How might sea level change affect arthropod biodiversity in anchialine caves: a comparison of Remipedia and Atyidae taxa (Arthropoda: Altocrustacea) (original) (raw)

Inherited landscapes and sea level change Inherited landscapes and sea level change Sierd Cloetingh and Bilal U. Haq* BACKGROUND: Knowledge of past sea level fluctuations is fundamental to geosciences and for exploration of Earth-bound resources. Recent years have seen a convergence of views between stratigraphers (who measure past sea level changes in marine strata) and geodynamicists (who investigate surficial expressions of lithospheric and mantle processes) with the realization that without understanding inherited topographies, their causal mechanisms and operative time scales, palinspastic (pre-diastrophic) reconstructions of the past landscapes and seascapes remain inchoate at best. Sequestrations of seawater on land or its subduction-related entrainment in the mantle are two direct means of lowering global sea level. Sea level can also be changed by modifying the container capacity of the ocean through numerous interconnected solid-Earth processes. Some of these can only refashion landscapes regionally, thus affecting local measures of sea level change. Disentangling these processes to uncover the likely cause(s) for the resultant topography poses considerable challenges. ADVANCES: Recent developments in seismic tomography and high-speed computing that allow detailed forward and inverse modeling, combined with new concepts in stratigraphy and geophysics that permit envisioning largescale transfers of material among depositional centers, have brought us closer to understanding factors that influence landscapes and sea levels and the complex feedbacks. As a result, estimates of the amplitude of longterm eustatic changes have converged using different data sets. We have learned that solid- Earth processes operating on decadal to multimillion- year time scales are all responsible for retaining lithospheric memory and its surface expression: On time scales of tens to hundreds of years, glacial isostatic adjustments cause local topographic anomalies, whereas postglacial rebound can be enhanced by viscous mantle flow on time scales of thousands to hundreds of thousands of years; on time scales of more than 1 million years, oceanic crustal production variations, plate reorganizations, and mantle-lithosphere interactions (e.g., dynamic topography) become more influential in altering the longer-wavelength surface response. Additionally, the lithosphere’s rheological heterogeneity, variations in its strength, and changes in intraplate stress fields can also cause regional topographic anomalies, and syn-rift volcanism may be an important determinant of the long-term eustatic change on time scales of 5 to 10 million years. OUTLOOK: Despite these remarkable advances, we remain far from resolving the causes for third-order quasi-cyclic sea level changes (~500,000 to 3 million years in duration). Ascertaining whether ice volume changes were responsible for these cycles in the Cretaceous will require discerning the potential for extensive glaciation at higher altitudes on Antarctica by modeling topographic elevation involving large-scale mantle processes. Extensive sea floor volcanism, plate reorganizations, and continental breakup events need to be better constrained if causal connections between tectonics and eustasy have to be firmly established. Another promising avenue of inquiry is the leads and lags between entrainment and expulsion of water within the mantle on thirdorder time scales. Future geodynamic models will also need to consider lateral variations in upper mantle viscosity and lithosphere rheology that require building on current lithospheric strength models and constructing global paleorheological models. Deep-drilling efforts will be of crucial importance for achieving the integrative goals.▪ RESEARCH SCIENCE sciencemag.org 23 JANUARY 2015 • VOL 347 ISSUE 6220 393 ON OUR WEB SITE ◥ Read the full article at http://dx.doi. org/10.1126/ science.1258375 .................................................. The list of author affiliations is available in the full article online. *Corresponding author. E-mail: bilhaq@gmail.com Cite this article as S. Cloetingh, B. U. Haq, Science 347, 1258375 (2015). DOI: 10.1126/science.1258375 BACKGROUND: Knowledge of past sea level fluctuations is fundamental to geosciences and for exploration of Earth-bound resources. Recent years have seen a convergence of views between stratigraphers (who measure past sea level changes in marine strata) and geodynamicists (who investigate surficial expressions of lithospheric and mantle processes) with the realization that without understanding inherited topographies, their causal mechanisms and operative time scales, palinspastic (pre-diastrophic) reconstructions of the past landscapes and seascapes remain inchoate at best. Sequestrations of seawater on land or its subduction-related entrainment in the mantle are two direct means of lowering global sea level. Sea level can also be changed by modifying the container capacity of the ocean through numerous interconnected solid-Earth processes. Some of these can only refashion landscapes regionally, thus affecting local measures of sea level change. Disentangling these processes to uncover the likely cause(s) for the resultant topography poses considerable challenges. ADVANCES: Recent developments in seismic tomography and high-speed computing that allow detailed forward and inverse modeling, combined with new concepts in stratigraphy and geophysics that permit envisioning largescale transfers of material among depositional centers, have brought us closer to understanding factors that influence landscapes and sea levels and the complex feedbacks. As a result, estimates of the amplitude of longterm eustatic changes have converged using different data sets. We have learned that solid- Earth processes operating on decadal to multimillion- year time scales are all responsible for retaining lithospheric memory and its surface expression: On time scales of tens to hundreds of years, glacial isostatic adjustments cause local topographic anomalies, whereas postglacial rebound can be enhanced by viscous mantle flow on time scales of thousands to hundreds of thousands of years; on time scales of more than 1 million years, oceanic crustal production variations, plate reorganizations, and mantle-lithosphere interactions (e.g., dynamic topography) become more influential in altering the longer-wavelength surface response. Additionally, the lithosphere’s rheological heterogeneity, variations in its strength, and changes in intraplate stress fields can also cause regional topographic anomalies, and syn-rift volcanism may be an important determinant of the long-term eustatic change on time scales of 5 to 10 million years. OUTLOOK: Despite these remarkable advances, we remain far from resolving the causes for third-order quasi-cyclic sea level changes (~500,000 to 3 million years in duration). Ascertaining whether ice volume changes were responsible for these cycles in the Cretaceous will require discerning the potential for extensive glaciation at higher altitudes on Antarctica by modeling topographic elevation involving large-scale mantle processes. Extensive sea floor volcanism, plate reorganizations, and continental breakup events need to be better constrained if causal connections between tectonics and eustasy have to be firmly established. Another promising avenue of inquiry is the leads and lags between entrainment and expulsion of water within the mantle on thirdorder time scales. Future geodynamic models will also need to consider lateral variations in upper mantle viscosity and lithosphere rheology that require building on current lithospheric strength models and constructing global paleorheological models. Deep-drilling efforts will be of crucial importance for achieving the integrative goals.▪ RESEARCH SCIENCE sciencemag.org 23 JANUARY 2015 • VOL 347 ISSUE 6220 393 ON OUR WEB SITE ◥ Read the full article at http://dx.doi. org/10.1126/ science.1258375 .................................................. The list of author affiliations is available in the full article online. *Corresponding author. E-mail: bilhaq@gmail.com Cite this article as S. Cloetingh, B. U. Haq, Science 347, 1258375 (2015). DOI: 10.1126/science.1258375