Large‐scale connectivity of fluvio‐deltaic stratigraphy: Inferences from simulated accommodation‐to‐supply cycles and automated extraction of chronosomes

Multiscale simulation of fluvio‐deltaic stratigraphy was used to quantify the elements of the geometry and architectural arrangement of sub‐seismic‐scale fluvial‐to‐shelf sedimentary segments. We conducted numerical experiments of fluvio‐deltaic system evolution by simulating the accommodation‐to‐sediment‐supply (A/S) cycles of varying wavelength and amplitude with the objective to produce synthetic 3‐D stratigraphic records. Post‐processing routines were developed in order to investigate delta lobe architecture in relation to channel‐network evolution throughout A/S cycles, estimate net sediment accumulation rates in 3‐D space, and extract chronostratigraphically constrained lithosomes (or chronosomes) to quantify large‐scale connectivity, that is, the spatial distribution of high net‐to‐gross lithologies. Chronosomes formed under the conditions of channel‐belt aggradation are separated by laterally continuous abandonment surfaces associated with major avulsions and delta‐lobe switches. Chronosomes corresponding to periods in which sea level drops below the inherited shelf break, that is, the youngest portions of the late falling stage systems tract (FSST), form in the virtual absence of major avulsions, owing to the incision in their upstream parts, and thus display purely degradational architecture. Detailed investigation of chronosomes within the late FSST showed that their spatial continuity may be disrupted by higher‐frequency A/S cycles to produce “stranded” sand‐rich bodies encased in shales. Chronosomes formed during early and late falling stage (FSST) demonstrate the highest large‐scale connectivity in their proximal and distal areas, respectively. Lower‐amplitude base level changes, representative of greenhouse periods during which the shelf break is not exposed, increase the magnitude of delta‐lobe switching and favour the development of system‐wide abandonment surfaces, whose expression in real‐world stratigraphy is likely to reflect the intertwined effects of high‐frequency allogenic forcing and differential subsidence.


Highlights
• A process-based forward stratigraphic model was used to simulate accommodation-to-sediment supply (A/S) cycles of varying wavelength and amplitude. • A post-processing software suite was developed to extract chronostratigraphically constrained lithosomes (or chronosomes). • The linkage between avulsion events and A/S cycles is documented. • Chronosomes formed during early and late falling stage (FSST) demonstrate the highest large-scale connectivity in their proximal and distal areas, respectively. & Weltje, 2008, or by process-based models that involve the direct coupling of sediment transport and hydrodynamics, such as Delft3D (http://oss.delta res.nl/web/delft3d) and Sedsim (Griffiths, 1996;Martinez & Harbaugh, 1993;Tetzlaff & Harbaugh, 1989). Models of the former type are also known as aggregated models because they employ a high level of abstraction in order to ensure computational efficiency. Those of the latter type is more complex and hence come with high computational overhead during simulation, which renders them as yet unsuitable for exploring the inherent uncertainty of initial and boundary conditions through multiple runs.
In this study, we focused on the role of sedimentation processes, specifically avulsions, in the formation and architectural arrangement of river-shelf sedimentary segments throughout a sequence, that is, a cycle of accommodation to sediment supply rates , which may be viewed as a natural stratigraphic unit (Catuneanu et al., 2009(Catuneanu et al., , 2011Karamitopoulos et al., 2014). For this purpose, we used SimClast, a basin-scale numerical model with a sub-grid parameterization of fluvio-deltaic processes and stratigraphy. Standard sequence stratigraphic terminology, including the concept of accommodation to sediment supply (A/S) ratio based on the regime theory of Swift and Thorne (1991) and Thorne and Swift (1991), was used for the analysis and interpretation of the results. A routine was implemented to extract chronosomes, short for chronostratigraphically constrained lithosomes (Schultz, 1982) from the synthetic stratigraphic records preserved throughout an A/S cycle. Chronosomes consist of channel-belt and delta-lobe sediments deposited in temporal continuity at a specific location within the basin (Dalman et al., 2015;Schultz, 1982). The aims of this study are to (1) investigate channel-network evolution throughout A/S cycles of varying amplitude and wavelength, (2) estimate net sediment accumulation rates to capture the time evolution of deposition and storage of fluvial-shelf segments, and (3) provide a coherent predictive model of lithofacies distribution and large-scale connectivity throughout the simulated A/S cycles.

