Tag Archives: Fossil

Geo-pic of the week: Amber

Amber_croppedandcolored

Pictured above are several polished samples of the fossil amber; the sample in the top left is unpolished. 

Amber is the fossilized resin of a tree.  As you can see, some of the wood of the trees got preserved with the resin, which gives this amber a wood-grain appearance .  These pieces were collected near Malvern, Arkansas, where amber is found in beds of lignite: a soft, low-grade coal.

People have prized amber since pre-historic times for its beauty and its scent.  It continues to be popular today in the production of jewelry and perfume. 

Geopic of the week: Archimedes

archimedes pitkin 3-2 for geopic trip

Pictured is the remains of an animal, called an Archimedes, that flourished in Arkansas about 350 million years ago.  At that time, Arkansas was covered by a warm tropical sea, and invertebrate organisms such as Archimedes lived by straining tiny food particles from the sea water.   Though similar filter-feeders exist today, this particular one is extinct.

In this photo, we see a cross section of the animal; the screw-like pillar supported it from the center and delicate, barely visible lattices whorled around the screw – in cross section they look like ribs of a fish bone (see picture).  Those were the filters the animal used to trap food.  Because the lattices were brittle, they were rarely preserved with the fossil, which makes this specimen exceptional.

The limestone pictured is from the Pitkin Formation in northern Arkansas.

For more views of Archimedes click here

Geopic of the week: Conical Nautiloid

Nautiloid

 

Above is the fossil remains of a marine organism called a conical nautiloid.  These were common in the shallow sea that covered Arkansas during much of the Paleozoic era 540 to 250 million years ago.  This one was collected from shale of the Pitkin Formation in pieces over a period of years as it weathered slowly out of the outcrop.

Conical nautiloids are extinct now, but they are the evolutionary forerunner of the sleeker, more deft coiled nautiloids that thrive in the ocean today.  They were marine predators, akin to squid, except that they had a shell.  They used their shells for protection, buoyancy, and as a means of propelling themselves through the water by squeezing a stream of water out of the empty chambers like a jet.

It’s common to find conical nautiloid fossils that are smaller than a pinky finger; however, some have been unearthed in Arkansas that were as long as 8 feet.

Geopic of the week: Fossiliferous limestone

archimedes

This is a picture of weathered fossiliferous limestone of the Pitkin Formation.  It was taken in a quarry near Batesville Arkansas.  The picture displays fossil remains of two common aquatic animals that lived in the shallow sea covering northern Arkansas between 360 – 320 million years ago. 

The screw-shaped remains are parts of bryzoans; they are commonly referred to as Archimedes screws.  The nut-shaped fossils- which also resemble rolls of smarties candies- are the remains of crinoids, commonly called sea-lilies, which have living relatives in the ocean today.  Both animals lived by attaching themselves to the sea floor and filtering food, such as plankton, from the ocean water.