Scholarly article on topic 'Sedimentary controls on the sequence stratigraphic architecture in intra-cratonic basins: An example from the Lower Permian Shanxi Formation, Ordos Basin, northern China'

Sedimentary controls on the sequence stratigraphic architecture in intra-cratonic basins: An example from the Lower Permian Shanxi Formation, Ordos Basin, northern China Academic research paper on "Earth and related environmental sciences"

CC BY-NC-ND
0
0
Share paper
Academic journal
Marine and Petroleum Geology
Keywords
{"Numerical modelling" / "Intra-cratonic basin" / "Sediment accumulation" / "Source-ward retrogradational stacking"}

Abstract of research paper on Earth and related environmental sciences, author of scientific article — Hongtao Zhu, Keyu Liu, Xianghua Yang, Qianghu Liu

Abstract Intra-cratonic basins are characterized by stable tectonic regimes, closed depositional systems, finite sizes of receiving basins and extremely low morphological gradients. This paper examines the effect of sediment accumulation on the sequence stratigraphic architecture and quantitatively evaluates its controls on the development of intra-cratonic sedimentary sequences using numerical modelling. A well documented intra-cratonic sedimentary sequence, the Lower Permian Shanxi Formation in the Ordos Basin, northern China, was used to illustrate a sequence stratigraphic model developed for intra-cratonic sedimentary basins. The studied sequence is characterized by a typical backstepping or source-ward retrogradation. A 2-D simulation software (SEDPAK) and a 3-D simulation software (SEDSIM) were used to model the intra-cratonic sequence. The modelling results indicated that sediment accumulation alone can produce the classical retrogradational stratigraphic stacking patterns. The sediment accumulation can (1) increase the retrogradational range of the original retrogradational stacking sequences, (2) change an original aggradational stacking sequence to a retrogradational stacking one, and (3) decrease the progradational range of an original progradational stacking sequence, or (4) even change an original progradational stacking sequence to a retrogradational stacking sequence. Understanding the relationship between the sediment accumulation and the stratigraphic development in an intra-cratonic basin is essential for interpreting the sequence stratigraphic framework and stacking patterns, and for predicting the distribution of potential reservoir sand-bodies within such basins. This work enriches the classic sequence stratigraphic models by providing a new model for intra-continental basins, and offers new insight on hydrocarbon exploration in intra-cratonic basins.

Academic research paper on topic "Sedimentary controls on the sequence stratigraphic architecture in intra-cratonic basins: An example from the Lower Permian Shanxi Formation, Ordos Basin, northern China"

ELSEVIER

Contents lists available at SciVerse ScienceDirect

Marine and Petroleum Geology

journal homepage: www.elsevier.com/locate/marpetgeo

Sedimentary controls on the sequence stratigraphic architecture in intra-cratonic basins: An example from the Lower Permian Shanxi Formation, Ordos Basin, northern Chinaq

Hongtao Zhua,b*, Keyu Liuc,d, Xianghua Yanga,b, Qianghu Liua,b

a Key Laboratory of Tectonics and Petroleum Resources, China University of Geosciences, Ministry of Education, Wuhan 430074, China b Faculty of Earth Resources, China University of Geosciences, Wuhan 430074, China c Research Institute of Petroleum Exploration and Development, PetroChina, Beijing 100083, China d CSIRO Earth Science and Resource Engineering, P.O. Box 1130, Bentley, WA 6102, Australia

ARTICLE INFO

ABSTRACT

Article history:

Received 18 December 2012

Received in revised form

22 April 2013

Accepted 24 April 2013

Available online 2 May 2013

Keywords:

Numerical modelling Intra-cratonic basin Sediment accumulation Source-ward retrogradational stacking

Intra-cratonic basins are characterized by stable tectonic regimes, closed depositional systems, finite sizes of receiving basins and extremely low morphological gradients. This paper examines the effect of sediment accumulation on the sequence stratigraphic architecture and quantitatively evaluates its controls on the development of intra-cratonic sedimentary sequences using numerical modelling. A well documented intra-cratonic sedimentary sequence, the Lower Permian Shanxi Formation in the Ordos Basin, northern China, was used to illustrate a sequence stratigraphic model developed for intra-cratonic sedimentary basins. The studied sequence is characterized by a typical backstepping or source-ward retrogradation. A 2-D simulation software (SEDPAK) and a 3-D simulation software (SEDSIM) were used to model the intra-cratonic sequence. The modelling results indicated that sediment accumulation alone can produce the classical retrogradational stratigraphic stacking patterns. The sediment accumulation can (1) increase the retrogradational range of the original retrogradational stacking sequences, (2) change an original aggradational stacking sequence to a retrogradational stacking one, and (3) decrease the progradational range of an original progradational stacking sequence, or (4) even change an original progradational stacking sequence to a retrogradational stacking sequence. Understanding the relationship between the sediment accumulation and the stratigraphic development in an intra-cratonic basin is essential for interpreting the sequence stratigraphic framework and stacking patterns, and for predicting the distribution of potential reservoir sand-bodies within such basins. This work enriches the classic sequence stratigraphic models by providing a new model for intra-continental basins, and offers new insight on hydrocarbon exploration in intra-cratonic basins.

© 2013 Elsevier Ltd. All rights reserved.

1. Introduction

1.1. Sequence stratigraphy of intra-cratonic basins

Within the last few decades, research on the cratonic basins has been primarily focused on the mechanism of the basin formation

q This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial-No Derivative Works License, which permits non-commercial use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Corresponding author. Key Laboratory of Tectonics and Petroleum Resources, China University of Geosciences, Ministry of Education, Faculty of Earth Resources, No. 388 Lumo Road, Hongshan District, Wuhan, Hubei 430074, China. Tel.: +86 27 67883563; fax: +86 27 67883051.

E-mail address: zhuoscar@sohu.com (Hongtao Zhu).

0264-8172/$ - see front matter © 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016lj.marpetgeo.2013.04.017

(e.g. De Rito et al., 1983; Klein and Hsui, 1987; Quinlan, 1987; Ahern and Dikeou, 1989; Coakley et al., 1994; Hartley and Allen, 1994; Baird et al., 1995; Howell and van der Pluijm, 1999; Kaminski and Jaupart, 2000; Hanne et al., 2004; Artyushkov et al., 2008; Downey and Gurnis, 2009; Armitage and Allen, 2010), while development of sequence stratigraphic analysis has been emphasized on the controls of base level and tectonic movement (e.g. Bond and Kominz, 1991; Burgess and Gurnis, 1995; Witzke et al., 1996; Burgess et al., 1997; Howell and van der Pluijm, 1999; Runkel et al., 2007). However, classic sequence stratigraphic models focus primarily on the rift, sag and foreland basin settings (e.g. Xie and Li, 1993; DeCelles and Giles, 1996; Catuneanu et al., 1998; Catuneanu, 2004; Hancox et al., 2002; Li et al., 2002; Feng et al., 2004; Escalona and Mann, 2006; Yang and Miall, 2008, 2009; 2010; Yang, 2011; Lash and Engelder, 2011) with little

research on intra-cratonic basins despite the fact that intra-cratonic basins are important hydrocarbon-bearing provinces throughout the world. Recent efforts of applying the sequence stratigraphic approach to the investigation of intra-cratonic basin stratigraphic sequences have yielded some progress (e.g. McLaughlin et al., 2004; Hoffmann et al., 2009; Zhu et al., 2010; Kanygin et al., 2010; Petty, 2010) but most of the investigations have been limited in geographic scope and some workers continue to question the suitability of such an approach (e.g. McLaughlin et al., 2004; Hoffmann et al., 2009; Petty, 2010). A stratigraphic framework comparable in scope and resolution to the comprehensive framework for the classic passive margin settings is yet developed for intra-cratonic stratigraphic sequences. It is clear that insufficient research efforts have been devoted to understanding the sequence stratigraphy of cratonic basins. Indeed, it is easy to understand how one may easily fall into the trap of trying to fit observations into rigid existing templates provided by various standard models (Catuneanu, 2006). Therefore this research on developing a sequence stratigraphic model for the intra-cratonic basin setting is of great importance for the completeness of the sequence strati-graphic models. The development of stratigraphic sequences is classically related to driving mechanisms, including eustasy, subsidence or uplift, and variations in sediment supply, and climate (Vail et al., 1991; Emery and Myers, 1996; Catuneanu, 2004). Moreover, the dominant factors for the formation of sequence stratigraphy vary among different basin types.

