Sedimentary Geology 176 (2005) 67–95 www.elsevier.com/locate/sedgeo Research paper Precambrian sequence stratigraphy

O. Catuneanua,T, M.A. Martins-Netob, P.G. Erikssonc aDepartment of Earth and Atmospheric Sciences, University of Alberta, 1-26 Earth Sciences Building, Edmonton, Alberta, Canada T6G 2E3 bGeology Department, Federal University of Ouro Preto, Caixa Postal 173, 35400-000, Ouro Preto/MG, Brazil cDepartment of Geology, University of Pretoria, Pretoria 0002, South Africa Received 3 May 2004; received in revised form 22 October 2004; accepted 20 December 2004

Abstract

Sequence stratigraphy studies the change in depositional trends in response to the interplay of accommodation and sediment supply, from the scale of individual depositional systems to entire sedimentary basin-fills. As accommodation is controlled by allogenic mechanisms that operate at basinal to global scales, the change in depositional trends is commonly synchronized among all environments established within a basin, thus providing the basis for the definition of systems tracts and the development of models of facies predictability. All classical sequence stratigraphic models assume the presence of an interior seaway within the basin under analysis and are centered around the direction and types of shoreline shifts, which control the timing of all systems tracts and sequence stratigraphic surfaces. In overfilled basins, dominated by nonmarine sedimentation, the definition of systems tracts is based on changes in fluvial accommodation, as inferred from the shifting balance between the various fluvial architectural elements. The method of sequence stratigraphy requires the application of the same set of core principles irrespective of the age of strata under analysis, from Precambrian to Phanerozoic. The study of Precambrian basins is often hampered by poorer stratal preservation and by a general lack of time control. However, where sedimentary facies are well preserved, the lack of time control may be partially compensated by a good knowledge of facies architecture and relationships, as well as by paleocurrent data. The latter are particularly important to understand the stratigraphic record of tectonically active basins, where abrupt shifts in paleoflow directions allow one to infer tectonic events and map the corresponding sequence-bounding unconformities. Arguably the most important contribution of Precambrian research to sequence stratigraphy is the better understanding of the mechanisms controlling stratigraphic cyclicity in the rock record, and hence of the criteria that should be employed in a system of sequence stratigraphic hierarchy. There is increasing evidence that the tectonic regimes which controlled the formation and evolution of sedimentary basins in the more distant geological past were much more erratic in terms of origin and rates than formerly inferred solely from the study of the Phanerozoic record. In this context, time is largely irrelevant as a parameter in the classification of stratigraphic sequences, and it is rather the stratigraphic record of changes in the tectonic setting that provides the key criteria for the basic subdivision of the rock record into basin-fill successions separated by first-order sequence boundaries. These first-order basin-fill successions are in turn subdivided into second- and lower-order sequences that result from shifts in the balance between accommodation and sedimentation at various scales of observation, irrespective of the time

T Corresponding author. E-mail address: [email protected] (O. Catuneanu).

0037-0738/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.sedgeo.2004.12.009 68 O. Catuneanu et al. / Sedimentary Geology 176 (2005) 67–95 span between two same-order consecutive events. Sequences identified in any particular basin are not expected to correlate to other first- and lower-order sequences of other basins that may be similar in age but may have different timing and duration. D 2005 Elsevier B.V. All rights reserved.

Keywords: Precambrian; Sequence stratigraphy; Depositional trends; Cyclicity mechanisms

1. Introduction sparked an intense debate, still ongoing, regarding the relative importance of eustasy and tectonism on 1.1. Overview sedimentation, which is highly important to the understanding of Earth history and fundamental Earth Sequence stratigraphy is a modern interdisciplinary processes. Beyond sea level change and tectonism, the approach in the broad field of sedimentary geology spectrum of controls on stratigraphic patterns is that revamps geological thinking and the methods of actually much wider, including additional subsidence facies and stratigraphic analyses. Modern research mechanisms (e.g., thermal subsidence, sediment com- trends show that staying within the boundaries of paction, isostatic and flexural crustal loading), orbital conventional disciplines brings little opportunity for forcing of climate changes, sediment supply, basin significant progress—it is rather the integration of physiography and environmental energy (Fig. 1). The various approaches, data sets, and subject areas that second issue, on the economic aspect of facies generates potential for breakthrough advances in predictability, provides the industry community with science. This is exactly the main theme of sequence a new and powerful analytical and correlation tool for stratigraphy, which integrates the methods of several exploration of natural resources. disciplines with the purpose of providing improved As with any modeling efforts, the reliability of the and reliable models on how sedimentary facies form sequence stratigraphic model depends on the quality and relate to each other within sedimentary basins and variety of input data, and so integration and (Fig. 1). mutual calibration of as many data sets as possible are As opposed to other, more conventional types of recommended. The most common data sources for a stratigraphy, such as biostratigraphy, lithostratigraphy, sequence stratigraphic analysis include outcrops, core, chemostratigraphy or magnetostratigraphy, sequence well logs, and seismic data (Fig. 1). In addition to the stratigraphy has an important built-in interpretation facies analysis of the strata themselves, sequence component that addresses issues such as (1) the stratigraphy also places a strong emphasis on the reconstruction of the allogenic controls at the time geological contacts that separate packages of strata of sedimentation, and (2) predictions of facies characterized by specific depositional trends. Such architecture in yet unexplored areas. The former issue contacts may represent event-significant bounding

Academic applications: genesis and internal architecture of sedimentary basin fills Industry applications: exploration for hydrocarbons, coal, and mineral resources

Sequence Stratigraphy

Integrated disciplines: Main controls: - Sedimentology Integrated data: - sea level change - Stratigraphy - outcrops - subsidence, uplift - Geophysics - modern analogues - climate - Geomorphology - drill core - sediment supply - Isotope Geochemistry - well logs - basin physiography - Basin Analysis - seismic data - environmental energy

Fig. 1. Sequence stratigraphy in the context of interdisciplinary research—main controls, integrated data sets and subject areas, and applications. O. Catuneanu et al. / Sedimentary Geology 176 (2005) 67–95 69 surfaces that mark changes in sedimentation regimes, generation of sequences and bounding unconform- and may be important both for regional correlation, as ities, an idea which is widely accepted today, but was well as for understanding the facies relationships largelyoverlookedintheearlydaysofseismic within the confines of specific depositional systems. stratigraphy. The success and popularity of sequence stratigra- The unconformity-bounded sequences promoted phy stems from its widespread applicability in both by L. Sloss and H. Wheeler in the pre-sequence mature and frontier exploration basins, where data- stratigraphy era provided the geological community driven and model-driven predictions of lateral and with informal mappable units that could be used for vertical facies changes can be formulated respectively. stratigraphic correlation and the subdivision of the These predictive models have been proven to be rock record into genetically related packages of strata. particularly efficient for hydrocarbon exploration, One limitation on this method of stratigraphic analysis although there is an increasing demand to employ is the lateral extent of sequence-bounding uncon- the sequence stratigraphic method for coal and formities, which in many instances are restricted to mineral resource exploration as well. basin margins. Hence, the number of sequences mapped within a sedimentary basin may significantly 1.2. Historical development of sequence stratigraphy decrease down dip, from the basin margins toward the basin center (Fig. 2). This limitation required a Sequence stratigraphy is generally regarded as refinement of the early ideas by finding a way to stemming from the seismic stratigraphy of the 1970s. extend sequence boundaries across an entire sedimen- In fact, major studies investigating the relationship tary basin. The definition of bcorrelative con- between sedimentation, unconformities and changes in formitiesQ, which are extensions towards the basin base level, which are directly relevant to sequence center of basin-margin unconformities, marked the stratigraphy, were published prior to the birth of birth of modern seismic and sequence stratigraphy seismic stratigraphy (e.g., Grabau, 1913; Barrell, (Fig. 3). The advantage of modern model sequences, 1917; Sloss et al., 1949; Sloss, 1962, 1963; Wheeler which are bounded by composite surfaces, consists in and Murray, 1957; Wheeler, 1958, 1959, 1964; Curray, their basin-wide extent—hence, the number of 1964; Frazier, 1974). Even before the 20th century, the sequences mapped at the basin margin equals the periodic repetition through time of processes of number of sequences that are found in the basin erosion, sediment transport and deposition was recog- center. Due largely to conceptual disputes regarding nized by James Hutton (18th century), setting up the foundation for what is known today as the concept of Basin Basin the dgeological cycleT. Hutton’s observations may be margin center considered as the first account of stratigraphic cyclic- ity, where unconformities provide the basic subdivi- D sion of the rock record into repetitive successions. The F link between unconformities and base-level changes C was explicitly emphasized by Barrell (1917), who G stated that bsedimentation controlled by base level will B result in divisions of the stratigraphic series separated E by breaksQ. A The term bsequenceQ was introduced by Sloss et al. (1949) to designate a stratigraphic unit bounded by subaerial unconformities. Sloss emphasized the unconformityA-G sequences importance of such sequence-bounding unconform- ities, and subsequently subdivided the entire Phaner- Fig. 2. The concept of the unconformity-bounded sequence of Sloss et al. (1949). As many unconformities are potentially restricted to ozoic succession of the interior craton of North the basin margins, the number of sequences mapped in the basin America into six major sequences (Sloss, 1963). Sloss center is often lower than the number of sequences present in an also emphasized the importance of tectonism in the age-equivalent succession along the rim of the basin. 70 O. Catuneanu et al. / Sedimentary Geology 176 (2005) 67–95

