, and sediment transport and deposition processes (e.g., Malarkey et al., 2015; Lai et al., 2018; Lichtman et al., 2018). An associated advance is the understanding that many sedimentary processes involve mixed grain-size and grain-type flows (polydisperse), and challenge established bedform-phase diagrams that assume very narrow (monodisperse) grain-size distributions, leading to reanalysis of many sedimentary structures, and process interpretations (Baas et al., 2016).
Sedimentologists are leading the re-appraisal of sediment-routing systems, with an emphasis on source-to-sink configurations and functioning across a range of modern to deep timescales (>105–106 year; e.g., Romans et al., 2016; Allen, 2017). A holistic perspective of sediment production, transport, and deposition is inherently integrative and fosters an interdisciplinary approach necessary to address important questions in the Earth Sciences. Advances in understanding the links between erosion-dominated catchments, through the fragmented depositional record of transfer zones, to the depositional record archived in sedimentary basins (Figure 1), have been supported by technological advances, such as single-grain based geochronology (e.g., Lawton, 2014), cosmogenic radionuclide dating (e.g., Mason and Romans, 2018), low-temperature thermochronologic estimates of long-term erosion rates (e.g., Carrapa, 2010), geophysical imaging of stratal geometries and sedimentary volumes (e.g., Covault et al., 2011), numerical modeling (e.g., Hawie et al., 2017), and unmanned aerial vehicle (UAV) and LiDAR technology (e.g., Buckley et al., 2010).
These technological advances in constraining timing and rates has led to quantification of sediment fluxes from source (catchments) to sink (sedimentary basins), which allows for examination of Earth surface change in response to external forcings. An emphasis on more complete sediment budgets, based on volume, and mass determination, instead of point-location sedimentation rates mitigates well-known issues related to stratigraphic incompleteness (Sadler, 1981; Sadler and Jerolmack, 2014). Moreover, the increased number of integrated onshore-to-offshore records have facilitated a more complete understanding of source-to-sink configurations (e.g., Clift, 2006; Sømme et al., 2009; Covault et al., 2011; Guillocheau et al., 2012; Richardson et al., 2017).
A recent focus among the Earth Science community has been on constraining the interactions and feedbacks between tectonic and climate processes at a range of spatial and temporal scales (e.g., Castelltort and Van Den Driessche, 2003; Armitage et al., 2011, 2013; Godard et al., 2013; Braun et al., 2015; Schlunegger and Castelltort, 2016). These studies complement traditional sequence-stratigraphic approaches that have emphasized accommodation signals by highlighting, and in some cases quantifying, the magnitude and variability of sediment delivery to a sedimentary basin. However, the quantification of responses to external forcings and environmental signal propagation at historic, millennial, and million-year timescales of the magnitude and timing of sedimentary system is in its infancy. For example, understanding if a climate signal is buffered or, in some cases, “shredded” (Jerolmack and Paola, 2010) en route to the stratigraphic record is critical if we are to use those archives to reconstruct past global warming events. To resolve these processes and controlling factors in the integrated sedimentary basin record requires the use of proxy records. The quantity and quality of proxy datasets are rapidly growing, including uplift and exhumation events in the sediment-source from high and low-temperature geochronology and numerical modeling, sediment-transport independent paleoclimate archives such as coral archives, pollen, and biomarkers. Sedimentary deposits proximal to major ice sheets have been shown to be valuable archives of the dynamics of these globally important features (Jaeger and Koppes, 2016). Other sedimentary archives with that may form more complete of environmental change remain underexploited, such as contourite drifts (e.g., Bahr et al., 2014), overbank deposits to submarine channel systems (e.g., Hansen et al., 2015; Hodgson et al., 2016), and submarine fans (e.g., Picot et al., 2016).
