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https://www.theclergyletterproject.org/Resources/apr2024newsletter.html#2

The Clergy Letter Project newsletter

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Peloid ooid grainstone with a large ooid nucleated on an intraclast containing very fine particles of quartz sand. Two generations of calcite cement mostly fill interparticle pores. Blue epoxy fills relict and dissolution pores. Field of view 1 mm, calcite is stained red. Smackover Formation, South Alabama. Images of thin rock slice viewed with a microscope.

Another view with more dissolution porosity and calcite replacing dolomite rhombs (white crystals partly replaced by red). 2.5 mm wide.

Large intraclast containing multiple ooids, which is on top of numerous small ovoid pellets (partially dolomitized; partially dedolomitized). 2.5 mm.

View with two intraclasts centered on relict pore. 2.5 mm.

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International Ichnofabric workshop 16A: held via zoom, and focused on younger faculty, students, and other early-career scientists. Registration & abstract-submission portals are open. The meeting will be November 13-14. https://www.uwa.edu/iiw16

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This blog must be starting to feel neglected. This weekend, as with so many recent weekends, I am working hard to catch up with various tasks, many of them self-imposed. I am working on a paleontology/sedimentology project with two other people, a study of a small carbonate buildup in North Alabama, which is more than 300 million years old. One of us, not me, plans to point count a large number of thin sections. Point counting is when you use a grid to randomly select points on a surface. At each place where the lines cross you identify what's there, and the result is a tabulation indicating which things are common and which others are less common or absent. Well, Doug can't count points unless he knows what he's looking at. We have been working on a dictionary, so to speak, of what he might find. One of the fossils in this rock is a microscopic alga (?). There may be several different species represented, and I have spent the last few days measuring, counting, and examining specimens of this critter so that we can define what we should call these little guys when they show up in the crosshairs. I think it's a lot of fun to figure this stuff out, but the early stages, lots and lots of measuring and counting, require loud rock music so that I can stay focused. Bands like Mott the Hoople and the Velvet Underground are particularly useful for this purpose. I will show you guys some pictures later, in case you are interested, once I figure out what's going on.

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The International Ichnofabric Workshop 16A, a virtual workshop, has been rescheduled for November 13-14, which is a weekend. The abstract and registration deadline is now September 30. This will allow more time for people to prepare abstracts in what has been a very difficult year. The registration fee is $40. The website will be live in about a week, and will include information about how to register and how to submit abstracts. Those who have already submitted abstracts will not need to resubmit them.

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 More pictures of the Mississippian microbial reef in North Alabama.   

 

 Broken and slightly displaced spheroidal microfossil in microbial thrombolite; likely cause is compaction. Image 1 millimeter in long dimension.

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 More pictures of the Mississippian microbial reef in North Alabama.  

Micropelletal thrombolite (microbial, clotted) "framework illustrating highly variable microfabric. Scale 1/5 millimeter.

 

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 More pictures of the Mississippian microbial reef in North Alabama.  

 

A microconchid (encruster) only a millimeter across itself encrusted by a microbial critter (arrow) in a Mississippian microbial reef in North Alabama.

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More pictures of the Mississippian microbial reef in North Alabama.  

 

A busy part of the reef, consisting of microbial thrombolitr (originally nonlaminated lime mud, which is commonly clotted or pelletal). B=fragment of a bryozoan, A="Problematicum A," a tubular fossil, S=a cement-filled shelter void (note semicircular single-chambered foraminiferan on the roof, left of "S"), lower arrow=multiple microfossils encrusting the bryozoan, left arrow=more on the top side, upper left arrow=a former void now filled with miscellaneous very fine particles (there's another on the lower right). Scale 0.5 millimeters. The reef grew in shallow warm marine water close to the shoreline, perhaps in a lagoon.

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More pictures of the Mississippian microbial reef in North Alabama. 

 

Thrombolite (microbial carbonate) with voids filled with micropelletal cement (P) separated by a dark pillar of thrombolite. White arrow points to calcite-filled fracture. Long dimension 2.5 millimeters.

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 More pictures of the Mississippian microbial reef in North Alabama. 

