If the reliable granular data is 100 years or so, and the core samples are known to be lacking granular indication… how a you prove that the spikes and dips are atypical?
This was a time period in which scientists actually improved these technologies and practices, and we stand on the shoulders of that progress. They were doing the best they could with what they had.
Geocentrism was also well on the way out 300 years ago.
My point is mostly that people in the past did some great work, and having weird beliefs didn’t diminish that. People in the future will think we were similarly clueless for all kinds of reasons. You just do the best you can with the information and environment you’ve got.
The part about measurements is fair (they weren’t standardized at the time), but the rest is irrelevant. The decision of whether or not to use data should be on the basis of its scientific rigour and veracity, not the scientist’s beliefs.