Basin Basin the scope and the step-by-step routine of the sequence margin center stratigraphic model development are the same irre- spective of the age of the studied sedimentary basin. D D Both Precambrian and Phanerozoic case studies share the common goal of elucidating the history of C C sedimentation in response to base-level changes, but often with different dammunitionT in terms of data B B available for analysis. The basic contrasts between Precambrian and Phanerozoic, in terms of aspects A A relevant to sequence stratigraphy, are summarized in Fig. 4. The amount and quality of data tend to deteriorate unconformity correlative conformity with increasing stratigraphic age, due to factors such as post-depositional tectonics, diagenesis and meta- Fig. 3. The concept of sequence as defined in seismic and sequence stratigraphy. The correlative conformities allow tracing of sequences morphism, which hamper Precambrian case studies across an entire sedimentary basin. A–G—sequences. relative to the Phanerozoic counterparts. Both the preservation potential and the available time control the timing of the correlative conformity relative to the for facies correlations are superior in the case of base-level cycle, this new concept of a sequence younger sequences, and hence the resolution of bounded by unconformities or their correlative con- sequence stratigraphic models that can be constructed formities is yet to be ratified by either the European or for Phanerozoic successions is usually significantly the North American commissions on stratigraphic better relative to what can be achieved for Precam- nomenclature. The concept of bunconformity- brian deposits. For this reason, the method of bounded unitQ (i.e., SlossTbsequenceQ) was only sequence stratigraphy has been developed essentially formalized by the European bInternational Strati- based on the study of Phanerozoic successions, being graphic GuideQ in 1994. subsequently expanded to the study of Precambrian sedimentary basins as well. 1.3. Precambrian vs. Phanerozoic sequence In spite of the limitations imposed by data stratigraphy availability and quality, the application of sequence stratigraphy to the Precambrian should not be The principles of sequence stratigraphy are inde- regarded simply as the low-resolution equivalent of pendent of the age of strata under analysis. Similarly, Phanerozoic sequence stratigraphy. The Precambrian

Precambrian Phanerozoic

Time span c. 88% of Earth ’s history c. 12% of Earth’s history

Relatively poor (due to Facies preservation post-depositional tectonics, Relatively good diagenesis, metamorphism)

Relatively poor (based Relatively good (marker Time control on marker beds and lower beds, biostratigraphy , resolution radiochronology) magnetostratigraphy , radiochronology)

Competing plume tectonics Plate tectonics, more Basin-forming and plate tectonics, more stable regime mechanisms erratic regime

Fig. 4. Main contrasts between Precambrian and Phanerozoic, in terms of aspects relevant to sequence stratigraphy. O. Catuneanu et al. / Sedimentary Geology 176 (2005) 67–95 71 offers not only challenges, but also unique opportu- a sedimentary basin. Authigenic processes (e.g., self- nities, because its time window into the Earth’s induced avulsion in fluvial and deep water environ- geological history is vastly wider relative to the ments) are particularly important at sub-depositional duration of the Phanerozoic (Fig. 4). This greater system scale, and are commonly studied using the time span provides the opportunity for observing methods of conventional sedimentology and facies Earth’s processes at a broader scale, and thus gaining analysis. Allogenic processes, on the other hand, are an improved understanding on issues such as the directly relevant to sequence stratigraphy, as they mechanisms governing stratigraphic cyclicity and the control the regional-scale architecture of the basin-fill. variability thereof. The study of the Precambrian Allogenic controls provide the common platform therefore provides better insights into some key issues that connects and synchronizes the depositional trends of sequence stratigraphy, for which the time span of recorded at any given time in all environments the Phanerozoic is simply too short to allow for any established within a sedimentary basin, thus allowing meaningful generalizations. for sequence stratigraphic models to be developed at The Precambrian record, which encompasses the basin scale. This in turn is the key for the facies nearly 90% of Earth’s history, allows one to see that predictability applications of sequence stratigraphy, the tectonic regimes leading to the formation of which are so much praised by both academic and sedimentary basins were, for the greater part of industry practitioners. The basic allogenic controls on geological time, not as stable or uniform as one might sedimentation include the climate, tectonics and sea infer from Phanerozoic case studies. This has pro- level changes; their relationships with sediment found implications on the selection of criteria that supply, accommodation and depositional trends are should be used to classify stratigraphic sequences, and summarized in Fig. 5. Eustasy and tectonics both helps to resolve existing debates generated from the control directly the amount of space (accommodation) study of the Phanerozoic record. This paper provides a that is available for sediments to accumulate. Climate set of core principles of sequence stratigraphy that are mainly affects accommodation via eustasy, as for valid irrespective of stratigraphic age. It also explores example during glacio-eustatic falls and rises in sea the unique insights offered by the Precambrian record, level. The effect of climate is also reflected in the especially in terms of allogenic controls on sedimen- amount of sediment supply, by modifying the tation and their relevance to the various aspects of efficiency of weathering, erosion, and sediment trans- sequence stratigraphy. port processes. This is why eustasy, tectonics and climate are all invoked when discussing the controls on sedimentation, but only eustasy and tectonics are 2. Basic principles of sequence stratigraphy usually accounted for when dealing with the controls on accommodation (Fig. 5). The principles of sequence stratigraphy have been It is important to note that the allogenic controls summarized in several recent volumes, including are dexternalT relative to the sedimentary basin, but not Emery and Myers (1996), Miall (1997), Posamentier necessarily independent of each other (Fig. 5). and Allen (1999) and Catuneanu (2003). The essential Eustatic fluctuations of global sea level are controlled aspects of the sequence stratigraphic method are by both tectonic and climatic mechanisms, over presented below. various time scales. Climatic fluctuations are primar- ily controlled by orbital forcing (Milankovitch 2.1. Controls on sedimentation and stratigraphic cycles), but at more local scales may also be triggered architecture by tectonic processes such as the formation of thrust- fold belts that may act as barriers for atmospheric Sedimentation is generally controlled by a combi- circulation. Tectonism is primarily driven by forces of nation of authigenic and allogenic processes, which internal Earth dynamics, which are expressed at the determine the distribution of depositional elements surface by plume- or plate-tectonic processes. Criteria within a depositional system, as well as the broader to differentiate between the signatures of eustasy, scale stacking patterns of depositional systems within tectonics and paleoclimate have been summarized in 72 O. Catuneanu et al. / Sedimentary Geology 176 (2005) 67–95

Allogenic Accommodation, Sediment supply controls sedimentation

uplift Tectonics subsidence

uplift, Accommodation tilt (space available for

rise sediments to fill) Eustasy fall

Sediment supply vs. Sedimentation Climate Transport capacity (depositional trends, (water, wind) shoreline shifts)

Fig. 5. Allogenic controls on sedimentation, and their relationship to sediment supply, accommodation and depositional trends (modified from Catuneanu, 2003). Note that the depositional trends (aggradation vs. erosion, progradation vs. retrogradation) represent the end result of this complex interplay between the allogenic controls on sedimentation. numerous publications (e.g., Aspler and Chiarenzelli, and the depositional surface (Jervey, 1988). As the 2002; Aspler et al., 2001; Eriksson et al., 2001a,b; base level itself is a conceptual and dynamic surface Martins-Neto et al., 2001; Ojakangas et al., 2001a,b; of equilibrium between deposition and erosion, Strand, 2002; Young et al., 2001; Catuneanu, 2003). largely dependent on fluctuations in environmental There is increasing evidence that the tectonic energy, the precise quantification of accommodation regimes which controlled the formation and evolution at any given time and in any given location is rather of sedimentary basins in the more distant geological difficult. For this reason, proxies and approximations past were much more erratic in terms of origin and are generally required for workable visualizations of rates than formerly inferred solely from the study of the available accommodation. At first approximation, the Phanerozoic record (e.g., Catuneanu, 2001; sea level is a proxy for base level (Jervey, 1988; Eriksson et al., 2004, this volume, a,b,c; Eriksson Schumm, 1993), and so the available accommodation and Catuneanu, 2004b).Themorerecentbasin- in a marine environment may be measured as the forming processes seem to be largely related to a distance between the sea level and the sea floor. Both rather stable plate-tectonic regime, whereas the for- the sea level and the sea floor may independently mation of Precambrian basins reflects a combination change their position with time relative to the center of competing mechanisms, including magmatic-ther- of Earth in response to various controls, and therefore mal processes (dplume tectonicsT) and a more erratic the amount of available accommodation fluctuates plate-tectonic regime (Fig. 4; Eriksson et al., this accordingly. Sea level is one of the primary allogenic volume, a,b). These insights offered by the Precam- controls on sedimentation, and it is in turn controlled brian record are critical for extracting the essence of by climate and tectonism, as discussed in the previous how one should categorize the stratigraphic sequences section (Fig. 5). The upward and downward shifts in that can be observed within a sedimentary succession the position of the sea floor relative to the center of at different scales. This issue is discussed in more Earth depend on two main parameters, namely the detail in the section dealing with the sequence- magnitude of total subsidence or uplift, and sedimen- stratigraphic hierarchy. tation. The amount of available accommodation at any given time and in any given location therefore equals 2.2. Sediment accommodation the balance between how much accommodation is created (or destroyed) by factors such as tectonism The concept of daccommodationT describes the and sea level change, and how much of this space is amount of space that is available for sediments to fill, consumed by sedimentation at the same time. The being measured by the distance between base level separation between these two members of the O. Catuneanu et al. / Sedimentary Geology 176 (2005) 67–95 73 accommodation equation (creation/destruction vs. created or lost during a period of time, rather than the consumption) is one of the key themes of sequence actual height of relative sea level at any given time. stratigraphy, which allows one to understand the The separation between relative sea level changes fundamental mechanisms behind the formation of and sedimentation is a fundamental approach in systems tracts and sequence stratigraphic surfaces. sequence stratigraphy, which allows for the compar- Fig. 6 helps to define some of the basic concepts ison between their rates as independent variables. The involved in the accommodation equation, such as balance between these rates (creation/destruction of eustasy (sea level relative to the center of Earth), accommodation vs. consumption of accommodation) relative sea level (sea level relative to a datum that is controls the direction and type of shoreline shifts, and independent of sedimentation), and water depth (sea implicitly the timing of all sequence stratigraphic level relative to the sea floor). A change in relative sea surfaces and systems tracts. This approach is therefore level is a proxy for how much accommodation was key to a proper understanding of sequence strati- created or lost during a period of time, independent of graphic principles. Failure to do so may result in sedimentation, whereas water depth is a proxy for confusions between relative sea level changes, water how much accommodation is still available after the depth changes, and the directions of shoreline shift. effect of sedimentation is also taken into account. The The above discussion on the controls on accom- datum in Fig. 6 monitors the total amount of modation is based on the assumption that sea level is a subsidence or uplift (including the effects of sediment proxy for base level. This is true at first approxima- compaction) recorded at any location within the basin tion, but in reality base level is commonly below the relative to the center of the Earth. This datum sea level, due to the energy flux brought about by reference plane is placed as close to the sea floor as waves and currents. As noted by Schumm (1993), this possible in order to capture the entire subsidence is also supported by the fact that at their mouths, component related to sediment compaction, but its rivers erode slightly below the sea level. The actual actual position is not as important as the change in the distance between base level and sea level depends on distance between itself and sea level. This is because environmental energy, as for example the base level is we are more interested in the changes in relative sea lowered during storms relative to its position during level, which reflect how much accommodation is fair-weather. Such energy fluctuations usually take

