Dear Geologists! Is there any truth to the Saginaw Crater?

[Jennstorck]

I stumbled across an article about my home county of Saginaw,Michigan. Apparently Canadian scientists created a theory that the Saginaw Bay was created by an impact crater 500 Mil years ago. If that was correct, then it was the biggest impact crater in the US. Looking at the terrain, it looks plausible. However, I don't see much info out there about it and I would love to know how factual it is. Any thoughts?

 

Thanks ~ Jennifer

[studiot]

Hello Jenn and welcome.

 

I know nothing of your Saginaw event, and unfortunately our pet geologist who have know escaped nearly a year ago.

 

However I can tell you that meteor impact is associated with what is known as the iridium spike because meteors often contain the very rare (on Earth) element iridium.

 

Googling gives lots of information about more famous impacts and craters, but I haven't found any measurements at your location. Perhaps you should ask your local college or library?

[Acme]

I stumbled across an article about my home county of Saginaw,Michigan. Apparently Canadian scientists created a theory that the Saginaw Bay was created by an impact crater 500 Mil years ago. If that was correct, then it was the biggest impact crater in the US. Looking at the terrain, it looks plausible. However, I don't see much info out there about it and I would love to know how factual it is. Any thoughts?

Thanks ~ Jennifer

Can you cite what you read with a link or give more details?

 

The material I find is the work of non-geologists and puts the impact at ~800,000 years and hitting ice 1 to 2km thick. The hypothesized impact is suggested as the source of the Carolina Bays structure. I find no mainstream support for the idea however and the impact formation hypothesis for the Carolina Bays has been rejected by professionals.

 

Amateur work: The Saginaw Impact Manifold

 

Carolina Bays @ Wiki: >>Carolina Bays

...

Impact event

 

The cometary impact hypothesis of the origin of the bays was popular among earth scientists of the 1940s and 50s. After considerable debate and research, geologists determined the depressions were both too shallow and lacking in any evidence for them to be impact features. Reports of magnetic anomalies turned out not to show consistency across the sites. There were no meteorite fragments, shatter cones or planar deformation features. None of the necessary evidence for hyperspeed impacts was found. The conclusion was to reject the hypothesis that the Carolina Bays were created by impacts of asteroids or comets (Rajmon 2009).

 

A new type of extraterrestrial impact hypothesis was proposed as the result of interest by both popular writers and professional geologists in the possibility of a terminal Pleistocene extraterrestrial impacts, including the Younger Dryas impact hypothesis. It said that the Carolina Bays were created by a low density comet exploding above or impacting on the Laurentide ice sheet about 12,900 years ago.[4] However, this idea has been discredited by OSL dating of the rims of the Carolina bays, paleoenvironmental records obtained from cores of Carolina bay sediments, and other research that shows that many of them are as old as, or older than, 60,000 to 140,000 BP (Brooks et al.1996, 2001, Grant et al. 1998, and Ivester et al. 2002, 2003, 2004b).

...

[Jennstorck]

Thank you to you both for replying! The links I found were not necessarily credited sources, which is my reasoning for reaching out. (I didn't go much beyond the first few google searches!) I don't even know how I discovered the theory, I just find it very interesting based on the terrain of the area. That puts it into more perspective, Thanks again ~~

[Cintos]

The saginaw impact hypothesis is indeed a product of “citizen scientists”. Outsiders, if you wish. After 15 years of proposing such a scenario over two dozen GSA/AGU/LPSC meeting talks and posters, the GSA has published two chapters in a recently released Special Paper 553 to codify the hypothesis. The GSA expresses their confidence that the work is "addressing an embryonic, speculative, but observationally supported, new concept worthy of further investigation."

Chapter 23 is open access:  https://doi.org/10.1130/2021.2553(23)

and Chapter 24 (30 pages) is all of $9.95 to the GSA if you have no subscription available:  https://doi.org/10.1130/2021.2553(24)

Given its status as a simple hypothesis, feel free to continue the five decade-old search for the 788,000 year old (i.e., yesterday) Australasian Tektite astrobleme in Southeast Asia.