From previous research, we suggest that the spatial and temporal distributions of the sediment sequences in an intra-cratonic basin are characterized by a typical source-ward retrogradation controlled by the interplay among the structural configuration of the basin margin, sediment supply, base-level fluctuations, palaeotopography, sediment accumulation, and climate (Zhu

et al., 2008, 2010). Investigations relating sediment accumulation effect to the sequence stratigraphic architectures are rare in the literature. In this paper we examine the sediment accumulation as an important factor that controls the development of intra-cratonic sedimentary sequences using numerical modelling. Based on the basic premise of mass balance and energy conservation, the volume of sediment accumulation supplied to a basin would result in the same new increment of accommodation space or water bodies within an enclosed intra-cratonic basin. Sediment accumulation can thus affect the sequence stratigraphic architecture of such a basin.

Intra-cratonic basins are characterized by generally stable tectonic regimes, closed depositional systems, finite sizes of receiving basins and extremely low morphological gradients (Fig. 1). Gradual sediment accumulation of the basin gives rise to a backstepping or retrogradational sequence due to the increase of relative accommodation space by sediment (including associated water) infill thereby causing the base level to "elevate" accordingly (e.g. Liang, 1996).

1.2. Quantitative forward stratigraphic modelling

Stratigraphic modelling has been increasingly used to assist stratigraphic interpretation and basin analysis, particularly in the field of petroleum exploration and production (e.g. Cross, 1990). Unlike traditional sequence stratigraphic analyses (Vail and Mitchum, 1977; Wilgus and Roskoski, 1988; Galloway, 1989; Van Wagoner et al., 1990), forward stratigraphic modelling provides a quantitative evaluation of the various geological parameters that control the formation of sedimentary sequences. It is an efficient tool to understand depositional processes and basin evolution intuitively.

Figure 1. Comparison of the geological characteristics of typical passive continental margin basins and intra-cratonic basins during a basin fill cycle. Note that the overall sequence for the intra-cratonic basin succession shows a distinct upward fining (deepening).

The first step in forward stratigraphic modelling is the estimation of the initial depositional conditions of the basin, including palaeotopography, bathymetry, climate, base level variations and sediment input. The process projects forward through geological time to produce stratigraphic models that match the target sequences. SEDPAK was one of the earliest forward modelling programs developed by the Stratigraphic Modelling Group at the University of South Carolina, USA (See Appendix for a detailed description). The program is based on geometric (empirical) rules that govern gradients and stacking patterns of sedimentary strata. The program simulates the 2-D geometry of sediment deposition by considering four primary geological parameters: the initial and evolving basin physiography, the rates of sediment supply, base level fluctuations and tectonically induced movement (Strobel et al., 1989; Kendall et al., 1991). SEDSIM is a 3-D stratigraphic forward modelling program originally developed at Stanford University in the 1980s and extensively modified and enhanced by Dr Cedric Griffiths' group (Griffiths et al., 2001) in Australia since 1997 (See Appendix for a detailed description). The core of the SEDSIM program is the hydrodynamic and sedimentation simulation engine, which is linked to a number of modules, including subsidence, base level change, wave transport, compaction, and slope failure (Tetzlaff and Harbaugh, 1989; Griffiths et al., 2001). Both strati-graphic modelling programs have been shown to be useful in complementing qualitative geological interpretations and in validating geological models (Tetzlaff and Harbaugh, 1989; Kendall et al., 1991; Liu et al., 1994, 1998; 2001, 2002; Griffiths et al., 2001). Further, the programs simulate basin fill process intuitively. Detailed descriptions of the two programs can be found in Strobel et al. (1989), Tetzlaff and Harbaugh (1989) and Griffiths et al. (2001).

We applied both the SEDPAK and SEDSIM computer programs to our modelling of the lower member of the Permian Shanxi Formation in the Ordos Basin, northern China. The primary objectives of this study include (1) the construction of a high-resolution sequence stratigraphic model for the period between 280 Ma and 270 Ma to guide seismic interpretation and well correlations; (2) the simulation of observed cyclothemic sequences; and (3) illustration of how sediment accumulation can control sequence stratigraphic architecture during the development of a complete cyclothem in an intra-cratonic basin.

2. Conceptual geological model for the Ordos Basin

The Ordos Basin is a non-marine intra-cratonic basin in central China that has several unique characteristics (Xue et al., 2002), including 1) a history of slow prolonged (290 Ma) vertical crustal movement that controlled the basin morphology and configuration; 2) a single depocentre shared by successive sedimentary systems; 3) low morphological gradients and diverse sedimentary facies; 4) thin sediment layers with little variations in thickness laterally and a slow depositional rate (about 5.9 m/Ma in the study area); and 5) a closed depositional environment. In contrast to marine intra-cratonic basins, terrestrial intra-cratonic basins such as the Ordos Basin are characterized by stable tectonic regime, closed depositional systems, finite sizes of receiving basins and extremely low morphological gradients, which result in some unique features of sediment accumulation (Fig. 1). One of the unique features is the enclosed receiving basin with finite accommodation space and being progressively filled during the basin evolution until the basin extinction. Considering the extremely low morphological gradients, a small-scale base-level rise could form a broad transitional zone. With a closed depositional system, the base level of a terrestrial intra-cratonic basin is isolated and is primarily controlled by climate rather than global eustasy.

The Ordos Basin is situated in the western part of the North China plate, bounded by the Luliang Mountains to the east, the Qinling Mountains to the south, the Liupan and Helan mountains to the west, and the Yin mountains to the north (Fig. 2A). It contains a relatively well preserved lower member of the Permian Shanxi Formation sequence of about 60 m thick. The basin has experienced a protracted history of crustal movement (He et al., 1996; Ye and Lu, 1997; Xue et al., 2002; Yang et al., 2005). The Shanxi Formation (Fig. 2B) is thought to represent a second-order sequence with its ascending hemi-cycle comprising the lower member of the Shanxi Formation, which is characterized by several coal seam-bearing beds and regressive sediment sequences. The upper member of the Shanxi Formation coincides with the falling hemi-cycle, which is characterized by a strong basin-ward regression. The Shanxi Formation consists of three third-order sequences SQ1, SQ2 and SQ3, each of which is characterized by an upward fining (deepening) succession (Fig. 2B).

The sequence stratigraphic cross-section shown in Figure 2C was constructed from the analysis of seismic-lithofacies, well logs and outcrops (Zhu et al., 2008). Three assemblages of sand-bodies in sequences SQ1, SQ2 and SQ3 appear to be retrogradational stacking patterns (sequentially landwards). Within each sequence, the sedimentary facies also display a distinct retrogradation with a sandstone-dominated lower part and a mudstone-dominated upper part (Fig. 2C). The reservoir sandstone units become thinner and finer grained in the southern part of the study area and in places become absent, indicating an overall landward retrogradation with sedimentary facies sequentially becoming finer away from the source area.