Sediment Shoreline (2) source area Fluvial profile (2) Sea level (1) Sea level (2) Continent Shoreline (1) Water depth(2) Lowest level of DATUM Relative continental denudation Sea sea floor level(2) (extension of sea level (2) beneath the landscape)

KEY: Eustasy (2) Sediment accumulated aggradation from time (1) to time (2) erosion ~

CENTER OF EARTH

Fig. 6. Eustasy, relative sea level, and water depth as a function of sea level, sea floor, and datum reference surfaces (modified from Posamentier et al., 1988). The datum is a subsurface reference horizon that monitors the amount of total subsidence or uplift. In this diagram, the DATUM corresponds to the ground surface (subaerial and subaqueous) at time (1). 74 O. Catuneanu et al. / Sedimentary Geology 176 (2005) 67–95 place at seasonal to sub-seasonal time scales, at a sumed more rapidly than is being created). In either frequency that is higher than most highest-frequency situation, the river mouth moves accordingly, land- cycles investigated by sequence stratigraphy. Longer- ward or seaward, connecting the continuously adjust- term shifts in base level, at scales relevant to sequence ing fluvial profile to the shifting base level. In the case stratigraphy, are generally controlled by the interplay of a delta that progrades during a stage of base level of eustasy and total subsidence. In other words, the rise, for example, the newly created space is not proxies used in the above discussion (i.e., sea level for sufficient to accommodate the entire amount of base level, and relative sea level changes for changes sediment brought by the river, and as a result the in accommodation) are acceptable in a sequence river mouth shifts seaward. This shift triggers a stratigraphic analysis. The most complete scenario change in depositional regimes from prodelta and that illustrates the interplay of the controls on delta front environments, where sedimentation is accommodation and shoreline shifts in a marine limited to the space between the sea floor and the environment is presented in Fig. 7. base level, to delta plain and alluvial plain environ- The contrast between the rates of change in ments (landward relative to the shoreline), where accommodation and the sedimentation rates in loca- depositional trends (aggradation, bypass, or erosion) tions placed in the vicinity of the shoreline allows one are governed by the relative position between the to understand why the shoreline may shift either fluvial graded profile and the actual fluvial profile. landward or seaward during times of relative sea level The fluvial graded profile is the conceptual (base level) rise. Accommodation outpacing sedimen- equivalent of the marine base level in the nonmarine tation generates transgression (i.e., accommodation is realm, as it describes the imaginary and dynamic created faster than it is consumed by sedimentation), surface of equilibrium between deposition and erosion whereas an overwhelming sediment supply may result in the fluvial environment. This equilibrium profile is in shoreline regression (i.e., accommodation is con- achieved when the river is able to transport its

Marine environment Transgressions and Regressions shoreline shifts Base level changes creation base level or relative to destruction Relative DATUM sea level changes Accommodation sea level base level relative relative to to sea floor Sea level DATUM changes

consumption

Eustasy Tectonics Energy flux Sedimentation sea level DATUM waves, currents sea floor relative to DATUM relative to the center of Earth

Fig. 7. Controls on accommodation and shoreline shifts in a marine environment (modified from Catuneanu, 2003). This diagram also applies to lacustrine environments by substituting sea level with lake level. See Fig. 6 for the definition of the DATUM. The energy flux lowers the base level via the effects of waves, wave-generated currents, tidal currents, contour currents or gravity flows. Short-term climatic changes (seasonal to sub-seasonal time scales) are accounted for under energy flux, whereas the longer-term climatic changes (e.g., Milankovitch type) are built into eustasy. O. Catuneanu et al. / Sedimentary Geology 176 (2005) 67–95 75

Fluvial system connected to a marine environment graded profiles, and implicitly on fluvial accommoda- tion, especially in the distal reaches of the fluvial creation system (Shanley and McCabe, 1994; Fig. 8). The or destruction position of graded profiles also depends on fluctua- Changes in tions in energy flux, which are mainly attributed to the fluvial graded profile effects of climate on a river’s transport capacity (Blum Fluvial graded profile accommodation and Valastro, 1989; Blum, 1990; Fig. 8). Such energy relative to DATUM graded profile relative fluctuations may be recorded over different time to ground surface scales, from seasonal climatic changes that may occur with a frequency higher than the highest-frequency consumption cycles studied by sequence stratigraphy, to Milanko- vitch-scale orbital forcing. Base level changes Energy flux Sedimentation The effect of base-level changes on fluvial base level relative river discharge river bed relative processes (aggradation vs. erosion) is only dfeltT by to DATUM and velocity to DATUM rivers within a limited distance upstream relative to Fig. 8. Controls on fluvial accommodation in the distal reaches of the river mouth, which is usually in a range of less a fluvial system. See Fig. 6 for the definition of the DATUM. The than 200 km (Miall, 1997). Beyond the landward limit energy flux is mainly controlled by short- to longer-term climatic of base-level influences, rivers respond primarily to a changes (especially the discharge component), but also by combination of tectonic and climatic controls (Fig. 9). tectonic tilt. Tectonism dictates the overall geometry of fluvial sequences, as the creation of fluvial accommodation sediment load without aggradation or degradation of follows the patterns of regional subsidence. For the channels (Leopold and Bull, 1979). In this example, the rates of subsidence induced by flexural context, the amount of fluvial accommodation is loading in a foreland basin increase in a proximal defined as the space between the graded profile and direction, toward the center of loading, whereas the the actual fluvial profile (Posamentier and Allen, rates of thermal and mechanical subsidence in an 1999). If we compare this definition with the concept extensional basin increase in a distal direction. These of marine accommodation, discussed above, the graded profile is the equivalent of the base level, Fluvial system isolated from marine influences and the actual fluvial profile is the counterpart of the sea floor in the marine environment. If we follow this creation comparison even further, we notice that the sea level, or destruction which is used as a proxy for base level, does not have Changes in an equivalent in the fluvial realm, which makes the fluvial graded profile visualization of fluvial accommodation rather difficult Fluvial graded profile accommodation as there is no physical proxy for the fluvial graded relative to DATUM profile. The only observable surface is the actual graded profile relative to ground surface fluvial landscape, whose position relative to an independent datum changes in response to surface consumption processes of aggradation or erosion (Fig. 6). In turn, these surface processes are triggered by an attempt of Tectonics Energy flux Sedimentation the river to reach its graded profile. d T DATUM relative to river discharge river bed relative The graded profile is anchored to the base level at center of Earth and velocity to DATUM the river mouth, and as the base level rises and falls this anchoring point moves either landward or seaward, or Fig. 9. Controls on fluvial accommodation in the proximal reaches of a fluvial system. See Fig. 6 for the definition of the DATUM. up or down, triggering an in-kind response of the The energy flux is mainly controlled by short- to longer-term graded profile (Posamentier and Allen, 1999). There- climatic changes (especially the discharge component), but also by fore, base-level changes exert an important control on tectonic tilt. 76 O. Catuneanu et al. / Sedimentary Geology 176 (2005) 67–95 patterns are reflected by the geometry of fluvial as the transgressive and regressive shifts of the sequences that may fill the basin. Superimposed on shoreline (Fig. 7). The types of shoreline shifts are these general trends, the climatic control on runoff and critical in a sequence stratigraphic framework, as they discharge also affect the position of graded profiles, as determine the formation of packages of strata with discussed above (Fig. 9). specific stacking patterns, known as systems tracts. The role of climate as a control on accommodation Three types of shoreline shifts may be recorded, as is always difficult to quantify because it operates via outlined below. other variables such as eustasy and environmental energy flux. In a marine environment, the short-term 2.3.1. Transgressions climatic changes (seasonal to sub-seasonal time scale) Transgressions take place when accommodation is translate into fluctuations in energy flux, whereas the created more rapidly than it is consumed by sed- longer-term changes are accounted for under eustasy imentation, i.e., when the rates of base-level rise (Fig. 7). In the case of fluvial environments, both outpace the sedimentation rates at the shoreline. This short- and longer-term climatic changes are reflected results in a retrogradation (landward shift) of facies. in the fluctuations in energy flux because there is no The scour surface cut by waves during the shoreline physical proxy for the graded profile that could be transgression (wave ravinement surface) is onlapped related to the longer-term climate shifts (Figs. 8 and by the aggrading and retrograding shoreface deposits 9). Climate is also relevant to the dsedimentationT box (Fig. 10). The combination of wave scouring in the in all cases (Figs. 7–9) because the amount of upper shoreface and deposition in the lower shoreface sediment supply transferred from source areas to the is required to preserve the concave-up shoreface sedimentary basin depends on the efficiency of profile that is in equilibrium with the wave energy weathering and sediment transport processes, both of during transgression (Bruun, 1962; Dominguez and which are partly dependent on climate. Wanless, 1991). The onlapping deposits that accumu- A significant debate still persists regarding the late in the lower shoreface dhealT the bathymetric relationship between base level and the fluvial graded profile of the seafloor that is oversteepened as a result profile. One school of thought argues that the term of the transgressive shoreline shift, which is why they dbase levelT should apply to both concepts, as the are known as dhealing phaseT deposits (Posamentier same definition can describe them both (i.e., a and Allen, 1993; Fig. 10). dynamic surface of equilibrium between deposition The rise in base level at the shoreline promotes and erosion; Barrell, 1917; Sloss, 1962; Cross, 1991; coastal aggradation in estuarine (river mouth) or beach Cross and Lessenger, 1998). A second school of (open shoreline) environments. However, the ten- thought restricts the term dbase levelT to the level of dency of coastal aggradation is counteracted by the the body of water into which the river debouches (sea wave scouring in the upper shoreface, as the latter level, lake level, or even another river), as used in this gradually shifts in a landward direction. The balance paper (Powell, 1875; Davis, 1908; Bates and Jackson, between these two opposing forces, of sedimentation 1987; Schumm, 1993; Posamentier and Allen, 1999; vs. erosion, determines the overall type of trans- Catuneanu, 2003). Terminology is trivial to some gressive coastline (Fig. 10). Coastlines dominated by extent, but we find value in keeping the concepts of aggradation lead to the preservation of estuarine or graded fluvial profile and base level separate because backstepping beach facies in the rock record. Coast- they are in a process–response relationship—i.e., the lines dominated by erosion are associated with position in space of the fluvial graded profile is in part unconformities in the nonmarine part of the basin, a function of the elevation of the base level, and whose stratigraphic hiatuses are age-equivalent with changes with time thereof. the transgressive marine facies. Regardless of the overall nature of coastal processes, the wave ravine- 2.3. Types of shoreline shifts ment surface is onlapped by transgressive shallow marine (dhealing phaseT) deposits, which provides a The interplay of base-level changes and sedimen- clue for understanding the transgressive nature of tation controls the available accommodation, as well some subaerial unconformities. O. Catuneanu et al. / Sedimentary Geology 176 (2005) 67–95 77