| Model description
SimClast, a basin-scale numerical model of river-shelf evolution (Meijer, 2002) combined with a sub-grid parameterization of fluvio-deltaic processes and stratigraphy (Dalman & Weltje, 2008, 2012 was used to obtain synthetic sedimentary sequences that form under the influence of time-variant external forcing in the form of sea-level cycles on a uniformly subsiding (0.1 mm/yr) substrate resembling a passive margin with a well-developed shelf and a clearly defined shelf break (model domain is 50 × 100 km) (Figure 1). The adopted gridcell size of 1 × 1 km represents the finest spatial discretization at which the model can operate, because the grid-cell size needs to be larger than the width of an individual channel. Sedimentary processes relevant to this study are included by the sub-grid parameterization of in-channel sediment transport able to produce divergent (aggrading: braided or meandering) and convergent (incising) channel networks, and most importantly, detailed representations of avulsions and mouth bar-induced bifurcations. Avulsions occur as a consequence of channel-belt aggradation (e.g., through base level rise) and resulting super-elevation, whereas mouth bar-induced bifurcations dominate the terminal parts of the sediment dispersal system where delta lobes prograde and topographic gradients are low. Fluvio-deltaic evolution in the model has been shown (Dalman et al., 2015) to be governed by a robust morphodynamic feedback loop under time-invariant forcing, which links the progradation rate with major avulsions, delta-lobe switches, and sequestration of sediments on the delta plain. It is expected that this feedback loop is influenced by external forcing, and therefore stratigraphic records formed under time-variant forcing conditions are presented in this study. Throughout the model runs, the net sediment accumulation record (d(t k )) was stored in dynamic arrays to register deposition (d(t k ) > 0), erosion (d(t k ) < 0), and stasis (d(t k ) = 0) for every grid cell throughout the simulation. A grid cell in stasis (which does not change its elevation) is in bypass if the site is occupied by an active channel or starved if the grid cell is far away from the active channel (Tipper, 2000(Tipper, , 2015.

| Scenarios
In order to maximize the preservation potential of modelled delta-topset areas, all simulations were run in the absence of differential subsidence, coastal processes (i.e., waves, tides, cross-shore transport), and bank-stabilizing vegetation. The initial topographic surface for all simulations was defined by running the model for 20 kyr under time-invariant forcing ( Figure 1a). Throughout the simulations, constant water discharge (Q w = 5 × 10 9 m 3 /yr) and sediment input (Q s = 1 × 10 6 m 3 /yr) (sand/clay ratio = 0.2) entered the transfer valley via a single entry point (Figure 1a). Two sets of numerical experiments were performed (Table 1): the first set consisted of 200-kyr model runs using low-and highamplitude sea-level cycles representative of greenhouse and icehouse periods, respectively (experiments RC1 and RC2; Figure 1b, green and blue curves, respectively) (Miller et al., 2005). The crucial difference between the two scenarios is that in the former, the sea level does not fall below the shelf break, whereas the shelf break is periodically exposed in the latter. The second set of experiments consisted of 100kyr model runs with a one-phase sea-level fall and rise with or without a superimposed higher frequency (25 kyr wavelength) signal (experiments RC3a and RC3b; Figure 1c, blue and red curves, respectively). The first set of experiments (RC1 and RC2) were aimed at the quantitative description of channel network and stratal architecture as a function of fixed topography and base level changes, whereas the second (RC3a and RC3b) focused on the architectural arrangement of sedimentary packages deposited during the periods of minimum A/S (i.e., falling stage systems tract or FSST for short). In order to quantify the variability of the synthetic stratigraphic records (captured in a probability distribution), 10 equiprobable realizations were obtained from the basecase scenario RC1 by applying random topographic noise to the initial surface.

| Post-processing
A stack data structure was designed and implemented as a linked list in C++ to load continuous records of synthetic stratigraphy (net sediment accumulation) in dynamic F I G U R E 1 (a) Initial model topography and inflow point (white arrow); relative sea-level curves of the first (b) and the second set (c) of numerical experiments (black line in 1B indicates shelf break position). Scenario RC3 is the compound signal of RC3a and RC3b (see Table 1  arrays. The algorithm implements sequentially a series of post-processing methods that allow estimation of net sediment accumulation rates over specified time intervals to outline the boundaries of delta-lobe chronosomes ( Figure 2). Figure 3 illustrates four delta lobes extracted from the base-case experiment, each covering a 2-kyr time interval. Large-scale connectivity has been quantified as the number of connected grid cells extracted by the cellular automata post-processing operation. In this particular application, connectivity represents the spatio-temporal continuity of high-net to gross fluvio-deltaic chronosomes. A detailed description of the methods is included in the Appendix A.