The characteristic retrogradation features and sand-body stacking patterns can be identified clearly along the N—S (direction) seismic sections within the Lower Shanxi Formation as shown in the selected seismic line in Figure 2D. Based on the seismic-lithofacies analysis, the seismic horizons can be traced along the NS seismic section. The three sandstone units are highlighted with blue, pink, and red broken arrowhead (Fig. 2D), corresponding to the three third order sequences, SQ1, SQ2 and SQ3. These three units are retrogressive landwards (northward) overall, consistent with the sequence stratigraphic correlation from wells and the interpreted spatial distribution of sand-bodies shown in Figure 2C.

The source-ward retrogradational stacking geological model established above underpins our modelling study of the lower member of the Permian Shanxi Formation sequence and can be summarised as follows: 1) the initial basin morphological gradients were extremely low, less than 1° (Liang and Li, 2006); 2) the interiors of the continent are relatively unaffected by the regional plate tectonics (Xue et al., 2002); 3) the stratal geometry and sequence architecture are primarily controlled by the interplay of sediment supply and accommodation availability; and 4) the climate-controlled lake-level curve of Ordos basin derived from the lithologic associations and cyclicities of the depositional strata (Yang, 2002; Zhu et al., 2008) strongly determines the cyclic nature of the modelled stratigraphic fluctuations.

Different cyclothem (cyclic depositional regime) motifs are characteristic of different paleogeographic positions within the evolving Ordos Basin. Individual cyclothems are controlled by the complex interplay of subsidence rate, sediment supply and lakelevel change (e.g. Saul et al., 1999). This conceptual model is tested quantitatively by forward stratigraphic modelling using the SEDPAK and SEDSIM computer programs.

3. Input parameters for simulations

The input parameters used in the simulations were derived from the generalized stratigraphic column of the lower member of the

Figure 2. Geological characteristics of the Lower Permian Shanxi Formation sequence in the Ordos Basin. (A), Map of the northeastern part of the Ordos Basin showing locations of outcrops, wells, seismic line and well correlation section; (B), Generalized stratigraphic column of the Permian Shanxi Formation, northeastern Ordos Basin, showing lithologies, sequence stratigraphic framework and lithology associations; (C), Sequence stratigraphic correlation section from Well S65 to Well S1 and reservoir sand-body distribution of the lower member of the Shanxi Formation along the N—S direction; (D), N—S seismic cross-section of the lower member of Shanxi Formation showing a distinct landwards (northward) retrogradation of the sand-bodies. See (A) for the location of the cross-section.

Permian Shanxi Formation, northeastern Ordos Basin (Fig. 2B). Within the simulation duration (270 Ma—280 Ma), the stratigraphic sequence of the lower member of the Permian Shanxi Formation is further subdivided into three third-order sequences, namely SQ1, SQ2 and SQ3 from base to top, corresponding to three 3rd-order cycles (Fig. 2B), separated by two basin-wide sequence boundaries

at 278 Ma and 273.75 Ma, respectively. The input parameters, including sediment thickness, sedimentary facies variations, chronology and palaeo-water depths, were derived from detailed sequence stratigraphic analyses (Zhang and Sun, 1997; Fan et al., 1999; Zhai and Deng, 1999; Hou et al., 2001; Zhu et al., 2002; Li et al., 2003; Zhu, 2005; Zhu et al., 2008).

3.1. Parameters used for simulating the "base case" without considering of the effect of sediment accumulation

The 2-D stratigraphic simulation (SEDPAK) was set to start at 280 Ma on an initial basin surface that mimics the inferred physiography and an interpreted bathymetry of the northeastern Ordos Basin at the time (Fig. 3A). This surface was derived by backstripping the overlying sediment sequence, and correcting for the unloading and decompaction effects. Sedimentation during the 10 Ma was then modelled in response to lake-level fluctuations and sediment supply (Fig. 3). The width of the basin cross-section simulated is 100 km. The effective modelling section selected is only 60 km wide (Fig. 3A) after discounting boundary effects. In the study area, some key wells were corrected with available borehole data. The initial morphological gradients were set between 0.1 ° and 0.3°.

The lake-level curve used in the simulation (Fig. 3B) was derived from the work of Yang (2002), supplemented by the lithologic association and cyclicity of the sequences described by Zhu et al. (2008). There are three stages of transgressive-regressive changes in the lake-level curve. The three transgressions include the primary stage ranging from 280 Ma to 278.5 Ma, the second stage from 277.75 Ma to 274.75 Ma, and the final stage beginning at 273.5 Ma and ending at 271.5 Ma. Overall the regression duration was set to increase gradually to mimic the sequence stratigraphic interpretation with 0.75 Ma, 1.25 Ma and 1.5 Ma for Sequences SQ1, SQ2 and SQ3, respectively. During the transgression, the rate of the lakelevel rise was set to the minimum in the deposition of SQ2 and to the maximum for SQ3. During the regression, the rates of the lakelevel fall were set to maximum during the deposition of SQ1 and minimum for SQ2. The lake-level change largely matches with that of the geological model.

Sediment supply rates were determined by backstripping the borehole cross-sections within the basin (Zhang and Sun, 1997; Hou et al., 2001; Zhu et al., 2008). As illustrated in Figure 3C and D, the clastic sediment influx rate (sand and shale supplied from the left-hand side of the basin) was quite slow. The coarse fraction of the terrigenous detritus (sand in Fig. 3C, shale in Fig. 3D) was set to vary in response to the lake-level fluctuations, i.e., a slight increase in the coarse sediment supply was allocated during lowstands.

Relatively high sediment supply rates for the coarse grained detritus and low rates for the fine grained detritus were inferred for the SQ1 sequence between 280 Ma and 278 Ma with a sand/shale ratio of >80% (the rate of sand was decreased by 17%, while the fine sediment (shale) input was increased by 25%). Sediment supply during the deposition of SQ2 (278 Ma—273.5 Ma) was decreased steadily, while the rate of sand supply continued to decrease. The rate of shale supply increased at a sand/shale ratio of >70% (the sand input rate was further decreased by 20% but the shale input rate was increased by 20%) (Fig. 3B). Sediment supply was allowed to decrease rapidly from 273.75 Ma to 270 Ma (SQ3) with a sand/ shale ratio of <50%; the sand input rate was further decreased by 50%, while the shale input rate was increased by a further 25% (Fig. 3C and D) (Table 1).

3.2. Parameters used for simulating the alternative case with consideration of the effect of sediment accumulation

The Ordos Basin was an under-filled basin during the simulation period. Mass balance and energy conservation calculations suggest that the volume of sediment accumulation in a receiving basin should result in an increment of the same amount of new accommodation space. During the simulation, the calibration curve of the lake-level was considered to be influenced by both lake-level

Figure 3. Input parameters used in the SEDPAK computer simulations: (A), Initial basin geometry at 280 Ma (MYBP) and the effective modelling section from 20 km to 80 km shown; (B), Lake-level curves used in the simulation, the solid line shows the lake-level of the "base case" without considering of the effect of sediment accumulation, the dotted line shows the lake-level of the alternative case by considering the effect of sediment accumulation; (C) and (D), Clastic sediment supply rates in square kilometres per ka for sand and shale, respectively.

Table 1

Sediment supply rates for sand and shale of three sequences.

