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Coryander

unknown mix of shells

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Coryander

What kind of mix is this?

It is solid (I mean I can not tear it apart with my nails).

Photos are from both sides.

I found it on the beach of Vila Real de Santo António, Algarve, Portugal.

Thank you.

 

 

 

 

IMG_0845.JPG

IMG_0846.JPG

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ynot

This type of rock is called a conglomerate.

It is made from sand, gravel and shells that have been cemented together by mineral precipitation.

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Max-fossils

Wow very cool! 

I know that you can find similar stuff in Zeeland (south-west NL). 

The little black rocks are possibly "glauconite". 

 

Otherwise, for the species it's very hard to say what is what without seeing the hinge, but I see stuff from Cardiidae, and stuff from the Astartidae/Veneridae families. 

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WhodamanHD

I don’t know much in the subject but it looks like you might have an inoceramid.

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Coryander

I couldn't find much concerning "glauconite" or " inoceramid".

 

This is the first fossil with this configuration that I found. I have a lot of other different conglomerates, like these:

 

 

 

 

other type.JPG

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ynot
5 minutes ago, Coryander said:

I couldn't find much concerning "glauconite" or " inoceramid".

 

This is the first fossil with this configuration that I found. I have a lot of other different conglomerates, like these:

To My understanding, "glauconite" is a clay mineral and I do not see it in Your rock.

The pieces added are more of a sandstone or siltstone with shell fossils.

Conglomerates are made from larger grains of rock. (Must have pebble sized or larger grains)

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WhodamanHD

Here’s Wikipedia’s picture of Inoceramus vancouverensis, an inoceramid (IE within the family Inoceramidae)

42A3E600-5EAA-46DC-A89C-4F1AFC170F7E.jpeg

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Plax

his sediments are possibly Miocene and almost for sure at least neogene. Too young for incoceranmus but not for Chione. The rock is loosely called "coquina" rock. I don't see any glauconite grains but there may be some phosphatic elements. Most of the dark bits look like dark shell. Max may have a better eye for seeing dark green though!

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ynot
6 minutes ago, Plax said:

The rock is loosely called "coquina" rock.

My understanding of cocquina is it is made primarily of shells and shell fragments with little (if any) sediments.

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Plax

I dare say most of the folks reading this would say the rock was coquina or shell hash or shell rock. Most wouldn't chose the word "conglomerate" as a first choice but it is generally correct also. Perhaps "very shelly conglomerate" would fit it as a technical definition. The wikipedia definition for coquina would even probably fit this rock though as many of the finer bits look like ground shell material. I do see a few quartz  pebbles in there though.

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ynot
On 8/27/2018 at 12:28 PM, Plax said:

I dare say most of the folks reading this would say the rock was coquina or shell hash or shell rock. Most wouldn't chose the word "conglomerate" as a first choice but it is generally correct also.

(On the first rock only) I agree with this wholeheartedly! But would add that most People on this site are more paleontology oriented rather than geologically.

 

From wiki...

Coquina (/koʊˈkiːnə/) is a sedimentary rock that is composed either wholly or almost entirely of the transported, abraded, and mechanically-sorted fragments of the shells of molluscs, trilobites, brachiopods, or other invertebrates.

 

Conglomerate (/kənˈɡlɒmərɪt/) is a coarse-grained clastic sedimentary rock that is composed of a substantial fraction of rounded to subangular gravel-size clasts, e.g., granules, pebbles, cobbles, and boulders, larger than 2 mm (0.079 in) in diameter.

 

Having more of a geology background I still go with a conglomerate.

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DPS Ammonite

Since there is a significant (more than 20%) amount of sand grains (less than 2 mm) the rock should be called a sandy conglomerate with shells or a shelly sandy conglomerate. 

 

See the ternary diagram in: 

https://books.google.com/books?id=zl4L7WqXvogC&pg=PA9&lpg=PA9&dq=sandy+conglomerate&source=bl&ots=l3FlPUcvvf&sig=QUfmaxERdMOXJnyP5ZCAD1Hvju4&hl=en&sa=X&ved=2ahUKEwielPvP65DdAhUMK3wKHaTzAAoQ6AEwF3oECAYQAQ#v=onepage&q=sandy conglomerate&f=false

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Plax
16 hours ago, ynot said:

(On the first rock only) I agree with this wholeheartedly! But would add that most People on this site are more paleontology oriented rather than geologically.

 

From wiki...

Coquina (/koʊˈkiːnə/) is a sedimentary rock that is composed either wholly or almost entirely of the transported, abraded, and mechanically-sorted fragments of the shells of molluscs, trilobites, brachiopods, or other invertebrates.

 

Conglomerate (/kənˈɡlɒmərɪt/) is a coarse-grained clastic sedimentary rock that is composed of a substantial fraction of rounded to subangular gravel-size clasts, e.g., granules, pebbles, cobbles, and boulders, larger than 2 mm (0.079 in) in diameter.

