About a month or so ago I received a sample of "microfossil dirt" from the Gene Autry Shale Member of the Golf Course Formation, which crops out in Johnston County, Oklahoma, in the Ardmore Basin. The Golf Course Formation is of Lower Pennsylvanian (Morrowan) age. The sample contains abundant foraminifera, although it is not rich in numbers of species. There are also some good ostracodes. Preservation is quite variable: a few specimens are essentially perfect, but most show varying degrees o
Diatoms are monocellular organisms which contain chlorophyll, and manufacture their own food in the same manner as plants, through the process of photosynthesis. They are one of the major producers of the Earth's oxygen. Their long geological history makes them very useful in the correlation of sedimentary rocks, and they are of equal value in reconstructing paleoenvironments. They are remarkably common everywhere there is any water at all! I have studied fossil marine diatoms for many years
I have always enjoyed looking at ostracodes of the family Trachyleberididae, for their varied and complex structures, and interesting ornamentation. The family seemingly first appeared in the Middle Jurassic, became abundant during the Cretaceous, and remains abundant in the seas of today.
About a month ago, in an exchange of microfossil material with an Italian friend, I received a sample of material from the Coralline Crag of southeastern England, a well-known and extensively studied Middle
In picking out my sample of microfossils from the Middle Pliocene Coralline Crag Formation, Suffolk, England, I noted a few fragments of what appeared to be a species of the ostracode genus Pterygocythereis, a particularly spiny-looking genus of the family Trachyleberididae. I assumed it to be Pterygocythereis jonesi (Baird, 1850), the common species of the North Sea. As luck would have it, while finishing the picking of the last bit of the sample, up popped a complete valve, in almost perfect
One of the problems I experience in studying microfossils is that of orienting a specimen so that crucial characters are visible. An example: for identification it is often necessary to check the shape of the tooth in the aperture of taxa in the family Hauerinidae. The tooth can be long or short, plain or bifid, present or missing, etc. The aperture is on the end of the test, so it isn't possible to look into it when the test is lying flat -- which it always does when the test is lying in a t
In a number of recent posts to the Forum I have complained incessantly about my inability to locate microfossils here in my home state of Arizona. Well, no more! A sample that I processed over the weekend produced a few nice ostracodes, and I am optimistic about finding more. The locality is the well-known Kohl Ranch site, just northeast of Payson, Arizona, reputed to be the best spot for collecting invertebrate fossils in the state. The material comes from the "beta" member of the Naco Form
In this second entry I would like to show well-preserved specimens of two ostracodes: the very long-ranging taxon Amphissites centronotus (Ulrich and Bassler, 1906), and the Permian taxon Cornigella parva Kellett, 1933. The former belongs in the family Amphissitidae, while the latter is placed in the family Drepanellidae.
This specimen is a relatively late instar, but not fully mature, as final instar specimens average about 50% larger. The species is very easy to reco
I recently received some samples of washed residues from various shales and marls noted for their microfossil content. One of the best of these is from southern Kansas, of Permian (Wolfcampian) age, from the Council Grove Group, Beattie Limestone Formation, Florena Shale Member. The sample is amazingly rich, and I have recovered numerous species of Foraminifera and Ostracoda, as well as many nice bryozoan fragments. In this blog entry I would like to show one of the more interesting microfoss
In 1958, Louis S. Kornicker and John Imbrie wrote a brief paper on the holothurian sclerites of the Florena Shale in which they described four species. I have found 3 specimens of one of these, Microantyx permiana Kornicker and Imbrie, 1958. Two of these specimens were badly broken, but one is in fair condition.
The sclerites are wheel-shaped with short spokes, and the openings between the spokes are roughly triangular. In this dorsal view we can see a distinctive tr
The Lomita Marl Member of the San Pedro Formation is a well-known source for Middle Pleistocene marine fossils, and its beautifully preserved molluscan fauna has been treasured by fossil fanatics for decades. There are outcrops in the city of San Pedro, California, although many of the "classic" localities have been destroyed by urban development. It is well-exposed in the Lomita Quarry, located in the Palos Verdes Hills northwest of the city. It has been dated at 400,000 to 570,000 years ago
Planktonic Foraminifera are particularly important in biostratigraphic studies and correlation, as they are ubiquitous in marine deposits, and evolve rapidly. They first appeared in Middle Jurassic time, and thus have a long geological history. There are many phylogenetic and correlational studies available, and their rapid evolution makes them exceptionally useful as temporal markers, or guide fossils.
I am currently looking at planktonic Foraminifera from a deep-water sample that
Since the upload of Part 1 succeeded, I'll now offer up Part 2, a look at two interesting taxa from the family Globigerinidae. This family contains most of the taxa that we associate with the idea of "planktonic forams", perhaps due to our familiarity with the "globigerina oozes" that form a significant part of the floor of the modern world oceans.
Globigerinoides ruber (d’Orbigny, 1839) is one of the two “red” species of globigerinids, as the specific epithet indicates. It is well
While picking specimens of Foraminifera from the Taylor Marl, of the Texas Cretaceous Gulfian Series, I found several fragments of a taxon that I could not recognize. However, today I found a nearly complete specimen of what is obviously the same organism.
Frondicularia christneri Carsey, 1926 does not look much like a typical member of the genus. The overall shape of the test is fairly normal, but the sutures form a rather unusual pattern, and they are raised above th
In this entry I would like to show two of the commonest Foraminifera from my sample of the Florena Shale. The most common forams by far are the fusulinids, but as these are not identifiable without thin sections, they will have to wait until I'm equipped to deal with them. Excepting the fusulinids, the commonest foram is Globivalvulina bulloides (Brady, 1876):
This taxon has an enrolled biserial structure, and in spiral view it typically exhibits one large and two smal
When I was preparing my previous entry on nodosariid forams from the Pecan Gap Chalk, I originally included a specimen that I had identified as a member of the genus Dentalina. This identification was incorrect, and I edited the entry to remove that specimen. Here it is again, with what I hope is the correct identification!
The genus Strictocostella is a member of the family Stilostomellidae, and this species is illustrated in Frizzell's "Handbook of Cretaceous Foramin
I have recently been studying a sample of washed residues from the Pecan Gap Chalk Formation of the Cretaceous Gulfian Series, from an outcrop in the vicinity of Austin, Texas. Most of the Gulfian formations are richly fossiliferous, and the Pecan Gap is no exception. It has abundant, well-preserved microfossils, particularly forams and ostracodes. In this blog entry I would like to show some forams of the family Nodosariidae, which I find of particular interest. All belong to the genus Fron