Sequence Rate of sand supply (km2/ka) Maximum Minimum Rate of shale supply (km2/ka) Minimum Maximum Sand/ shale ratio

SQ3 0.00020 0.00010 0.00012 0.00015 <50%

SQ2 0.00025 0.00020 0.00010 0.00012 >70%

SQ1 0.00030 0.00025 0.00008 0.00010 >80%

fluctuations and sediment influx rates. During the relative lakelevel rises, the rising rate of the calibration curve was set to decrease gradually and eventually approach to zero when the rate of sediment flux (corresponding to the effect of sediment accumulation) are less than the lake-level rises; the rising rate of the calibration curve only responses to the influence of topography when the rate of sediment flux matches or exceeds the lake-level rises. If the relative lake-level falls, the rising rate of calibration curve will be significantly larger than that of the previous stages and keeps increasing rapidly.

In this simulation, the elevation increment of the lake-level (Ah) equals to the volume of the sediment accumulation divided by the width/area of the basin. The final calibration curve of lake-level for the simulation for the alternative case with consideration of the effect of sediment accumulation is shown in Figure 4. The simulation of the effect of sediment accumulation was achieved by using the calibrated curve to correct the actual lake-level curve derived from the geological model, while the other depositional parameters for the clastics were kept identical as the base case (Fig. 3).

For the base case (without considering the sediment accumulation) (Fig. 3B), the overall relative lake-level keeps falling during the entire simulation. Over time, cumulative sediment accumulation caused the declining range of the lake-level to increase with the declining rate being diminished gradually. Compared with the range of changes in transgression and regression, the change during the first stage (SQ1) is the maximum, whereas that for the third stage (SQ3) is the minimum (Fig. 3B). Compared the simulations for the two cases sediment accumulation has apparently enhanced the rates of transgression and suppressed the regression.

4. Discussion of simulation results

4.1. Two-dimensional stratigraphic simulation

The output of the SEDPAK simulation includes two dimensional diagrams which show sequences, facies, lithological ratios

14 -i-

о •+-1-1-1-1-

-280 278 276 274 272 270

Age (MaBP)

Figure 4. Correction curve of lake-level by considering sediment accumulation.

(sandstone vs shale) and chronostratigraphy (Fig. 5). In the simulation results, the facies plots show the presence of repetitive unconformity-bounded cyclothems, and associated stratal stacking patterns. The lithologic plots display the lateral distribution and vertical variations of different lithologies. The chronostratigraphic diagrams show the position of the shoreline through time, indicating the migration distance of deposits. Figure 5A displays the simulation results of the "base case" without considering of the effect of sediment accumulation. The simulation results in the modelled basin cross-section closely mimic the documented stratigraphy of the northeastern Ordos Basin (Fig. 2). The axial sand-body distribution along the north—south direction is characterized by a sequential retrogressive landwards from sediment accumulation of SQ1, through SQ2 to SQ3 for the alternative case with consideration of the effect of the sediment accumulation (Fig. 5B), with the percentages of strata thickness being similar between the simulated "base case" and geological model (cf Figs. 5B and 2C). In addition, the main difference between Figure 5B2 and A2 is that the former is slightly more retrogradational in the lower sequence changed from aggradational stacking patterns and more aggrada-tional in the middle and upper sequence changed from prograda-tional stacking patterns owing to sediment accumulation effect.

In detail, however, each modelled cyclothem is unique, as they are controlled by a particular combination of lake-level and sediment supply. This is consistent with field observation of the cyclothems (Figs. 2B and 6). Although the SEDPAK modelling result does not reproduce every detail of these motifs, the modelled cyclothems which correspond to phases of sediment progradation and retrogradation show a strong similarity to the sequence motif described by Zhu et al. (2008, 2010) from the northeastern Ordos Basin section (Fig. 2C). Overall, then SEDPAK modelling presents a reasonable simulation of the motif patterns. Based on the above-mentioned simulation results, a comparative assessment can be achieved on how sediment accumulation process controls on sequence stratigraphic architecture. For the convenience of discussion, the model is subdivided into three phases corresponding to the SQ1, SQ2 and SQ3 sequences (Figs. 5 and 6).

4.1.1. Basin evolution

4.1.1.1. SQ1 (280 Ma—278 Ma). When the sediment accumulation effect was not taken into account as in the "base case", the initial phase of the basin model was marked by a low elevation and a major pulse of rapid sediment aggradation and progradation, occurred between 280 Ma and 278 Ma (Fig. 5A). During this period, fluvial sedimentary facies extended to the basin margin. A termination of transgression at 279.25 Ma can be attributed to the deceleration of lake-level rise. The SQ1 sequence developed largely in response to the initial model conditions of a relatively high rate of the lake-level rise. The initiation of progradation or regression at 279.25 Ma occurred in response to increase in sedimentation rate, which caused the shoreline to migrate to the basin centre. A forced regression event at 278.5 Ma was probably caused by the fall of lake-level. This was followed by a steady fall of the lake-level and enhanced erosion of the basin margin. Termination of SQ1 (278 Ma) was marked by the onlapping of an unconformity surface.

Under the influence of sediment accumulation, as shown in Figure 5B, compared with the vertical stacking sequence sets of the "base case" between 279.5 Ma and 279.25 Ma, the stacking patterns of the alternative case with consideration of the effect of sediment accumulation had changed from aggradational stacking sequences to retrogradational stacking sequences (Table 2). Apart from the stage of retrogradation, the spatial range of the original prograda-tional stacking patterns also decreased. Migration of the shoreline shown on the chronostratigraphic diagram can be used to analyse the effect of sediment accumulation. The shoreline has migrated to

Figure 5. Two sequence stratigraphie models produced by the SEDPAK computer program. The "base case" without considering the effect of sediment accumulation is shown to compare with the alternative case which takes consideration of the effect of sediment accumulation. Only one variable (lake-level) was changed between the two simulations. Note that the changes of the facies distribution, stratal geometry and the overall sequence architecture. The colours in the lake-level curve correspond to the coloured packages in the sequence plots. The legends at the bottom for the facies plots are in terms of palaeo-water depth in metres below lake-level. Condensed section initiation timing and duration are also indicated in the chronostratigraphic diagram.

the landward during retrogradation. Comparing with the shoreline migration of the "base case", the alternative case, which takes consideration of the effect of sediment accumulation, remains largely migrating source-ward. The position of the sedimentary slope break shifted from 49.5 km to 48 km with a lateral migration of about 1.5 km (Table 3; Fig. 6). These features in the SQ1 sequence are controlled largely by the relatively rising lake-level and the extremely low morphological gradients.

4.1.1.2. SQ2 (278 Ma—273.75 Ma). The Phase 2 sequence (SQ2) is characterized by an unconformity overlied onlapping sediments at

278 Ma, where the topset is replaced by onlap, and the stacking sequence sets change from progradation to retrogradation (Fig. 5A). From 278 Ma to 277 Ma, sedimentation rate outpaced the rate at which new accommodation space was added, resulting in basin-ward migration of the shoreline. Rising lake level from 277 Ma to 275.75 Ma was accompanied by retrogradation and accumulation of highstand deposits. During transgression, the shoreline migrated landward, covering a distance that exceeded landward migration of the shoreline during the preceding stage (SQ1). In addition, the percentages of shaley sediment increase accordingly. The maximum flooding surface denoting the time of maximum lake

Figure 6. Comparison of sequence architectures and stacking patterns between the SEDPAK simulation sequence plots for the "base case" without considering the effect of sediment infilling (A) and the alternative case which takes consideration of the effect of sediment accumulation (B) using "Pseudo wells". Diagram (C) shows the shoreline migration positions corresponding to various sequence boundaries.

level was dated at 275.75 Ma. This was followed by a reduction of lake level and a consequent construction of a progradational stacking pattern of facies (Table 2).

