Humboldtians in Focus

Peepholes into the Earth's Past

By Uschi Heidel

To Yamirka Rojas-Agramonte, grey lumps of rock are precious treasure. With their aid, the Cuban geologist is trying to fill in the blank spots on her country's geological map. A portrait. 

When the customs officer at the airport lifts her suitcase, groaning: "I suppose your suitcase is loaded with rocks," Yamirka Rojas-Agramonte needn't hesitate to reply, "Yes". This Cuban woman likes to travel with heavy luggage. Where other passengers put their clothes, the 33-year-old will often enough store rocks from her home country. She has an impressive selection of them on the wooden table in her Mainz study. The laymen will only see misshapen, grey lumps, but the geoscientist knows that they are treasure troves containing information from primordial times. She wants to recover these treasure troves scientifically, she wants to crack them in the most literal sense, and she hopes that in their core, she will gain new insights into Cuba's geological birth and formation.

There are enough theories and models relating to the tectonic development of the Caribbean's largest island and its region, but secure data is lacking. Cuba's political and, hence, academic isolation has resulted in numerous blank spots on the geological map - terra incognita for the international geoscientific community. In the country itself, teaching and research conditions are modest. "Data is inaccurate because instruments and methods are lacking. Specialist literature usually dates back to Soviet days and lags far behind the state of the art," says Yamirka Rojas-Agramonte.

When she was studying in Pinar del Rio, in Western Cuba, in the early nineties, the situation worsened dramatically owing to the collapse of the Soviet Union. "Sometimes, we would even consider ourselves fortunate to get something to eat." Since then, the situation has eased, she explains, "but anyone wishing to engage in serious academic activity has to use analytical methods and modern apparatus abroad" - but always keep coming back to Cuba. After all, "A geologist belongs in the field," the Humboldt Fellow stresses.

Her "field" comprises 112,000 square kilometres. Yamirka Rojas-Agramonte takes samples everywhere in Cuba: volcanic rock, sediment deposits, metamorphous rock that was formed by high pressure or extreme temperatures - an unbelievably long time ago. Some of it dates back to the Cretaceous Period, around 120 to 130 million years back. After their journey in the suitcase, the Cuban finds do the rounds of analysis at Mainz University's Institute of Geosciences. This is where the Fellow engages in research with her host, Professor Alfred Kröner.

The illustrations on her laptop screen show Cuba as a colourful carpet the patterns of which can only be interpreted by geologists. Yamirka Rojas-Agramonte explains in straightforward terms where and how the Caribbean Plate once hit the North American Plate, and how the collisions resulted in faults that continue to be active. One research focus is on the Southeast, in the Sierra Maestra, which the scientist has become very familiar with in the course of several excursions. This volcanic mountain range with Cuba's tallest mountain, the almost 1,800-metre high Pico Turquino, and steep slopes plunging down to the Caribbean Sea that reaches a depth of around 6,600 metres at this point, is an instructive area in terms of geological development.

“I love to work outside in the field. The difficulties in getting to the rocks, the unpredictability of nature - these experiences are all part of it. And then there is that feeling of happiness when I have actually discovered something new.”

Yamirka Rojas-Agramonte is looking for traces of the past in the vicinity of the Oriente transform fault, at the point where the North American and the Caribbean Plates drift past one another and the friction this causes has different geological impacts. "The geological evolution of the Caribbean is the result of complex interaction between various lithosphere plates. How and in what direction the plates moved at some time is usually a matter of speculation," says the geologist. She wants to gather so much new data that it can be used as a basis to develop a plausible evolution model of the region. This is her goal, this is what gives her the determination and discipline needed for the strenuous and adventurous research in the field and the extremely laborious analysis in the laboratory. "I love to work outside in the field. The difficulties in getting to the rocks, the unpredictability of nature - these experiences are all part of it. And then there is that feeling of happiness when I have actually discovered something new," the scientist explains, the words pouring out of her.

Back at the laboratory, she does most of the analyses herself, applying palaeomagnetic methods in combination with geochronology and structural analysis. What is all this about? Palaeomagnetics helps to identify the geographic latitude that a rock has developed at. As the orientation of the Earth's magnetic field always remained the same during geological periods, it is possible to determine the magnetic orientations that have been "frozen" into the rock. But since the continental plates wander across the globe, the "frozen" magnetic orientation will change as well. This enables scientists to establish a rock's rough palaeogeographic position when it was formed. This is the work that Yamirka Rojas-Agramonte carries out at Munich University's palaeomagnetic laboratory.

The "gem" zircon

In geochronology, the age of a rock can be determined with the aid of radioactive methods. Here, zircon, one of the Earth's oldest known minerals, is of particular importance because it incorporates the radioactive element uranium in its crystal lattices. Zircon occurs mainly in the Earth's crust, in igneous rock such as granite, in sedimentary and in metamorphous rock. "This mineral is very robust and resistant, which makes it extremely useful in dating rock," the scientist explains. In the Mainz laboratory, she puts particles of zircon under the microscope. The sight of them thrills her each time. The longish minerals look like light-coloured jewels. However, it takes a lot of researcher's sweat before these gems become visible on the slide. Yamirka Rojas-Agramonte has to saw apart the lumps of rock and crush them into coarse dust. Then water and vibration separate the light from the heavy particles. Afterwards, the heavy particles containing the zircon are separated from one another according to their magnetic or non-magnetic properties. Finally, at some risk due to toxicity, the particles are separated chemically with bromoform and diiodomethane.

"Later, comes the big moment. Was the whole procedure really worth it? Can zircons be found?" Yamirka Rojas-Agramonte describes the excitement her research causes. If the analysis has been successful, the zircons are examined with regard to the composition of their isotopes, using mass spectrometry because the minerals can store geological events in their isotope combinations, making them peepholes into what is anything but the grey past of our planet.

When the geologist left Cuba for the first time, in 1997, and came to Germany, she neither knew a single foreign colleague nor was she familiar with the international standards of her discipline. "I went through an absolute culture shock," she recalls. But this did not daunt her. Again and again, she cleared the bureaucratic hurdles of the socialist state, wrote her doctoral thesis in Salzburg and, on Friday afternoons, taught her not very agile colleagues salsa and merengue. Then the Alexander von Humboldt Foundation's Georg Forster Research Fellowship, which sponsors outstanding junior researchers from developing and threshold countries, took her to Mainz. "Today, I know lots of people and cooperate closely with colleagues in international projects," she says. "Geology is a very interdisciplinary subject."

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Yamirka Rojas-Agramonte Yamirka Rojas-Agramonte 

Yamirka Rojas-Agramonte (33), born in Florencia, Cuba. Studied Geology at the University of Pinar del Rio, Cuba. Did her doctorate at the University of Salzburg, Austria. Humboldt Fellow at the Institute of Geosciences, Mainz University, also: Associate Professor at the Geological Faculty, Institute of Mining and Metallurgy in Moa, Province of Holguín, Cuba.

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