 

Having more of a geology background I still go with a conglomerate.

I stand by what I said previously. No geologist would look at this rock and state it was "conglomerate" without at least the qualifiers stated by DPS Ammonite. No fossil collector or probably even a paleontologist would simply call this conglomerate. I didn't check your web references but doubt that anything was depicted there that looked like the original posts pics.  "Conglomerate" is a far to general term for these rocks.

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Plax
15 hours ago, DPS Ammonite said:

Since there is a significant (more than 20%) amount of sand grains (less than 2 mm) the rock should be called a sandy conglomerate with shells or a shelly sandy conglomerate. 

 

See the ternary diagram in: 

https://books.google.com/books?id=zl4L7WqXvogC&pg=PA9&lpg=PA9&dq=sandy+conglomerate&source=bl&ots=l3FlPUcvvf&sig=QUfmaxERdMOXJnyP5ZCAD1Hvju4&hl=en&sa=X&ved=2ahUKEwielPvP65DdAhUMK3wKHaTzAAoQ6AEwF3oECAYQAQ#v=onepage&q=sandy conglomerate&f=false

Shell whether sand sized or almost complete make up the bulk of this rock by volume to me. I see a few quartz pebbles. The point I've been trying to make is that this isn't simply "conglomerate" and would certainly not be identified as such by anyone looking at it. Link below of conglomerate pics

https://www.google.com/search?q=conglomerate&client=firefox-b-1&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiC_crcw5LdAhUDZd8KHQvCBFkQ_AUICigB&biw=1784&bih=1312

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DPS Ammonite

Look at figure 4 on page 51 for a picture of a shelly, sandy, pebble conglomerate.

http://www.thebookshelf.auckland.ac.nz/docs/Tane/Tane-37/5 Fossil communities.pdf

 

The OP's rock is not a classic pure conglomerate because it has added sand and shells. Neveless, if you only had one word to describe it, you would say that it is a conglomerate.

 

@Plax Did you have another name in mind for the rock? In one word, what would you call the rock?

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Max-fossils

Inoceramids and/or Chione shells are not found in the European Miocene. 

 

On 8/27/2018 at 4:18 PM, Max-fossils said:

but I see stuff from Cardiidae, and stuff from the Astartidae/Veneridae families. 

These are some of the options, and it's gonna be incredibly hard to identify which genera/species they belong to. We could only guess, but even then our guesses would be most likely inaccurate (and therefore pretty much pointless). 

 

Let's just say that the Miocene was an "apogee" for the bivalves and gastropod all over western Europe, which at the time was mostly covered by shallow seas. Mollusks thrived in this environment, and therefore hundreds of different species evolved. All of the families were so vast then (and many still are now). So, taking in mind this incredible diversity, if you would want to properly ID a bivalve or a gastropod, you would need a well-preserved complete specimen, where both the hinge/mouth-opening are visible and the sculpture is recognizable. Seeing that all the shells in the rock of the OP are all fragments, and on top of that the hinge isn't visible for most of them, IDing them down to genus or species is going to be very difficult and time-consuming. Plus the "results" have a low chance of being accurate. And that is why I have retained myself to just pointing towards the possible families :) 

 

About the glauconite, I really just said that because I've heard that it is mostly black and appears in Miocene sediments, so I thought there could be some in here. But my geology knowledge is nowhere near as high as yours, so I'll leave the geology talk to you guys :P 

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Max-fossils
On 8/27/2018 at 8:47 PM, Coryander said:

 

other type.JPG

 

The bottom two seem to have Turritella shells in them (as in from the family Turritellidae. Could be from the Turritella genus, but not sure).

The top one has some kind of bivalve (can't see well from pic due to angle). 

 

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Plax
1 hour ago, DPS Ammonite said:

Look at figure 4 on page 51 for a picture of a shelly, sandy, pebble conglomerate.

http://www.thebookshelf.auckland.ac.nz/docs/Tane/Tane-37/5 Fossil communities.pdf

 

The OP's rock is not a classic pure conglomerate because it has added sand and shells. Neveless, if you only had one word to describe it, you would say that it is a conglomerate.

 

@Plax Did you have another name in mind for the rock? In one word, what would you call the rock?

I stand by what I said originally and am sorry I brought it up to be honest with you. This has descended into semantics. Single words such as "rock" or conglomerate don't describe what was posted here. This is my last word on the subject and I apologize for taking up so much space on the subject.

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DPS Ammonite

No apologies needed. It is a cool rock that I would have picked up.

 

Rock naming gets a little complicated when you mix a lot of different things together. It is hard to estimate the percentages of each component. Experts often disagree on exact names.:)

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Coryander

Thank you all.

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