https://doi.org/10.1130/G45507.1

Manuscript received 20 August 2018 Revised manuscript received 25 January 2019 Manuscript accepted 6 March 2019

© 2019 The Authors. Gold Open Access: This paper is published under the terms of the CC-BY license. Published online 22 March 2019

The largest delta plain in Earth’s history Tore Grane Klausen1,2, Björn Nyberg1, and William Helland-Hansen1 1Department of Earth Science, University of Bergen, Allégaten, 41, 5020 Bergen, Norway 2Petrolia NOCO AS, Espehaugen 32, 5836 Bergen, Norway

ABSTRACT marine-influenced parts of river systems (Blum Delta plains host heavily populated and extensive agricultural areas with strong anthropo- and Roberts, 2009; Bhattacharya et al., 2016). genic overprints on the natural evolution of these important landforms. Furthermore, mod- Siliciclastic sedimentation in the TBO started ern delta plains have formed over a short geological time frame, representing immature end with very high sedimentation rates shortly after members to ancient counterparts in Earth’s history—it could thus be argued that these are the Permian-Triassic event (Eide et al., 2017), poor analogues for deciphering the sedimentary rock record. Our present study offers unique resulting in kilometer-thick siltstone-dominated insight into the controls and potential extent of ancient deltas by investigation of the Triassic successions prograding >1000 km into the basin Boreal Ocean, where a large delta plain has been traced across >1.65 × 106 km2. We show by during the Induan (Early Triassic) and creat- comparison that the Triassic Boreal Ocean delta plain is larger than all modern and known ing a relatively shallow epicontinental basin. ancient counterparts. Supply-driven progradation of this delta system proceeded uninter- After a reduction in sediment influx during the rupted on a 106 yr scale, indicating relative sea-level stability during this period—in support ­Olenekian and part of the Anisian, indicated by of a Triassic Greenhouse without pronounced glaciations. Reconstructed paleo-bathymetric the slight backstepping of sedimentary pack- relief shows the Triassic Boreal Ocean to have been one order of magnitude smaller than ages relative to the Induan (Fig. 1C), sediment modern equivalents, explaining its vast extent. Despite its extent, the delta plain shows similar supply resurged in the Middle Triassic Ladinian geomorphological characteristics to many modern delta plains, supporting their validity as interval. Because the northwestern boundary of analogues to the ancient, although scales might vary significantly. this system cannot been defined, it is impossible to say how far the system prograded, but it had INTRODUCTION resuming the depositional style characterizing to prograde >500 km to cover the entire basin Understanding the character and develop- foregone periods with prolonged highstands, with deltaic sediment. This westward migration ment of delta plains is crucial to constraining such as the Triassic, when low-gradient delta of its main depocenter could be explained by past eustatic sea level (Haq et al., 1987; Miller plains developed over the large marine areas the Ladinian humid interval (Bernardi et al., et al., 2005), paleogeographic reconstructions that are today occupied by continental shelves. 2018) and later Carnian pluvial events (Hochuli (Miller et al., 2013), past climate (Hochuli To investigate the character and extent of and Vigran, 2010) as possible climatic drivers and Vigran, 2010), and the evolution of life a large-scale delta plain unaffected by human that facilitated resurgence in sediment supply (Woodroffe et al., 2006; Greb et al., 2006). interaction, we use seismic reflection data and to the basin. Our understanding of the nature and character well logs to study the subsurface succession Semi-parallel subsurface seismic reflec- of ancient deltaic depositional environments is of the Triassic Boreal Ocean (TBO; Fig. 1). tions are tied to specific periods within the Tri- complicated by how modern delta plains have This succession is characterized by a large assic according to biostratigraphic information developed in an anomalous Holocene highstand (hundreds-of-kilometers areal extent) deltaic (Vigran et al., 2014) and are traceable throughout period with strong anthropogenic influence. For river system of Carnian age (237–227 Ma) the greater Barents Sea basin. Within the Mid- example, sediments trapped upstream by dams across the entire present-day Barents Sea and dle to Upper Triassic (Ladinian to early Norian) combined with bank-stability measures and a is also exposed in outcrops in islands along the Snadd Formation, each progradational package rising global sea level (Syvitski et al., 2009) uplifted northern flank of the basin (Klausen approximates 2–5 m.y. (Paterson and Mangerud, result in net land loss downstream (Blum and et al., 2015). We consider the overall extent of 2017), and within these discrete rock intervals, Roberts, 2009)—directly affecting the shape the TBO delta plain in relation to ancient and characteristic contrasts in acoustic properties of delta plains (Syvitski and Saito, 2007). With modern analogues, and discuss the exceptional enable identification of geomorphological fea- global sea level expected to rise (Rahmstorf, circumstances required to produce the largest tures down to ~15 m thickness in three-dimen- 2007) and delta plains continuing to subside delta plain in Earth’s history. sional (3-D) seismic data, and are used together (Syvitski et al., 2009), present geomorphologi- with core and well logs to interpret fluvial and cal characteristics of deltas are being affected CHARACTERISTICS OF THE TRIASSIC interbedded shallow marine depositional envi- by extreme and anomalous effects of anthropo- BOREAL OCEAN DELTA PLAIN ronments. Three-dimensional seismic data show genic interference. Given that this interference A delta plain is defined as the coastal areas large-scale channel belts up to 25 km wide and is not counteracted, the present interglacial high- with a common gradient profile, controlled by >50 m thick with pronounced lateral accretion stand could be sustained (Archer and Ganopol- backwater-length, toward a proximal knickpoint surfaces in the eastern part of the basin, formed ski, 2005) while deltas will be prevented from between the alluvial plain and the fluviatile to during the early Carnian interval (Fig. 2). This is

