Archive for June 9th, 2013

Sediments, fossils and vistas at the Capo Milazzo Peninsula, Sicily

June 9th, 2013

1. Capo Milazzo 060913CATANIA, SICILY, ITALY–This was the last day of our International Bryozoology Association pre-conference field trip through Sicily. We had an excellent time and covered an extraordinary amount of territory on this large Mediterranean island. We started our final day on the Capo Milazzo Peninsula in the northeastern portion of Sicily. The view above is looking north from the base of the with the main lighthouse on the right and bay on the left. Just peeking around the headland in the distance is one of the Aeolian Islands. We climbed down to study the rocks in the middle distance.
2. Eckart Conglomerate 060913One of the most striking units we saw was this Pliocene conglomerate at the base of a small paleobasin cut into a Paleozoic metamorphic complex. The clasts are a variety of metamorphic rocks, from high-grade schists and gneisses to low-grade greenstones. Eckart Hakansson for scale.
3. Closer conglomerate 060913This is a closer view of the conglomerates. The matrix is a foraminiferan-rich marl almost identical to the marl which lies above it (see the next image).
4. Foram Marl 060913This Pleistocene (Gelasian) marl above the conglomerates is almost 95% planktonic foraminiferans, or at least it looks that way with a handlens. There are some other fossils (see below) and a few sand-sized lithic fragments, but otherwise this is a foraminiferan ooze deposit.
5. Pliocene marl octocorals 060913Besides the foraminiferans, the most common fossils in the Pliocene marls on the Capo Milazzo Peninsula are these stick-like objects. They are gorgonian octocoral internodes, probably from the species Keratoisis melitensis. I grabbed a handful and thereby tripled Wooster’s collection of fossil octocorals.
6. Pleistocene bored Miocene 060913Included in the marls are these cobbles and boulders of Miocene limestones slumped in from the slopes above. They often have large borings from lithophagid bivalves (producing Gastrochaenolites) and a smaller background boring by clionaid sponges (making Entobia).
7. Stromboli 060913There are spectacular views from Capo Milazzo. This is looking north at the volcanic island of Stromboli. We spent a long time staring at it because every half-hour or so it spouts steam and smoke for a few seconds. I didn’t get to see an event, but there was a continual very light plume blowing from the right to the left.
8. Mark Stromboli 060913This is the only time I handed my camera to a colleague and asked for my picture taken. I couldn’t resist a view with Stromboli in the background. I also wanted to show off my new Italian hat. (I lost my regular and well-worn field hat somewhere along the way.)
9. Etna Smoking 060913As we were leaving the peninsula, Mount Etna to the south let out a large puff of steam and gases into the murky air.
10. Hotel in Milazzo 060913Finally, a few shots from today to show a bit how our field trip worked. Above is our hotel in Milazzo, typical of the places we stayed around Sicily. Note all the little Fiat cars. In every city and town these cars were constantly buzzing by.
11. Bus interior 060913This is a view from my seat in our bus. Our intrepid leader Antonietta Rosso from the University of Catania is speaking in the microphone. We are very grateful to her for her planning, energy and good humor. My legs here, by the way, are extending well into the aisle because they just did not fit in these tiny Italian seats.
12. Field trip lecture 060913Antonietta Rosso is here giving us a field lecture before we descend down to the Capo Milazzo outcrops. The man taking photographs in the background is a keen Italian amateur who was very helpful. I wish I caught his name. He said one lifetime isn’t enough to enjoy all the wonders of this planet — and then there’s space!
13. Milazzo Castle 060913Just before lunch we had the requisite castle visit, this one in Milazzo. The Milazzo Castle suffered some bombing damage in World War II. The Germans and Italians used Milazzo and its port as a supply center for the Afrika Korps, and then later as a communications center for their resistance to the Allied invasion in 1943. The walls we are looking at here were built by the Spanish (Aragonese) in the 15th Century.
14. Messina Strait 060913Finally we passed by the Strait of Messina, with mainland Italy visible through the haze. This narrow body of water is extraordinarily deep and its sides continue to be uplifted by tectonic activity. These waters have wicked currents and have been known as a navigational hazard since antiquity. When we saw this strait we knew we had rounded the corner of Sicily and nearly completed our journey around the entire island.

Thank you again to our University of Catania leaders, especially Antonietta Rosso and Rossana Sanfilippo. Now we have a few hours to rest before the official International Bryozoology Association Conference begins tomorrow morning.

Wooster’s Fossil (and Mineral) of the Week: Marcasite worm burrows from Bolivia

June 9th, 2013

MarcasiteBurrowsBoliviaFixedHere’s a type of fossil I’ve never seen: worm burrow casts made entirely of the mineral marcasite. These come from the George Chambers (’79) gift collection, so we know only that they were found in Bolivia. Despite the lack of information about them, they’re curious enough to be featured in our series.

As best as I can figure out, these started as tunnels burrowed into a muddy substrate by worms of some kind. Iron sulfide, in the form of the mineral marcasite, precipitated within the abandoned tunnels, eventually filling them completely. Later the mud matrix was eroded away, leaving these intertwined tubes of silvery marcasite.

The tunnel walls were probably coated with an organic slime from the original worms or later bacteria. Sulfate-reducing bacteria may have then colonized the organic material, precipitating the pyrite in a manner described by Schieber (2002) and Virtasalo et al. (2010). The marcasite would ordinarily have converted to the more common (and stable) form of iron sulfide, pyrite (see Murowchick, 1992), but for some reason this did not happen here.

A cool combination of mineralogy and paleontology!

References:

Murowchick, J.B. 1992. Marcasite inversion and the petrographic determination of pyrite ancestry. Economic Geology 87: 1141–1152.

Schieber, J. 2002. The role of an organic slime matrix in the formation of pyritized burrow trails and pyrite concretions. Palaios 17: 104–109.

Virtasalo, J.J., Löwemark, L., Papunen, H., Kotilainen, A.T. and Whitehouse, M.J. 2010. Pyritic and baritic burrows and microbial filaments in postglacial lacustrine clays in the northern Baltic Sea. Journal of the Geological Society 167: 1185-1198.