Definition
The Viséan is a chronostratigraphic stage and corresponding geochronologic age in the Lower Carboniferous (Mississippian) series, spanning approximately 346.7 ± 0.4 to 330.9 ± 0.2 million years ago.
Overview
The Viséan follows the Tournaisian and precedes the Serpukhovian within the Carboniferous system. It is globally recognized in the International Chronostratigraphic Chart and is represented by distinct lithostratigraphic units in many regions, such as the Viséan formations of western Europe, the Appalachian Basin of North America, and parts of Asia. The stage is characterized by widespread shallow marine carbonate deposition, extensive reef development, and significant evolutionary events among marine invertebrates and early terrestrial vertebrates.
Etymology / Origin
The name “Viséan” is derived from the French city of Vienne, located in the Isère department of southeastern France. The term was introduced in the 19th century by French geologists who identified characteristic limestone sequences in the region that typify the stage.
Characteristics
- Temporal Boundaries: Base at ~346.7 Ma, defined by the first appearance datum (FAD) of the conodont Siphonodella sulcata; top at ~330.9 Ma, marked by the FAD of the conodont Gnathodus semialbus.
- Lithology: Dominated by carbonate rocks (limestones, dolomites) in epicontinental seas, interbedded with shales and occasional sandstones reflecting fluctuating sea levels.
- Paleontology: Rich fossil assemblages include brachiopods, crinoids, rugose and tabulate corals, fusulinid foraminifera, and diverse conodonts. Early tetrapod footprints and plant spores indicate the colonization of terrestrial habitats.
- Paleoenvironment: Warm, humid climate with high eustatic sea levels leading to extensive shallow marine platforms. Tectonic activity associated with the assembly of the supercontinent Pangaea influenced basin development and sedimentation patterns.
- Stratigraphic Markers: Conodont biostratigraphy is primary for global correlation; supplemental markers include ammonoid zones, fusulinid assemblages, and palynological data.
Related Topics
- Carboniferous Period – The geological period encompassing the Viséan, noted for extensive coal-forming forests.
- Mississippian Subsystem – The lower subdivision of the Carboniferous, of which the Viséan is a constituent stage.
- Tournaisian and Serpukhovian Stages – Adjacent stages that bracket the Viséan temporally.
- Conodont Biostratigraphy – The use of conodont fossils to define and correlate the boundaries of the Viséan.
- Carbonate Platform Development – Geological processes that produced the widespread carbonate deposits characteristic of the Viséan.