Tamiami Formation----A first report of microtektites from the shell beds of southwestern Florida

[Plantguy]

 

I saw this and thought it was pretty wild as I've been poking around in the Tamiami here in Florida for quite awhile--not sure I've ever noticed one.  I dont have full access to the pdf but heres the abstract and article in ScienceDaily. 

@MikeR

Regards, Chris 

https://www.sciencedaily.com/releases/2019/07/190722132520.htm

Cosmic pearls: Fossil clams in Florida contain evidence of ancient meteorite

Date:

July 22, 2019

Source:

Florida Museum of Natural History

Summary:

Researchers picking through the contents of fossil clams from a Sarasota County quarry found dozens of tiny glass beads, likely the calling cards of an ancient meteorite.

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Credit: © trahko / Adobe Stock

 

 

Researchers picking through the contents of fossil clams from a Sarasota County quarry found dozens of tiny glass beads, likely the calling cards of an ancient meteorite.

Analysis of the beads suggests they are microtektites, particles that form when the explosive impact of an extraterrestrial object sends molten debris hurtling into the atmosphere where it cools and recrystallizes before falling back to Earth.

They are the first documented microtektites in Florida and possibly the first to be recovered from fossil shells.

Mike Meyer was a University of South Florida undergraduate when he discovered the microtektites during a 2006 summer fieldwork project led by Roger Portell, invertebrate paleontology collections director at the Florida Museum of Natural History.

As part of the project, students systematically collected fossils from the shell-packed walls of a quarry that offered a cross-section of the last few million years of Florida's geological history. They pried open fossil clams, washing the sediment trapped inside through very fine sieves. Meyer was looking for other tiny objects -- the shells of single-celled organisms known as benthic foraminifera -- when he noticed the translucent glassy balls, smaller than grains of salt.

"They really stood out," said Meyer, now an assistant professor of Earth systems science at Harrisburg University in Pennsylvania. "Sand grains are kind of lumpy, potato-shaped things. But I kept finding these tiny, perfect spheres."

After the fieldwork ended, his curiosity about the spheres persisted. But his emails to various researchers came up short: No one knew what they were. Meyer kept the spheres -- 83 in total -- in a small box for more than a decade.

"It wasn't until a couple years ago that I had some free time," he said. "I was like, 'Let me just start from scratch.'"

Meyer analyzed the elemental makeup and physical features of the spheres and compared them to microtektites, volcanic rock and byproducts of industrial processes, such as coal ash. His findings pointed to an extraterrestrial origin.

"It did blow my mind," he said.

He thinks the microtektites are the products of one or more small, previously unknown meteorite impacts, potentially on or near the Florida Platform, the plateau that undergirds the Florida Peninsula.

Initial results from an unpublished test suggest the spheres have traces of exotic metals, further evidence they are microtektites, Meyer said.

Most of them had been sealed inside fossil Mercenaria campechiensis or southern quahogs. Portell said that as clams die, fine sediment and particles wash inside. As more sediment settles on top of the clams over time, they close, becoming excellent long-term storage containers.

"Inside clams like these we can find whole crabs, sometimes fish skeletons," Portell said. "It's a nice way of preserving specimens."

During the 2006 fieldwork, the students recovered microtektites from four different depths in the quarry, which is "a little weird," Meyer said, since each layer represents a distinct period of time.

"It could be that they're from a single tektite bed that got washed out over millennia or it could be evidence for numerous impacts out on the Florida Platform that we just don't know about," he said.

The researchers plan to date the microtektites, but Portell's working guess is that they are "somewhere around 2 to 3 million years old."

One oddity is that they contain high amounts of sodium, a feature that sets them apart from other impact debris. Salt is highly volatile and generally boils off if thrust into the atmosphere at high speed, Meyer said.

"This high sodium content is intriguing because it suggests a very close location for the impact," Meyer said. "Or at the very least, whatever impact created it likely hit a very large reserve of rock salt or the ocean. A lot of those indicators point to something close to Florida."

Meyer and Portell suspect there are far more microtektites awaiting discovery in Florida and have asked amateur fossil collectors to keep an eye out for the tiny spheres.

But no one will be recovering microtektites from the original quarry any time soon. It's now part of a housing development.

"Such is the nature of Florida," Meyer said.

Peter Harries of North Carolina State University also co-authored the study.

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Story Source:

Materials provided by Florida Museum of Natural History. Original written by Natalie van Hoose. Note: Content may be edited for style and length.

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Related Multimedia:

• Images of the the microtektites

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Journal Reference:

1. Mike Meyer, Peter J. Harries, Roger W. Portell. A first report of microtektites from the shell beds of southwestern Florida. Meteoritics & Planetary Science, 2019; DOI: 10.1111/maps.13299

 

 

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Christopher

 

 

Meteoritics & Planetary Science

Original Article

A first report of microtektites from the shell beds of southwestern Florida

Mike Meyer 

 

Peter J. Harries 

 

Roger W. Portell

First published: 06 May 2019

 

https://doi.org/10.1111/maps.13299

 

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Saw this an thought this was pretty wild as I've been poking around in the Tamiami here in Florida for quite awhile. 

Abstract

The Plio‐Pleistocene Upper Tamiami Formation (Pinecrest beds) of Florida is well known for its fossiliferous shell beds, but not for its extraterrestrial material. Here we report the first occurrence of tiny (~200 μm in diameter) silica‐rich microspherules from this unit and from the state. This material was analyzed using petrographic and elemental methods using energy dispersive X‐ray spectroscopy (EDS). The majority of microspherules are glassy and translucent in reflected light with some displaying “contact pairs” (equal‐sized micro‐spherules attached to each other). Broken microspherules cleave conchoidally, often with small internal spherical vesicles, but most lack any other evidence of internal features, such as layering. Using the EDS data, the microspherules were compared to volcanic rocks, microtektites, and cosmic spherules (micrometeorites). Based on their physical characteristics and elemental compositions these are likely microtektites or a closely related type of material. The high Na content in the examined material deviates significantly from the abundances usually found in micrometeorites and tektite material; this is enigmatic and requires further study. This material may be derived from a nearby previously unknown impact event; however, more material and sites are required to confirm the source of this material. Because of the focus on molluscan fossils in southwestern Florida shell beds, microtektite material has likely been overlooked in the past, and it is probable that these microspherules are in abundance elsewhere in these units and possibly throughout the region.

[fossilnut]

In a 5/17/19 TFF post "Plio-Pleistocene Microtektites......" Mike Meyer responded to his paper being posted to the Forum. HU_Paleo. I wrote to him about my find and he sent me a copy of the paper. Unfortunately I do not know how to post it to the Forum. If you would like it give me an email address and I believe I could send it that way to you. The back story and his persistence for 10 years is quite fascinating. They are extremely small so you would not see them unless you were sifting for forams-but perhaps you do that?

[Plantguy]

 

 

11 hours ago, fossilnut said:

In a 5/17/19 TFF post "Plio-Pleistocene Microtektites......" Mike Meyer responded to his paper being posted to the Forum. HU_Paleo. I wrote to him about my find and he sent me a copy of the paper. Unfortunately I do not know how to post it to the Forum. If you would like it give me an email address and I believe I could send it that way to you. The back story and his persistence for 10 years is quite fascinating. They are extremely small so you would not see them unless you were sifting for forams-but perhaps you do that?

Looks like I was napping when Paul posted the exact same thing a couple months ago.....thanks for the headsup! I'll msg Mike...

 

Regards, Chris