When accounting for the influence of sediment accumulation, as shown in Figure 5B, the rate of the lake-level rise increased relatively and led to the stacking sequence sets changed from progradation to retrogradation during the period from 277.25 Ma to 277 Ma (Table 2). The progradational amplitude of the original progradation (from 278 Ma to 277.25 Ma) was decreased; while the subsequent retrogradation range was increased. During the retrogradation stage, the lacustrine system was triggered by a rise in lake-level at a rate higher than the sedimentation rate at the shoreline. The region of hiatus was reduced greatly and migrated

towards the source area (Fig. 5B4). The position of the sedimentary slope break shifted from 51.0 km to 42.5 km with a lateral migration of about 8.5 km (Table 3), a significant increase in the migration distance. In general, the percentage of shale kept increasing during this stage (SQ2).

4.1.1.3. SQ3 (273.75 Ma-270 Ma). The final phase of the basin evolution includes deposition of dominantly silt and clay sediment across the basin axis, marking a major highstand of the last half million years (Fig. 5A). A prolonged, relatively stable period from 273.5 Ma to 272.25 Ma resulted in accumulation of a retrograda-tional stacking pattern. At the same time, the region of sedimentary hiatus (erosion or non-deposition) continued to be reduced and

Table 2

Comparison of sequence stacking patterns, timing and duration for the "base case" without considering of the effect of sediment accumulation and the alternative case with consideration of the effect of sediment accumulation.

Sequence Base case Alternative case

Sequence stacking patterns Timing (Ma) Duration (Ma) Duration (Ma) Timing (Ma) Sequence stacking patterns

SQ3 Progradation 272.25—270 2.25 2.25 272.25—270 Progradation

Retrogradation 273.5—272.25 1.25 1.25 273.5—272.25 Retrogradation

SQ2 Progradation 275.75—273.5 2.25 2.25 275.75—273.5 Progradation

Retrogradation 277—275.75 1.25 1.25 277—275.75 Retrogradation

Progradation 278—277 1 0.25 277.25—277 Retrogradation

0.75 278—277.25 Progradation

SQ1 Progradation 279.25—278 0.75 0.75 279.25—278 Progradation

Aggradation 280—279.25 1.25 0.75 279.5—279.25 Retrogradation

0.5 280—279. 5 Aggradation

migrated to the source area. During the period of the deposition of Sequence SQ3, a major flooding event occurred at 272.25 Ma, which was followed by progradation of medium-grained sediment towards the basin margin, and shaley sediment in the centre of the basin. Lake-level rose from 272.25 Ma to 271.5 Ma, but at a gradual rate resulting in the sedimentation rate outpacing the rate that new accommodation space was added. After 271.5 Ma, the lake-level began to decrease. The genetic types of parasequence sets from 271.5 Ma to 270 Ma correspond to a forced regression, which is progradation driven by base-level fall (Table 2). Finally, a correlative conformity surface that marks the change in stratal stacking patterns from a highstand normal regression to a forced regression was produced.

When adding the influence of sediment accumulation, as shown in Figure 5B, a rising lake-level and a diminishing sediment supply resulted in an increase in shale. The region of sedimentary hiatus (erosion or non-deposition) has further migrated shoreward. The position of the sedimentary slope break changed from 27 km to 17.5 km, a 9.5 km lateral migration (Table 3). During the deposition of the SQ3 sequence, the rate of lake-level rise gradually weakened, resulted in a progressively reduced influence of sediment accumulation on the sequence stratigraphic architecture.

4.1.2. Quantitative evaluation of the influence of sediment accumulation

One of the objectives of this study is consideration of sediment accumulation as a key factor that controls the development of intra-cratonic sedimentary sequences using quantitative modelling. Based on the lateral distribution and vertical variations of the different lithologies and some key wells in the study area, five pseudo-wells (at 40, 50, 60, 70 and 80 km in the modelled section, respectively) were used to establish vertical sections and a sequence stratigraphic framework (Fig. 6A and B). From the 40 km pseudo well to the 80 km pseudo well, the percentage of HST increases steadily, indicating an overall rise of lake-level. Compared with the "base case", the percentage of the HST and the shale/sand ratio in the alternative case with consideration of the effect of sediment accumulation, increases within the corresponding pseudo-well.

Table 3

Comparison of the position changes of sedimentary slope break for the "base case" without considering of the effect of sediment accumulation and the alternative case with consideration of the effect of sediment accumulation.

Sequence Position of sedimentary Position of sedimentary Lateral migration slope break for the slope break for the distance (km) "base case" (km) alternative case (km)

SQ3 27.0 17.5 9.0

SQ2 51.0 42.5 8.5

SQ1 49.5 48.0 1.5

As shown in Table 2, during the entire simulated period from 280 Ma to 270 Ma, the durations of progradation, aggradation and retrogradation were respectively 6.25 Ma, 1.25 Ma and 2.5 Ma for the "base case" without considering the effect of sediment accumulation. In contrast, the corresponding durations for the alternative case with consideration of the effect of sediment accumulation were 6.0 Ma, 0.5 Ma and 3.5 Ma, respectively. The effects of sediment accumulation resulted in a decrease of the durations of progradation and aggradation but an increase of the retrogradation durations. Therefore, the sediment accumulation in the basin had 1) increased the retrogradational range of the original retrogradational stacking sequences, changed the originally aggradational stacking sequence to a retrogradational sequence; 2) decreased the progradational range of an originally progradational stacking sequences; or 3) even changed an originally progradational stacking sequence to a retrogradational stacking sequence.

In order to analyse the effect of sediment accumulation quantitatively, the sequence boundaries and sequence stratigraphic framework of sediment accumulation were compared repeatedly (Fig. 6C) to determine the migration distance of the sequence stratigraphic units. In contrast to the "base case" in the simulation of the alternative case with consideration of the effect of sediment accumulation the sand-bodies of Sequence SQ1 migrated source-ward from 27.0 km to 25.0 km, the sand-bodies of Sequence SQ2 migrated source-ward along the basin slope from 17.5 km to 13.0 km, and the sand-bodies of Sequence SQ3 continued to migrate source-wards from 10.0 km to 4.5 km (Table 4) with the overall migration range for each individual sequence reduced progressively.

4.2. Three-dimensional stratigraphic simulation

After several calibration runs to test the sensitivity of the simulated depositional system by changing the bathymetric gradient, source location, grid size, input flow rates and sediment

Table 4

Comparison of the positions of intersection between sequence top boundary and basement for the "base case" without considering of the effect of sediment accumulation and the alternative case with consideration of the effect of sediment accumulation.

Sequence Positions of intersection Position of intersection Lateral migration

between sequence top between sequence top distance (km) boundary and basement boundary and basement for the "base case" (km) for the alternative case (km)

SQ3 10.0 4.5 5.5

SQ2 17.5 13.0 4.5

SQ1 27.0 25.0 2.0

Figure 7. SEDSIM simulation lithological outputs of the "base case" without considering the effect of sediment accumulation, showing the characteristics of source-ward retro-gradational stacking patterns from SQ1 to SQ3. (A), simulated lithological fence diagram. (B), selected well correlation section from the study area, shown in (A). (C), geological model of the well section modelled.

concentrations, and degree of erosion of the underlying sediment, the final SEDSIM simulation results are shown in Figures 7 and 8.

