Exhuming my thesis area over 40 years later

My 1982 M.Sc. thesis, Regional cross section of the Southern Province adjacent to Lake Huron, Ontario: implications for the tectonic significance of the Murray Fault Zone (ResearchGate) proposed a plate-tectonic (Wikipedia) setting around 1.9 billion years ago, in the Proterozoic (late Pre-Cambrian). I presumed there was another buried land mass south of what I called the Manitoulin Island Discontinuity. While plate tectonics was well established in the later Phanerozoic (Wikipedia) record, it took a lot longer to be accepted earlier in the geologic time scale with lot scanter rock record to go by (more at the bottom).

A recent paper on the Alaska Rockies, however,  a discussion that Denali Fault tore apart ancient joining of two landmasses (Univ. of Alaska Fairbanks): the author described how an earlier 1993 paper had the seeds of the idea of "suturing" terranes (coalescing then separating landmasses). That reminded me that I also had suggested a foreign terrane south of my field area, with no direct evidence as it was under the Great Lakes. After my thesis I left academia and the geological survey in the mid-eighties to pursue a career in computer mapping and GIS. I also lost track of Isi (Isidore) Zietz, my go-to for Mid-Continent gravity & magnetic data, that was also less accessible then. I therefore missed that, at about the same time as said seminal paper in the early nineties, a geophysical program in the US Mid-Continent led to interpreting terranes... and plate tectonics  around 1.9Ga along strike to the West (USGS, figure in Geology)!

That prompted me now to look up geophysical data (aeromagnetic anomalies, Wikipedia): will it allow to glimpse terranes in the subsurface below the Great Lakes, as well as earlier Archean and later Phanerozoic features such as, respectively, the Wawa Lineament and the Niagara Escarpment? Lo-and-behold, I found aeromagnetic data (NOAA) and sketch-mapped them below on my desktop GIS (Esri)!

interpretation (click to enlarge)

raw data (click to enlarge)

There you have it: to find out that while neither mapped precisely nor published, my idea might prove to be correct after all! This map is, of course, just a sketch that needs fleshing out; I posted source, interpreted sketch and raw data above: enjoy!

More:

Here is a Copilot AI (here) query (see more about AI in this blog here and on Medium here):

Q: Plate tectonic animation to 2B years before present 

A: Creating a comprehensive animation of plate tectonics over the span of 2 billion years is quite the feat! Although I can't generate an animation directly, I can offer a brief overview of the major tectonic events that have shaped our planet over the last 2 billion years.

1. 1.8 Billion Years Ago: The supercontinent Columbia (or Nuna) was formed. This was one of the earliest known supercontinents.

2. 1.2 Billion Years Ago: Columbia broke apart, and eventually, the supercontinent Rodinia was formed.

3. 750 Million Years Ago: Rodinia began to break apart, leading to the formation of smaller land masses.

4. 600 Million Years Ago: The supercontinent Pannotia formed and quickly broke apart.

5. 300 Million Years Ago: The supercontinent Pangaea began to assemble. This is the most well-known supercontinent.

6. 200 Million Years Ago: Pangaea started to break apart, leading to the formation of the continents as we know them today.

You can find detailed animations and visualizations of these events through various geological and scientific resources online. If you want, I can look for specific resources or additional information on this topic. Just let me know!

Q: Show me a video animation 

A: Here's a video animation that shows the plate tectonic evolution over the past billion years [ 1 ]. It's a fascinating journey through Earth's geological history. 

Would you like to explore more about plate tectonics or any specific geological events?

Note: check here for a complete video since Earth's beginning c/w environmental factors (temperature, atmospheric composition,  length of day, evolution etc.).