The dominant channel branches and their associated major avulsion sites occurring more than 5 km from coastline were extracted using the method described in detail by Karamitopoulos et al. (2014). The method involves a Boolean transformation of grid cells (channelized vs. non-channelized flow) based on a threshold discharge (Q thr = 3.0 × 10 9 m 3 / yr) followed by a calculation of differences between Boolean channel networks at successive time steps. Major avulsions occurring more than 5 km away from coastline were identified at the intersection of the old and new channel branches ( Figure 4). In addition, we estimated the Euclidian distance of the river-mouth shift owing to the major avulsion, which we named the magnitude of the delta-lobe switch (M DLS ). This metric is indicative of the impact of the major avulsions at the coastline.

| Stratigraphic terminology
The concept of accommodation to sediment supply (A/S) cycles (or sequences) provides an attractive way to analyse the morphodynamic evolution of fluvio-deltaic systems as a function of spatial and temporal patterns of sedimentation (Allen, Lang, Musakti, & Chirinos, 1996;Jervey, 1988;Martinius et al., 2014;Martinsen et al., 1999;Muto & Steel, 2002;Schlager, 1993;Shanley & McCabe, 1993;Tipper, 2000). However, putting this concept into practice is not exactly straightforward owing to the fact that traditional sequence-stratigraphic definitions and naming conventions that stem from the 2-D world cannot be directly applied to real-world 3-D basin fills. Clarification and justification of the terms we employ is therefore in order.
The terminology of A/S cycles acknowledges the fact that A and S cannot be directly inferred from the stratigraphic record owing to its generally fragmentary nature (incomplete preservation) and limited time control, which implies incomplete knowledge of the past. The A/S ratio is a dimensionless number (a ratio of two rates) and thus by definition independent of time control. The A/S regime in the vicinity of the paleo-shoreline gives rise to unique stacking patterns (aggradational, degradational, progradational, and retrogradational; ADPR for short) that can be observed in the stratigraphic record. Thus, A/S > 1 results in the retrogradational stacking (which implies transgression), A/S = 1 results in aggradational stacking (which implies a stationary coastline), 0 < A/S < 1 results in progradational stacking (which implies "normal" regression), and A/S < 0 results in degradational stacking (which implies "forced" regression). Traditional sequence stratigraphic terminology mixes observation and interpretation, because changes in boundary conditions (which can only be inferred under certain assumptions) are directly employed in the naming of stratigraphic units (systems tracts). The terms regression and transgression refer to the basinward and landward movement of the shoreline, respectively, whereas the terms highstand and lowstand refer to the relative (not absolute) sea level. None of these quantities can be directly observed in the stratigraphic record, and therefore, using such terms to describe stratigraphic units is questionable. In light of these considerations, the historical naming of systems tracts is unfortunate and continues to create unnecessary confusion, as all of their names refer to unobservable phenomena: the movement of the shoreline ("transgressive" systems tract, or TST) or the sea level ("highstand" systems tract, or HST; "lowstand" systems tract, or LST; "falling stage" systems tract, or FSST).
The modern usage of systems tracts emphasizes their definition as physical rock bodies with observable characteristics, that is, bounding surfaces and internal architecture ), devoid of unnecessary interpretative connotations. Thus, it seems reasonable to refer to the LST as the PA-tract, the TST as the R-tract, the HST as the AP-tract, and the FSST as the D-tract. However, this is not (yet) widely accepted by the research community. In this study, we will stick to the use of conventional terms for systems tracts and their bounding surfaces, for the simple reason that there is no widely accepted neutral alternative for the genetic description of stratigraphy. Therefore, the stratigraphic record was subdivided into system tracts using conventional 2-D sequence stratigraphic concepts (Emery & Myers, 1996;Frazier, 1974;Galloway, 1989;Helland-Hansen & Martinsen, 1996;Hunt & Tucker, 1992;Plint & Nummedal, 2000;Posamentier & Allen, 1999;Posamentier, Jervey, & Vail, 1988;Vail, 1987).
