Coquina

 Brody Dymond

Coquina is a type of sedimentary rock composed mostly of  shells and fossils. They can vary in hardness, ranging from crumbly to more hard like cement. The word Coquina comes from the Spanish word for “cockle” and “shellfish.” 

Coquina can be found all over the world. It forms when shells accumulate in shallow water areas where waves break such as beaches, bars, and raised banks. They are usually formed from salt water organisms, though Coquina that contain freshwater organisms can also be found. Some of the organisms that form Coquinas include mollusks, brachiopods, trilobites, and other invertebrates. The shells in Coquinas are usually 2mm or larger. 

The specimen I studied was an Ordovician period coquina limestone from the Cincinnati Arch near Liberty, Indiana. This specimen was totally packed with fossils and fossil fragments, and is very hard. Fossils included bryozoans, brachiopods, horn corals, and other organisms.

The photos below were taken by Brody with a digital microscope. 

Sources

https://legacy.igws.indiana.edu/compendium/harrodsburg-limestone

https://en.wikipedia.org/wiki/Coquina

https://www.sandatlas.org/coquina/ 

https://www.volusia.org/residents/history/volusia-stories/plantation-ruins/coquina-floridas-native-stone.stml 

Brody Dymond is a 5th grade science lover with a sketchbook full of Earth facts and creepy creatures.

Pebble Pups Celebrate National Poetry Month

 Grand Traverse Area Rock And Mineral Club's

Pebble Pups Celebrate National Poetry Month

Pebble Pup Haiku Poetry

 

Inside is lightning
It looks kind of like copper
The shape of a state
—Brody Dymond
 
Metamorphic rock
It shines like a red diamond
If is very hard
—Brody Dymond
 
Gray coral with holes
It looks like a nest of bees
But it’s really not
—Brody Dymond
 
 

 
 

Pyramid Poems

 

Ice Age Mammoth

Large, hairy

Stomping, running, living

I wish they weren’t extinct, don’t you?

—Landon Chichester

Dinosaur

Big and fierce

Stomping, eating, fighting

I would like to see a dinosaur (if it didn’t eat me)

—Brody Dymond

 
 

Ocean

Cool and clear

Alluring, waving, and sailing

Source of marine life. Would you go swimming here?

—Elly Maher

 
 
 
 
The Diamonds
Hard and beautiful
Shinning and sparkling
Quietly
Hidden with sapphires
—Elly Maher
 
Fossil
Hard and rough
Hiding and asleep
Quietly
A fossil fish
—Landon Chichester
 
 

A Diamond
Clever and blue
Wanting and waiting
Awesomely
The hardest mineral
—Brody Dymond

 
 

Pachyteuthis densus

  by Brody Dymond

The Pachyteuthis densus was the fossil of a belemnite found in the Upper Sundance formation in Buffalo, Wyoming. Belemnites were a type of squid that lived many years ago. 

Image of the Pachyteuthis densus study specimen.
Photo date 2024 by B. Dymond.

Belemnites evolved to have a different way of protecting themselves from other types of marine animals. They were fast swimmers! Instead of having an external shell, their shell was internal, which helped them speed through the water to escape from predators. The internal shell of a belemnite is the part that was fossilized. There are three parts of the internal shell: the pro-ostracum, the phragmocone, and the rostrum. 

A group of belemnites was called a battlefield. The average size of the belemnites when they were alive was 30 - 50 centimeters long. Belemnites could be found worldwide in shallow waters close to the shore. Belemnites ate small fish, other marine animals, and possibly other belemnites. 

The belemnite’s tentacles did not have suction cups like squid today. Instead, they had curved hooks. While squids today have eight arms, the belemnites had ten arms and on each arm were 30-50 curved hooks. They used the hooks on their arms to capture and eat small marine animals. While some squids today are the same size as belemnites, some squids can get much bigger. For example, Colossal Squid can get up to 14 meters (46 feet) long! 

The Belemnites went extinct at the end of the Cretaceous Period roughly 65.5 million years ago. They died around the same time as the dinosaurs.  

A concept of what Pachyteuthis densus looked like
when it was alive. Artwork by B. Dymond.