 

These show parts of the same fenestrate (grid-like) bryozoan. White arrowheads point to sections through parts of the grid. White areas beneath the fossil were sheltered by it and kept open (shelter porosity). Later, calcite crystals grew to fill all the open space. Stitched together from photos with vertical dimensions of 2.5 millimeters.

 

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More pictures of the Mississippian microbial reef in North Alabama.

 

 
Dense clotted thrombolite (dT) and loose (lT) forming framework of reef. Voids filled with coarse calcite cement (F) or micropelletal calcite cement (upper arrow). Fossils include fenestraye bryozoa (B) and microconchids (lower arrow). 2.5 millimeters in long direction.

 

 

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Yay! I took more pictures of the Mississippian microbial reef in North Alabama.

 Oblique cut through a large burrow filled with micropelletal calcite cement. Surrounded by thick burrow wall constructed of similar, but denser, material. One millimeter in long direction.

 

 

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Fossils of the Black Belt 21 (2021) — a Hands-on Field Workshop

The Geological Survey of Alabama and the University of West Alabama take the lead in presenting Fossils of the Black Belt 21, the latest in a long-running series of annual field paleontology workshops for teachers. This year's workshop will focus on paleoecology and paleoenvironmental analysis, the science of understanding environments and living things of the distant past.

The workshop will be in two parts. In part one, Alabama paleontologists will present the geologic history of West Alabama, the origin and nature of the chalk, as well as methods and aims of paleoecology and paleoenvironmental analysis. These lectures will be prerecorded and delivered via Zoom. They will be viewable beginning a few days before the field workshop, and you can watch them whenever it's convenient. The field workshop will take place on Tuesday October 12 on a large chalk outcrop near Selma. You will divide into groups and, by examining the chalk and its fossils, develop hypotheses about the origin of the chalk. This field activity will be conducted using social distancing, and masks will be required. Depending on the nature of the health crisis at that time, and the possibility of severe weather, the field activity may need to be canceled. If this happens, we will mail the guidebook, Jim Lacefield's book, and all other handouts, to registrants. The Zoom lectures will be provided even if the field workshop is canceled.

We will meet at Harrell Station, a productive Cretaceous fossil site on private land near Selma, Alabama. The workshop will take place on Tuesday, October 12 2021. The cost is $28 for this one-day workshop. This includes lunch and a vast array of science-education goodies, including the famed book by Jim Lacefield, Lost Worlds in Alabama Rocks (a $25 value).

To register, please contact Dr. David Kopaska-Merkel, 205-246-9346, dkm@gsa.state.al.us.

 

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Microbial reef (T=thrombolite) containing cement-filled shelter voids (C) and an odd ooid (circular object in center). Ooid nucleus is spheroidal microfossil stuffed with quartz silt (white) and lime mud (dark). Long dimension of field of view 1 millimeter, Mississippian, North Alabama.

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Section through a fragment of a large fenestrate bryozoan. These critters made stony skeletons resembling wire mesh. The lozenge-shaped linked light areas are cuts through seven successive "wires" of the skeleton. This fossil is embedded in a microbial reef; scale at bottom is 0.2 millimeters. These bryozoans were most common in warm shallow marine water.Mississippian, North Alabama.

 

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Beautiful ooid surrounded by calcite crystals. Ooids are spheres, formed when seafloor sand-size sediment is rolled regularly, typically by tides. Concentric layers form in warm water with the right chemistry.Ooid cortices usually form around nuclei, in this case a fine quartz grain. Viewed with cross-polarized light, long dimension of field of view = 1 millimeter, Mississippian, North Alabama.

Part of a study of a very small fossil reef made by a consortium of corals and diverse microbes. The ooid was washed in from a nearby shoal during a storm, and overgrown by the reef.

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Echinoderm fragment (E) with cement overgrowth in optical continuity (syntaxial, S) embedded in microbial reef (thrombolite, T). Field of view 1 millimeter in long dimension, Mississippian, North Alabama.

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Bryozoan (B) encrusted by tiny microbial critter (arrow), which made a series of cells with dark walls, now filled with white calcite. Field of view 1 millimeter in long dimension, Mississippian, North Alabama.

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 Chunk of micropelletal thrombolite (I), a piece of a nearby microbial reef, in fine sediment containing scattered fossils and quartz sand grains (Q). Image area 1 millimeter high, Mississippian, North Alabama.