Another complication arises from the fact that the assumption that some of the bounding surfaces of systems tracts are isochronous is not generally valid. This is not a serious problem in the applications of sequence stratigraphy to the 2-D world, but it does complicate the distinction of bounding surfaces in 3-D. As an example, consider the case in which a prograding delta is flanked by two stretches of coastline subject to erosion, such that progradation and retrogradation occur at the same time in different parts of the system. Then there is a choice between two alternatives: (1) acknowledging the diachroneity of bounding surfaces to preserve the unique internal stacking patterns of systems tracts, or (2) regarding bounding surfaces as isochronous by definition, thus allowing some variability in stacking patterns within the basal and topmost parts of systems tracts. Because we conducted numerical simulations and thus had direct access to boundary conditions, we opted for the latter and defined the bounding surfaces of the systems tracts (with the exception of the sequence boundary) as system-wide isochronous surfaces separating sedimentary packages that have different stacking patterns on average. The bounding surfaces were defined as follows. Maxima and minima of the non-dimensional shoreline curve, that is, the ratio of marine to non-marine grid cells, corresponding to the ages of maximum flooding (MFS) and maximum regressive surfaces (MRS), respectively. This metric is similar in spirit to the shoreline approximation metric defined by Martin et al. (2009)  (BSFR) and the correlative conformity (CC, sensu Hunt & Tucker, 1992) correspond to the highest and lowest values of the base-level curve, respectively. These four chronostratigraphic surfaces allow us to uniquely subdivide sequences into systems tracts. We thus ignored the fact that in real-world stratigraphy, the actual surfaces will record a certain degree of diachroneity depending on differential subsidence and locally varying rates of sediment supply (Catuneanu et al., 2009;Madof et al., 2016). Figure 5 illustrates the morphodynamic evolution of the RC1, RC2, RC3a, and RC3b experiments. In the base case scenario (RC1), the sea-level fluctuation was modelled as a sinusoid with a wavelength of 100 kyr and an amplitude of 50 m, representative of Pleistocene glacio-eustatic sea-level fluctuations (Figure 5a). During the deposition of the early FSST, delta-plain aggradation and progradation are regulated by the rate of the relative sea-level fall as well as the shelf and river-profile gradients (Karamitopoulos et al., 2014). Widespread erosion occurs especially when the sea level drops below the shelf break. During the TST, progradation shifts to retrogradation, which favours the development of super-elevation of alluvial ridges of the active channels. This increases the probability of avulsion, which peaks around the transition from the TST to the HST, that is, around the maximum flooding surface or the maximum aggradation level (as defined by Martinius et al., 2014) at the turn-around from retrogradation to progradation. Shelf break exposure during basin-fill evolution in scenarios RC3a and RC3b results in similar morphodynamics and sedimentation patterns (Figure 5c,d). In contrast, during RC2 basin-fill evolution the shelf break is not exposed and sedimentation takes place in the absence of pronounced localized erosive features (i.e., shelf-edge canyons) (Figure 5b). Subdivision into systems tracts by the extraction of bounding surfaces is illustrated for the base-case scenario (RC1) in Figure 6 the distinct ADPR stacking pattern discussed above: the TST is characterized by retrogradational (R) stacking, with some aggradational (A) components in its oldest and youngest parts, the HST has aggradational-to-progradational (AP) stacking, the FSST is predominantly degradational (D), with a progradational (P) component during early stages, and the LST shows progradational-to-aggradational (PA) stacking. The thickness distribution of systems tracts varies considerably: the TST and FSST are on average much thicker than the LST and HST, as a result of the interaction between antecedent topography and the relative sea-level signal employed in the base-case simulation, which governs the spatio-temporal distribution of accommodation. Post-processing of the net sediment accumulation records (d(t k )) was used to extract preserved delta-lobe chronosomes by estimating net sediment accumulation rates over 1-kyr time intervals (Figure 7). The paleo-discharge network output was used accordingly to extract the dominant active channels throughout basin-fill evolution (Figure 8a,b). The extraction of the dominant channels allows us to detect the location of major avulsion sites (Figure 9a) and their distribution in the time-space (Wheeler) domain (Figure 9b). Figure 9b illustrates how the magnitude of a delta-lobe switch varies throughout the A/S cycle of the base case scenario. During early periods of relative sea-level fall only a few major avulsions occur in the vicinity of the sediment entry point. The frequency of major avulsions gradually diminishes during periods of fixed drainage when sea level drops below the shelf break. Base-level rise induces upstream aggradation which in turn increases avulsion frequency which peaks around the MFS, at the turnaround from retrogradation to progradation (TST to HST). The magnitude of delta-lobe switching is correlated with the location of major avulsion sites: proximal sites located close to the sediment entry point induce higher magnitudes of delta-lobe switching than distal sites.

