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Université de Fribourg

Integrated bio- and cyclostratigraphy of Middle Triassic (Anisian) ramp deposits, NW Bulgaria

Ajdanlijsky, George ; Strasser, André ; Götz, Annette E.

In: Geologica Carpathica, 2019, vol. 70, no. 4, p. 325–354

A cyclostratigraphic interpretation of peritidal to shallow-marine ramp deposits of the early Middle Triassic (Anisian) Opletnya Member exposed in outcrops along the Iskar River gorge, NW Bulgaria, is presented. Based on facies trends and bounding surfaces, depositional sequences of several orders can be identified. New biostratigraphic data provide a time frame of the studied succession with...

Université de Fribourg

Last phase of the Little Ice Age forced by volcanic eruptions

Brönnimann, Stefan ; Franke, Jörg ; Nussbaumer, Samuel U. ; Zumbühl, Heinz J. ; Steiner, Daniel ; Trachsel, Mathias ; Hegerl, Gabriele C. ; Schurer, Andrew ; Worni, Matthias ; Malik, Abdul ; Flückiger, Julian ; Raible, Christoph C.

In: Nature Geoscience, 2019, vol. 12, no. 8, p. 650–656

During the first half of the nineteenth century, several large tropical volcanic eruptions occurred within less than three decades. The global climate effects of the 1815 Tambora eruption have been investigated, but those of an eruption in 1808 or 1809 whose source is unknown and the eruptions in the 1820s and 1830s have received less attention. Here we analyse the effect of the sequence of...

Université de Fribourg

Convexity of complements of tropical varieties, and approximations of currents

Adiprasito, Karim ; Babaee, Farhad

In: Mathematische Annalen, 2019, vol. 373, no. 1, p. 237–251

The goal of this note is to affirm a local version of conjecture of Nisse–Sottile [19] on higher convexity of complements of tropical varieties, while providing a family of counter-examples for the global Nisse–Sottle conjecture in any codimension and dimension higher than one. Moreover, it is shown that, surprisingly, this family also provides a family of counter-examples for the...

Université de Fribourg

Cyclostratigraphy of shallow-marine carbonates – limitations and opportunities

Strasser, André

In: Stratigraphy & Timescales, 2018, vol. 3, p. 151–187

The sedimentary record of ancient shallow-marine carbonate platforms commonly displays a stacking of different facies, which reflects repetitive changes of depositional environments through time. These changes can be induced by external factors such as cyclical changes in climate and/or sea level, but also by internal factors such as lateral migration of sediment bodies and/or changes in the...

Université de Fribourg

A tropical approach to a generalized Hodge conjecture for positive currents

Babaee, Farhad ; Huh, June

In: Duke Mathematical Journal, 2017, vol. 166, no. 14, p. 2749–2813

In 1982, Demailly showed that the Hodge conjecture follows from the statement that all positive closed currents with rational cohomology class can be approximated by positive linear combinations of integration currents. Moreover, in 2012, he showed that the Hodge conjecture is equivalent to the statement that any (p,p)-dimensional closed current with rational cohomology class can be...