Based on the selected well correlation section in the study area, we used the lithological output along the same cross-section to

compare the results of the two SEDSIM simulations. By conferring to the original geology model, the well correlation section of the "base case" shown in Figure 7 and that in the alternative case (with consideration of the effect of sediment accumulation) shown in Figure 8 were evaluated.

Figure 8. SEDSIM simulation lithological outputs of the alternative case which takes consideration of the effect of sediment accumulation, showing the characteristics of source-ward retrogradational stacking from SQ1 to SQ3. (A), simulated lithological fence diagram. (B), selected well correlation section from the study area, shown in (A) (Lower section) and the selected well section in Figure 7B (Upper section), showing the migration of sequence boundary of two cases. (C), enlarged section of (B), showing the distinct upward fining succession.

For the "base case" (Fig. 7), the lithological section from Well S208 to Well S209 shows the sand-bodies of the SQ1 to SQ3 sequences retreating towards the source. The sand-bodies in the SQ1 sequence are primarily confined by the basal morphology and lake-level fluctuations. The thickness of SQ1 Sequence varies laterally. From SQ1 to SQ3, the sequences pinch out towards the source direction, with the pinch-out points shown in the chart. The stratigraphic pinch-out point of SQ1 lies north of Well SH7. Rising base level caused SQ2 to retrograde farther landwards to the vicinity of Well S142. With the rising base level coupled with diminishing sediment supply, Sequence SQ3

retrograded further landwards. The distance between the pinch-out points of the SQ1 and SQ2 sequences is approximately 13.5 km (Fig. 7B). The thickness of SQ1 and SQ2 showed no difference among the three sequences, all of which are characterized by retrogradation.

When accounting for the influence of sediment accumulation, as shown in Figure 8, the three assemblages of sand-bodies in SQ1, SQ2 and SQ3 appear to be retrogressive. Sedimentary facies of each sequence also display obvious regression sequentially source-ward. The sand-bodies are characterized by fining-upward successions with a sandstone-dominated lower

part and a mudstone-dominated upper part. The sandstones in SQ1 retrograded landwards to the area near Well SH9. Similar to SQ1, the sandstones in SQ2 retrograded landwards to the area near Well S205. Sequence SQ3 continued to be retrograded further source-ward. The distance between the pinch-out points of sequences SQ1 and SQ2 increased to 18 km, which approximates the pinch-out distance of geological model (about 14.5 km).

In contrast to the "base case", the sand-bodies in SQ1 migrated source-ward 4.5 km after considering the effect of sediment accumulation (Fig. 8B). The sand-bodies in SQ2 migrated along the basin slope source-ward for approximately 8.0 km (Fig. 8B). The sand-bodies in SQ3 continued to migrate source-ward along the slope. In general the range of the migrating rate from SQ1 to SQ3 was progressively reduced, comparable to the two-dimensional SEDPAK simulation results (cf Figs. 6—8). The percentages of stratal thickness among the three sequences largely match that from the geological model quite well.

5. Conclusions

(1) The simulated high-resolution sequence stratigraphic model from 280 Ma to 270 Ma indicated that the stacking patterns of the SQ1 sequence comprise both aggradational (280— 279.25 Ma) and progradational (279.25 Ma—278 Ma) deposits; the stacking patterns of the SQ2 sequence comprise progradation (278 Ma—277 Ma), retrogradation (277 Ma— 275.75 Ma) and progradation (275.75 Ma—273.5 Ma); the stacking patterns of the SQ3 sequence consist of retrogradation (273.5—272.25 Ma) and progradation (272.25—270 Ma).

(2) For the entire simulated period (10 Ma), the sediment accumulation appears to have a pronounced effect on the sequence development: the duration of the progradation decreased from 6.25 Ma to 6.0 Ma, the duration of the aggradation decreased from 1.25 Ma to 0.5 Ma, and the duration of retrogradation increased from 2.5 Ma to 3.5 Ma. The simulations illustrated that the sediment accumulation can increase the retrogradational range of the original retrogradational stacking sequences, change an originally aggradational stacking sequence to a retrogradational sequence, and decrease the progradational range of an originally progradational stacking sequence, or even change an originally progradational stacking sequence to a retrogradational stacking sequence.

(3) This study has also demonstrated that numerical simulation is a powerful and effective tool for investigating sequence strat-igraphic geometry and stacking patterns quantitatively, understanding depositional processes and basin fill history, and predicting the spatial-temporal distribution of sedimentary facies intuitively.

Acknowledgements

This study was supported by the National Natural Science Foundation of China (No. 40702024), the "Element and process constraint petroleum system modeling" project (No. 2011A-0207) under the PetroChina Science Innovation program, the Special Fund for Basic Scientific Research of Central Colleges, China University of Geosciences (Wuhan) (CUGL100412 and CUG130104), and the Henry Fok Education Foundation (132020). We are grateful to the anonymous reviewer and Finn Surlyk, the editor of Marine and Petroleum Geology, for their constructive comments and suggestions, which have greatly improved the manuscript. We would like to thank the Stratigraphic Modelling Group of the University South Carolina, USA, for providing the SEDPAK program and CSIRO Earth

Science and Resource Engineering for access to the SEDSIM (Demo)

program.

Appendix A

SEDPAK provides a conceptual framework for modelling the sedimentary fill of basins by visualizing stratal geometries as they are produced between sequence boundaries. The simulation is used to substantiate inferences drawn about the potential for hydrocarbon entrapment and accumulation within a basin. It is designed to model and reconstruct clastic and carbonate sediment geometries which are produced as a response to changing rates of tectonic movement, eustasy, and sedimentation. The simulation enables the evolution of the sedimentary fill of a basin to be tracked, defines the chronostratigraphic framework for the deposition of these sediments, and illustrates the relationship between sequences and systems tracts seen in cores, outcrop, and well and seismic data. http://sedpak.geol.sc.edu/

Sedsim is a software package which determines how sediments change in both time and space by recreating the physical processes that deposit, erode and rework sediments. It is a sedimentary process modelling software. Sedsim models multigrain and carbonate erosion, transport and deposition/production at a very wide range of spatial and temporal scales. The output is produced in a testable form consisting of grainsize distributions, porosity and composition. http://www.csiro.au/products/Sedsim

The effect of sediment accumulation on lake level:

Throughout the text the effect of sediment accumulation refers to the contribution of sediments deposited in a finite and enclosed basin on the lake level rise, which is often ignored for marine basins, where the water body is regarded infinite and thus the overall sea level would not be affected by the sediment accumulation in the basins.

References

Ahern, J.L., Dikeou, P.J., 1989. Evolution of the lithosphere beneath the Michigan Basin. Earth and Planetary Science Letters 95, 73—84.

Armitage, J.J., Allen, P.A., 2010. Cratonic basins and the long-term subsidence history of continental interiors. Journal of the Geological Society 167 (1), 61—70.

Artyushkov, E.V., Tesakov, Y.I., Chekhovich, P.A., 2008. Ordovician sea-level change and rapid change in crustal subsidence rates in eastern Siberia and Balto-scandia. Russian Geology and Geophysics 49, 633—64 .

Baird, D.J., Knapp, D.J., Steer, D.N., Brown, L.D., Nelson, K.D., 1995. Upper-mantle reflectivity beneath the Williston basin, phase-change Moho, and the origin of intracratonic basins. Geology 23, 431—434.

Bond, G.C., Kominz, M.A., 1991. Disentangling middle Paleozoic sea level and tectonic events in cratonic margins and cratonic basins of North America. Journal of Geophysical Research 96 (B4), 6619—6639.