| Subdivision of the FSST
Previous outcrop-and seismic-based studies have illustrated the offlapping and downlapping of stratal packages interpreted to be the product of a descending shoreline trajectory during the late falling stage (Fielding, 2010(Fielding, , 2015Li, Bhattacharya, & Zhu, 2011;Plint & Nummedal, 2000;Zhu et al., 2012). Note numerical experiments show that there might be other formative mechanisms for these stratal packages . Formation of the FSST occurs during the time interval marked by the BSFR and the surface corresponding to the lowest point on the relative sea-level curve (CC sensu Hunt & Tucker, 1992), and thus corresponds in duration to the maximum stratigraphic gap represented by the composite sequence boundary (Figure 6c). The abrupt decrease of major avulsions, which roughly coincides with the timing of shelf-break exposure, may be used to separate early from late FSST deposits (Figure 10b). All chronosomes that originated during the A/S cycle, with the exception of those formed during intervals in which sea-level drops below the shelf break, are mostly aggradational and may be subdivided into units bounded by delta-lobe abandonment surfaces associated with major avulsions (Figure 10b) (Dalman et al., 2015;Karamitopoulos et al., 2014). Owing to incision at the shelf edge and the near-absence of major avulsions, abandonment surfaces are not present in late FSST chronosomes, and their internal architecture is fundamentally different. Therefore, spatially distinct late FSST chronosomes that can be identified by the post-processing routines tend to have larger volumes, which is also expressed by their high degree of connectivity.

| Icehouse versus Greenhouse stratigraphy
The architecture of fluvial, delta-plain, and cross-shelf sedimentary segments is governed by the location of the river mouth and by the degree of shelf-break exposure. In the subaerial part of the system, the segments occupy the main pathways by which sediments are transferred from onshore to offshore areas. This is consistent with the previous field, experimental and numerical studies concerned with the origin, formation, and architectural arrangement of fluvial-shelf stratal units (Blum & Aslan, 2006;Blum & Hattier-Womack, 2009;Blum, Martin, Milliken, & Garvin, 2013;Holbrook, Scott, & Oboh-Ikuenobe, 2006;Martin et al., 2009;Pellegrini et al., 2017;Strong & Paola, 2008). High rates of base-level change as in the base case scenario (RC1), which represents icehouse periods, may expose the shelf-break during late FSST and initiate a phase of fixed and focused drainage marked by incision and lack of major avulsions (Figures 8a  and 9b), dominated by mouth-bar induced bifurcations and high rates of progradation. The increased sediment discharge during the late falling stage in real-world systems caused by the merging of adjacent drainage areas (Blum et al., 2013) will increase the rate of progradation of late falling-stage chronosomes relative to our base-case scenario.
