Fossil prospecting combining geological maps and google earth

[Dimitris]

Hello all!

I am trying to find some new areas around my place. So far there is not a single reference for fossils in this place, so I need somehow to choose some spots to prospect.

There are some common rules like road cuttings, rivers & creeks that cut into the formations, abandoned quarries etc, all of which are beautifully presented in this post.

However, I need to know how to take advantage of all information provided in a geological map.

 

Which place would you check first for fossils?

There are faults, borders between two geological ages etc.

 

What are those numbers next to this symbol that looks like T (sometimes inversed)? 

*As per the legend this T represents foliated and stratified rocks.

 

Additionally, on the legend there is description of the rock composition of each formation.

Which of those would you consider to check first?

Sandstones, clay, sandstone clay, marl. I guess these must be my best candidates while volcanic and metamorphic deposits like amphibolite and tuff should be excluded.

 

Using Photoshop, I managed to create a picture that combines the geological map onto the actual map.

First I need to have both maps at the same scale, then I create two layers in Photoshop. My main layer is the geologic map and the actual map is placed upon the other.

Using the opacity, I can change the transparency of the layer and like this I am able to pin point the exact location of interest.

 

Here is the place of interest

 

Looking forward to hearing your comments and ideas on prospecting.

Happy hunting 

[DPS Ammonite]

Look for rocks that are marine. Also, find papers that describe the rocks in that area. The papers often will describe the rocks in more detail than maps and usually mention fossils. Once you know the formation names then use the geological map. Do the rock descriptions give the formation name for each unit or does it just describe the rock type for each unit? I can’t read Cyrillic.

[Dimitris]

5 minutes ago, DPS Ammonite said:

Look for rocks that are marine. Also, find papers that describe the rocks in that area. The papers often will describe the rocks in more detail than maps and usually mention fossils. Once you know the formation names then use the geological map. Do the rock descriptions give the formation name for each unit or does it just describe the rock type for each unit? I can’t read Cyrillic.

Unfortunately I have found papers that describe only the alluvial deposits of the Sophia basin and some information concerning the orogenesis of the surrounding mountains.

My point of interest in this area is only upper Cret. and there is not a named formation, just rock type. All upper Cretaceous is describe like "Sandstone-marl unit (alternation between sandstone, marls and another type of sandstone I cannot translate/understand).

 

On the middle and upper part of the map, there are some familiar formations, which I have explored in other areas of the country. 

Sorry for the Cyrillic. The coloration of the units follows the international standards (Green Blue Pink) for Mesozoic. Then its Permian (brown) Carboniferous (light grey Upper Paleozoic (white) Undefined? volcanic rocks (red) Devonian (brown) Silurian (olive oil green). These are more or less the main formations before Paleogene era.

[EMP]

4 hours ago, Dimitris said:

Hello all!

I am trying to find some new areas around my place. So far there is not a single reference for fossils in this place, so I need somehow to choose some spots to prospect.

There are some common rules like road cuttings, rivers & creeks that cut into the formations, abandoned quarries etc, all of which are beautifully presented in this post.

However, I need to know how to take advantage of all information provided in a geological map.

 

Which place would you check first for fossils?

There are faults, borders between two geological ages etc.

 

What are those numbers next to this symbol that looks like T (sometimes inversed)? 

*As per the legend this T represents foliated and stratified rocks.

 

Additionally, on the legend there is description of the rock composition of each formation.

Which of those would you consider to check first?

Sandstones, clay, sandstone clay, marl. I guess these must be my best candidates while volcanic and metamorphic deposits like amphibolite and tuff should be excluded.

 

Using Photoshop, I managed to create a picture that combines the geological map onto the actual map.

First I need to have both maps at the same scale, then I create two layers in Photoshop. My main layer is the geologic map and the actual map is placed upon the other.

Using the opacity, I can change the transparency of the layer and like this I am able to pin point the exact location of interest.

 

Here is the place of interest

 

Looking forward to hearing your comments and ideas on prospecting.

Happy hunting 

 

Look for road crossings over creeks/rivers, bends in roads, and mountainous/hilly terrain. When roads are constructed they are built in a way to minimize constant ups and downs, and the best way to do this is by "cutting" hills and "filling" valleys to achieve a more level rise/descent. These cuts are more frequent in hilly/mountainous terrain where the roads would otherwise be too steep to be safe to cross. They are also great for fossil hunting, as they can expose potentially hundreds of feet of rock from different geological units (and plus they tend to be newer exposures, and not completely overgrown, and easy to access). 

 

Creeks and other moving bodies of water are powerful erosional forces and can cut through geologic layers, potentially exposing fossiliferous beds. In areas with hard bedrock, creeks tend to form generally steep valleys which expose potentially fossiliferous rock, and also increases the likelihood of roadcuts. With creeks, however, do note that the immediate deposits around them (like the floodplains and levees) are usually more recent deposits and cannot bare fossils by definition.

 

Old quarries are also good places to look. Faults can be hit or miss as some faults can actually burry fossiliferous layers, or downfault them below unfossiliferous ones. 

 

As for what geological formations to look for, sedimentary is almost always the way to go (rarely some metamorphic and igneous units can preserve fossils, like some slate or ash beds). Limestones, sandstones, shales, siltstones, etc. Dolomites, conglomerates, breccias, and others tend to be more unfossiliferous even though they are sedimentary, so be aware of that. 

 

 

[FranzBernhard]

7 hours ago, Dimitris said:

What are those numbers next to this symbol that looks like T (sometimes inversed)? 

*As per the legend this T represents foliated and stratified rocks.

