Welcome to TheNaughtyNautilus Seaway of Fossil Ammonites
Take a peak under the ancient Pierre Shale Seaway and discover the many beautiful iridescent Ammonite Fossils & Minerals.
See us at Hill Top Gem & Mineral in Ashland Plaza Mall
"Museum Quality" Assemblage of Cretaceous Age Fossils & Septarian Minerals
Fluorescent Ammonite fossils occur in large concretions in the 73.5-million-year-old Pierre Shale Formation in Meade County, S.D. The Specimens are often preserved with their very colorful and iridescent shells. The fluorescent Golden Barite & Yellow Calcite specimens from this location are some of the best in the world.
Golden Barite
Superb orthorhombic crystals of the mineral Barite occur in cavities in large septarian concretions in the ancient Seaway exposed along the Cheyenne River Basin. The Barite crystals can be yellow, amber, root beer or wine colored; are quite transparent; and are often implanted on yellow calcite and associated with Ammonite fossils. The Barite Fluoresces and Phosphoresces brightly under short wave UV light.
Placenticeras meeki & ornamental intercalare
Placenticeras meeki and intercalare were the Queens of Ammonite fossils. These coiled, horned and iridescent beauties grew up to three feet in diameter, with the Females being three times larger than the males. Using new preparation methods, we can now remove the specimens completely from the matrix and mount on a designer stand. The shell minerals calcite and aragonite, fluoresces greenish-white under UV light.
Scaphites
Many smaller sized ammonite fossils from the Scaphite Family, Genus Hoploscaphites, occur within the Cheyenne River Basin. These include nodosus, brevis, furnivali & quadrangularis. Most have the beautiful mother-of-pearl shell in reds, greens, & pastels. The shell minerals Calcite & Aragonite fluoresce under UV light. Jeletzkytes is now a junior subjective synonym (Landman et al., 2010).
Baculites
Many distinct species of uncoiled Ammonite fossils , called Baculites occur within the Cheyenne River Basin. They range in age from 69 to 74 million years old. They include; grandis, baculus, eliasi, jenseni, reesidei, cuneatus & compressus, are found in groupings, and often display both the mother-of-pearl minerals and suture patterns.
Minerals of North America
The Minerals in this section are mostly from North America. They represent special specimens, unique localities, passionate personal interests and/or have been self-collected and prepared.
Nautilus
Nautiloids, Eutrephoceras dekayi & nebrascensis; these beautiful carnivorous Cephalopods had a thicker shell than their relatives, which enabled them to withstand deeper ocean depths and pressures, and most importantly, defense from hungry marine predators.
Partials, Special Items, Calcite, Whewellite & Wholesale Flats
In this group we have prepared a number of specimens that allow us to creatively "Show Case" some of the more unique, rare and scientifically interesting aspects of each of these amazing Fossils and Minerals. Wholesale Calcite Flats now available. YellowCalcite.com coming soon.
"Climate Change" in the Pierre Seaway 73 Million Years Ago
Explore our Educational Sets. During the Cretaceous Period 65-145 mya, Earth was at its warmest temperatures and highest CO2 concentrations. A worldwide greenhouse condition existed, the Polar Poles were covered in delta forests and sea level was 250 feet higher than today. Dinosaurs ruled the land and swimming reptiles cruised the vast oceans in search of their favorite food, the Calamari of the Sea, Ammonites!
Fox Hills Formation Ammonites
Above the Pierre Shale lays the Fox Hills Formation, the youngest (69 myo) marine sediments in South Dakota. These amazing, iridescent ammonite fossils, have been a treasure for Ammonite collectors since the early 1800s.
Fluorescence & Phosphorescence
The minerals Barite, Calcite, Whewellite and numerous Ammonite Fossils from this locality fluoresce and occasionally phosphoresce a strong yellowish-white, greenish-white and purplish-white respectfully. The Elk Creek, South Dakota location is one of the "Top 50" Mineral & Fossil localities in North America.
Cheyenne River Basin, South Dakota
The Cheyenne River and associated Tributaries cut through this 69-74 million-year-old seabed, exposing large concretions filled with extinct Ammonites such as Placenticeras, Baculites & Scaphites, Nautilus and the giant clam Inoceramus. Over two dozen different Cephalopods and six associated Septarian Minerals occur at this amazing locality.