Conversely, low-amplitude sea-level change, representative of greenhouse periods (Figure 1a: green curve), prevents shelfbreak emergence during the relative sea-level fall and hence the inherited topography (i.e., river and shelf gradients, shelf width) and the rate and amplitude of A/S variations regulate channel-network evolution. This morphodynamic pattern favours the residence of large sediment volumes along a limited shelf range (both at highstand and lowstand coastlines) which may be remobilized by coastal processes to give a massive accumulation of slope and basin-floor sediments (Blum & Hattier-Womack, 2009;Blum et al., 2013;Carvajal & Steel, 2006;Gong, Steel, Wang, Lin, & Olariu, 2016;Harris et al., 2020;Posamentier & Kolla, 2003;Ridente, 2016;Sømme, Helland-Hansen, Martinsen, & Thurmond, 2009;Steel, Olariu, Zhang, & Chen, 2019;Sweet & Blum, 2016). Major avulsions with relatively large river-mouth shifts dominate the entire sequence, in contrast with the icehouse pattern (Figure 8a,b). It is also clearly evident that the low-amplitude base-level changes increase the magnitude and frequency of delta-lobe switches (Figure 8b,c). and with a superimposed higher-frequency allogenic signal (25 kyr wavelength), respectively. As shown in Figure 11c, high-frequency allogenic forcing may cause landward and basinward fluctuation of the mouth bar and shoreline areas, which severs the connection between the fluvial distributary segment and the area beyond the shelf break, causing fragmentation of the coarse-grained units. This is consistent with previous experimental work on coastal-plain and cross-shelf paleovalley formation in response to high-frequency sealevel change which demonstrated a disequilibrium response to external forcing (Strong & Paola, 2008). From a sequencestratigraphic perspective, the result of such high-frequency fluctuations has been previously described as a "stranded parasequence" (Plint & Nummedal, 2000) and/or high-frequency cut and fill cycle (Zhu et al., 2012). Our simulations suggest that such "stranded" units may represent short episodes of stagnant or rising base level during an overall baselevel fall. Figure 12 illustrates how large-scale connectivity varies throughout the base case scenario. The earliest and late FSST chronosomes demonstrate the highest large-scale connectivity in their proximal and distal areas, respectively. Avulsion frequency increases during the periods of relative sea-level rise as a consequence of the combined effect of auto-and allogenic aggradation, which in turn decreases large-scale connectivity. LST and early TST chronosomes demonstrate moderate connectivity which is amplified in the vicinity of the shelf break owing to higher back-fill rates in the major trunk channel and the adjacent topographic lows.

| CONCLUSIONS
In this paper, we used a process-based stratigraphic model of fluvio-deltaic stratigraphy to simulate fluvio-deltaic system evolution by simulating accommodation-to-sedimentsupply (A/S) cycles of varying wavelength and amplitude. A number of post-processing routines were developed to investigate channel-network evolution throughout the A/S cycles, estimate net sediment accumulation rates and extract chronostratigraphically constrained lithosomes (or chronosomes). As shown in Figure 12, post-processing provides a straightforward measure of large-scale connectivity, that is, the spatial distribution of high net-gross lithologies. Our approach permits the quantification of sub-seismic-scale sedimentary heterogeneity of fluvio-deltaic deposits and provides a coherent predictive model of lithofacies distribution throughout the modelled A/S cycles. The earliest and late FSST chronosomes demonstrate the highest largescale connectivity in their proximal and distal areas, respectively. LST and early TST chronosomes demonstrate moderate connectivity which is amplified in the vicinity of the shelf break owing to higher back-fill rates in the major trunk channel and the adjacent topographic lows. The magnitude and frequency of delta-lobe switches vary throughout the A/S cycle. The stratigraphic expression of a delta-lobe switch marked by a major avulsion provides the key to a high-resolution subdivision of fluvio-deltaic deposits into chronosomes. The timing of avulsion-induced abandonment surfaces in real-world stratigraphy will most likely be influenced by the intertwined perturbations of high-frequency allogenic forcing and differential subsidence. Sedimentary packages of the late FSST form in response to the exposure of the shelf edge at the terminal parts of the incisedvalley transfer system, and become physically isolated to form "stranded" segments. The architectural arrangement of these late FSST chronosomes, which develop during periods of sporadic major avulsions, is fundamentally different from that of the other chronosomes, which develop under the conditions of (local) aggradation by means of rapid avulsion-induced depocentre shifts. High-frequency allogenic forcing may cause the landward and basinward fluctuation of the mouth bar and shoreline areas and interrupt the connection between the fluvial distributary segment leading to "stranded" coarse-grained segments.

| Future research
The results of this study suggest that subsurface lithology prediction at sub-seismic scales may strongly benefit from the analysis of synthetic 3-D stratigraphic records generated with process-based numerical models that account for allogenic and autogenic forcing. The predictive capabilities of process-based stratigraphic models may be improved by (1) expanding the experimental parameter space and using the proposed post-processing routines to expand on the generic lessons learned in this study and (2) directly matching to real-world settings by linking surface processes to substrate characteristics (e.g., groundwater table fluctuation and subsidence) as well as by integrating multiscale, multitype datasets (including satellite and geophysical/geological data supported by absolute and relative dating techniques) in order to approximate the initial and boundary conditions of prospective sedimentary basins; thus more accurately reconstruct the genetic structure and physical continuity of fluviodeltaic chronosomes. The former approach may be used in settings were data density is limited, the latter in settings were enough knowledge is present to allow a reasonable estimate of the necessary model parameters to obtain a good fit.