Variscan orogeny

Imaggeo on Mondays: Angular unconformity

André Cortesão November 27, 2017

Angular unconformity. Credit: Daniele Penna (distributed via imaggeo.egu.eu)

It is not unusual to observe abrupt contacts between two, seemingly, contiguous rock layers, such as the one featured in today’s featured image. This type of contact is called an unconformity and marks two very distinct times periods, where the rocks formed under very different conditions. Telheiro Beach is located at the western tip of the Algarve; Portugal’s southernmost mainland region and the ...[Read More]

Imaggeo on Mondays: How chloritoid tells a story of colliding continents

Sara Mynott October 21, 2013

Chloritoid is a metamorphic mineral commonly found inside phyllite rocks – which is shale (a type of mudstone containing clays, silts and muds) that has been metamorphosed several times. Confusingly, chloritoid does not actually contain the element chlorine but instead is an iron magnesium manganese alumino-silicate hydroxide. This particular specimen is from Lyon, France: In larger sized specimen ...[Read More]

Imaggeo on Mondays: Metamorphosis

Sara Mynott March 11, 2013

This fold is part of the metamorphic core of the Pyrenees. The shear zone is almost vertical, producing a small parasitic fold (a smaller fold within a larger one), which looks almost as if it continues into the sky. The metamorphic sediments are about 500 million years old and have been deformed several times, most recently during the alpine orogeny. The alpine orogeny was period of extensive mou ...[Read More]