CITATION: Klausen, T.G., Nyberg, B., and Helland-Hansen,W., 2019, The largest delta plain in Earth’s history: Geology, v. 47, p. 470–474, https://​doi.org​ /10​ ​ .1130​/G45507.1

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Downloaded from http://pubs.geoscienceworld.org/gsa/geology/article-pdf/47/5/470/4680578/470.pdf by guest on 24 September 2021 Figure 1. Area and strati- A B Stratigraphy Lithostrat. Fm. pronounced eustatic sea-level lowering (Reijen- graphic context of study, Greenland North Pole o Ma WE o 0 E Rhaetian stein et al., 2011). Large parts of LGM delta Barents Sea region. 80 N 40oE A,B: Regional setting of 208 Norian plains could therefore be net degradational. To uholmen Franz Josef Upper

modern Barents Sea (A), Svalbard Fr avoid underestimation, the full possible extents oo Land 227 hosting Boral Ocean in 7080 NN Carnian of these LGM delta plains are considered (see 237 Triassic, a period when FiGreenlang. 2 d Barents Sea Snadd the Data Repository). We exclude the arctic iassic 7 Ladinian basin was dominated 0 0° Novaya Tr ° 242 N 20° Barents and Kara shelves from LGM estimates by several phases of Svalbard C Zemlya Middle Anisian 40 Kobbe °

Norway 247 because they were characterized by grounded delta progradation (B). r

Olenekian rt C: Regional cross sec- Barents

ve ice sheets during glaciations (Jakobsson et al., Klappmyss Russia 251 400 km Se Lowe