Burgess, P.M., Burnis, M., Moresi, L., 1997. Formation of sequences in the cratonic interior of North America by interaction between mantle, eustatic, and strati-graphic processes. Geological Society of America Bulletin 109,1515—1535.

Burgess, P.M., Gurnis, M., 1995. Mechanisms for the formation of cratonic strati-graphic sequences. Earth and Planetary Science Letters 136 (3—4), 647—663.

Catuneanu, O., 2004. Retroarc foreland system — evolution through time. Journal of African Earth Sciences 38, 225—242.

Catuneanu, O. (Ed.), 2006. Principles of Sequence Stratigraphy. Elsevier, Amsterdam, pp. 1—375.

Catuneanu, O., Hancox, P.J., Rubidge, B.S., 1998. Reciprocal flexural behaviour and contrasting stratigraphies: a new basin development model for the Karoo ret-roarc foreland system, South Africa. Basin Research 10, 417—439.

Coakley, B.J., Nadon, C., Wang, H.F., 1994. Spatial variations in tectonic subsidence during Tippecanoe I in the Michigan Basin. Basin Research 6,131—140.

Cross, T.A. (Ed.), 1990. Quantitative Dynamic Stratigraphy — a Workshop, a Philosophy, a Methodology. Prentice Hall, Englewood Cliffs, pp. 3—20.

DeCelles, P.G., Giles, K.A., 1996. Foreland basins systems. Basin Research 8 (2), 105—123.

De Rito, R.F., Cozzarelli, F.A., Hodges, D.S., 1983. Mechanisms of subsidence in ancient cratonic rift basins. Tectonophysics 94,141—168.

Downey, N.K., Gurnis, M., 2009. Instantaneous dynamics of the cratonic Congo basin. Journal of Geophysical Research 114,1-29.

Emery, D., Myers, K.J. (Eds.), 1996. Sequence Stratigraphy. Blackwell, Oxford, pp. 1-45.

Escalona, A., Mann, P., 2006. Sequence-stratigraphic analysis of Eocene clastic foreland basin deposits in central Lake Maracaibo using high-resolution well correlation and 3-D seismic data. American Association of Petroleum Geologists Bulletin 90 (4), 581-623.

Fan, T.L., Guo, Q.J., Wu, X.S., 1999. Features of sequence stratigraphy and distribution regularities of upper Paleozoic reservoir rocks in northern the Ordos Basin, China. Xiandai Dizhi 13 (1), 32-36 (in Chinese with English Abstract).

Feng, Y.L., Zhou, H.M., Li, S.T., Liu, Y.H., Dong, Y.X., Cao, Z.H., 2004. Sequence types and subtle trap exploration in continental rift basin. Earth Science - Journal of China University of Geosciences 29 (5), 603-608 (in Chinese with English Abstract).

Galloway, W.E., 1989. Genetic stratigraphic sequences in basin analysis I: architecture and genesis of flooding-surface bounded depositional units. American Association of Petroleum Geologists Bulletin 73,125-142.

Griffiths, C.M., Dyt, C., Paraschiviou, E., Ciu, K., 2001. SEDSIM in hydrocarbon exploration. In: Merriam, D.F., Davis, J.C. (Eds.), Geological Modeling and Simulation: Sedimentary Systems: Computer Applications in the Earth Sciences. Kluwer Academic Publishers, MA, p. 7197.

Hancox, P.J., Brandt, D., Edwards, H., 2002. Sequence stratigraphic analysis of the Early Cretaceous Maconde Formation (Rovuma basin), northern Mozambique. Journal of African Earth Sciences 34 (3-4), 291-29 .

Hanne, D., White, N., Butler, A., Jones, S., 2004. Phanerozoic vertical motions of Hudson Bay. Canadian Journal of Earth Science 41,1181-1200.

Hartley, R.W., Allen, P.A., 1994. Interior cratonic basins of Africa: relation to continental break-up and role of mantle convection. Basin Research 6, 95-113.

He, D.F., Dong, D.Z., Lu, X.X., Cao, S.L., 1996. The Analysis of Cratonic Basin. Petroleum Industry Press, Beijing, pp. 95-124 (in Chinese).

Hoffmann, K.L., Totterdell, J.M., Dixon, O., Simpson, G.A., Brakel, A.T., Wells, A.T., Mckellar, J.L., 2009. Sequence stratigraphy of Jurassic strata in the lower Surat Basin succession, Queensland. Australian Journal of Earth Sciences 56, 461 -476.

Hou, Z.J., Chen, H.D., Tian, J.C., Liu, W.J., Zhang, J.Q., 2001. Study on sequence stratigraphy of continental deposits in Ordos Basin during later Paleozoic Era. Journal of Mineralogy and Petrology 21 (3), 114-123 (in Chinese with English Abstract).

Howell, P.D., van der Pluijm, B.A., 1999. Structural sequences and styles of subsidence in the Michigan basin. Geological Society of America Bulletin 7, 974-99 .

Kaminski, E., Jaupart, C., 2000. Lithosphere structure beneath the Phanerozoic intracratonic basins of North America. Earth and Planetary Science Letters 178, 139-149.

Kendall, C.G.St.C., Strobel, J., Cannon, R., Bezdek, J., Biswas, G., 1991. Simulation of the sedimentary fill of basins. Journal of Geophysical Research 96, 6911-6929.

Klein, G.D., Hsui, A.T., 1987. Origin of cratonic basins. Geology 15 (12), 1094-1098.

Kanygin, A., Dronov, A., Timokhin, A., Gonta, T., 2010. Depositional sequences and palaeoceanographic change in the Ordovician of the Siberian craton. Palae-ogeography, Palaeoclimatology, Palaeoecology 3, 285-296.

Lash, G.G., Engelder, T., 2011. Thickness trends and sequence stratigraphy of the Middle Devonian Marcellus Formation, Appalachian Basin: implications for Acadian foreland basin evolution. American Association of Petroleum Geologists Bulletin 95 (1), 61-103.

Li, S.T., Pan, Y.L., Lu, Y.C., Ren, J.Y., Xie, X.N., Wang, H., 2002. Key technology of prospecting and exploration of subtle traps in lacustrine fault basins. Earth Science - Journal of China University of Geosciences 27 (5), 592-598 (in Chinese with English Abstract).

Li, W.H., Qu, H.J., Wei, H.H., Chen, Q.H., Liu, R.E., Zhao, H., 2003. Sequence stratigraphy of late Paleozoic deposits in Suligemiao area, Inner Mongolia. Journal of Stratigraphy 27 (1), 41-76 (in Chinese with English Abstract).

Liang, J.W., Li, W.H., 2006. High-resolution sequence stratigraphy of Shanxi formation (Permian) in Northwestern Portion of Ordos Basin. Acta Sed-imentologica Sinica 24 (2), 251-258 (in Chinese with English Abstract).

Liang, T.C.K., 1996. Sedimentary Environments and Sequence Stratigraphy of Nonmarine Intracratonic Deposits: Lower to Middle Jurassic of the Surat Basin. The Australian National University, Australia, p. 477. PhD thesis.

Liu, K., Griffiths, C.M., Dyt, C., 2001. Computer modelling of the Oxfordian deposi-tional system, Kendrew Trough, Dampier Sub-basin. The APPEA Journal 41, 463-48 .

Liu, K., Liang, T.C.K., Paterson, L., Kendall, C.G.St.C., 1998. Computer simulation of the influence of basin physiography on condensed section deposition and maximum flooding. Sedimentary Geology 122,181-191.

