Sedimentary Development of the Pearl River Estuary Based on Seismic Stratigraphy

Journal of Marine Systems 82 (2010) S3–S16

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Journal of Marine Systems

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Sedimentary development of the Pearl River Estuary based on seismic stratigraphy

Cheng Tang a,b,⁎, Di Zhou a, Rudolf Endler c, Jinqing Lin d, Jan Harff c a Key Laboratory of the Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China b Yantai Institute of Coastal Zone Research for Sustainable Development, Yantai, 264003, China c Institut für Ostseeforschung Warnemünde, Rostock, D-18119, Germany d Guangzhou Marine Geology Survey, Guangzhou, 510320, China article info abstract

Article history: The Pearl River Estuary in the Southern China was studied both by applying concepts of seismic stratigraphy Received 20 December 2006 to the interpretation of high resolution seismic profiles and by correlating with borehole records. The Received in revised form 20 June 2008 correlation between seismic facies and borehole stratigraphy of the estuary enables to propose a seismic Accepted 12 January 2010 stratigraphy model of the estuarine infill. The stratigraphy and evolution of the Holocene succession of the Available online 12 February 2010 estuary were reconstructed. The history of estuarine sedimentary development consists of five stages represented by 5 seismic units bounded by laterally sub-continuous seismic interfaces and being consistent Keywords: Pearl River Estuary with the 5 borehole subdivisions: (i) The basal stage deposits, represented by BU and the borehole section P, Holocene might represent the paleo Pearl River alluvial deposits in the Late Quaternary. (ii) The stage I deposits, Sequence stratigraphy represented by SU1 and the borehole section A, might be late glacial prodeltaic deposits that occurred during Seismic stratigraphy Marine Isotope Stage 3 highstand. (iii) The stage II deposits, represented by SU2 and the borehole section B, consist of relatively coarse-grained sediments deposited during the post glacial transgression about 20–10 ka BP. (iv) The stage III deposits (SU3 and the borehole section C) were generated when the rate of sea level rise decreased in ∼20–10 kz BP, which forced sediments to be deposited inside the estuary, where a tidal ravinement surface was characterized by strong erosions and channel formations in the outer zone of the estuary. (v) The stage IV deposits (SU4 and the borehole section D) are the infillings of the estuarine highstand progradation during the last 6000 yrs when the sea surface almost reached the present level. © 2010 Elsevier B.V. All rights reserved.

1. Introduction physiography, filling history, hydrologic regime, and sea level fluctuations (Dabrio et al., 2000; Yoo and Park, 2000; Lericolais Sequence stratigraphy has been systematized as a general et al., 2001; Milia and Giordano, 2002; Lobo et al., 2003; Liu et al., methodology for the reconstruction of stratigraphic framework 2004; Hori et al., 2004; Ridente and Trincardi, 2005; Tanabe et al., since the late 1980s (Vail, 1987). In the beginning of the 1990s, the 2006; Liu et al., 2007). sequence stratigraphic concept was used in incised valley successions High resolution seismic profiles allow us to obtain continuous comprise a wide range of facies and a number of widespread and geophysical records of the surficial sedimentary units in shallow mappable stratigraphic discontinuities (Dalrymple, et al., 1992; Allen water, which improves our understanding of the sedimentary record and Posamentier, 1993; Dalrymple and Zaitlin, 1994; Lessa et al., of sea level change, with special references in the Estuarine study (Yoo 1998). Present-day estuaries typically originated as fluvial incised and Park, 2000; Lobo et al., 2005; Ridente and Trincardi, 2005). As one valleys that formed during the late Pleistocene eustatic sea level fall of the key regions to study land–sea interactions, the Pearl River and were drowned during the subsequent Holocene sea level rise. Estuary (PRE) in the Southern China has been extensively studied in Plentiful research activities with implementation of sequence strati- fields including hydrology, chemistry, biology and geology since the graphic concept have been used in determining recent geological 1980s as a rapid urbanization and industrialization in the surrounding history of shallow water systems and for establishing a relationship Pearl River Delta (PRD) was developed. Regarding with geology, many between their long-term evolution and delta/estuarine/prodelta authors (e.g. Long, 1997; Davis, 1999; Liu et al, 2004; Owen, 2005; Yim et al., 2006) have studied the Late Quaternary deposits in the Pearl River Delta and northern South China Shelf using seismic reflection profiling and borehole data, but few PRE records have been addressed about Holocene sedimentary environment change. In particularly, the * Corresponding author. Yantai Institute of Coastal Zone Research, Yinhai Rd. 26, sedimentary history of the estuarine filling is still poorly understood, Mailbox 1488, Laishan, Yantai, China. 264003. Tel.: +86 535 6910565; fax: +86 535 fl 6910566. especially referring to effects of late Pleistocene sea level uctuations E-mail address: [email protected] (C. Tang). on the preservation potential of depositional sequences.

