Eriksson's Oldest Lithified Dune Barberton [39525]

Eriksson’s Dune from Barberton Mountains, South Africa

Eriksson’s Dune, a remarkable geological formation in the Barberton Mountains of South Africa, provides a unique window into our planet’s ancient past. The tidal marks on this ancient dune, dating back 3.22 billion years (Ga), reveal the fascinating dynamics of the Earth-Moon system from the earliest chapters in "deep time."

Earth-Moon System: A Dynamic Dance

During the early Earth, around 3.22 Ga, our planet spun rapidly, completing a day in about 13 hours. The Moon orbited Earth in a low orbit, much closer than it does today. As Earth rotated, its gravitational pull on the Moon created tides. These tidal forces caused friction, gradually transferring angular momentum from Earth’s rotation to the Moon’s orbit. Over eons, the Moon’s orbit expanded, moving farther from Earth, while Earth’s rotation slowed down due to tidal effects.

Layered Sandstone-Shale

The alternating layers of sandstone and shale in Eriksson’s Dune reveal tidal cycles. Researchers found a periodicity of 15 layers, corresponding to variations in tidal strength during neap (weaker) and spring (stronger) tides. Assuming mixed tidal systems, two cycles were either 30 lunar days (dominant semi-diurnal tides) or 30 sidereal days (dominant diurnal tides).

Earth-Moon Distance

Using Kepler’s third law and conservation of angular momentum, scientists estimated that the Earth-Moon distance 3.2 billion years ago was approximately 70% of today’s value. During this period, Earth’s solar day was around 13 hours.

Specimen Details

Size: 21mm X 19mm X 10mm
Weight: 4.6 grams
This specimen ships with a Certificate of Authenticity, tag, and information about the specimen. Macro pictures are 3X magnification and are of this exact specimen's rind and front. Faint layering can be seen in this 3.22 Ga specimen.

Legal Collection

This material was legally and professionally collected. Now you have a limited opportunity to add this phenomenal geological specimen to your collection!