Earth’s interior dynamics drive marine fossil diversity cycles of tens of millions of years
Proceedings of the National Academy of Sciences of the United States of America, Jul 10, 2023
The fossil record reveals that biotic diversity has fluctuated quasi-cyclically through geologica... more The fossil record reveals that biotic diversity has fluctuated quasi-cyclically through geological time. However, the causal mechanisms of biotic diversity cycles remain unexplained. Here, we highlight a common, correlatable 36 ± 1 Myr (million years) cycle in the diversity of marine genera as well as in tectonic, sea-level, and macrostratigraphic data over the past 250 Myr of Earth history. The prominence of the 36 ± 1 Myr cycle in tectonic data favors a common-cause mechanism, wherein geological forcing mechanisms drive patterns in both biological diversity and the preserved rock record. In particular, our results suggest that a 36 ± 1 Myr tectono-eustatically driven sea-level cycle may originate from the interaction between the convecting mantle and subducting slabs, thereby pacing mantle-lithospheric deep-water recycling. The 36 ± 1 Myr tectono-eustatic driver of biodiversity is likely related to cyclic continental inundations, with expanding and contracting ecological niches on shelves and in epeiric seas.
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Papers by Bilal Haq
Recent advances in seismic and tomographic imaging, coupled with high-resolution numerical simulations, have fostered an emerging convergence between geodynamic theory and stratigraphic records of Phanerozoic sea-level curves – particularly for second-order (multi-million years) Meso-Cenozoic variations. These efforts also cast doubt on earlier reconstructions based solely on continental flooding metrics without accounting for evolving hypsometries. Superimposed on these tectonic signals are third-order cycles driven largely by Earth's orbital rhythms: long-period Milankovitch modulations (∼1.2 Myr obliquity, especially common during refrigerations, and ∼2.4 Myr eccentricity, recurrent during warm intervals) leave clear imprints in sequence stratigraphic, deep-sea hiatuses, fossil diversity patterns, and stable-isotopic records. Meanwhile, the capacity of small, hydrous mantle plumes to shuttle water across the core-mantle boundary – and the topographic uplift associated with flood basalt provinces – emerges as an underappreciated influence on regional sea-level anomalies. Despite these advances, reconstructing pre-Cretaceous sea-level history remains hampered by scant constraints on ancient spreading and subduction systems. Addressing these gaps and achieving further advancements demands enhanced temporal resolution and more complete datasets – especially for younger intervals where the oceanic lithosphere is preserved with greater fidelity. Seismic and tomographic surveys in under-sampled regions, such as Africa, South America and West Antarctica, are especially critical. Legacy industry data could help fill key gaps, and broader access to publicly funded datasets is vital. Sea-level change stands as one of the most societally-relevant challenges in geoscience and meeting its demands will require sustained investment in advanced data collection, robust modeling, and collaborative partnerships between academia and industry.
Download the paper at: https://doi.org/10.1016/j.earscirev.2025.105166
geologically well documented at Milankovitch timescales, controlled in part by climatically
(insolation) driven sea-level changes.
At the longer (tens of Myr) timescales connection between astronomical parameters
and sedimentation via cyclic solar-system motions within the Milky Way has also been
proposed, but this hypothesis remains controversial because of the lack of long geological
records. In addition, the absence of a meaningful physical mechanism that could explain the
connection between climate and astronomy at these longer timescales led to the more
plausible explanation of plate motions as the main driver of climate and sedimentation
through changes in ocean and continent mass distribution on Earth.
Here we statistically show a prominent and persistent ~36 Myr sedimentary cyclicity
superimposed on two megacycles (~250 Myr) in a relatively well-constrained sea-level (SL)
record of the past 542 Myr (Phanerozoic eon). We also show two other significant ~9.3 and
~91 Myr periodicities, but with lower amplitudes. The ~9.3 Myr cyclicity was previously
attributed to long-period Milankovitch band based on the Cenozoic record. However, the ~91
Myr cyclicity has never been observed before in the geologic record. The ~250 Myr cyclicity
was attributed to the Wilson tectonic (supercontinent) cycle. The ~36 Myr periodicity, also
detected for the first time in SL record, has previously been ascribed either to tectonics or to
astronomical cyclicity.
Given the possible link between amplitudes of the ~36 and ~250 Myr cyclicities in SL
record and the potential that these periodicities fall into the frequency band of solar system
motions, we suggest an astronomical origin, and model these periodicities as originating
from the path of the solar system in the Milky Way as vertical and radial periods that
modulate the flux of cosmic rays on Earth. Our finding of the ~36 Myr SL cyclicity lends
credibility to the existing hypothesis about the imprint of solar-system vertical period on the
geological record. The ~250 Myr megacycles are tentatively attributed to a radial period.
However, tectonic causal mechanisms remain equally plausible.
The potential existence of a correlation between the modeled astronomical signal and
the geological record may offer an indirect proxy to understand the structure and history of
the Milky Way by providing a 542 Myr long record of the path of the Sun in our Galaxy.
coupled plate-mantle system. Connection between Earth’s interior and external climate drivers, e.g., Milankovitch insolation forcing, has not been investigated at multi-Myr timescale, because tectonics and astronomical
influences at these longer timescales have long been thought as independent pacemakers in the evolution of the Earth system. Here we have analyzed time-series from multiple geological datasets and found common periodicities of 10 and 35 Myr. Additionally, we have highlighted the modulation in amplitude of the 10 Myr cycle band by the 35 Myr cyclicity in sedimentary sea-level data. We then demonstrate the same physical amplitude modulation relationship between these two cyclicities in astronomical (Milankovitch) variations, and establish correlation between Milankovitch and sea-level variations at these two frequency bands. The 10 and 35 Myr cycles are prominent in the geological records, suggesting either unresolved fundamental Milankovitch periodicities, or reflecting a sedimentary energy-transfer process from higher to lower Milankovitch frequencies, as argued here via amplitude modulation analysis in both astronomical and sea-level data. Finally, we find a coherent correlation, at the 35 Myr cycle band, between Milankovitch, sea-level and geodynamic (plate subduction rate) variations, hinting at a coupling between Earth’s interior and surface processes via Milankovitch paced climate. Thus, our findings point to a coupling between Milankovitch and Earth’s internal forcings, at 10 to 10s of Myr. The most likely scenario that could link insolation-driven climate change to Earth’s interior processes is Earth’s interior feedbacks to astro-climatically driven mass changes on Earth’s surface. We suggest that Earth’s interior processes may drive large-amplitude sea-level changes, especially during greenhouse periods, by resonating to astro-climatically driven Earth’s surface perturbations.