shoreline shift Transgressive shorelines: shoreface aggradation & onlap regressive deposits downlap the scour generated in the retrogradation lower subtidal zone (Fig. 11). At the same time, the A. Coastal aggradation subaerially exposed area is subject to sediment coastal aggradation starvation, as well as fluvial and wind degradation. (estuary or backstepping beaches) The amount of nonmarine downcutting is proportional base level rise (2) (1) shoreface erosion to the magnitude of base-level fall (see Posamentier, wave scouring shoreface sedimentation 2001, for a discussion of incised vs. unincised fluvial bypass systems). In the case of river-dominated deltas, the angle of estuarine or beach facies (2) repose of delta front clinoforms is generally steeper wavescour fluvial facies “healing phase” deposits progradation & offlap Forced regressions: incision shoreline sh ift B. Coastal erosion 1. Wave-dominated coastline (open shoreline, fluvial erosion wave-dominated delta) coastal erosion (1) onset of base level fall (2) (2) (1) (1) (3) shoreface erosion (4) (4) receding coastline fluvial erosion shoreface sedimentation marine erosion sedimentation at time (2), etc. subaerial erosion erosion at time (2), etc. coastal erosion (receding cliff) (2) newgraded profile forced regressive wave scour HST=(1) (2) shoreface deposits “healing phase” deposits (3) (4) fluvial scour marine scour conformable clinoforms Fig. 10. Shoreline trajectory in transgressive settings (from Catuneanu, 2003). Transgressions are driven by base level rise, 2. River-dominated delta where the rates of base level rise outpace the sedimentation rates in the shoreline area. The balance between the opposing trends of (1) onset of base level fall (2) (1) aggradation (in front of the shoreline) and wave scouring (behind (3) (4) (4) the shoreline) determines the type of transgressive coastline. In fluvial erosion addition to this, shallow-gradient coastal plains are prone to coastal sedimentation at time (2), etc. aggradation, whereas steeper coastal plains are prone to coastal erosion. In both cases, the gradients may be shallower than the average shoreface profile (ca. 0.38). forced regressive HST=(1) (2) shoreface deposits 2.3.2. Forced regressions (3) (4) Forced regressions occur during stages of base- fluvial scour conformable clinoforms level fall, when the shoreline is forced to regress by the falling base level, irrespective of sediment supply. Fig. 11. Shoreline trajectory in forced regressive settings (modified In wave-dominated coastal settings, such as open from Catuneanu, 2003). Forced regressions are driven by base level shorelines or wave-dominated deltas, the preservation fall, irrespective of sediment supply, and the rates of progradation of the concave-up sea floor profile that is in are generally high. Wave-dominated subtidal settings are charac- equilibrium with the wave energy requires coeval terized by shallow gradients of the seafloor, which is subject to deposition and erosion in the upper and lower parts of wave scouring in order to preserve a profile that is in equilibrium with the wave energy. River-dominated deltas generally have delta the subtidal area, respectively (Bruun, 1962; Plint, front clinoforms that are steeper than the wave equilibrium profile, 1988; Dominguez and Wanless, 1991; Fig. 11). As the and therefore no wave scouring takes place during forced shoreline shifts basinward, the upper subtidal forced regression. HST—highstand systems tract. 78 O. Catuneanu et al. / Sedimentary Geology 176 (2005) 67–95

1. Uninterpreted seismic line sions and transgressions with fluvial, estuarine, and even shallow marine deposits (Fig. 12).

2.3.3. Normal regressions Normal regressions occur in the early and late stages of base-level rise, when the sedimentation rates outpace the low rates of base-level rise at the shoreline. In this case, sedimentation totally fills the 2 km 100 ms newly created accommodation, sediment bypass accompanies aggradation (the surplus of sediment 2. Interpreted seismic line for which no accommodation is available), and facies prograde (Fig. 13). The process of coastal aggradation, in response to rising base level, is an important diagnostic feature that separates normal regressive from forced regres- sive deposits (Figs. 11 and 13). As a result, a topset package of delta plain (in river mouth settings) or beach/strandplain (in open shoreline settings) sedi- ments accumulates and progrades over the shallow 100 ms 2 km marine delta front/shoreface facies. The preservation potential of this topset package is higher in the case of Fig. 12. A seismic example of an incised valley filled with fluvial the early rise (dlowstandT) normal regressive deposits (lower large arrow) and estuarine (higher large arrow) deposits. The d T smaller arrows indicate onlap of estuarine facies. because the late rise ( highstand ) normal regressive strata are potentially truncated by subaerial uncon- formities (Fig. 11). than the gradient required to balance the energy of the waves, so there is no reason for wave scouring in the 2.4. Sequence stratigraphic models lower delta front area (Fig. 11). Therefore, the marine scour surface that forms in shallow marine wave- The concept of a dsequenceT is only as good, or dominated settings during forced regression is missing acceptable, as the boundaries that define it. As a from the stratal architecture of forced regressive river- shoreline shift dominated deltas. In the former case, a vertical profile Normal regressions: aggradation through the shallow marine forced regressive succes- progradation sion shows an abrupt shift of facies from offshore fluvial/delta plain/strandplain base level rise muds to subtidal sands, whereas this facies shift is (4) (4) (1) gradational in the river-dominated deltas. lateral changes (1) (2) (3) Stages of forced regression are generally charac- of facies terized by a significant increase of sediment supply to shoreface/delta front aggradation and progradation the deep-water depositional systems. This is due to (1) a lack of accommodation in the fluvial to shallow Fig. 13. Shoreline trajectory in normal regressive settings (from marine environments, and therefore the terrigenous Catuneanu, 2003). Normal regressions are driven by sediment sediment tends to bypass these settings and be supply, where the rates of base level rise at the shoreline are delivered to the deep-water environment; and (2) outpaced by sedimentation rates. Normal regressions occur during additional sediment may be supplied by erosional early and late stages of base level rise, when the rates of base level processes in the fluvial and lower shoreface environ- rise are low. Progradation rates are generally lower relative to forced regressions. Aggradation occurs in coastal environments ments. On continental shelves, forced regressions may (delta plains in river mouth settings, or strandplains along open result in the formation of incised valleys, which are shorelines), which triggers fluvial aggradation on the adjacent filled during subsequent dlowstandT normal regres- alluvial plain. O. Catuneanu et al. / Sedimentary Geology 176 (2005) 67–95 79 matter of principle, it is useless to formalize a unit Geology in an exciting new direction of conceptual whose boundary definitions are left to the discretion and practical opportunities, even though along a of the individual practitioner. The dsequenceT defined bumpy road punctuated by disagreements and by Sloss et al. (1949) as an unconformity-bounded controversy. unit, was widely embraced (and formalized in the Early work on seismic and sequence stratigraphy 1994 International Stratigraphic Guide) because the published in the AAPG Memoir 26 (Payton, 1977) concept of unconformity was also straightforward and the SEPM Special Publication 42 (Wilgus et al., and surrounded by little debate. Modification of the 1988)resultedinddepositional sequenceT being original concept of sequence, by the introduction of defined as the primary unit of a sequence strati- correlative conformities as part of its bounding graphic model. This stratigraphic unit is bounded by surfaces, triggered both progress and debates at the subaerial unconformities on the basin margin and onset of the seismic and sequence stratigraphy era. their correlative conformities toward the basin The main source of contention relates to the nature center. The depositional sequence was subdivided and timing of these correlative conformities, and into lowstand, transgressive and highstand systems consequently a number of different models are now tracts on the basis of internal surfaces that corre- in use, each promoting a unique set of terms and spond to changes in the direction of shoreline shift bounding surfaces. This creates unnecessary jargon from regression to transgression and vice versa. and confusion, and hampers communication of ideas Variations on the original depositional sequence and results. A few reasons for this variety of theme resulted in the publication of several slightly approaches in sequence stratigraphy include: (1) modified versions of the depositional sequence the underlying assumptions regarding the primary model (Figs. 14 and 15). controls on stratigraphic cyclicity; (2) the type of Soon after the SEPM Special Publication 42, basin from which models were derived; and (3) the Galloway (1989), based on Frazier (1974), proposed gradual conceptual advances that allowed for alter- that maximum flooding surfaces, rather than subaerial native models to be developed. Present-day sequence unconformities, be used as sequence boundaries. This stratigraphy can thus be described as a still devel- unit was termed a bgenetic stratigraphic sequenceQ, oping field that takes the science of Sedimentary also referred to as a regressive–transgressive (R–T)