This indicates Strike and dip (link to wikipedia) of the rock layers / bedding planes. Number may indicate the dip angle:

Franz Bernhard

[Dimitris]

17 hours ago, EMP said:

 

Look for road crossings over creeks/rivers, bends in roads, and mountainous/hilly terrain. When roads are constructed they are built in a way to minimize constant ups and downs, and the best way to do this is by "cutting" hills and "filling" valleys to achieve a more level rise/descent. These cuts are more frequent in hilly/mountainous terrain where the roads would otherwise be too steep to be safe to cross. They are also great for fossil hunting, as they can expose potentially hundreds of feet of rock from different geological units (and plus they tend to be newer exposures, and not completely overgrown, and easy to access). 

 

Creeks and other moving bodies of water are powerful erosional forces and can cut through geologic layers, potentially exposing fossiliferous beds. In areas with hard bedrock, creeks tend to form generally steep valleys which expose potentially fossiliferous rock, and also increases the likelihood of roadcuts. With creeks, however, do note that the immediate deposits around them (like the floodplains and levees) are usually more recent deposits and cannot bare fossils by definition.

 

Old quarries are also good places to look. Faults can be hit or miss as some faults can actually burry fossiliferous layers, or downfault them below unfossiliferous ones. 

 

As for what geological formations to look for, sedimentary is almost always the way to go (rarely some metamorphic and igneous units can preserve fossils, like some slate or ash beds). Limestones, sandstones, shales, siltstones, etc. Dolomites, conglomerates, breccias, and others tend to be more unfossiliferous even though they are sedimentary, so be aware of that. 

 

 

Thanks for the valuable advice.

Looks like that the majority of the area I am interested in, is result of volcanic activity, but for some small areas that seem to worth checking.

My main problem is that its hard to locate the formation on the actual map. These geological maps were drawn before 1990, when Bulgaria was part of Soviet Union, therefore many roads that exist now were agricultural land back then. This is the reason I am picking locations and using Photoshop, I create two layers, Google map version against old geological map.

 

Concerning the type of rocks I agree, though sandstones has been quite plentiful to me a couple of times. So all in all, I should target mostly limestone? What about chert?

14 hours ago, FranzBernhard said:

This indicates Strike and dip (link to wikipedia) of the rock layers / bedding planes. Number may indicate the dip angle:

Franz Bernhard

Thanks Franz! Helpful link, I read it. Indeed the number must indicate the dip angle.

[cmwilson101]

smart idea to layer your maps in Photoshop!  

[cngodles]

Limestone is excellent for marine fossils. Shales immediately above and below are

also common areas to find. Sandstones are tricky. They do preserve limited fossils, but are difficult to work with. The only sandstone fossil I’ve found of any value was an impression of a Carboniferous tree trunk/bark.

 

Limestone is formed in warm shallow seas. These are typically full of life and all of the shells, teeth, etc eventually rest in the sediment and later form rock. Limestone is mostly made of the remains of sea creatures, however it can be mixed with silt/sand as well. There are freshwater limestones as well, from lakes.

 

Also, I’ve learned that geological maps are not always accurate. They don’t often physically measure every formation boundary and make educated guesses for portions. They are good guesses, but can be off by many meters. They consider elevation and any syncline/anticlines in the area. Also any faulting.

 

Local research is very helpful. The person I correspond with from neighboring West Virginia exclaims that he is literally writing the book on local fossil fauna because nobody has studied his particular area.

[Dimitris]

 

On 17/1/2021 at 3:09 AM, cngodles said:

Limestone is excellent for marine fossils. Shales immediately above and below are

also common areas to find. Sandstones are tricky. They do preserve limited fossils, but are difficult to work with. The only sandstone fossil I’ve found of any value was an impression of a Carboniferous tree trunk/bark.

True, limestone is the king. I dislike shales because all those I have searched tend to have fragile fossils with poor preservation. As per the sandstones, I do not have much experience there. I have encountered them two times. First one gave some nice pectens and barnacles (Zanglean) and the other some amazing Clypeasters. The fossils were sparse, but those found were very nicely preserved.

I had the advantage to prospect in a pit mine, so found some stuff in piles while the others, I excavated directly from the formation. The second method was harder because I had to dig the wall hoping I would find something. Soon as I found the "height" of the formation that was fossil ferrous, my odds were improved.

On 17/1/2021 at 3:09 AM, cngodles said:

 

Limestone is formed in warm shallow seas. These are typically full of life and all of the shells, teeth, etc eventually rest in the sediment and later form rock. Limestone is mostly made of the remains of sea creatures, however it can be mixed with silt/sand as well. There are freshwater limestones as well, from lakes.

 

Also, I’ve learned that geological maps are not always accurate. They don’t often physically measure every formation boundary and make educated guesses for portions. They are good guesses, but can be off by many meters. They consider elevation and any syncline/anticlines in the area. Also any faulting.

 

Local research is very helpful. The person I correspond with from neighboring West Virginia exclaims that he is literally writing the book on local fossil fauna because nobody has studied his particular area.

Can't agree more on the inaccuracy of the maps. I hunt in two countries, Greece and Bulgaria.

Greek geological maps are very rare and hard to find them online. Some of them are sold by the Hellenic Survey of Geology and Mineral Exploitation, but they cost a lot like 70$ for one map 1:50000

The Bulgarian ones are available online and free, however they are outdated. They were drawn before 1989, thus many roads/rails are not depicted. Some formations are guesses as you say, based on a core of drilling.

 

Given the situation, my best chance looks like being the combination of those old geo maps with google maps

Nevertheless, thank you for your input!