Forum User Names

[BeachBill]

Interesting thread. Thanks, Guitar George.

From my user name I'm sure you can tell where I live and my first name.

[Swamp Yankee]

Originally Posted by Silurian

Ordovician comes from the Silure's northern neighbours the Ordovices.

The Cambrian period comes from Cambria, the latin for Cymru (Wales).

add two more items to my list of "didn't know" items

I have a hunch that the geologist(s) that named these periods was (were) English.

[Rockysdad]

My Boston Terrier is named Rocky, I'm his dad........ clever eh?

[Inyo]

Originally Posted by Silurian

Ordovician comes from the Silure's northern neighbours the Ordovices.

The Cambrian period comes from Cambria, the latin for Cymru (Wales).

Originally Posted by Swamp Yankee

add two more items to my list of "didn't know" items

I have a hunch that the geologist(s) that named these periods was (were) English.

You would be correct.

An added insight into the naming of geological periods is that for "ages" geologists formally recognized NO Ordovician Period. There was the Cambrian (oldest period of the Paleozoic Era, which began about 542 million years ago), and right after that the Silurian.

Problem was, there was a big bunch of time missing. There were loads-o'-rocks exposed that just couldn't be definitively placed into either the Cambrian or the Silurian Period. Much debate ensued.

Then, a most paleontologically perspicacious fellow named Charles Lapworth began to recognize that a critter long overlooked, and summarily discarded as a fossil "nothingburger," as it were, could be utilized as an invaluable asset to help constrain the geologic age of the mysterious stratigraphic interval situated between the older Cambrian and younger Silurian-age rocks.

And, that paleontologic organism was none other than the graptolite--an extinct marine, colonial hemichordate (somewhat resembling the modern pterobranch) that secreted a skeleton originally composed of either collagen or chitin. They commonly dominate what's customarily called a "graptolitic shale facies," where prodigious numbers of their preserved remains occur alongside a rather depauperate fauna consisting of Caryocaris crustaceans and brachiopods.

Through a most fortuitous stratigraphic coincidence, graptolites just happened to reach their zenith of adaptive speciation (greatest numbers of genera and associated species) during that missing expanse of geologic time now called the Ordovician Period.

So, by painstakingly identifying the unique suites of graptolites always associated ONLY with those rocks that could not be officially categorized as either Cambrian or Silurian (the Silurian produces its own special kinds of graptolites), Charles Lapworth eventually settled the argument once and for all, erecting a brand new period that occurred between the Cambrian and the Silurian--the Ordovician Period, officially created in 1879, which according to the most recent stratigraphic calibrations happened between 488.3 and 443.7 million years ago.

Below is a fossil graptolite I collected a number of years ago from the lower Ordovician Al Rose Formation, which is one of California's premier graptolite-bearing geologic formations. Numerous Al Rose graptolite remains--including the specimen shown here--have been naturally coated by the iron mineral limonite ((FeO(OH)), giving the extinct hemichordates a distinctive "golden" glow, an aesthetically pleasing visual contrast with the dark-greenish shales upon which they have been preserved.

This is a "wishbone-shaped" (or tuning fork, if you will) graptolite called scientifically, Didymograptus protobifidus (it occurs exclusively in the Ordovician Period). The actual living colonial animals would have resided inside those saw blade-like notches (such structures in graptolites are called thecae) situated along the interiors of the two "prongs"--technically termed stipes. In paleontological terminology, the entire graptolite colony is referred to as a tubarium (or, rhabdosome in older literature).

[Tico]

Sometimes when I'm drunk I try to order Mexican food.

[saxonblue]

Originally Posted by Rockysdad

My Boston Terrier is named Rocky, I'm his dad........ clever eh?

My Australian Cattle Dog is called Saxon & he is blue (well, mostly )