Sequences Sloss (1949, 1963)

Depositional Sequence I (Seismic Stratigraphy) Mitchum et al. (1977)

Sequence Stratigraphy

Depositional Sequence II Depositional Sequence III Depositional Sequence IV Haq et al. (1987) Van Wagoner et al. (1988,1990) Hunt and Tucker (1992, 1995) Posamentier et al. (1988) Christie-Blick (1991) Plint and Nummedal (2000)

Genetic Sequences T-R Sequences Galloway (1989) Embry (1993, 1995) Frazier (1974) Curray (1964)

Fig. 14. Family tree of sequence stratigraphy (modified from Donovan, 2001). The various sequence stratigraphic models mainly differ in the style of conceptual packaging of strata into sequences, i.e., with respect to where the sequence boundaries are picked in the rock record. 80 O. Catuneanu et al. / Sedimentary Geology 176 (2005) 67–95

Sequence model Depositional Depositional Depositional Genetic T-R Events Sequence II Sequence III Sequence IV Sequence Sequence

HST early HST HST HST RST end of transgression TST TST TST TST TST end of (*) regression late LST LST LST late LST (wedge) (wedge) end of (**) base level fall early LST late HST early LST FSST RST (fan) (fan) (fan) onset of base level fall early HST HST HST HST (wedge)

end of transgression sequence boundary Time (*) in a marine succession (**) in a nonmarine succession onset of end of systems tract boundary base level fall regression within systems tract surface end of base level fall

Fig. 15. Timing of systems tract and sequence boundaries for the sequence models currently in use. Abbreviations: LST—lowstand systems tract; TST—transgressive systems tract; HST—highstand systems tract; FSST—falling stage systems tract; RST—regressive systems tract; T– R—transgressive–regressive. Note that the conformable portion of the sequence boundary of the depositional sequence II was originally considered to form during early sea level fall (Posamentier et al., 1988), which was later revised to the onset of sea level fall (Posamentier et al., 1992), as represented in this table. sequence. Finally, Embry and Johannessen (1992) that signify changes in the type of shoreline shifts; i.e., proposed a third type of stratigraphic unit, named a the onset of forced regression, the end of forced btransgressive–regressive (T–R) sequenceQ, corre- regression, the end of (normal) regression and the end sponding to a full cycle of transgressive and regres- of transgression (Fig. 16). These events separate sive shoreline shifts (Figs. 14 and 15). systems tracts, and result in the formation of four The various sequence models that are currently in sequence stratigraphic surfaces: the basal surface of use differ from each other mainly in the style of forced regression (=correlative conformity sensu conceptual packaging of the stratigraphic record, Posamentier et al., 1988), the correlative conformity using a different timing for systems tract and sequence (sensu Hunt and Tucker, 1992), the maximum boundaries in relation to a cycle of base-level shifts regressive surface (=transgressive surface), and the (Figs. 14 and 15). Each sequence model may work maximum flooding surface respectively (Fig. 16). best under particular circumstances, and no one model Three more sequence stratigraphic surfaces form is universally applicable to the entire range of case during particular stages of shoreline shift, such as studies (Catuneanu, 2002). The applicability and the subaerial unconformity during forced regression practical limitations of each approach are discussed (fluvial scour in Fig. 11), the regressive surface of in detail by Catuneanu (2003). marine erosion during forced regression in wave- Irrespective of the model of choice, a common dominated settings (marine scour in Fig. 11), and the theme emerges in the sense that a full cycle of base- wave ravinement surface during transgression (wave level changes records four main stratigraphic events scour in Fig. 10). The correct identification of these O. Catuneanu et al. / Sedimentary Geology 176 (2005) 67–95 81

Systems tracts Base level Events Sequence stratigraphic surfaces

Time Onset of forced regression Basal surface of forced regression ** NR (HST) End of transgression Maximum flooding surface T (TST) } Wave ravinement surface End of regression Maximum regressive surface NR (LST) * End of forced regression Correlative conformity Subaerial unconformity Full cycle FR (FSST) and (-A) Regressive surface of marine erosion } ** Onset of forced regression Basal surface of forced regression

* sensu Hunt and Tucker (1992) Rise Fall ** = correlative conformitysensu Posamentier et al. (1988)

Fig. 16. Timing of sequence stratigraphic surfaces relative to the main events of the base level cycle (modified from Catuneanu et al., 1998; Embry and Catuneanu, 2002; Catuneanu, 2003). Each of these seven surfaces of sequence stratigraphy can serve, at least in part, as systems tract boundaries. Abbreviations: (ÀA)—negative accommodation; FR—forced regression; NR—normal regression; T—transgression; FSST— falling stage systems tract; LST—lowstand systems tract; TST—transgressive systems tract; HST—highstand systems tract. The nomenclature of systems tracts conforms with the depositional sequence IV model (Fig. 15). sequence stratigraphic surfaces is the key for a robust 3. Sequence stratigraphic hierarchy sequence stratigraphic interpretation, regardless of how we name the systems tracts between them, or 3.1. Introduction where we choose to place the sequence boundary (Fig. 15). Criteria for identifying sequence stratigraphic A sequence hierarchy assigns different orders to surfaces are now firmly established, based on the stratigraphic sequences and bounding surfaces based nature of contacts, nature of facies that are in contact on their relative importance. Within a hierarchical across the surface, and types of stratal terminations system, the most important sequence is recognized as that are associated with each particular type of surface of dfirst-orderT and may be subdivided into two or (Fig. 17). Catuneanu (2003) discusses these criteria in more dsecond-orderT sequences. In turn, a second- detail. order sequence may be subdivided into two or more

Nature Stratal Stratigraphic surface Strata below Strata above Temporal attributes of contact terminations Subaerial unconformity Scoured or Variable NonmarineTruncation, toplap, Variable hiatus top of paleosol (where marine, c-u) fluvial onlap, offlap Correlative conformity * Conformable Marine, c-u Marine Downlap Low diachroneity (c-u on shelf)

Regressive surface Scoured Shelf, c-u Shoreface, c-uTruncation, downlap High diachroneity of marine erosion

Basal surface Conformable Marine, variable Marine, c-uDownlap Low diachroneity of forced regression ** or scoured (c-u on shelf) Maximum regressive Conformable Variable Variable Downlap, Low diachroneity surface (where marine, c-u) (where marine, f-u) marine onlap

Maximum flooding Conformable Variable Variable “Downlap surface” Low diachroneity surface or scoured (where marine, f-u) (where marine, c-u)

Wave ravinement Scoured Variable Marine, f-uCoastal onlap High diachroneity surface (where marine, c-u)

Fig. 17. Diagnostic features of sequence stratigraphic surfaces (modified from Embry and Catuneanu, 2002; Catuneanu, 2003). *Sensu Hunt and Tucker (1992); **correlative conformity sensu Posamentier et al. (1988). Abbreviations: c-u—coarsening-upward; f-u—fining-upward. 82 O. Catuneanu et al. / Sedimentary Geology 176 (2005) 67–95

r first and sequence stratigraphy (Vail et al., 1977; Fig. 19). orde order This time-based hierarchy emphasizes eustasy as the frequency) high main driving force behind stratigraphic cyclicity, (low second order which in turn is controlled by a combination of plate tectonic and orbital mechanisms. As eustasy is global third in nature, the philosophy behind this hierarchy system order led to the construction of global cycle charts (Vail et fourth al., 1977), whose validity is currently under intense order r scrutiny (Miall, 1992, 1997). orde fifth frequency) low order 3.2. Hierarchy system based on boundary frequency (high Fig. 18. Diagrammatic representation of the concept of hierarchy. In addition to the controversy brought about by This pyramid approach assumes that the events leading to the global cycle charts, the application of the hierarchy formation of the most important sequences and bounding surfaces system based on sequence duration poses an impor- (first-order) occurred less frequently in the geological record relative to the events leading to the formation of lower order sequence tant practical problem, which is the fact that good time boundaries. control is required to ensure that a dthird-orderT sequence falls indeed within the 1–10 My duration dthird-orderT sequences, and so on (Fig. 18). The more bracket (Fig. 19; Vail et al., 1977), and so on. Such important sequences are designated as dhigh-orderT (at time control is often difficult to acquire even for the top of the hierarchy pyramid), and generally have Phanerozoic successions, and it becomes more and a low frequency in the stratigraphic record. The less more unrealistic with increasing stratigraphic age. In important sequences are of dlower-orderT and are more spite of this practical limitation, the hierarchy system common in the rock record (Fig. 18). based on sequence duration, which was originally The critical element in developing a system of developed based on Phanerozoic case studies (Vail et sequence hierarchy is the set of criteria that should be al., 1977), was eventually extrapolated to the Precam- used to differentiate between the relative importance brian as well (Krapez, 1996, 1997). Krapez (1996) of sequences and bounding surfaces. Two different provides average durations for sequence orders as approaches are currently in use, based on the study of follows: fourth=90–400 ky, third=1–11 My, sec- the Phanerozoic record: (1) a system based on ond=22–45 My, and first=approximately 364 My. boundary frequency (sequence duration), and (2) a Each of these orders of stratigraphic cyclicity is system based on the magnitude of base-level changes genetically related to particular tectonic (and to a which resulted in boundary formation (independent of much lesser extent climatic) controls whose perio- sequence duration). The former system has historical dicity is assumed to be more or less constant during priority, having being proposed at the dawn of seismic geological time. For example, the 364 My duration of

