Middle Marker Chert Oldest Sedimentary Unit [219 g ~ 3.47 Ga]

Middle Marker Chert – Barberton Greenstone Belt

Step back nearly 3.5 billion years to one of Earth’s earliest sedimentary horizons — the Middle Marker Chert, a fine-grained, carbon-rich rock preserving the faint biological textures of the Archean.

Geological Context

Stratigraphy & Setting

Located at the base of the Hooggenoeg Formation (Onverwacht Group) within the Barberton Greenstone Belt, Mpumalanga, South Africa.

Geochronology

Detrital zircon dating places the succession at approximately 3.472 billion years, among the oldest sedimentary successions on Earth.

Distinctive Features for "Clotted Chert"

Definition of “Clotted Chert”

Clotted chert is a carbonaceous, fine-grained silica rock characterized by irregular, patchy dark domains (“clots”) dispersed within a microcrystalline quartz matrix. The clots typically reflect kerogen-rich microdomains formed by early microbial activity and/or diagenetic redistribution of organic matter, rather than the continuous laminae seen in classic stromatolites.

• Texture: Mottled, patchy “clots” of organic carbon within chert; locally wavy or crinkly micro-laminations.
• Origin: Biosedimentary/diagenetic—microbial mats and organic gels silicified early, then altered during burial.
• Diagnostic contrast: Unlike stromatolites (continuous, organized laminae), clotted chert shows discontinuous, blob-like carbon clusters.
• Significance: Serves as an early biosignature style in Archean settings, recording microbial carbon fixation prior to well-organized stromatolitic fabrics.

Organic Carbon–Rich Chert

Kerogen-like particles impart a subtle clotted or mottled fabric from local silica–to–organic carbon variations.

Shallow-Water Deposition

Light cross-bedding and wavy laminations indicate low-energy, near-shore conditions in a relatively stable, isolated basin with minimal tidal influence.

Volcaniclastic Lull

Sparse volcaniclastic input records waning volcanism — a quiet interval conducive to early microbial colonization.

Biofabrics & Microbial Mats

Micro-wavy laminae, minor trough bedding, cross-stratification, and crinkly film-like textures consistent with pre-stromatolitic microbial mats.

Scientific Significance

Early Bio-sedimentary Systems

The Middle Marker Chert provides rare physical evidence of early microbial activity and carbon cycling prior to the widespread appearance of classic stromatolites.

Specimen Details & Provenance

• Location: Barberton Greenstone Belt, Mpumalanga, South Africa
• Formation: Hooggenoeg Formation, Onverwacht Group
• Age: ~3.472 Ga (Archean)
• Dimensions: 77 mm (L) × 68 mm (W) × 25 mm (D)
• Weight: 219.4 g
• Legality: Professionally and legally collected

What’s Included

• Certificate of Authenticity
• Specimen tag and acrylic tag stand
• Relevant scientific reference articles
• 3 × 5 in microscopy photograph
• In situ color field photographs

Not Included: Display base and photo cube.

Collector Value

Why This Specimen Matters

• Tangible record of early microbial processes in shallow Archean settings
• Carbon-rich fabrics ideal for teaching and research collections
• Premium provenance from a globally significant early Earth terrane

Add Middle Marker "Clotted Chert" to Your Collection

Secure an authentic piece of Archean history from South Africa’s Barberton Greenstone Belt — a mini-museum collectible, rare clotted chert that helps to capture the dawn of life on Earth.

This scientific material is Guaranteed Authentic. It was professionally and legally collected and arrives with a Certificate of Authenticity and information about Middle Marker clotted chert.