Gelasian
Generated by GPT-5-miniExpansion Funnel Raw 58 → Dedup 0 → NER 0 → Enqueued 0
| Gelasian | |
|---|---|
| Name | Gelasian |
| Unit | Age |
| Time start | 2.58 |
| Time end | 1.80 |
| Time unit | Ma |
| Color | #B3CDE3 |
| Preceded by | Piacenzian |
| Followed by | Calabrian |
Gelasian
The Gelasian is an internationally recognized Pleistocene age and stage used in global chronostratigraphy, defined at a boundary that integrates stratigraphic, paleontological, and magnetostratigraphic criteria. It was ratified by stratigraphic bodies to formalize the early Pleistocene interval and is tied to specific type sections and key correlation points used by researchers working on Quaternary stratigraphy, International Commission on Stratigraphy, and regional chronologies such as the European Pleistocene framework. The Gelasian is referenced across multidisciplinary studies involving ice-sheet history, faunal turnover, and sedimentary records from sites like Vrica section, Gubbio, and marine cores from the Mediterranean Sea.
Etymology
The name derives from the type stratotype near the town of Gela in Sicily, reflecting historical practice linking stage names to geographic localities; it was proposed in connection with stratigraphic work by Italian and international stratigraphers who correlated Sicilian sections with marine and continental archives. The formalization involved proponents associated with institutions such as the International Union of Geological Sciences, the Subcommission on Quaternary Stratigraphy, and regional geological surveys including the Italian Geological Survey.
Definition and Scope
The Gelasian is defined as the lowermost stage of the Pleistocene Series, replacing earlier informal units when the International Commission on Stratigraphy extended the Quaternary. Its base is fixed at a Global Boundary Stratotype Section and Point (GSSP) characterized by a combination of magnetostratigraphic reversal and biostratigraphic markers used to correlate sections from the Mediterranean Sea, the Atlantic Ocean, and continental basins across Europe, Africa, and the Americas. The stage encompasses climatic events documented in the marine isotope record, regional lithostratigraphic units, and fossil assemblages linked to faunal turnover events recognized by paleontologists working on sites like Atapuerca, Boxgrove, and the Olduvai Gorge region.
Geological Setting and Stratigraphy
Gelasian stratigraphic markers appear in carbonate platforms, siliciclastic shelves, deep-sea cores, lacustrine basins, and fluvial terraces. Key reference sections include the type section at the Vrica section in southern Italy and correlated sections in the Monte San Nicola area, sections in the Po Basin, and marine cores from the North Atlantic and the Mediterranean Sea. Stratigraphers correlate Gelasian successions with isotope stages recorded in benthic and planktonic foraminifera assemblages from the Blake Nose and Ocean Drilling Program cores, and with tephrochronological markers tied to eruptions documented in the Etna and Vesuvius records.
Age and Chronostratigraphy
The Gelasian spans from about 2.58 Ma to 1.80 Ma (million years ago), coinciding with the onset of cyclic Northern Hemisphere glaciation as identified in the marine isotope record pioneered by researchers working on the LR04 stack and the Stack of Lisiecki and Raymo. Its lower boundary coincides with the Gauss-Matuyama magnetic reversal recognized in global paleomagnetic records and correlated to paleomagnetic studies from sites like DSDP Site 607 and ODP Hole 677A. The upper boundary aligns with isotope and biostratigraphic changes that stratigraphers correlate to changes documented by workers examining the Pleistocene stratigraphy of Europe and the Calabrian GSSP.
Lithology and Depositional Environments
Lithologies associated with Gelasian deposits are variable: shelf and slope marls, pelagic limestones, shallow-marine sandstones, fluvial conglomerates, and lacustrine silts. Marine sediments often show alternations of hemipelagic marls and turbidites in cores from the Mediterranean Sea and North Atlantic Ocean, while continental deposits include alluvial fan sequences in the Apennines and loess-palaeosol successions documented in the Chinese Loess Plateau and European loess regions. Volcaniclastic layers serve as chronostratigraphic markers in sections influenced by volcanic centers such as Mount Etna and Campi Flegrei.
Paleontology and Fossil Record
The Gelasian fossil record records turnover among vertebrate faunas including early representatives of genera studied from Villafranca, Tuscany, and Spanish sites; micromammal, large mammal, and marine microfossil assemblages provide important biozonation. Marine foraminifera, planktonic and benthic species changes, and nannofossil events used by micropaleontologists correlate Gelasian strata across the Mediterranean, Indian Ocean, and Pacific Ocean. Terrestrial records preserve hominin-implicated archaeological horizons studied at Dmanisi, Atapuerca, and Ubeidiya that are often discussed in contexts with faunal lists including genera from Equus, Mammuthus, and Hippopotamus lineages.
Depositional History and Tectonic Context
The Gelasian sedimentary record reflects interactions between glacioeustatic sea-level changes, regional tectonics, and sediment supply modulated by uplift across margins such as the Apennine Mountains, the Iberian Massif, and the East African Rift System. Active tectonism influenced basin subsidence in the Adriatic Basin, the Po Basin, and rift basins in East Africa, while glacial-interglacial cycles controlled sediment flux to continental shelves recorded in cores from the North Atlantic and Mediterranean Sea. Volcanic activity in the Aeolian Islands and the Anatolian region contributed tephra layers used for tephrochemical correlation.
Significance and Research History
The establishment of the Gelasian as a formal stage resolved long-standing debates in the Quaternary community about where the Pleistocene begins and provided a standardized framework for correlating marine, continental, and ice-core records. Key contributors include researchers associated with the International Commission on Stratigraphy, paleoceanographers using records from the Ocean Drilling Program, and terrestrial geologists studying European and African sequences. Ongoing research integrates magnetostratigraphy, biostratigraphy, and isotope stratigraphy from sites such as Vrica section, ODP cores, and continental sequences in China and Africa to refine correlations and to elucidate the processes driving early Pleistocene environmental change.