Hierarchical order Duration (My) Cause

First order 200-400 Formation and breakup of supercontinents Second order 10-100 Volume changes in mid-oceanic spreading centers Third order 1-10 Regional plate kinematics

Fourth and fifth order 0.01-1 Orbital forcing

Fig. 19. Tectonic and orbital controls on eustatic fluctuations (modified from Vail et al., 1977; Miall, 2000). These hierarchies are NOT proposed here for orders of stratigraphic sequences (see text for details). Local- or basin-scale tectonism is superimposed and independent of these global sea level cycles, often with higher rates and magnitudes, and with a range of time scales. O. Catuneanu et al. / Sedimentary Geology 176 (2005) 67–95 83 first-order cycles is calculated based on the assump- 3.3. Hierarchy system based on the magnitude of tion that nine equal-period global tectonic (Wilson) base-level changes cycles of supercontinent assembly and breakup took place during the 3500–224 Ma interval (Krapez, 1993, A hierarchy system based on the magnitude of 1996). The need for a hierarchy system based on base-level changes that resulted in boundary forma- sequence duration is based on the argument that tion provides a classification in which the order of a bThere are no physical criteria with which to judge the sequence depends on the physical attributes of its rank of a sequence boundary. Therefore, sequence bounding surfaces, and is independent of sequence rank is assessed from interpretations of the origin of duration (Embry, 1995; Fig. 20). Six attributes have the strata contained between the key surfaces, and of been chosen to establish the boundary classification: the period of the processes that formed these strataQ the areal extent over which the sequence boundary (Krapez, 1997, p. 2). can be recognized; the areal extent of the uncon- More important than the current practical limita- formable portion of the boundary; the degree of tions related to the availability of time control, or the deformation that strata underlying the unconformable lack thereof, which may be resolved in the future as portion of the boundary underwent during the the resolution of dating techniques improves, is the boundary generation; the magnitude of the deepening fundamental question of whether or not the nature and of the sea and the flooding of the basin margin as periodicity of tectonic mechanisms controlling strati- represented by the nature and extent of the trans- graphic cyclicity were indeed constant throughout the gressive strata overlying the boundary; the degree of Earth’s history, as assumed by the proponents of time- change of the sedimentary regime across the boun- based hierarchy systems. The Phanerozoic time dary; and the degree of change of the tectonic setting window into the geological past is simply too small of the basin and surrounding areas across the to provide an unequivocal answer to this question, and boundary. Five different orders of sequence bounda- therefore the study of the Precambrian most likely ries have been defined on the basis of these character- holds the key to this debate. The hierarchy systems istics (Embry, 1995; Fig. 20). based on sequence duration are fundamentally pre- Two potential pitfalls with this classification dicated on the assumption that the controls on scheme have been discussed by Miall (1997, pp. cyclicity at specific hierarchical orders are predictable, 330–331). One is that it implies tectonic control in repetitive, and unchanged during the evolution of sequence generation. Sequences generated by glacio- Earth. This implies that the controls on stratigraphic eustasy, such as the Upper Paleozoic cyclothems of cyclicity are governed by the law of uniformitarianism North America and those of Late Cenozoic age on throughout the Earth’s history, allowing equal perio- modern continental margins, would be first-order dicity for stratigraphic cycles of the same hierarchical sequences in this classification on the basis of their order, irrespective of age. However, recent work on areal distribution, but lower-order on the basis of the Precambrian geology (Catuneanu and Eriksson, 1999; nature of their bounding surfaces. The second prob- Eriksson et al., 2004, this volume, a,b) points to very lem is that this classification requires good preserva- different conclusions, emphasizing that the mecha- tion of the basin margin in order to properly assess the nisms controlling the formation and evolution of areal extent of the unconformable portion of the sedimentary basins, for the greater part of geological boundary or the degree of deformation across the time, were far more diverse and erratic in terms of boundary. Beyond its practical limitations, the hier- activity rates than originally inferred from the study of archy system based on the magnitude of base-level the Phanerozoic record (Fig. 4). This means that time shifts has the advantage of employing physical criteria is the last, or at least not the primary, variable that one for boundary delineation, irrespective of the time span should employ in designing a universally applicable between sequence boundaries that show similar hierarchy system. Instead, alternative criteria need to attributes. This represents a major advantage in the be identified for a more flexible conceptual frame- case of Precambrian case studies, where the lack of work that can be used irrespective of basin type and time control is generally the norm. This approach also stratigraphic age. bypasses the problem of the erratic nature and 84 O. Catuneanu et al. / Sedimentary Geology 176 (2005) 67–95

1. BASIN BASIN 2. MARGIN CENTRE st 1 order 2 4th order 4 4th order 3rd order 4 4th order 2nd order 2nd order 3 3rd order 2 3rd order 3rd order 3 3rd order 4th order 3 2nd order 3rd order 5th order Subaerial 3 unconformity 3rd order Maximum regressive 2 surface