Seattle Mineral Market Show May 17th & 18th, 2025
The "Cheyenne River Basin" Assemblage of Cretaceous Age Fossils & Minerals
The "Cheyenne River Basin" Assemblage of Cretaceous Age Fossils & Minerals
The "Cheyenne River Basin" Assemblage of Cretaceous Age Fossils & Minerals
Please return regularly to see our seasonal updates as we continually collect, prepare and add new specimens. Have fun learning about the last significant Climate Change Event through the study and enjoyment of the "Cheyenne River Basin" Assemblage of Cretaceous Age Fossils and Septarian Minerals from South Dakota.
"2021" South Dakota Mineral Collecting Trip
The "Cheyenne River Basin" Assemblage of Cretaceous Age Fossils & Minerals
The "Cheyenne River Basin" Assemblage of Cretaceous Age Fossils & Minerals
This 2021 Barite and Calcite Collecting Trip was one of our best ever! We collected many fluorescent Barite & Calcite Specimens. The color and quality of the Crystals were stunning. Many of the "Best of the Best" piece's will be at Tucson, Arizona in February 2022, at several of the CollectorsEdge.com locations, including the Main Show.
"2022" South Dakota Fossil Ammonite Collecting Trip
The "Cheyenne River Basin" Assemblage of Cretaceous Age Fossils & Minerals
"2022" South Dakota Fossil Ammonite Collecting Trip
What an amazing group of Cephalopods we collected this season! Including many large and colorful Placenticeras meeki and intercalare, Scaphites, Baculites, and the giant clam, Inoceramus. We will be adding new Specimens to our website daily as we prepare for our March 18th & 19th, 2023 Show in Medford, Oregon.
Ammonites - "Iridescence vs Suture Patterns"
Ammonites - "Iridescence vs Suture Patterns"
"2022" South Dakota Fossil Ammonite Collecting Trip
The shell of the Ammonite is comprised of alternating layers of Aragonite, about the thickness of the wave-length of visible light, which refracts and reflects light, like passing through a prism. The chambered portion of the shell is divided by partitions called septa. The contact of these septa with the external shell produces a distinct suture pattern.
Globidens dakotensis -mosasaurs
Ammonites - "Iridescence vs Suture Patterns"
Crater Rock Museum 2023 Craterrock.com
"The shell crushing Mosasaurs" Globidens dakotensis was a very specialized mosasaurs with round, ball shaped teeth and a short, heavily built skull. It fed on clams and other shellfish that lived on the bottom of the shallow sea that covered South Dakota and much of the middle of North America during the Cretaceous Period.
Crater Rock Museum 2023 Craterrock.com
Ammonites - "Iridescence vs Suture Patterns"
Crater Rock Museum 2023 Craterrock.com
In 2023 we donated a beautiful Golden Barite on Calcite Specimen to the Crater Rock Museum in Central Point, OR. That specimen was from a portion of a large Concretionite, with Ammolite from a 73.5-million-year-old Placenticeras meeki. Also on loan are a number of other colorful Cephalopods we find exposed on Elk Creek, S.D.
Concretionites.com Meteorite Impact Map
TheTalentGallery.art & Wine Room
Summer 2024 Excursions Elk Creek, South Dakota
Recent discoveries show a link between meteorite impacts within the Cretaceous age Pierre Seaway of South Dakota, and large concretion formation in the Seaway over a 12-million-year period. Four scientifically dated impact sites, within the Western Interior Seaway, have been age correlated to match four large septarian concretion and fossil ball horizons exposed along the shale banks of Elk Creek, South Dakota.
Summer 2024 Excursions Elk Creek, South Dakota
TheTalentGallery.art & Wine Room
Summer 2024 Excursions Elk Creek, South Dakota
By studying these Concretionites, their size and fossilized contents, we can literally piece together a detailed picture of those fateful impacts 70 mya and their aftermath. This knowledge not only enriches our understanding of Earth's history but also helps us better prepare for potential future meteorite impacts including climate change. Large Placenticeras meeki and complete Concretionite seeking a Western Interior Seaway Exhibit space.
TheTalentGallery.art & Wine Room
TheTalentGallery.art & Wine Room
TheTalentGallery.art & Wine Room
Visit our new Gallery location in downtown (111 Talent Ave.) Talent, Oregon. See our new discoveries, and seasonal updates of our fossil and mineral specimens. Enjoy tasting local wines and culinary delights as you casually tour the Gallery and learn about the many passions of our member Artists. Achieving the impact of art through natural mineral & fossil specimens is the goal, not a competition, but a convergence.