Induan Ha 2 Urals tion shows continuity of 0 a ° 2016). The largest polar LGM shelf is located study interval (pink box Study interval Devonian-Permian O shore marine Non-marine in the Chukchi Sea, covering ~8.26 × 105 km2 or within Carnian interval Basement Late Cretaceous Intrusions Shallow marine in B)—stretching beyond C 7324/7-1S Flattened on Top Jurassic approximately half the size of the conservative limits of our data set to TBO delta plain estimate (Fig. 4B). Outside of west and toward Novaya polar regions, the LGM shelf of the Gulf of Car- Zemlya in east. Well pentaria (Australia) represents an area of 9.01 × 7324/7-1S was one of sev- 5 2 eral wells used to tie the 10 km , and the Yellow Sea represents an area of stratigraphic intervals to 8.56 × 105 km2. The Sunda shelf is also large but regional seismic profiles 200 ms 500 km comprised two distinct paleo-deltaic draining and 3-D seismic cubes systems from the north and south (Reijenstein (data were made available et al., 2011; Sathiamurthy and Voris, 2006), rep- by the Norwegian Petroleum Directorate). The regional seismic section is flattened on the 5 2 5 regional seismic reflector tied to the top of the Jurassic package. Black lines are formation resenting areas of 8.81 × 10 km and 4.98 × 10 boundaries. Triassic strata are marked with purple fill; Jurassic with blue fill. Westward migra- km2 respectively, amounting to a combined area tion of the main depocenter is initiated in Middle Triassic Ladinian interval, representing the of 1.38 × 106 km2. Despite our overestimates of lower part of the Snadd Formation. Lithostrat.—lithostratigraphy; Fm.—formation. the extents of LGM deltas, the TBO delta plain out-scales all. characteristic of meandering river systems form- deposits attests to steady generation of accom- Estimating the size of net-aggradational ing in proximal parts of delta plains. The late modation (Fig. DR2 in the Data Repository) delta plains in the rock record is challenging Carnian shows similar but narrower channelized without periods of substantial degradation. because discrete delta plain boundaries are not deposits, with both delta plains stretching across This is an important characteristic of the TBO: readily constrained and commonly, due to post- the basin (Klausen et al., 2015). its delta plain was overall net aggradational depositional erosion, are incomplete. Tectonic In this study, we restrict the TBO delta out- across its widespread extent. overprint is also a limiting factor. An approxima- line to the present shelf edge of the Barents Sea tion is offered by comparison of the conservative that overlies Triassic strata with deltaic depos- COMPARISON TO MODERN AND outline for the TBO delta plain to interpreted its. Areas with time-equivalent deltaic deposits ANCIENT COUNTERPARTS outlines of formations with known large delta in eastern Greenland and the Canadian Sver- Modern delta plains are geologically young systems (Reijenstein et al., 2011; Broughton, drup Basin (Hamann et al., 2005; Omma, 2009; and started prograding ~10 k.y. ago following 2016; Blum et al., 2017) and areas with exten- Sømme et al., 2018) are excluded from the total eustatic sea-level rise in response to the retreat sive near-coast terrestrial deposition (Golonka, area (see the GSA Data Repository1). This is of ice coverage of the Last Glacial Maximum 2007) (Fig. 4C). Epicontinental seas, such as the a conservative approach to defining the actual (LGM; Hanebuth et al., 2000; Berné et al., Western Interior Basin (WIB, North America), potential size of the delta, as its basinward termi- 2007). This contrasts with the TBO delta plain, were as much as 3.5 × 106 km2 in extent and cov- nation is not observed within the present outline. where each progradational package approxi- ered by terrestrial deposits at maximum regres- Prodeltaic, shallow marine, and bay deposits, mates 2–5 m.y. (Klausen et al., 2015) and sion, but comprised multiple discrete deltas not however, interfinger with terrestrial deposits, developed in a basin with steady accommoda- necessarily coeval or in a state of net aggra- demonstrating that this is a delta plain, not a tion. Comparing the areal extent of ancient and dation (Bhattacharya et al., 2016). One large floodplain (Klausen et al., 2015). The conserva- modern delta plains illustrates how different delta plain of the WIB in a net-aggradation state tive estimate compensates for post-depositional these geomorphological features can be at their at maximum regression is represented by the tectonic stretching, which acted to extend the mature and juvenile stages. The largest modern Late Cretaceous McMurray Formation (western area over which the delta was originally depos- delta plain is associated with the Amazon River Canada). Although parts of this succession have ited (Faleide et al., 2008). Restricted by the pres- and covers ~1.08 × 105 km2 (Fig. 4A), more been eroded, lower delta plain deposits observed ent shelf and the easternmost observations of than an order of magnitude smaller than the in northern outcrops constrain parts of the del- terrestrial Carnian deposits, the TBO delta plain TBO delta plain. taic part of this system (Broughton, 2016) and is measured to cover >1.65 × 106 km2 (Fig. 3). Cenozoic glacio-eustatic lowstands caused suggest that it is comparable in size (~1.02 × Despite subaerial exposure indicators such delta plains to extend across the shallow marine 106 km2, based on outlines of Benyon et al. as paleosols, the TBO delta plain shows no areas now characterized as continental shelves [2014]) to the TBO delta plain. Global paleogeo- signs of incision exceeding tens of meters (Hanebuth et al., 2000). The LGM represents the graphic reconstructions are poorly constrained (Klausen et al., 2015). The limited incision last of a series of lowstand stages and its depos- for comparison with the TBO delta plain, but can explained by autogenic processes, which its shaped modern shelves that consequently we note that some ancient coastal regions with together with thick successions of terrestrial provide an estimate for the possible extent of terrestrial deposition approach conservative esti- delta plains developed during lowstand eustatic mates of the extent of the TBO delta plain, all 1GSA Data Repository item 2019177, supplemen- conditions. Pleistocene deposits of the northern ~1.3 × 106 km2 (Table DR1 in the Data Reposi- tary text and figures for delta outline estimates, and table of outline values, is available online at http://​ Sunda shelf (southeast Asia) is an example of tory). These paleogeographic reconstructions www​.geosociety​.org​/datarepository​/2019/, or on such a LGM delta plain, and within its strati- (Golonka, 2007) do not discriminate between request from editing@​geosociety​.org. graphic record are indications of incision during possible multiple deltaic systems, and go beyond

