Meghalayan: Collapse of Ancient Agricultural Civilizations Defines Holocene’s Youngest Stage | Geology, Geoscience | Sci-News.com

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Meghalayan: Collapse of Ancient Agricultural Civilizations Defines Holocene's Youngest Stage

Jul 18, 2018 by News Staff / Source

The Meghalayan, the youngest stage of the current Holocene epoch, began at the time when ancient agricultural societies experienced an abrupt and critical mega-drought and cooling 4,200 years ago, according to the International Commission on Stratigraphy (ICS), which is responsible for standardizing the Geologic Time Scale.

International chronostratigraphic chart 2018. Image credit: International Commission on Stratigraphy.

Agricultural-based societies that developed in several regions after the end of the last Ice Age were impacted severely by the 200-year climatic event that resulted in the collapse of civilizations and human migrations in Egypt, Greece, Syria, Palestine, Mesopotamia, the Indus Valley, and the Yangtze River Valley. Evidence of this climatic event has been found on all seven continents.

The ICS experts approved the definition of the beginning of the Meghalayan based on the timing of this event.

Furthermore, they approved proposals for two other ages: the Northgrippian and the Greenlandian with beginnings defined at climatic events that happened about 8,300 years and 11,700 years ago, respectively.

The three ages comprise the Holocene epoch, which represents the time since the end of the last Ice Age.

"The Meghalayan Age is unique among the many intervals of the Geologic Time Scale in that its beginning coincides with a global cultural event produced by a global climatic event," said Long Beach State University's Professor Stanley Finney, Secretary General of the International Union of Geological Sciences (IUGS).

"The convergence of stratigraphy and human cultural evolution is extraordinary," added Brock University's Professor Martin Head, Chair of the International Commission on Quaternary Stratigraphy.

"This decision is a significant moment in the history of Holocene climate and archaeology science," said Yale University Professor Harvey Weiss.

Portion of the Indian stalagmite that was sectioned and analyzed layer by layer, and contains the layers chosen to define the beginning of the Meghalayan Age, 4,200 years ago. Image credit: International Commission on Stratigraphy.

Units of the Geologic Time Scale are based on sedimentary strata that have accumulated over time and contain within them sediment types, fossils and chemical isotopes that record the passage of time as well as the physical and biological events that produced them.

The three new ages of the Holocene are represented by a wealth of sediment that accumulated worldwide on the sea floor, on lake bottoms, as glacial ice, and as calcite layers in stalactites and stalagmites.

Those intervals of sedimentary strata on which the ages are based are referred to as stages, and together the strata of three new stages comprise the Holocene.

The lower boundary of the Greenlandian and Northgripppian stages are defined at specific levels in Greenland ice cores.

The lower boundary of the Meghalayan Stage is defined at a specific level in a stalagmite from a cave in the state of Meghalaya in northeast India.

The ice cores and the stalagmite are now identified as international geostandards, and have been placed in protected archives accessible for further study.

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