GeoLog

Quaternary

Imaggeo on Mondays: Earth Wave

Imaggeo on Mondays: Earth Wave

Take a stroll along the norther beaches of the French Channel Coast, some kilometers east from the entrance of the Channel Tunnel, and you’ll encounter an imposing cliff of soft, sandy composition which dominates the landscape.

On close inspection, the sediments which make up the Quaternary aged deposits of the Sangatte Cliff, are beautiful, revealing intricate patterns which hold the key to the geological processes that formed them. Even at present, the landscape is being continuously shaped by marine processes which continuously erode the Quaternary soft deposits – especially during storms coupled with high tide events.

The Sangatte sedimentary sequence outcrops along a stretch of about 1.5 km along the French coast. Today’s featured image was taken by Pierre Antoine, at the base of the Quaternary sequence of the Sangatt Cliff. It corresponds to an observation window of about 80 cm large.

“At this location, explains Pierre, the Quaternary record is composed of raised beach deposits (flint pebble bar and sandy beach deposits, ± 3m thick) dating from a Middle Pleistocene interglacial (± 300 ka) and to a high sea level (± 5 m above the present day level), covered by a thick succession of chalky periglacial slope deposits, formed during periods of repeated freezing and thawing, associated with loesses and fossil soils know as palaeosols (8 to 12m).”

The greenish sandy deposits exposed at the base of the photo represent the top of the ancient marine beach deposits. These were overlain by a thin, dark bown, peat layer indicative of a phase of sea level drop. It is likely that during this time a peat bog, which was isolated from the sea by wind-driven sand dunes, developed .

This peat layer has, more recently, been strongly compressed and reworked during the deposition of the overlying thick bed of dense chalk mud. The greyish muds are the result of the weathering of the massive chalky slopes of the Sangatte Cliff,  which occurred following a cold period after the sea-level decrease. The delicate rusty bands seen in the otherwise creamy chalky muds, are the result of infiltration of iron oxide minerals throughout the cliff.

Reference:

Antoine, P. 1989. Stratigraphie des formations pléistocènes de Sangatte (Pas-de-Calais), d’après les premiers travaux du Tunnel sous la Manche. Bulletin de l’Association Française pour l’Etude du Quaternaire, 37, 5-17.

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. Submit your photos at http://imaggeo.egu.eu/upload/.

Introducing the new EGU Bloggers!

Since it started, the EGU Blog Network has had great coverage of geochemistry, palaeontology and geoscience in global development, but what about the other fields in the geosciences? Well, over the past couple of months we’ve been seeking out some fantastic Earth science bloggers who are keen to share their knowledge, experiences and the latest research in their fields with you.

They’ve put together six super geoscience blogs covering mineralogy, climate change and volcanology as well as the atmospheric, Quaternary and soil sciences. Like the other network blogs, their aim is to put complex scientific research into context, sharing findings beyond the usual suspects to open science up to a much wider audience.

So, without further ado, welcome to:

Four-Degrees-profile-updateFour Degrees – a climate blog by Flo Bullough and Marion Ferrat

Flo and Marion will discuss issues in environmental geoscience from the scientific literature, political chamber and the media, putting research into a policy framework and taking a look at current problems from an inter-disciplinary perspective.

Geology Jenga - profile (square)Geology Jenga – a Quaternary science blog by Laura Roberts and Daniel Schillereff

Focussing on science from the Quaternary period Laura and Daniel will share snippets from their own research disciplines to provide a more holistic understanding of landscape evolution.

Polluting the internet - profile (square)

Polluting the Internet – an atmospheric science blog by Will Morgan

Will is polluting the internet with excellent science, and will explore all aspects of air pollution and atmospheric science, focussing on what the impact of aerosols, both natural and man-made, is on atmospheric processes.

An Atom's Eye View - profile

An Atom’s-Eye View of the Planet – a mineralogy blog by Simon Redfern

Simon, an esteemed professor and science communicator, explores how the solid Earth responds to changing temperature, pressure and chemistry. Wondering what minerals are up to? He will explain mineral processes from the biosphere to the deepest inner core.

between a rock and a hard place - profile (square)Between a Rock and a Hard Place – a volcanology blog by Elspeth Robertson and Charly Stamper

Look out for some explosive action on this one as volcanologists Charly and Elspeth bring you the latest in volcanological research and share their experiences during their first footholds in academia.

G-Soil - profileG-Soil – a soil science blog coordinated by Antonio Jordán and the G-Soil team

The EGU’s own Soil System Sciences Division have put together a great blog that brings soil science into the public eye, detailing the latest research in the field and highlighting the importance of soils to both people and the environment.

We hope you look forward to reading them – we certainly do!

You can follow the blogs using the hashtag #EGUblogs on twitter and keep up to date with the EGU bloggers using this Twitter list.