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Downloaded from http://pubs.geoscienceworld.org/gsa/geology/article-pdf/47/5/470/4680578/470.pdf by guest on 24 September 2021 Figure 2. Distribution and character of channelized 7131/4-1 deposits on Triassic Boreal 2. AA′ Ocean (TBO) delta plain. Root mean square (RMS) relative signal strength attribute maps Bjørnøya are from 11 different three- dimensional seismic surveys (two surveys are merged in northwest) extracted on 100 ms 5 km horizon equivalent to maxi- mum regressive stage in 1. 10 km early Carnian. Channelized deposits with lateral accre- N tion characterize proximal 7324/7-1S parts of study area, whereas Present 7321/8-1 A coastline western parts are dominated 2. A′ Seismic pro le by ribbon-shaped, elongated (Figure DR1) 7324/10-1 channelized deposits. Change Wellbores used from belt to ribbon approxi- in Figure DR2 1. mate change from trunk river Channel belts Lorem ipsum to distributary rivers in lower Channel lls delta plain. Stratigraphic inter- Lateral accretion val illustrated in these attribute maps is shown in Figure DR2 (see footnote 1). Scale bar applies to all surveys, and 3-D seismic their relative distance is at RMS Amplitude scale, showing vast extent Max over which these channel- ized deposits are mappable. 1. Island of Bjørnøya (Svalbard) Min is included for geographical reference. 3-D—three-dimen- N 50 km sional; Max—maximum; Min—minimum. Inset 1 is close-up of lateral accretion surfaces characterizing channel belt deposits in eastern parts of study area. Inset 2 is cross section through meander bend in inset 1, showing lateral accretion surfaces relative to a well (7131/4-1 [data were made available by the Norwegian Petroleum Directorate]; gamma ray log in yellow, core interval in white) in near-angle offset two-dimensional seismic data.

the limited regions strictly defined as deltaic to sourced from the southeast controlled sediment relief in front of the prograding delta (Fig. 4D). include all terrestrial deposits. The largest area distribution to its associated delta plain (Klausen This relief has been defined using reconstructed defined as deltaic (Golonka, 2007) is represented et al., 2015). High precipitation was facilitated prodeltaic clinoform surfaces following methods by the Kamienna Group in southeastern Europe, by monsoonal climate (Hochuli and Vigran, outlined in Klausen and Helland-Hansen (2018) estimated to cover ~7.1 × 105 km2. 2010). Most important for extensive prograda- and indicate a paleobathymetry of ~400 m (Fig. Estimates of the TBO drainage area equal tion was, however, a restricted paleobathymetric DR3). Although modern deltas could potentially those of the largest in the world (Fig. 3); within migrate rapidly seaward in the more restricted this drainage area, Uralide topography likely water depths characterizing modern shelves 80°N 85°N 85°N 80°N Modern surpassed that of the present, ranging from 4 watersheds (~120 m), created during late Holocene flood- TBO delta to 6 km based on plate tectonic configurations 40°W outline ing (Hanebuth et al., 2000), this progradation Catchment (Puchkov, 2009). Although multiple smaller estimates (km2) would be halted by an increase in bathymetric P 6 rivers likely contributed to the overall water min 1.12 x 10 relief ranging from 2000 m to 4000 m at their b P 6 20°W mean 3.32 x 10 and sediment discharge in the catchment, the P 6 shelf edge (Fig. 4D), as deltas have repeatedly Fig. DR4 max 6.76 x 10 presence of a single major trunk river system Topography (m) been throughout the Cenozoic. Steady accom- 10°W Fig. 2 4000 a modation and the likely absence of incision 0 negate eustatically driven relative sea-level falls –6000 of ~50 m as inferred in the TBO basin by Haq P Figure 3. Areal extent and drainage estimates min et al. (1987). Although smaller-scale sea-level of Triassic Boreal Ocean (TBO) delta plain. 0° Shown are conservative estimate of TBO delta variations likely occurred and could, in addi- tion to autocyclic delta lobe switching, explain plain outline, supported by previous studies Pmean (Miller et al., 2013; Klausen et al., 2015), and parasequence-scale flooding surfaces, the large-

