Possible Jurassic Marine Site? Advice Needed

[Ged]

I'd like to start by saying I am a complete novice. But I have always been very interested in prehistoric life and paleontology. After recently getting back into the hobby I researched my local area. I have an interest in marine reptiles and was hoping to find a mostly untouched site with the possibility of finding some. Reviewing various bedrock maps and surveys I found one site that might work. I am aware I will need to review permitting and regulations before doing anything but for now i'd like to just identify areas with potential. I was wondering if anyone would help me assess it given the information I have found. Site description:

 

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Name

Jurassic marine rocks

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Geologic age

Devonian to Late Jurassic

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Lithologic constituents

Major

Sedimentary > Clastic > Sandstone (Bed)Feldspathic to volcaniclastic

Metamorphic > Metasedimentary > Metaclastic > Slate

 

Minor

Igneous > Volcanic (Pyroclastic)

Metamorphic > Metasedimentary > Metaclastic > Argillite

Incidental

Sedimentary > Clastic > Mudstone (Bed)

Metamorphic > Metasedimentary > Metaclastic > Quartzite

Sedimentary > Clastic > Conglomerate (Bed)

Sedimentary > Chemical > Chert (Bed)

Igneous > Volcanic > Mafic-volcanic > Andesite (Flow, Volcaniclastic)

Sedimentary > Clastic > Siltstone (Bed)

Sedimentary > Carbonate > Limestone (Bed)

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Comments

Primarily argillite, slate, feldspathic to volcaniclastic sandstone, and pyroclastic rocks. Includes some rocks of Paleozoic age

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Here is my thinking:

 

The geologic age of the rocks ranges from the Devonian to the Late Jurassic. Marine reptiles, such as ichthyosaurs and plesiosaurs, first appeared in the Late Triassic and continued to evolve and diversify throughout the Jurassic. Therefore, rocks from the Late Jurassic are particularly promising for finding marine reptile fossils.

 

The rock types present at this site also suggest a good chance of finding fossils. A large portion of the site consists of sedimentary rocks such as sandstone, mudstone, conglomerate, siltstone, and limestone. These rock types are known to often contain fossils, as they form from the accumulation of sediment, which can include the remains of organisms. Additionally, the presence of marine sedimentary rocks such as limestone is a strong indicator of a past marine environment, where marine reptiles would have lived.

 

Furthermore, although there is some metamorphic rock present, such as slate and argillite, these are low-grade metamorphic rocks that have undergone only mild metamorphism. This type of metamorphism is less likely to destroy fossils compared to the high-grade metamorphism that produces rocks like gneiss and schist which is common in other formations in the area. The presence of volcanic rocks and pyroclastic suggest some volcanic activity, which can sometimes be associated with excellent preservation conditions if organisms are rapidly buried by ash.

 

I am trying to find pictures of the rocks in the area but it is a bit challenging. I'll update the thread if I can find some decent ones.

Please let me know your thoughts on this location from a purely geological perspective.

 

Thank you,

-Ged

[patelinho7]

I think you have done your homework! There is not much left to add. I won’t say how productive this site may be as I don’t know enough about Late Jurassic sites, I’d recommend looking at posts on here about the Jurassic Coast of UK. You may find information that may aid you on your own search. 
 

What I will say, however, is that you should go ahead and move forward with your search! You’ve done a good job assessing the area yourself, and the next step is to start scouting for fossils! If you are wrong, it’s part of the process. If you are right, great!

[Ludwigia]

I don't at all mean to discourage you, but sedimentary rocks don't automatically contain fossils. Actually, most of them don't, proportionally speaking. It would certainly make sense if you could first of all come up with a list of fossils for this site. Comparisons to similar sites in the area of Spain you are referring to could also be helpful, The types of deposits on the Jurassic Coast of the UK or other such foreign ones could vary radically from yours, so comparisons to them probably wouldn't bring much other than general info. That's also quite a range to have to explore, from Devonian to Late Jurassic. That's an awful lot of Periods to work through. In the end, you just need to get into the field, explore the area, find the sedimentary outcrops, determine their age and get down to excavating if it seems worth the effort.

[FranzBernhard]

7 hours ago, Ged said:

Site description:

This "site" contains nearly everything. How big is that site?

Franz Bernhard

[Ged]

The description I gave is for the overall formation however I am looking at one area in particular. There is a stream that cuts through the middle of the formation with exposed rock which looks sedimentary from what I can see. I have provided an image of it to see what you guys think. I also researched fossils in the area. Near this specific site two marine reptiles have been found (thalattosaurs) as well as an ichthyosaur in the greater area. On top of this many ammonites and shells have been found making me believe there is a high chance this specific site contains fossils.

 

there are also higher limestone outcrops which may be a good place to look. I have provided a picture of those as well.

 

 

 

Edited July 5, 2023 by Ged

[FranzBernhard]

Looks all good! Check out that river and that ridge! Nothing compares to ground work!

Good luck!
Franz Bernhard

[Ludwigia]

I agree with Franz. But be patient. You might be lucky and find something right away, but you might not find anything all day , so be prepared to return several times in order to cover the entire area. I would suggest you try first of all to determine whether the sedimentary layers are laid down horizontally or at an angle and then try to follow them upwards perpendicularly in order to familiarize yourself with their constitution and to determine which layers might be fossiliferous. Scouring the ground at the bottom of the cliffs could also produce evidence of things which have fallen from above.

[Ged]

Thank you everyone for your thoughts. I'm quite busy this month and this area is a bit of a drive from me but when I have the chance I will have to check it out. I'll make sure to update this thread with any findings or lack there of.