Fig. 20. Hierarchy system based on the magnitude of base level changes that resulted in the formation of bounding surfaces (modified from Embry, 1993, 1995). (1) Schematic depiction of five orders of sequence boundaries determined from boundary characteristics that reflect base level changes. (2) Principles of determining the order of a sequence: a sequence cannot contain within it a sequence boundary of equal or greater magnitude than its lowest magnitude boundary; the order of a sequence is equal to the order of its lowest magnitude boundary. periodicity of the controls on stratigraphic cyclicity This working methodology places the emphasis on manifest throughout Earth’s history, as discussed the nature of the tectonic setting and changes thereof. above. As a result, the most fundamental events in the rock record that led to changes in tectonic setting and basin 3.4. Discussion type are marked as first-order sequence boundaries, irrespective of the time span between two such Because the sequence hierarchy systems that are consecutive events. In this context, first-order sequen- currently in use present conceptual and/or practical ces correspond to entire sedimentary basin-fills, limitations, the practitioner of sequence stratigraphy regardless of the origin and life span of each particular still faces the dilemma of how to deal with the variety basin. Within this framework, second-order cycles of sequences that are more or less important relative to provide the basic subdivision of a first-order sequence each other. As argued by Catuneanu (2003), the (basin-fill) into packages with unique character that easiest solution to this problem is to deal with the reflect overall shifts in the balance between accom- issue of hierarchy on a case-by-case basis, assigning modation and sedimentation, and so on as we decrease hierarchical orders to sequences and bounding surfa- the scale of observation. These sequences are not ces based on their relative importance within each expected to correlate to other first- and lower-order individual basin. This approach is an adaptation of sequences of other, separate basins, which most likely Embry’s (1995) method of sequence delineation, and have different timing and duration. This method may requires the partitioning of the stratigraphic record prove to be more flexible and realistic given the fact into successions that are the product of sedimentation that each basin is unique in terms of formation, in discrete sedimentary basins. In this context, the evolution and history of base-level changes. most important sequence boundaries in the strati- Our conclusions are supported by statistical sur- graphic record are genetically related to shifts in the veys of the duration and thickness of stratigraphic tectonic setting that led to changes in the type of sequences, which demonstrated that there is no sedimentary basins. evidence for a hierarchy in the rock record that can O. Catuneanu et al. / Sedimentary Geology 176 (2005) 67–95 85 be linked to the periodicity of recurrence of the same- which requires a time control that is unavailable in order bounding surfaces (Algeo and Wilkinson, 1988; many Precambrian (and even Phanerozoic) case Carter et al., 1991; Drummond and Wilkinson, 1996). studies. As pointed out by Drummond and Wilkinson (1996), bdiscrimination of stratigraphic hierarchies and their designation as nth-order cycles [based on cycle 4. Case studies duration] may constitute little more than the arbitrary subdivision of an uninterrupted stratigraphic continu- An increasing number of case studies of Precam- umQ. The link between hierarchical orders and brian sequence stratigraphy have become available in temporal durations is artificial and meaningless to a recent years, allowing us to see the complexity of the large extent, as multiple sequence-generating mecha- controlling factors on sedimentation and stratigraphic nisms that do not readily fall into simple temporal cyclicity at a scale larger than originally made classifications may interact and contribute to the possible by the study of the Phanerozoic record. architecture of sequences in the rock record (Miall, More meaningful generalizations can now be formu- 1997). The combination of such independent controls lated as a result of this research. This section often results in sequences whose durations and synthesizes the results of some of these case studies, thicknesses have log-normal distributions that lack from the ca. 3.0–2.0 Ga (Late Archean–Early Proter- significant modes (Drummond and Wilkinson, 1996). ozoic) interval of the Kaapvaal craton of South Africa Similar conclusions are reflected by the work of to the ca. 1.75–0.65 Ga (late Paleoproterozoic–late Algeo and Wilkinson (1988), as well as that of Peper Neoproterozoic) interval of the Sa˜o Francisco craton and Cloetingh (1995), who demonstrated that calcu- and Arac¸uaı´ fold belt of eastern Brazil. These case lated periodicities of stratigraphic cycles may have studies cover more than 2 Gy of Precambrian Earth’s random distributions relative to any given sequence- evolution. forming mechanism. An added bonus of this case-by-case basin 4.1. Kaapvaal craton of South Africa approach is the simplification of terminology because modifiers such as first-order, second-order, etc., have The stratigraphy and tectonic evolution of the straightforward meanings, reflecting relative impor- Kaapvaal craton of South Africa during the ca. 3.0– tance independent of time connotations. In contrast, 2.0 Ga (Late Archean–Early Proterozoic) interval are the time-based hierarchy systems are permeated by presented in detail by Eriksson et al. (this volume, b). unnecessary and sometimes conflicting jargon. For Relevant to this paper is the fact that the ca. 1 Gy example, the bsupersequenceQ of Krapez (1996) is record of Kaapvaal evolution was marked by a referred to as a bsequenceQ by Vail et al. (1977); the combination of plate tectonic and plume tectonic bsequenceQ of Krapez (1996) corresponds to the regimes, whose relative importance determined the bmesothemQ of Ramsbottom (1979),ortothe type of tectonic setting and sedimentary basin bmegacyclothemQ of Heckel (1986); the bparacycleQ established at any given time. The shifting balance of Krapez (1996) is equivalent to the bmajor cycleQ of between these two allogenic controls on accommo- Heckel (1986), etc. Further, the term dparacycleT (and dation resulted in a succession of discrete basins, its corresponding dparasequenceT) is particularly con- starting with the Witwatersrand (accommodation fusing, because parasequences (as bounded by provided by subduction-related tectonic loading), dflooding surfacesT) may not even technically be a followed by the Ventersdorp (accommodation gener- type of sequence, depending on what the flooding ated by thermal uplift-induced extensional subsi- surface actually is (see discussion in Catuneanu, dence), and lastly by the Transvaal (accommodation 2003). Beyond the terminology issue, which may be created by extensional and subsequent thermal sub- trivial to some extent, the real danger consists of the sidence). The end of the Transvaal cycle was marked fact that each of these terms (e.g., megasequence, by a relatively short-lived plume tectonics event, supersequence, parasequence, etc.) is associated with which led to the emplacement of the Bushveld a specific time connotation (sequence duration), igneous complex. The sedimentary fill of these three 86 O. Catuneanu et al. / Sedimentary Geology 176 (2005) 67–95 basins, each of which is genetically related to different al., 2001). Each of these major sedimentary succes- tectonic settings, represents an unconformity-bounded sions represents a first-order depositional sequence, first-order depositional sequence. which is the record of an unconformity-bounded, The temporal duration of the Kaapvaal first-order single basin-fill cycle (Martins-Neto et al., 2001). cycles varied greatly with the type of tectonic setting, Collectively, these basins track major plate reorgan- from ca. 5 My in the case of the plume-related izations that affected the Sa˜o Francisco craton through Ventersdorp thermal cycle, to N600 My in the case of a time interval greater than 1 Gy, which marks one the extensional Transvaal Basin. This first-order episode of aborted lithospheric stretching, and a cyclicity was independent of the Wilson-type cycles complete cycle of supercontinent breakup and assem- of supercontinent assembly and breakup, being rather bly. The Espinhac¸o Basin records a stage (ca. 1.73– a reflection of the interplay between plate tectonics 1.50 Ga) of aborted lithospheric stretching of the Sa˜o (e.g., extension or subduction-related tectonic loading) Francisco–Congo continental mass that had amalga- and plume tectonics. It is noteworthy that the first- mated during the Transamazonian–Eburnian orogeny order cycles controlled by plate tectonics lasted about (ca. 2.2–2.0 Ga; Trompette, 1994; Alkmim and two orders of magnitude longer (ca. 102 My) relative to Marshak, 1998). The Macau´bas Basin (ca. 950–700 the plume tectonics cycles (ca. 100 My). Each of the Ma) comprises rift-to-drift successions that were Kaapvaal first-order cycles is subdivided into second- deposited during the breakup of the supercontinent order cycles, whose temporal duration also varies Rodinia and the opening of the Brazilide–Adamastor greatly, from ca. 1 My in the case of the Ventersdorp ocean (Dalziel, 1997). The Bambuı´ Basin (ca. 800– plume tectonics-controlled basin to ca. 100 My in the 650 Ma) formed as a consequence of thrust loading case of the plate tectonics-controlled basins. related to shortening in the Brası´lia fold belt on the The case study of the Kaapvaal craton suggests that western flank of the Sa˜o Francisco craton (Fig. 21) time, and implicitly the frequency of occurrence of during the closing of the Brazilide ocean and the same-order sequence boundaries in the rock record, are amalgamation of the Gondwana supercontinent. irrelevant to the hierarchy of stratigraphic cycles. This Because most deposits of the Espinhac¸o and Bambuı´ is a consequence of the fact that processes controlling basins are well exposed in cratonic areas or in the the formation and evolution of sedimentary basins in weakly deformed external domains of the Arac¸uaı´ the geological past were far more erratic than orogenic belt, sequence stratigraphy can be applied to originally inferred from the study of the Phanerozoic their successions. record. The extrapolation of principles developed from Phanerozoic case studies (e.g., Vail et al., 1977; Fig. 4.2.1. Espinhac¸o Basin 19) to the entire geological record based on the law of Sedimentologic, paleogeographic, stratigraphic, uniformitarianism is therefore inadequate for provid- structural and tectonic studies in the Paleo/Mesopro- ing a unified approach to the concept of sequence terozoic metasedimentary Espinhac¸o first-order hierarchy. This conclusion reinforces the idea that the sequence in southeastern Brazil indicate deposition classification of sequences and bounding surfaces in a rift-sag basin (Martins-Neto, 2000). The basin should be approached on a case-by-case basis, starting displays a dsteer’s-headT geometry where four basin from the premise that each sedimentary basin-fill evolution stages are recognized (pre-rift, rift, transi- corresponds to a first-order sequence. tional and flexural). These four stages form the basic subdivision of the first-order basin-fill sequence and 4.2. Sa˜o Francisco craton and Arac¸uaı´ fold belt of therefore can be equated with unconformity-bounded eastern Brazil second-order sequences. The unconformities are recognized in the field and are mapped on a regional A record of the late Paleoproterozoic to late scale. The pre-rift and rift second-order sequences of Neoproterozoic history of the Sa˜o Francisco craton the Espinhac¸o Basin consist of nonmarine depositio- and Arac¸uaı´ fold belt of eastern Brazil (Fig. 21)is nal systems that were deposited during continental preserved by sedimentary successions in the Espin- lithosphere stretching. The recognition of 3rd order hac¸o, Macau´bas, and Bambuı´ basins (Martins-Neto et unconformities allowed the recognition and mapping O. Catuneanu et al. / Sedimentary Geology 176 (2005) 67–95 87

Fig. 21. Location of the Sa˜o Francisco Basin in the context of the Sa˜o Francisco Craton and its surrounding orogenic belts (modified after Alkmim and Marshak, 1998). of three 3rd order synrift sequences within the rift 2nd At increased detail, the ca. 900-m-thick second- order sequence. The first marine incursion within the order flexural (dConselheiro MataT) succession of the Espinhac¸o Basin marks the change in the subsidence Espinhac¸o Basin is subdivided into three third-order regime of the basin from extensional to thermally transgressive–regressive sequences (Fig. 22). These driven, and is due to thermal contraction of the third-order sequences were first recognized by lithosphere during cooling when the transitional and Dupont (1995), each with a transgressive base and flexural stages evolved. The transitional stage was a progradational top. The first sequence (250–400 m characterized by relatively low subsidence rates. thick) contains transgressive barred nearshore depos- Higher subsidence rates and a consequent base-level its and progradational beach to shallow marine rise characterize the flexural stage of the Espinhac¸o deposits. Its maximum flooding surface marks the Basin. greatest expansion of the Espinhac¸o sea (Martins- 88 O. Catuneanu et al. / Sedimentary Geology 176 (2005) 67–95

W E Progradatio n Max. flood ing surface Sequence 3 ço Transgression Progradatio erosion n Conselheiro Mata Post-Espinha 2nd-order sequence glaciogenic Progradatio e n (flexural stage) Sequence 2 Transgressio Max. flooding surface n

Sequence 1 Transgression Galho do Miguel 2nd-order sequence (transitional stage)

Fig. 22. Schematic stratigraphic cross-section showing the three third-order transgressive–regressive sequences of the Conselheiro Mata (second-order) succession of the Espinhac¸o Basin (modified after Dupont, 1995). The eastern section is about 900 m thick.

Neto, 2000). The second sequence (250–350 m defined by transgressive mixed siliciclastic-carbonate thick) comprises transgressive shelf deposits overlain shelf deposits overlain by coastal to fluvial sedi- by progradational alluvial plain to coastal succes- ments. The top of the third sequence marks the final sions. The third sequence (200–300 m thick) is filling of the Espinhac¸o Basin and therefore corre-

W E Prograding 2nd-order sequences STRATIGRAPHY TRÊS MARIAS FORMATION siltstone, arkose, sandstone, conglomerate

SERRA DA SAUDADE FORMATION shale, siltstone

LAGOA DO JACARÉ FM.

e, mudstone limestone, calcarenite, oolitic limestone, siltstone

FORMATION sandston SERRA DE SANTA HELENA FM. shale, mudstone,

SAMBURA siltstone

conglomerate, D SETE LAGOAS FORMATION S dolostone (D), shale, calcarenite, calcilutite (locally with stromatolite -S)

C CARRANCAS F ORMATION (C) diamictite, conglomerate

Fig. 23. Stratigraphic chart of the Bambuı´ first-order sequence (modified after Martins-Neto et al., 2001). The succession is about 3000 m thick. Note that the three, inverted thin black triangles show the three second-order sequences within the Bambuı´ first-order sequence. O. Catuneanu et al. / Sedimentary Geology 176 (2005) 67–95 89 sponds to a first-order sequence boundary. Each of m thick, overlie much of the Sa˜o Francisco Craton. these third-order sequences has an estimated duration They are also exposed in the Brasiliano/Pan in the range of tens of million years and is African fold belts surrounding the craton, mainly considered to be the product of in-plane stress in the Brası´lia fold belt on its western flank (Fig. variations (Martins-Neto, 2000). 21). Recent studies (e.g., Castro and Dardenne, 2000; Martins-Neto et al., 2001) indicate deposition 4.2.2. Bambuı´ basin in a foreland basin that was generated during The carbonate to siliciclastic deposits of the thrusting and crustal loading in the Brası´lia fold Bambuı´ first-order sequence, which are up to 3000 belt along the western margin of the Sa˜o Francisco