three potential catchment areas for this delta Pmax scale delta architecture seems to have been con- plain (minimum, mean, and maximum cases trolled by transgressive-regressive cycles driven constrained by different paleogeographic scenarios discussed in Data Repository [see by normal progradation during prolonged sea- footnote 1]) compared to modern watersheds level highstand interrupted by transgressions at in same area. Yellow lines indicate position of 10°E time scales of 106 yr. These transgressive-regres- published geologic sections (Hamann et al., sive cycles were likely caused by tectonically 2005; Faleide et al., 2008), which indicate that TBO delta plain extended beyond conserva- (Watts, 1982) and climatically (Hochuli and tive estimates used in present study (Fig. DR4 01500 ,000 Vigran, 2010) driven variations in subsidence [see footnote 1]). km and sediment supply.

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Downloaded from http://pubs.geoscienceworld.org/gsa/geology/article-pdf/47/5/470/4680578/470.pdf by guest on 24 September 2021 A Amazon Mississippi YangtzeINile rrawaddy Orinoco plains of this scale normally form on passive linked with the Carnian Pluvial Episode: Nature margins with relatively high preservation poten- Communications, v. 9, 1499, https://​doi​.org​/10​ TBO .1038​/s41467​-018​-03996​-1​. Ganges- Mekong Niger km tial (­Woodcock, 2004). Brahmaputra 0 750 1 500 Berné, S., Jouet, G., Bassetti, M.A., Dennielou, B., and We conclude that (1) compared to a wide Taviani, M., 2007, Late Glacial to Preboreal­ sea- B Sunda Shelf Gulf of Chukchi Sea Yellow Sea Bering Sea range of delta plains, some of which are likely level rise recorded by the Rhône deltaic system Carpentaria composed of multiple river systems, the largest (NW Mediterranean): Marine Geology, v. 245, delta plain in Earth’s history developed in the p. 65–88, https://​doi​.org​/10​.1016​/j​.margeo​.2007​ .07​.006​. TBO of northern Pangea; (2) widespread delta Bhattacharya, J.P., Copeland, P., Lawton, T.F., and Java Sea plains require high sediment input from a large Holbrook, J., 2016, Estimation of source area, East Siberian Laptev Sea North Sea drainage area, but the most important prerequi- river paleo-discharge, paleoslope, and sediment Sea budgets of linked deep-time depositional sys- Sea of Okhotsk site for the TBO was the shallow marine basin it prograded into; and (3) thick successions of tems and implications for hydrocarbon potential: Earth-Science Reviews, v. 153, p. 77–110, https://​ nonmarine deposits indicate prolonged sea-level C Paleocene Jurassic Triassic Permian Carboniferous doi​.org​/10​.1016​/j​.earscirev​.2015​.10​.013​. Gulf of Mexico Kamienna Group highstand uninterrupted by significant shoreline Blum, M.D., and Roberts, H.H., 2009, Drowning of SE Europe the Mississippi Delta due to insufficient sediment Chinle Fm Val Gardena translocations, negating glacially driven eustatic Brent Group W America Sandstone Dwyka Group changes and supporting a persistent Triassic supply and global sea-level rise: Nature Geosci- Late Cretaceous North Sea Europe SW Africa greenhouse setting (Miller et al., 2005). ence, v. 2, p. 488–491, https://​doi​.org​/10​.1038​ /ngeo553​. McMurray Fm Neuquen Basin Saad/Aheimer The TBO delta plain comprises a delta plain N America S America Fm Blum, M.D., Milliken, K.T., Pecha, M.A., Snedden, NE Africa end member unaffected by anthropogenic fac- J.W., Frederick, B.C., and Galloway, W.E., 2017, Detrital-zircon records of Cenomanian, Paleocene, TBO delta outline Silurian tors and major fluctuations in global sea level— Gulf of Mexico Delta outlines Titicaca Group Mereenie illustrating how extensive progradation and and Oligocene Gulf of Mexico drainage integration Outline of coastal SW America Sandstone and sediment routing: Implications for scales of Australia terrestrial deposits net land gain characterize delta progradation. basin-floor fans: Geosphere, v. 13, p. 2169–2205, D Despite profound differences, the character of TBO shelf