The present study driven by issues mentioned above focuses on 2. Regional setting the stratigraphic model of the Pearl River Estuary. In this paper, we have a closer look at geometry and acoustic characteristics of the The Pearl River, the third longest river in China, is about 2216 km latest Pleistocene–Holocene sequence of the PRE and discuss long and comprises of the West, the North, and the East rivers (Fig. 1). depositional systems and their bounding surfaces on the basis of the The Pearl River drainage catchment covers a total area of approxi- conceptual framework of the sequence stratigraphic analysis. Main mately 453,000 km2 with an annual water discharge exceeding goals of the present work are: (1) to identify the seismic stratigraphic 300,000 million m3 and an annual sediment load of 87 million tons. architecture of the estuarine sedimentary fill; (2) to elaborate a About 18,000 million m3 discharge flow into the PRE, while 30 million Holocene sequence stratigraphic model based on the correlation tons of suspend sand go into the estuary by estimation (Zhao, 1990). between seismic facies and estuarine deposits. Data used in the study The PRE is located on the northern margin of the South China Sea are high resolution reflection profiles and sediment cores. between 21°20′ N–23°30′ N, and 112°40′ E–114°50′ E (see Fig. 2).

Fig. 1. Location of Pearl River estuary and the Pearl River Delta (PRD) in Southern China. The graph. C. Tang et al. / Journal of Marine Systems 82 (2010) S3–S16 S5

Fig. 2. Locations of cores in the Pearl River Estuary with bathymetric depth. Base map and water depth data were overlaid after State Navigation channel chart of Zhujiang Kou and approaches in 2002.

