


We can hardly believe it, but today was our last field day in Trinidad. Didn’t our plane land, like, an hour ago? Today we saw the fantastic features of the Mayaro Formation, as well as our fourth(!) mud volcano field!


The day began bright and early for us in the Trinidad Squad, racing across the island from west to east to beat the tide on the western shore, our first stop. We planned to study cutaway sections of the rocky outcrops rising out of the sandy beach. After a long bumpy ride, a snack stop for some “Doubles” (a delicious Trinidadian dish of fried flatbread and curried chickpeas), and a slightly hairy orientation in a rusting abandoned warehouse, we got down to the beach.
Two particularly badass geologists in the mangrove stands at the beach.
We started at the south end of the beach and walked north, observing changes in dip, lithology, grain size, and bedding along the way. The sands and muds of the Mayaro formation are Pliocene in age (~5-0.5 million years old), and represent the ancient delta of the massive Orinoco river, which reaches the ocean just to the south of Trinidad, in Venezuela. The various layers of sand and silt represent the different depositional environments of a river delta: streams, beaches, tidal flats, and coastal shelves. As the basin expanded, the sediments sloughed down the shelf, creating faults and folds that we could see preserved in the cliffs. As the sediments were buried, water was pressed out of them, creating spectacularly huge “flame” and “pillow” structures.


A giant flame structure! (dank hand model for scale)
Fossilized ripple marks from an ancient beach!

The scale of the sediments in the cliffs was unreal.
More giant flame structures, with slumped bedding and hummocks. (smol geologist for scale)
Nowadays, it hosts numerous offshore oil and gas deposits which are mined from oil rigs in the Columbus basin to the east. Coming to the northern terminus of our trek, we discovered trace fossils of mantis shrimp burrows - tubular structures of dark-colored rock embedded in the material above our heads. After some investigation (i.e. wet shoes), we noted that the tide was coming in and that it might be time to make haste for the bus.

We also found a number of other seaside oddities on the beach: for instance, numerous spiral-shaped planktonic structures; washed-up Portuguese Man-O’-Wars as small as a fingernail or as big as a fist; barnacle-studded wooden rafts; and albatross, osprey, vultures, and pelicans gliding overhead.
DANGER: POISON ZIPLOC.
Our next and last stop of the day was the spookily-named Devil’s Woodyard, a mud volcano complex located just west of San Fernando, along the same fault as the Digity mud volcano we visited a few days ago. According to Amerindian legend, the volcano was caused by a demon, possibly Satan himself, coming to Earth to cut timber; this is probably inspired by the mud volcano’s tassik - its radius of harsh salt and undeveloped clay which is barren of all but the hardiest opportunist plants.


The central cone at Devil's Woodyard.
One of the secondary cones... still bubbly!
The Devil’s Woodyard mud volcano erupted explosively only a year ago, turning what once was a relatively benign park into a muddy moonscape. We clambered up the 2-meter-high wall of mud onto the surface of the field, where about 15 small mud cones were calmly gurgling away.The largest was located right in the centre: about a meter tall and bubbling every minute or so, with a flow of thick mud rippling down the side and congealing a salty white.


BEHOLD: ALEX THE GREAT, CONQUEROR OF VOLCANOES.

Our guide from the other day, Xavier, has done some fantastic research on this particular mud volcano. By photographing the volcano from the air with a drone over the course of weeks and months, he measured slight elevation changes in the surface of the mudpile. Essentially, he was watching the volcano breath! Super cool.


This stop also represented our latest (and, thus far, greatest) attempt to enjoy fresh coconuts, since our previous efforts were stymied by poor technique, small size, and seawater. This time, though, there were large dry coconuts within easy taking range - we had to try again! We bashed some open with hammers then haphazardly held them over our mouths while coconut water spilled everywhere. It was messy, but it worked! Finally, Marc managed to split a coconut right down the middle, so that he and Tess could enjoy a civilized coconut-on-the-half-shell.


Tess enjoys some fresh coconut water, while the mud volcano looms in the background


At last, we retreated back to San Fernando, to pack up and enjoy one last night on the town. The mayor of San Fernando himself has invited us to tonight’s steel pan performance! How cool is that?


That’s it from us for now. Tomorrow, we’re trading in our mud volcanoes for real volcanoes!


Cheers,


Adam Brudner and Marc Roberge-Pika

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