RETREAT

In 2002-2009, I was a co-PI on a project funded by the Continental Dynamics Program at NSF: Collaborative research—Retreating trench, extension, and accretion tectonics (RETREAT)—A multidisciplinary sturdy of the northern Apennines, Italy. The overall goal of the project was to develop a dynamic model explaining the syn-convergent extension that characterizes some mountain belts. RETREAT focused on the northern Apennines in Italy, an orogenic wedge formed as the Adria microplate has been consumed beneath the Italian Peninsula and the Corsica-Sardinia block since about 35 my ago. Our methods comprised: GPS geodesy; tectonic geomorphology; low-temperature thermochronometry; structural geology and synthesis of wedge evolution; seismic studies; and geodynamic modeling.

My Yale colleague and co-PI Mark Brandon and I are writing a paper on the 30 Ma to present evolution of the northern Apennine wedge. We aim to determine the mass flux into [accretion] and out of [decretion] the wedge and the length of Adria continental crust subducted beneath the wedge. We presented very preliminary results at the 2008 AGU annual meeting [see abstract].

I based the diagram in the image on a diagram by Elter (1975). The block, oriented northeast-southwest, schematically illustrates the stacking order of the diverse tectonic units—nappes—in the northern Apennines. the Alpi Apuane expose deeply buried and exhumed parts of the subducted Adria microplate. The youngest strata in the Tuscan nappe and all of the foredeep strata accumulated in basins successively subsiding as the nappes advanced onto the microplate. The Ligurian nappe is an enigmatic unit famous that contains mass-flow deposits and blocks of Jurassic ophiolitic rocks. Note that I did not depict the normal faults that are extending the western part of the wedge.

Click on the image for a larger version.