Uninterpreted seismic line

Prograding second-order sequences

Bambuí first-order } sequence

First-order Paranoa/CanastraParanoa/Canastra first-order sequencefirst-ordersequence sequence boundaries

Fig. 24. Reflection seismic profile in the cratonic area of the Sa˜o Francisco Basin, showing the seismic expression of first-order sequences and sequence boundaries. The Bambuı´ first-order sequence is composed of three prograding second-order sequences. Note that the older two second-order sequences of the Bambuı´ succession show siliciclastic deposits at their bases and carbonate deposits at their tops. The Paranoa´/ Canastra first-order sequence represents passive-margin deposits of the western flank of the Sa˜o Francisco craton, whose closure generated the Brası´lia fold belt. 90 O. Catuneanu et al. / Sedimentary Geology 176 (2005) 67–95

Craton, related to the ca. 800 to 650 Ma arc– continent to continent–continent collision (Pimentel et al., 2000). Three second-order transgressive– regressive sequences characterize the fill of the Bambuı´ Basin (Dardenne, 1981; Figs. 23 and 24). Each of these sequences represents the record of initial flooding of the basin (higher accommodation relative to sediment supply as a result of flexural loading and rapid subsidence) and the subsequent filling of accommodation by a prevailing sediment supply. The organic-rich marine shales of the Sete Lagoas Formation (Fig. 23) were deposited in the central and western parts of the basin. Distal deposits near an inferred forebulge consist of a carbonate ramp succession of limestone (locally with stromatolites), dolostone and argillaceous limestone. The carbonate ramp prograded westward over the deeper-water pelites, and produced the first transgressive–regres- sive second-order sequence. Dolomitized supratidal Fig. 25. High-frequency prograding sequence of the Lagoa do Jacare´ deposits with microbial mats, dissolution structures, Formation showing storm-influenced rhythmites at the base and tepees and birds-eye structures as well as mud cracks, coastal oolitic calcarenites at the top. The section is approximately characterize the top of the unit, indicating subaerial 6 m thick. exposure and marking the second-order sequence boundary. to sediments deposited in alluvial environments The second transgressive–regressive second-order (Fig. 23). sequence begins with shale and argillaceous limestone of the Serra de Santa Helena Formation (Fig. 23), which shows an upward increase in the abundance of 5. Discussion and conclusions siltstone beds and storm-wave reworking. Limestone, calcarenite, oolitic limestone and siltstone, which The principles of sequence stratigraphy may be were deposited in a storm-influenced ramp of the applied at different spatial scales, from individual Lagoa do Jacare´ Formation, prograded over the Serra depositional systems to entire sedimentary basin-fills. de Santa Helena Formation. Higher frequency pro- The common theme, irrespective of scale, is the study grading deposits occupy the transitional interval of the sedimentary response to changes in accom- between the deeper-water facies of the Serra de Santa modation. Within the boundaries of individual depo- Helena Formation and the shallower-water facies of sitional systems, changes in accommodation result in the Lagoa do Jacare´ Formation. Each sequence predictable shifts with time in the types of deposi- comprises storm-influenced shale-calcilutite rhythmite tional elements and lithofacies that accumulate in each at the base, and coastal oolitic calcarenite at the top particular environment. As changes in accommoda- (Fig. 25). tion are in turn controlled by allogenic mechanisms The uppermost transgressive–regressive second- that operate at basin scales, such shifts in depositional order sequence consists at its base of the marine trends are synchronized across the basin, allowing the shale and siltstone of the Serra da Saudade grouping of depositional systems into systems tracts Formation, which are overlain by siltstone, sand- characterized by specific stacking patterns and facies stone, arkose and conglomerate of the Treˆs Marias relationships. Formation that were deposited in a storm-dominated Sequence-stratigraphic surfaces and systems tracts shallow marine system, and finally passing upward may be identified at particular locations within the O. Catuneanu et al. / Sedimentary Geology 176 (2005) 67–95 91 basin, such as boreholes (using core and/or well log surfaces. All classic sequence-stratigraphic models data) or outcrops, or at broader scales involving (Fig. 15) account for the presence of a shoreline mapping and correlations of outcrop and/or surface within the basin under analysis, thus justifying a (well log, core, seismic) data. The criteria identified systems-tract nomenclature that makes specific refer- in Fig. 17 for the recognition of sequence strati- ence to transgressions and regressions. In overfilled graphic surfaces (and especially the nature of basins, however, the depositional environment may be contacts and juxtaposed facies associated with each entirely nonmarine, and so the application of sequence contact) may be applied in any given location, stratigraphy must be adapted accordingly. In such without requiring time control. The identification of cases, the systems-tract nomenclature makes direct stratal terminations usually requires a broader scale reference to the amount of available accommodation of observation, and is best performed on seismic (i.e., low vs. high accommodation systems tracts) as lines and in large outcrops. Time control is inferred from the ratio between fluvial architectural generally desired for correlation, but the lack elements (e.g., see Eriksson and Catuneanu, 2004a; thereof, which is a common theme in Precambrian Ramaekers and Catuneanu, 2004, for Precambrian case studies, may be compensated for by a good case studies). knowledge of facies architecture and relationships Basins related to plume-controlled first-order within the study area. cycles (i.e., plume tectonics) are prone to a domi- In tectonically active basins, the most important nantly nonmarine sedimentation regime because the breaks in the rock record (e.g., second-order net amount of thermal uplift generally exceeds the sequence boundaries that provide the basic subdivi- amount of subsidence created via extension above the sion of the first-order basin-fill) are commonly ascending plume. As plume tectonics was much more associated with stages of tectonic reorganization prevalent in the Precambrian relative to the Phaner- within the basin, which usually lead to changes in ozoic, the low- and high-accommodation systems tilt directions across the major unconformities. In tracts seem to be more commonly applicable with such cases, paleocurrent data provide the key to infer increasing stratigraphic age. In contrast, basins related tectonic events during the basin’s evolution and to to plate tectonic activity are dominated by subsidence, map event-significant sequence boundaries across the and so they are prone to be transgressed by interior basin. This is the case with the Early Proterozoic seaways. Even such subsidence-dominated basins, Athabasca Basin in Canada, where each second- however, may reach an overfilled state under high order sequence is characterized by unique fluvial sediment-supply conditions, in which case the recog- drainage systems, with abrupt shifts in paleocurrent nition of fully fluvial systems tracts (low vs. high patterns across the second-order sequence boundaries accommodation) becomes the only option for the (Ramaekers and Catuneanu, 2004). In this basin, sequence-stratigraphic approach. Case studies of such paleocurrent data provide the best evidence to overfilled plate-tectonic-related basins have been constrain regional correlations and to compensate documented for both Precambrian and Phanerozoic for the general lack of time control in a succession successions (e.g., Boyd et al., 1999; Zaitlin et al., that is relatively homogeneous from a lithofacies 2000, 2002; Wadsworth et al., 2002, 2003; Leckie and point of view. Boyd, 2003; Eriksson and Catuneanu, 2004a; Ram- Sequence stratigraphy uses the same set of core aekers and Catuneanu, 2004). principles irrespective of the age of strata under The application of sequence stratigraphy to Pre- analysis. In that respect its application to Precambrian cambrian basins has considerably enlarged the per- deposits is no different from the methods applied to spective of fundamental principles governing the Phanerozoic successions. Where sedimentary basins processes of sedimentary basin formation and the are transgressed by interior seaways, the shifts in mechanisms controlling stratigraphic cyclicity in the shoreline position, which are in turn controlled by the rock record. The latter principles are perhaps the most interplay of accommodation and sediment supply, important contribution of Precambrian research to represent the fundamental element that constrains the sequence stratigraphy because the large time span of timing of all systems tracts and sequence stratigraphic the Precambrian affords a better understanding of the 92 O. Catuneanu et al. / Sedimentary Geology 176 (2005) 67–95 allogenic controls on sedimentation and hence of the Alkmim FF, Marshak S. Transamazonian orogeny in the southern criteria that should be used in a system of sequence Sa˜o Francisco craton region, Minas Gerais, Brazil: evidence for paleoproterozoic collision and collapse in the Quadrila´tero stratigraphic hierarchy. At the broader scale of Earth’s Ferrı´fero. Precambrian Res 1998;90:29–58. geological history, the tectonic regimes governing the Aspler LB, Chiarenzelli JR. Mixed siliciclastic-carbonate storm- formation and evolution of sedimentary basins are dominated ramp in a rejuvenated palaeoproterozoic intra- shown to have been much more erratic in terms of cratonic basin: upper Hurwitz Group, Nunavat, Canada. In: nature and rates than originally inferred solely from Altermann W, Corcoran PL, editors. Precambrian sedimentary environments: a modern approach to ancient depositional systems the study of the Phanerozoic record. This indicates Spec Publ IAS, vol. 33. Oxford7 Blackwell; 2002. p. 293–321. that time is largely irrelevant as a parameter in the Aspler LB, Wisotzek IE, Chiarenzelli JR, Losonczy MF, Cousens classification of stratigraphic sequences; instead, it is BL, McNicoll VJ, et al. Paleoproterozoic intracratonic basin rather the change in the tectonic setting that affects the processes, from breakup of Kenorland to assembly of key criteria for subdividing the rock record into Laurentia: Hurwitz Basin, Nunavat, Canada. 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