Wyniki wyszukiwania - Biblioteka Nauki

Nowa wersja platformy, zawierająca wyłącznie zasoby pełnotekstowe, jest już dostępna.
Przejdź na https://bibliotekanauki.pl

Ograniczanie wyników

1 Geotourism / Geoturystyka

1 2023

Znaleziono wyników: 1

Liczba wyników na stronie

Wyniki wyszukiwania

Sortuj według:

Ogranicz wyniki do:

Ordovician spatial patterns of climate change inferred from isotope thermometers

100%

Ma X.-L. , Fan Y.

tom nr 1-2 (72-73)

45--45

Ordovician was an extremely turbulent period for the Earth system, where the Great Ordovician Biodiversification Event (GOBE) occurred in the early-middle Ordovician. Many hypotheses were proposed, taking into account both biotic and abiotic factors. One such hypothesis posits that global cooling led to a transition from greenhouse to icehouse climate systems, which further triggered feedback mechanisms such as increased oceanic circulation, bio-productivity, and oxygenation during the middle Ordovician. Direct evidence, however, is still scarce. Here, we have compiled a comprehensive dataset of δ18O (10,636) from carbonate rocks and fossil shells as well as clumped isotope temperature data (Δ47; 88) spanning the entire Ordovician. Our study investigates climate change from both temporal and spatial perspectives. We assessed the effects of the late diagenesis alteration, lithological differences, different depositional environments and water depths on the carbonate δ18O, and corrected the latitudinal effect of the δ18O in seawater. The latitudinal temperature gradient (LTG) was introduced to account for the spatial patterns of climate change, which here refers to the difference in sea-surface temperature between low (<20°) and low-to-middle (20–40°) latitudes. We observed a gradual increase in the LTG from Tremadocian to Dapingian, indicating an amplified thermal contrast between low and low-middle latitudes. It suggested a remarkable climate cooling and shift towards an icehouse climate state, coinciding with the GOBE. From Darriwilian to Sandbian, the LTG weakens significantly and the temperature difference decreases, which is consistent with the plateau of global temperatures and the slow change in species diversity. After Sandbian, a progressive steepening of LTG was observed, which provides the first evidence for low paradoxical atmospheric CO2 at the Late Ordovician. Our study supports the global cooling hypothesis and sheds light on the links between climate change and biological evolution across the Ordovician.