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Marine Concretion on a Copper Fragment

By Jay, on October 2nd, 2011%
Kure Copper Side Lighted for Relief - photo by J. Sents, 2011

Earlier in the Summer on a trip to Kure Beach, North Carolina, I just happened to find a small piece of copper in the Coquina Rocks.  In a nutshell, the Coquina Rocks are essentially a partially submerged outcrop of sedimentary rocks found near the southern end of Kure Beach near the Fort Fisher Recreational Area.  More on Coquina Rocks later…

I was walking along, carefully maneuvering through the Coquina Rocks during during Maximum Ebb Tide this one day. Many people apparently scout the micro-lagoons formed in the cracks and crevasses of the rocks during Low Tide looking for sharks teeth. I really don’t care for sharks, let alone their teeth but these people do. I looked down and saw a gold-red glint with a hint of bright green. Below are some photographs of what I found:

The rule is for scale. It is a standard engineer rule with 1/10th-inch graduations. What is the green stuff? Well that would be considered a marine concretion. First, the environment here is [or has been] oxygenated enough that copper and copper alloys would corrode and oxidize. Chemically unweathered copper is a golden, reddish-brown in most cases. An oxidized copper surface is usually black . . . → Read More: Marine Concretion on a Copper Fragment

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Imbrication

By Jay, on August 23rd, 2011%
Clast-supported imbrication of a shell bed on a beach (photo by J. Sents - 2011)

Imbrication is one of those geologic phenomenon that occur and are recorded at a scale that we can readily see. What is it? Imbrication is the orderly, overlapping arrangement of flattened or sub-spheroidal grains in the direction of flow. Flow in this case is usually water flow, but it can be other types of fluid flow [ice, wind, and even metamorphism]. Grains are commonly sand- to gravel-sized particles. However, with other types of fluid flow or metamorphism, these can often be large-scale or even microscopic.

For the purposes of this discussion, we’re going to focus on water flow and gravel-sized particles. Below is a diagram from the University of Montana Geology Department [2011] depicting varying degrees of imbrication:

Three varying degrees of pebble imbrication with respect to flow direction. (UMT, 2011)

On a recent trip to Wrightsville Beach in Wilmington, North Carolina, I came across this shell bed. Can you see the imbrication in the photograph? I put my sunglasses in for scale, and some background into the scene so you could see the orientation of the beach with respect to the Atlantic Ocean:

Clast-supported imbrication of a shell bed on a beach. (photo by J. Sents – . . . → Read More: Imbrication

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Happy Memorial Day

By Jay, on May 30th, 2010%

Thanks to those that have served in the Armed Forces.  You and your families’ sacrifices to America are appreciated.  I hope you all have a wonderful day tomorrow.

As for me, I’m going to try and get out tomorrow and do a little local geology.  It just rained pretty heavy here at the end of last week, so now that the stream levels have fallen back to normal flow there is a place north of Raleigh that I’d like to go to and take some photographs of some sand and gravel deposits.

UPDATE: I did get up to Lassiter Mill and found some good stuff; however, I’ve got some weather coming and may have to suspend computer activities until the lightning storm passes.

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