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Geology/stratigraphy - transgressively


What's real definition of the word "transgressively" in sentence  "mezosoic rocks lay transgressively over paleozoic"? is the term "transgressively" always related to sea transgression or transgresively means something else (like structural term: concordont, erosive, discordant,...)

Thank you


Hi Tom,
Good question.  "Transgression" means exceeding boundaries or limits.  In geological terms that "exceeding boundaries" means an unconformable change from marine (above) to non-marine (below) sediments.  

In geological terms, transgression is always taken to mean the spread of seas over the land.  So, your sentence "Mesozoic rocks lay transgressively over Paleozoic" would mean that the Mesozoic rocks were deposited in a marine environment that covered the terrestrial rocks, due to sea level rise or land subsidence.

If the sentence used "regressively" that would have indicated the lowering of sea level resulting in terrestrial over marine sediments.  The confusion might have come from the fact that the sediments usually have unconformable boundaries.

Hope this helps.


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C. Robert Reszka, Jr.


I can answer any general geology question (rocks, minerals, stratigraphy, geomorphology etc.). My expertise is in the geology of the Michigan Basin, PreCambrian, Paleozoic and Recent. I can answer questions concerning mining and petroleum exploration and production and the laws concerning those activities. I can also answer questions concerning stratigraphy of the Michigan Basin. I will also answer questions about mineral and rock collecting in the Basin. I won`t be able to answer many specific questions on hydrology, geophysics or geochemistry. I may be able to answer very general questions in those venues.


I have been working for the State of Michigan for 36 years as a Geologist and a Resource Analyst. I have experience with Subsurface Geology and Petroleum Geology, mining in Michigan, and Sand Dune Mining and Protection issues.

Michigan Basin Geological Society

Decade of North American Geology.
Bedrock Geology of Michigan

BS Wayne State University

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