https://​doi​.org​/10​.1130​/GES01410​.1​. Amazon shelf the TBO delta plain and associated river sys- Broughton, P.L., 2016, Alignment of fluvio-tidal point bars in the middle McMurray Formation: Impli- Sunda shelf Mississippi shelf tem resemble Quaternary counterparts in terms 100 km 1000 m of delta plain development, demonstrating that cations for structural architecture of the Lower Cretaceous Athabasca Oil Sands Deposit, north- discharge and equilibrium profiles control depo- Figure 4. Comparison of surface area for large- ern Alberta: Canadian Journal of Earth Sciences, scale deltas from different periods. A: Triassic sitional styles in modern and ancient times alike. v. 53, p. 896–930, https://​doi​.org​/10​.1139​/cjes​ Boreal Ocean (TBO) delta plain from Figure Although partly countered by high global sea -2015​-0137​. 3 compared to modern deltas: the Amazon level, increased river discharge from climatic Eide, C.H., Klausen, T.G., Katkov, D., Suslova, A.A., River Delta, Brazil; the Mississippi River Delta, change (Meehl et al., 2005) can potentially facil- and Helland-Hansen, W., 2017, Linking an Early USA; The Yangtze River Delta, China; the Nile Triassic delta to antecedent topography: Source- River Delta, Egypt; the Irrawaddy River Delta, itate future TBO delta plain equivalents under to-sink study of the southwestern Barents Sea Myanmar; the Orinoco River Delta, Venezuela; prolonged interglacial conditions (Rahmstorf, margin: Geological Society of America Bulle- the Ganges-Brahmaputra River Delta, India 2007). Their extent will however be restricted tin, v. 130, p. 263–283, https://​doi​.org​/10​.1130​ and Bhangladesh; the Mekong River Delta, by bathymetric relief, current plate-tectonic /B31639​.1​. Vietnam; and the Niger River Delta, Nigeria. distributions, and topographic hinterland relief, Faleide, J.I., Tsikalas, F., Breivik, A.J., Mjelde, R., B: Possible Last Glacial Maximum (LGM) delta Ritzmann, O., Engen, Ø., Wilson, J., and Eld­ outlines: Sunda Shelf, Southeast Asia; Gulf of lowering the likelihood for out-scaling the TBO holm, O., 2008, Structure and evolution of the Carpentaria, Australia; Chukchi Sea, Laptev delta plain. continental margin off Norway and the Barents Sea, East Siberian Sea and Sea of Okhotsk, Sea: Episodes, v. 31, p. 82–91. Russia; Bering Sea; Russia and USA; North ACKNOWLEDGMENTS Golonka, J., 2007, Late Triassic and Early Jurassic Sea, northern Europe; Java Sea, Indonesia. This study was funded in full by the Research Council palaeogeography of the world: Palaeogeogra- C: Ancient terrestrial basins. All delta plain of Norway through the ISBAR (Source-to-Sink of the phy, Palaeoclimatology, Palaeoecology, v. 244, outline polygons are of similar scale, as pre- Triassic Barents Sea) project, grant number 267689. p. 297–307, https://doi​ .org​ /10​ .1016​ /j​ .palaeo​ .2006​ ​ sented in A. Fm—formation. D: Comparisons Open Access was made possible with support from .06​.041​. of reconstructed bathymetric profile from TBO the University in Bergen and the ISBAR project. Greb, S.F., DiMichele, W.A., and Gastaldo, R.A., (Fig. DR3 [see footnote 1]) to some modern We are grateful for access to seismic data provided 2006. Evolution and importance of wetlands counterparts. Projection and constraints on by TGS-Nopec (Oslo, Norway) and the Norwegian in Earth History, in Greb, S.F., and DiMichele, delta outlines and bathymetry are discussed Petroleum Directorate, and academic software licenses W.A., eds., Wetlands through Time: Geological in Data Repository (see footnote 1). provided by Schlumberger and Esri (California, USA). Society of America Special Paper 399, p. 1–40, Marina Rabineau, three anonymous reviewers, and https://​doi​.org​/10​.1130​/2006​.2399​(01)​. editor Mark Quigley are gratefully thanked for many Hamann, N.E., Whittaker, R.C., and Stemmerik, L., CONCLUSIONS AND IMPLICATIONS thoughtful comments and suggestions that improved 2005, Geological development of the Northeast the manuscript considerably. 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