Improved constraints on the duration, and rates, of sedimentation in all archives necessitates integration with other Earth Science disciplines. A potentially rich area of collaboration is the integration of source-to-sink analysis with astrochronology. Identifying cycles within sedimentary successions, and tuning these to the astronomical target curves, has allowed calibration of most of the Cenozoic time scale (Hilgen et al., 2006), and permits the estimation and duration of sedimentary successions and rates of sediment accumulations. Earth's orbital parameters govern climatic patterns through seasonality and solar intensity. The recognition and impact of Milankovitch cycles have been reported in a wide range of environments from loess (Maher, 2016), evaporitic (Anderson, 1982), shallow lagoonal and reefal carbonates (De Vleeschouwer et al., 2015), deltaic (Marshall et al., 2017), turbiditic (Payros and Martínez-Braceras, 2014), and deep marine (Hinnov and Hilgen, 2012) records. However, advancements still need to be made in order to link with source-to-sink datasets. For example, understanding the link between the onset and termination of climatic events (“nodes”) remain challenges due to issues of sensitivity and non-linearity of the proxy's response to the climate forcing.
Another important approach in this theme is the application and integration of landscape evolution models and stratigraphic/depositional models (e.g., Forzoni et al., 2014) to formulate working hypotheses of sedimentary system response to climate and tectonics that can be tested in the stratigraphic record. In addition to sedimentary signal propagation and response, the concepts of sedimentary system “sensitivity” (analogous to climate sensitivity) will become increasingly important. At shorter timescales, this research area is closely aligned to quantitative geomorphology and landscape-evolution modeling. If we want to advance source-to-sink studies, and understand how sedimentary successions record past changes in environmental conditions, we need to document geomorphic processes, and “read” stratigraphic archives to quantify paleoenvironmental change. One focus has been to derive scaling relationships between the onshore catchments and the offshore depositional sink (e.g., Sømme et al., 2009; Bhattacharya et al., 2016), which can be used to guide likely source-area characteristics from the depositional record in a semi-quantitative manner.
Lastly, at the sedimentary basin-scale, sedimentary archives chronicle the erosional history of their sediment sources and mechanisms of basin formation, offering invaluable information about tectonic histories and continent- or orogen-scale sediment dispersal patterns. New areas of research exploring interactions between tectonics and sedimentation and refined analytical methods for linking sources to their sinks will continue to lead advances in basin studies. This is reflected in the central role of stratigraphers when constraining large-scale and long-term crustal deformation patterns (Fosdick et al., 2015).
These are exciting times for sedimentologists, stratigraphers, and sediment geochemists! There is an unprecedented breadth of techniques and tools available. For example, novel age-dating approaches that allow better links between landscape evolution and the stratigraphic record; there is widespread availability of huge topographic, bathymetric, and seismic reflection datasets; new technology permits the monitoring of geophysical flows at high fidelity, which are supported by advances in numerical and analog modeling capabilities. The opportunities to monitor modern systems in detail, and to extract more information from ancient archives, have never been greater, or more pertinent in order to better understand and predict future risks facing society.
SSD research is central to many societally-relevant problems in addition to fundamental questions in the Earth Sciences. We need to communicate the importance of SSD research in the context of all the grand challenges in the Earth Sciences that, in one way or another, use sediments and the stratigraphic record. To lead these advances as an interdisciplinary community, we need to actively engage, or reengage, with engineering, biosciences, climate sciences, environmental economists, and more. An ongoing challenge will be to demonstrate the continued need to invest in SSD research ideas, technology, and training of early career personnel to develop the next generation of SSD-facing geoscientists. There might be (major) uncertainties in understanding of particulate transport and deposition, in stratigraphic shapes and patterns, in the exact products of flows of different fluid-sediment mixes in a range of media, but our knowledge will lead to more accurate evaluation of data, of models, of output. SSD is a cornerstone of geochemical, paleontological, and paleoclimatic research, and is central to interpreting the stratigraphic record of past environmental change, and to better forecast how sedimentary systems may respond to our changing climatic conditions and sea-level state. Research excellence in SSD, in description and interpretation, must be integral to associated disciplines.
The SSD section of Frontiers in Earth Science will publish high-quality papers on all aspects of theoretical and applied research that use field, remote sensing, geophysical, and analog and modeling approaches. Our