STUDENT’S VOICE Geologic Adventures in Trieste, Italy Cortney Cameron,
cortney.cameron@
gmail.com
This June, I had the privilege of embarking on a research internship at the University of Trieste in northeastern Italy in the pursuit of my master’s degree at North Carolina Central University. Virtually surrounded by active faults, Italy’s high seismic activity (on dramatic display this past August, October, and January) has fostered world-class expertise at the University of Trieste’s Department of Mathematics and Geosciences. My department tapped this knowledge for collab- oration in modeling seismic hazard for the Watts Bar Nuclear Power Plant in the understudied eastern Tennessee seismic zone. Those results are forthcoming in conference abstracts; for now, my task is to attempt to do justice, in limited space, to other highlights of the trip.
The geological history of Trieste and the region at large is every bit as fascinating as the human history, which, per H. heidelbergensis fossils, could reach back as far as 400,000 years. The name Trieste seems to stem from Tergeste, an ancient Indo-European word for “market.” Evidence of human habitation appears about 2000 BC, and the Romans conquered the area around 177 BC; a few Roman artifacts still exist, including an amphitheater. Perennial tourist favorites include the Castle Miramare (once home of the short-lived and ill- fated Emperor Maximilian of Mexico) and its nature reserve, as well the Piazza Unità d’Italia, the largest open square on a sea. The unique rocks of the Karst and the vegetation they support give rise to local culinary specialties such as the much- recommended wines like vitovska, malvasia, and terrano.
Civico Orto Botanico: Geopaleontological Route
Returning to the geology, Trieste’s Civico Orto Botanico offers an excellent introduction to the region’s distinctive geological history. This public garden, which is free to visit, includes a Geopaleontological Route featuring the area’s char- acteristic rocks with explanatory placards alongside the park’s vibrant flowers. The numerically ordered placards walk the visitor from the past to the near-present, watching in the rocks as the region transforms from an ancient carbonate platform into modern Trieste.
As explained in the park, the word karst derives from the Indo-European word kar or karra meaning “rock,” adopted into English to describe the landscape typical of carbonate regions. The Classical Karst proper refers to a limestone plateau cov- ering 170 mi2 across northeastern Italy and southwestern Slovenia. One hundred million years ago, the Karst lay at a balmy 30 degrees latitude as a large undersea carbonate plat- form (today the Karst is at the much less reef-friendly latitude of 45 degrees north). The limestones range in age from 140 Ma to 47 Ma and are capped by flysch, a marine sedimentary sequence of sandstone and marl, laid down 47 to 40 Ma ago as the ongoing Alpine orogeny threw sediments into the sea.
www.aipg.org
Figure 1- A) Rocks of the Karst Plateau as displayed at the Civico Orto Botanico in Trieste; see text for description. B) Map of Karst Plateau with cross section. Redrawn from the Civico Orto Botanico. C) Depositional environments of rocks shown in A. Redrawn from the Civico Orto Botanico.
Figure 1 shows most of the rocks displayed in the garden; I’ve followed the park’s numbering as of June 2017, with descriptions after the Civico Orto Botanico.
1. Black limestone, Albian-Cenomanian (113–93.9 Ma). Mud-supported, fetid limestone with microscopic fossils. Deposited in a backreef lagoon in a reducing environment.
2. Calcareous dolostone, Albian (113–100 Ma). Black, fetid, and mud-supported limestone with Requienia fossils (rudists). Deposited in an oxygenated backreef with moderate to low sedimentation.
3. Calcareous dolostone, Albian-Cenomanian (113–93.9 Ma). Crystalline, fetid, compact, dark grey, and calcareous dolostone with irregular fractures.
4. Fossiliferous calcareous dolostone, Cenomanian 100.5– 93.9 Ma. Crystalline, fetid, compact, dark grey, and calcare- ous dolostone with irregular fractures and Chondrodonta (molluscs) and rudist bioconstructions. Deposited in an inner carbonate platform.
Jul.Aug.Sep 2017 • TPG 55
Now an eroded anticline trending northwest-southeast, the plateau emerged from the waters about 20 Ma ago.
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