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MSA MEETING PROGRAM & PLACE
Franciscan Renewal Center, (Piper Hall),
October 15, 2026 @ 7.30 pm Arizona time
"Do Earth’s Orbital Cycles
Control Where Crystals Form?"
Presented by
DAVID TIBBITS
* Please bring refreshments to share.
* MEETING will be (In-Person and Zoom).
OCTOBER
MINERAL OF THE MONTH
QUARTZ
(Okay to bring 1-2 examples)
The Mineralogical Society of Arizona is pleased to welcome one of our own, David Tibbits, as presenter for our October 15 program "Do Earth’s Orbital Cycles Control Where Crystals Form?" Join us at Piper Hall on campus of Franciscan Renewal Center, Scottsdale, for an evening exploring the surprising links between planetary motion and mineral formation.
Can the wobbles of Earth's orbit, tens or hundreds of millions of years ago, determine where we find crystals today? This talk starts with the basics. David Tibbits introduces the Milankovitch cycles: orbital eccentricity, axial tilt (obliquity), and precession. These cycles pace Earth's climate by changing how much sunlight reaches the surface, and where and when it arrives.
Climate cycles can become rock cycles, preserved as rhythmic layers in sedimentary sequences. This has made geologists partners with astronomers. Computer models of planetary orbits become unreliable beyond about 50–60 million years because of chaotic behavior, so ancient sedimentary records provide the ground truth for reconstructing Earth's orbital history in deep time.
The Newark Supergroup is one of the world's finest examples of cyclical sedimentary rocks. Between about 233 and 197 million years ago, rift lakes formed as the supercontinent Pangaea began to break apart. Their deposits alternate between red mudstones laid down in dry intervals and black, organic-rich shales from deep lakes during strong monsoon phases. In those black shales, decaying organic matter fueled bacteria that produced sulfide, which combined with iron to grow pyrite crystals. Therefore, in these rocks, the climate rhythm directly controls the mineralogy.
With that foundation, the talk turns speculative: where else might an orbital heartbeat be hiding? In the Herkimer Diamond district of New York, cyclic layering in the Cambrian Little Falls Dolostone may influence where crystal-bearing cavities occur. In the Franklin Marble of New Jersey, famous for its fluorescent minerals, Tibbits asks whether the repeated franklinite seams could be a climate signal. If the ores formed on an ancient seafloor, as some models propose, rhythmic changes in ocean chemistry might have left their mark even through a billion years of metamorphism. These are open questions. The goal is to learn how to recognize cyclicity, then imagine where we might go looking for it next.
Mark your calendars for a program by one of the Mineralogical Society of Arizona's rising stars!
David Tibbits is a PhD student in Geology at Rutgers University and a Department of Defense National Defense Science and Engineering Graduate (NDSEG) Fellow. His passion for minerals has fueled his academic career thus far. He earned a B.S. in Earth and Environmental Engineering from Columbia University. His research focuses on the relationship between sedimentary environments and the minerals which later form in them, with field areas in the Newark Basin, the Colorado Plateau, the Little Falls Dolostone, and the Franklin Marble. He is also an educator at the Sterling Hill Mining Museum.
David joined the Mineralogical Society of Arizona (MSA) at age 16 and was honored as the 2018 MSA Junior Rockhound of the Year. As an MSA Legacy Life Member, he has remained an active presence in the collecting world ever since. His personal collection centers on worldwide thumbnail minerals and the minerals of Peru.
His competitive exhibiting has earned numerous honors at the Tucson Gem and Mineral Show®, including the 2025 Walt Lidstrom Memorial Trophy for the single best mineral specimen in competition and the 2026 Paul Desautels Memorial Trophy for the finest crystalized mineral exhibit in competition, as well as the Kay Robertson Educational Display Award from Friends of Mineralogy for his collaborative “Earth's Timekeepers” exhibit at the 2025 Tucson Gem and Mineral Show®.
Recognized for his leadership within the mineralogical community, he has been invited to serve as Competitive Exhibits Chairman for both the Tucson Gem and Mineral Show® and the Phoenix Heritage Mineral Show. He currently serves on the boards of Friends of Mineralogy (National), the Geological Association of New Jersey, and the Flagg Mineral Foundation.
The Mineralogical Society of Arizona is honored to welcome David for this special program. We are grateful for his many contributions to thumbnail mineral collecting and competition, his leadership within the greater mineral collecting community, and his enduring support of our society.
Cyclical lacustrine (lake) sediments from the
Lockatong Formation (217-222 Ma).
Photo from Paul E. Olsen.
~20 kyr Precession Cycle is modulated by a ~100 kyr Eccentricity Cycle which is modulated further by a 405 kyr grand eccentricity cycle and further still by a ~1.8Myr cycle. This is based on semi-quantitative measurements of drill cores from the Newark Basin Coring Project
Graphic from Olsen and Kent 1996.
Examples of “Depth Rank” semi-quantitative
proxy of lake depth in the Newark Basin.
Core Example from Olsen 1996.
Meeting starts at 7.30PM Arizona time.