Liu, K., Paterson, L., Jian, F.X., 1994. Depositional modelling of the Gippsland Basin and the Barrow-Exmouth Sub-basins. The APPEA Journal 34 (1), 350-365.

Liu, K.Y., Paterson, L., Patrick, W., Qi, Q., 2002. A Sedimentological approach to Upscaling. Transport in Porous Media 46, 285-310.

McLaughlin, P.I., Brett, C.E., Taha, S.L., Cornell, M.R., 2004. High-resolution sequence stratigraphy of a mixed carbonate-siliciclastic, cratonic ramp (Upper Ordovi-cian; Kentucky-Ohio, USA): insights into the relative influence of eustasy and tectonics through analysis of facies gradients. Palaeogeography, Palae-oclimatology, Palaeoecology 210, 267-294.

Petty, D.M., 2010. Sequence stratigraphy and sequence boundary characteristics for upper Tournaisian (Mississippian) strata in the greater Williston basin area: an

analysis of a third-order cratonic carbonate-evaporite depositional cycle. Bulletin of Canadian Petroleum Geology 58 (4), 375-402.

Quinlan, G.M., 1987. Models of subsidence mechanisms in intracratonic basins and their applicability to North American examples. In: Beaumont, C., Tankard, A.J. (Eds.), Sedimentary Basins and Basin-forming Mechanisms. Canadian Society of Petroleum Geologists, Memoirs, vol. 12, pp. 463-481.

Runkel, A.C., Miller, J.F., Mckay, R.M., Palmer, A.R., Taylor, J.F., 2007. High-resolution sequence stratigraphy of lower Paleozoic sheet sandstones in central North America: the role of special conditions of cratonic interiors in development of stratal architecture. Geological Society of America Bulletin 119 (7-8), 860-88 .

Saul, G., Naish, T.R., Abbott, S.T., Carter, R.M., 1999. Sedimentary cyclicity in the marine Plio-Pleistocene of Wanganui basin (N. Z.): sequence stratigraphic motifs characteristic of the last 2.5 Ma. Geological Society of America Bulletin 111, 524-53 .

Strobel, J., Cannon, R., Kendall, C.G.St.C., Biswas, G., Bezdek, J., 1989. Interactive (SEDPAK) simulation of clastic and carbonate sediments in the shelf to basin settings. Computer Geoscience 15,1279-1290.

Tetzlaff, D.M., Harbaugh, J.W. (Eds.), 1989. Simulating Elastic Sedimentation. Van Nostrand Reinhold, New York.

Vail, P.R., Audemard, F., Bowman, S.A., Eisner, P.N., Perez-Cruz, G., 1991. The Strati-graphic signature of tectonics, eustasy and sedimentation-an overview. In: Einsele, G., Ricken, W., Seilacher, A. (Eds.), Cycles and Events in Stratigraphy. Springer-Verlag, Berlin, pp. 617-659.

Vail, P.R., Mitchum, R.M., 1977. Thompson S. Seismic stratigraphy and global changes of sea level. In: Payton, C.E. (Ed.), Seismic Stratigraphy - Applications to Hydrocarbon Exploration. American Association of Petroleum Geologists Memoir, vol. 26, pp. 83-97.

Van Wagoner, J.C., Mitchum, R.M., Campion, K.M., Rahmanian, V.D., 1990. Silici-clastic Sequence Stratigraphy in Well Logs, Cores and Outcrops. In: American Association of Petroleum Geologists Methods in Exploration Series, vol. 7, p. 55.

Wilgus, H., Roskoski, R., 1988. Inactivation of tyrosine-hydroxylase activity by ascor-bate in vitro and in rat PC12 cells. Journal of Neurochemistry 51 (4), 1232-1239.

Witzke, B.J., Ludvigson, G.A., Day, J., 1996. Introduction: Paleozoic applications of sequence stratigraphy. In: Witzke, B.J., Witzke, B.J., Ludvigson, G.A., Day, J. (Eds.), Paleozoic Sequence Stratigraphy: Views from the North American Craton. Geological Society of America Special Paper 306, pp. 1 -6.

Xie, X.N., Li, S.T., 1993. Characteristics of sequence stratigraphic analysis in terrestrial basin. Geological Science and Technology Information 12 (1), 22-26 (in Chinese with English Abstract).

Xue, S.H., Liu, W.L., Xue, L.Q., Yuan, X.J. (Eds.), 2002. Lake Basin Deposit Geology and Petroleum Exploration. Petroleum Industry Press, Beijing, pp. 12-15 (in Chinese).

Yang, R.C. (Ed.), 2002. Research on Sedimentary Facies and Sequence Stratigraphy in the Palaeozoic in the Eastern Part of Ordos Basin. Northwest University, Shanxi, pp. 56-78 (in Chinese with English abstract).

Yang, Y.T., 2011. Tectonically-driven underfilled-overfilled cycles, the middle Cretaceous in the northern Cordilleran foreland basin. Sedimentary Geology 233,15-27.

Yang, Y.T., Li, W., Ma, L., 2005. Tectonic and stratigraphic controls of hydrocarbon systems in the Ordos basin: a multicycle cratonic basin in central China. American Association of Petroleum Geologists Bulletin 89 (2), 255-269.

Yang, Y., Miall, A.D., 2008. Marine transgressions in the mid-Cretaceous of the Cordilleran foreland basin re-interpreted as orogenic unloading deposits. Bulletin of Canadian Petroleum Geology 56, 179-198.

Yang, Y., Miall, A.D., 2009. Evolution of the northern Cordilleran foreland basin during the middle Cretaceous. Geological Society of America Bulletin 121, 483-501.

Yang, Y.T., Miall, A.D., 2010. Migration and stratigraphic fill of an underfilled foreland basin: Middle-Late Cenomanian Belle Fourche Formation in southern Alberta, Canada. Sedimentary Geology 227, 51 -64.

Ye, J.R., Lu, M.D., 1997. Geohistory modelling of cratonic basins: a case study of the Ordos Basin, NW China. Journal of Petroleum Geology 20 (3), 347-362.

Zhai, A.J., Deng, H.W., 1999. Sequence stratigraphy and reservoir prediction of upper Palaeozoic in the Ordos Basin. Oil and Gas Geology 20 (4), 336-340 (in Chinese with English Abstract).

Zhang, Z.L., Sun, K., 1997. Sedimentology and sequence stratigraphy of the Shanxi formation (Lower Permian) in the northwestern the Ordos Basin, China: an alternative sequence model for fluvial strata. Sedimentary Geology 112,123-136.

Zhu, H.T., 2005. Research on High Resolution Sequence Stratigraphy and Sedimentary Models of Shanxi Formation in the Northeastern Part of Ordos Basin. China University of Geosciences, Wuhan, pp. 11-64 (in Chinese with English abstract).

Zhu, H.T., Chen, K.Y., Liu, K.Y., He, S., 2008. A sequence stratigraphic model for reservoir sand-body distribution in the Lower Permian Shanxi Formation in the Ordos Basin, northern China. Marine and Petroleum Geology 25 (8), 731 -743.

Zhu, H.T., Li, M., Liu, K.Y., Liu, Q.H., Huang, Z., Du, W.B., 2010. Sequence stratigraphic architectures of intra-cratonic basin and its controlling factors. Earth Science -Journal of China University of Geosciences 35 (6), 1035-1040 (in Chinese with English Abstract).

Zhu, X.M., Kang, A., Wang, G.W., Wang, L.Q., 2002. The upper Paleozoic sequence stratigraphic and sedimentary system characteristics of the southwest Ordos Basin. Petroleum Geology and Experiment 24 (4), 327-333 (in Chinese with English Abstract).