Thursday, November 26, 2020

New Jersey Stromatolites

While driving through northeastern New Jersey recently, my wife and I made a detour to see a rock outcrop I had read about but never seen. It's located in the middle of a private housing development in Hamburg, a small town in northwestern New Jersey. It's a beautiful rock outcrop but also geologically significant.


So what is it? The rock type itself is unremarkable. It's called the Allentown Dolomite by geologists. Dolomite, or dolostone, is similar to limestone - a common rock made of the mineral calcite or CaCO3. Dolostone, on the other hand, is composed of dolomite which is basically calcite with a bit of magnesium replacing some of the calcium - CaMg(CO3)2.

This particular dolostone was deposited between the Middle Cambrian to the start of the Ordovician Periods of geologic time - roughly 500 million years ago. At that time, North America was rotated 90° clockwise and what's now the east coast of the United States was the south coast and in subtropical southern latitudes. The area was under seawater and part of the continental shelf. You can see similar dolostones of the same age here in the Hudson Valley. They're called the Wappinger Group and are well exposed in eastern Dutchess County - here are some SUNY Ulster students examining the rock on Lime Kiln Road off I-84 near Fishkill.


When these rocks were being deposited as seafloor sediments, there was no life at all on land. The seas were teeming with marine invertebrates and even a few early chordates (eel-like animals) but no true vertebrates (fish) yet. But, for almost 3 billion years (yes, billion!), a very special group of organisms existed on the world's seafloors and without whom there would possibly be no animal life on Earth.

The fossils in the Hamburg, NJ outcrop are called stromatolites. They actually formed from single-celled bacteria called cyanobacteria (cyan referring to a blue-green color). Cyanobacteria were among the first organisms on Earth to develop the process of photosynthesis - something today we associate with green plants. Photosynthesis basically takes water and carbon dioxide, with the energy of sunlight, and creates glucose (a simple sugar) and oxygen as a waste product.

The early Earth's atmosphere had no oxygen. It did, however, have plenty of carbon dioxide. Mats of these cyanobacteria sat on the shallow seafloor and happily photosynthesized carbon dioxide into oxygen. For billions of years. Once oxygen levels built up enough, simple bacterial cells evolved (through a process called endosymbiosis) into more complex cells with a nucleus and organelles. This led, in short order (geologically-speaking) to multicellular life (metazoans) which used the oxygen now existing in the atmosphere.

Even though the individual cyanobacteria cells were microscopic, together they formed sticky mats on the seafloor which trapped sediments over time. The bacterial cells grew up on top of the sediments and trapped some more. Over and over again eventually forming finely laminated mounds of sediment. While the cyanobacteria themselves were not preserved, the layered mounds were and are called stromatolites. Stromatolite fossils are found in other places - here in New York you can also view them (about the same age as those in New Jersey) just east of Saratoga Springs at a place called Lester Park.


Stromatolites still exist today, although they are quite rare and found only in a few environments (most notably, Shark Bay in Western Australia). Half a billion years ago, in shallow subtropical waters of a continental shelf in what's now New Jersey, these stromatolites lived their lives.


Thank them - the oxygen they produced made it possible for our earliest ancestors to evolve.

Thursday, July 16, 2020

Geology of the Hudson Valley book

Finally!

Several years ago, I completed a manuscript for a book on the Geology of the Hudson Valley.  I developed this while teaching a summer field course of the same name at SUNY Ulster County Community College. I talked to a publisher and they liked the manuscript but wanted some more stuff for it that would take additional work and I didn't have all the figures I wanted, etc.

Then life intervened and the manuscript essentially got shelved. I used it for my classes but otherwise left it in manuscript form.

With COVID-19 putting everything on pause here in New York State back in March of 2020, I decided to get back to the manuscript, finish up all the illustrations, and publish with Amazon. Finished it up in June and it's now available to anyone interested.

It's written for the intelligent lay person who has an interest in the geologic history of the Hudson Valley. I promise that it is an interesting story.

Geology of the Hudson Valley: A Billion Years of History

Sunday, June 18, 2017

I'm on Pulse of the Planet

I obviously took a break from writing this blog. Eventful year, not in a good way, but that's life.

I did want to post a link to some podcasts that I participated in for Pulse of the Planet. The Executive Producer, Jim Metzner, lives close to where I teach. The podcasts are only two minutes long and on fossils.

According to their website: "Pulse of the Planet is broadcast over 252 public and commercial stations around the world and on the Armed Forces Radio Network, reaching over one million listeners weekly."

The different podcasts aired on four dates in May - 23, 24, 30, & 31. They can be found on the website here:

Tuesday, May 3, 2016

Rosendale Cement geology walk

For those of you who are local to the Ulster County area...

Have you ever wondered about those mines and kilns you see in the woods on the sides of the road between the towns of Rosendale and Kingston?

Want to learn more about their original purpose and history?

Are you familiar with the Delaware & Hudson (D & H) Canal?  Did you know that it's intimately associated with the 19th century Rosendale Cement industry?
Would you like to enter a room and pillar cement mine with a geologist who will explain what you're looking at (in layman's terms)?

Are you interested in how those rocks formed some 420 million years ago and what makes them special?

Did you know there are fossil coral reefs throughout our local area?

Did you know Rosendale Cement was once nationally famous?

Join me on Sunday, May 8 at 1:00 pm for a family-friendly geology walk at the Century House Historical Society in Rosendale, NY.  We'll see some kilns, remnants of the D&H Canal, coral fossils in outcrop, and go inside of the Widow Jane Mine.

A suggested $5 donation supports the all-volunteer, tax-deductible work of the Society in preserving the mine and grounds of the A.J. Snyder Estate historical property.