Actualistic snapshot of the early Oligocene Alps: the Alps–Apennines knot disentangled

The geological framework of eastern Papua New Guinea allows us to obtain direct insight into how the Alpine region might have looked like during its earliest stages of tectonic growth, and to shed light on the spatial and temporal relationships between subduction and formation of relief before tightening of the Alps–Apennines junction. In both Alpine and Papuan cases, exhumation of high-pressure rocks was not associated with any significant erosion, but took place while adjacent sedimentary basins were virtually starved of orogenic sediments and largely characterized by slow accumulation of deep-water mudrocks and limestones. The subduction and exhumation stages were thus well distinct and separated in time from the genesis of topographic relief, which did not take place until many millions years later.