Defining the timing of the Ordovician sediment deposition in southern Quebec and Ontario (Canada) using K-bentonite tephrochronology

The St. Lawrence Platform in southern Quebec is a series of Cambrian-Ordovician (539-443Ma) sedimentary rocks containing K-bentonites, altered volcanic ash beds. These ashes have zircon and apatite, minerals that are difficult to alter, retain the original characteristics of the ashes and can provide distinct chemical fingerprints associated with separate eruptions. The presence of bentonites in the Montreal area rocks can cause complications during the construction of urban infrastructures considering their low cohesion and swelling properties. Furthermore, bentonites are excellent marker horizons in sedimentary strata. Their study aims to help reduce delays and additional costs caused by geotechnical difficulties for construction companies, such as those currently planning the new metro lines. The Ordovician (485.5-443.8Ma) is a geological period that saw a series of coupled changes in the Earth’s biosphere and palaeogeography. The rocks show the opening of a vast ocean followed by its closure during the Appalachian formation. This led to the formation of volcanic arcs, causing explosive eruptions and the ejection of large quantities of ash into the atmosphere. Defining the extent and the chemical properties of these ashes makes it possible to estimate the climatic and biological impacts of the eruptions and understand the complex evolution of the Platform.

Faculty Supervisor:

Joshua Davies

Student:

Partner:

ETH Zurich

Discipline:

Earth science

Sector:

Education

University:

Université du Québec à Montréal

Program: