Bedrock Formation in Canada's Niagara Peninsula

Earlier this year I paid a visit to Hidden Bench Winery Estate which is located in the Beamsville sub-appellation of the Niagara Peninsula appellation (illustrated graphically below). Being totally unfamiliar with the region, I decided to do a deep dive into its characteristics before discussing the estate and its wines.

As shown in the top-left image of the chart above, Canada currently recognizes four province-level wine regions: British Columbia (BC), Ontario, Quebec, and Nova Scotia. Of these four regions, BC and Ontario have formed in-province regulatory mechanisms -- Vintners Quality Alliance (VQA) -- which guarantees the high quality and authenticity of origin for Canadian wines made under the system. The VQA is similar to the wine regulatory systems currently implemented in the major European wine-producing countries.

Our immediate interest lies in the Ontario wine region as it is within its boundaries that Hidden Bench lies.

The Michigan Basin
The rocks underlying the Niagara Peninsula include igneous and metamorphic rocks formed during the Precambrian Age (4520 - 542 million years ago (mya)) and more recent sedimentary rocks laid down in the Michigan Basin between 540 and 250 mya (see figure below).

The Michigan Basin is the oval-shaped formation in the center of the map above and is the key determinant of the soil types currently resident in the region. It is 250 km wide and 5 km deep (at its deepest point) and extends beyond Niagara Falls to the east, beyond Prairie du Chen (Wisconsin) to the west, to the edge of the Michigan peninsula in the north, and just beyond the Michigan-Ohio border in the south.

It is not clear how this basin formed originally but we do know that sediments from between 24 and 30 transgressions from a shallow sea were deposited therein. Sea conditions varied from incursion to incursion and this was reflected in the sedimentation.

Paleozoic sea conditions	Results/Drivers
Warm and clear	Supporting a myriad of shelled creatures
Muddy	As a result of receiving great volumes of fine silt and decaying vegetation from low-lying land
Desert conditions	Seas excessively salty supporting little life or brackish  with gypsum and sulfide and chloride minerals
Shallow, huge swamp	Vegetation

Below is a cross section of the deposits in the Michigan Basin through the Paleozoic age.

Landscape Formation
Glaciation
Beginning about 2.6 mya, the region was subjected to several periods of glaciation. Continental glaciers, advancing from the north, eroded the softer rocks down to the harder limestones and, in the northern portions of the Great Lakes Basin, the Precambrian rocks. The eroded rocks were converted to sand, silt, clay, and gravel that were carried along with the advancing glaciers. As the glaciers receded, the melting of glacial ice deposited entrained detritus on the surface as loose, unconsolidated stones. The most recent period of glaciation ended approximately 10,000 years ago.

The figure above shows small deposits of Jurassic Era rocks as the upper most strata in the Michigan Basin Series. These deposits, plus the presence of the Precambrian rocks of the Canadian Shield on the surface in the north of the Great Lakes Basin, points to erosion of the uppermost layers of the Great Lakes Basin rocks by the advancing glaciers; down to the basement rock in the places where the glaciers had the greatest mass, and the harder limestones where the mass was less.

Niagara Escarpment
Sedimentary layers made of the shells and skeletons of ancient sea animals become the hard rocks limestone and dolostone. Layers made from sand form the similarly hard sandstone. Layers comprised of mud form the weak and crumbly shale rock. In above-water environments, the weaker rocks erode at a faster rate than do the stronger rocks, forming, in some places, an overhang and subsequent collapse. Such a process is illustrated graphically below.

Escarpment retreat.
Source: http://spartan.ac.brocku.ca/~ffueten/niagara/detail2.html

In the case of the Michigan Basin, its edge was defined by such an escarpment comprised of the thick, strong layers of limestone and dolostone (Lockport Formation) which serve as the caprock of the Niagara Escarpment. Normally, the erosion-collapse sequence of escarpment retreat proceeds in the direction of the erosion. The Niagara Escarpment is stabilized by vegetation and is not retreating much.

Niagara Escarpment.
Source: http://spartan.ac.brocku.ca/~ffueten/niagara/detail2.html

Bedrock Geology of Niagara Peninsula
The figure below shows a two-dimensional view of the bedrock geology of the Niagara Peninsula while the figure immediately below shows it in cross-section. Note the heavy brow of the Niagara Escarpment (Lockport Formation) in the second picture.

Source: Dr. Anthony B. Shaw, Diagrams and Technical
Information for the Niagara Peninsula

In my next post I will focus on the soils and climate of the region.

©Wine -- Mise en abyme