There are two deep channels from the mouth of the estuary up to the towards the estuary, reaching a maximum in the upstream of the PRE head of the estuary. The water depth increases from the north to the (Mao et al., 2004). Wave heights are usually less than 0.2 m within the south, 2.8 m in the upper estuary to 20 m at the estuary mouth (Xia, inner estuary, but up to 2.5 m during the typhoons season (Huang, 2005). 2000). The annual temperature of the PRE area varies from 22 to 22.5°C The basement of the Pearl River delta and estuary was formed in and annual precipitation is between 1500 and 2000 mm. The average Early Tertiary. The strong block-faulting in the Late Tertiary made the wind speed is about 2.0–4.5 m/s. Typhoon mostly happens between Pearl River basin a chessboard shaped. Three groups of faults trending June and October. The tides in the PRE mainly flow from the Pacific NW, NE, and W shaped the area into blocks. In the middle late oceanic tidal propagation through the Luzon strait (Ye and Preiffer, Pleistocene, deposition processes started to form today's delta plain 1990) with a mean tidal range between 1.0 and 1.7 m. The estuarine (Huang et al., 1982). hydrodynamics are commonly characterized as well stratified during the wet season and well mixed during the dry season with repect to 3. Data and methods the salinity field (Dong et al., 2004). The PRE is a low energy microtidal estuary with a mean range of 0.86 to 1.69 m. The surface About 1000 km of high resolution seismic profiles inside the PRE tidal currents are moderate with peak velocities mostly less than were obtained in 2001 by South China Sea Institute of Oceanology, 100 cm/s only taking one-third of that in the bottom waters. The flood Chinese Academy of Science (SCSIO), using GeoPulse and GeoChirp by current moves approximately in a south–north direction with quite Geoacoustic Corp. with a shot interval of 500 ms and a recording scale different velocities in the parts of shoal and trough. The average tidal of 1000 ms. The other 1000 km high resolution seismic profiles were range was small in the offshore waters and increases gradually obtained by the Guangzhou Marine Geology Survey (GMGS) in 2004 S6 C. Tang et al. / Journal of Marine Systems 82 (2010) S3–S16 and 2005, using a single channel seismic system Delph Seismic by Elics conducted by accelerator mass spectrometry (AMS) at the Institute Corp. with a 250 ms recording interval and 800 J source. Both seismic of Physics Radiocarbon Laboratory, Silesian University of Technology, data track lines are digitalized and shown on Fig. 1, although their Poland. Another 3 sediment cores including NNZ1, NNZ2 and NZ2 positioning was achieved using different GPS. The original GeoPulse together with their analysis results are got from GMGS in 2003 and data were stored in SegY format and reinterpreted by the Baltic Sea 2004. Other cores' information were from the literature. Research Institute (IOW) using SeisReader (Seismic profile reading The stratigraphic framework was reconstructed using a sequence program developed by IOW). An average velocity of 1600 m/s (Lu and stratigraphic approach, following its applications to other shallow Liang, 1995) was used for time-to-depth conversion, providing estuarine systems (Lessa et al., 1998; Hori et al., 2001; Lobo et al., credible estimates for both thickness of seismic units and depths to 2003). The analysis was carried out by: (1) identifying key seismic seismic horizons which are taken as inputs into an ArcMap® based GIS surfaces; (2) analyzing sediment-body geometries and seismic facies; database for a further analysis. Bathymetry was extracted partly from (3) correlating them with the stratigraphic subsections identified in the navigation map and partly from the seismic profiles. The presence boreholes; and (4) interpreting depositional environments. of gas especially in the west part of PRE, greatly attenuates seismic signals causing acoustic shield where large tracts of the sea floor are rendered acoustically impenetrable (Davis, 1999; Xia et al., 2006). 4. Results Semi-transparent and elliptic polygons in Fig. 1 show the acoustic turbidity coverages. 4.1. Seismic units 12 sediments cores totally are collected as shown in Fig. 2. Five of them were from SCSIO in 2002, among which two (e.g. ZK1 and ZK5) According to seismic stratigraphic analysis, 5 seismic units: BU, were sent to IOW for specific analysis of water content, TC, TN, TS and SU1, SU2, SU3, and SU4 are recognized from old to young. They are heavy metals as well. The maximum penetration of these 5 cores was confined by 5 seismic horizons BH, SH1, SH2, SH3, SH4 within the about 41 m. Radiocarbon dating of samples ZK1 and ZK5 was study area.

Fig. 3. GeoPulse seismic profile (A) and interpretation (B) in the north part of the estuary. The nearby core SX97 (Yu et al., 2003) was projected onto the seismic profile (for seismic line and core location see Figs. 1 and 2). The core's description and legends are also shown on Fig. 7. The dating numbers beside the cores were corresponding to the sample layers on the profile. SU1 is locally cut by the paleo-channels. C. Tang et al. / Journal of Marine Systems 82 (2010) S3–S16 S7

4.1.1. BU 4.1.2. SU1 The constitute basement high (BH), generally located at the margins SU1, bounded by seismic horizons SH1 and SH2, shows highly of the estuarine valley, indicating that the location of the valley is irregular, incoherent reflectors with moderate to low lateral continu- strongly constrained by basement elevations (Lobo et al., 2003). Free- ity and moderately high amplitudes. The acoustic response of this reflection acoustic responses identified at the base of the estuarine fill of seismic unit is moderately reflective. SU1 has a relatively uniform the PRE are indicative of basement rocks. Seismic surveys usually thickness of 10–12 m throughout the study area (see Fig. 6, isopach penetrated the first 40–45 m in the north of PRE profiles (Fig. 3), while in map of SU1). The highly irregular, incoherent reflectors internal the the southern sector the BH horizon were locally detected at depths more SU1 show moderate to low lateral continuity and moderately high than 60–100 m (Fig. 8) and deepens seaward which can be seen on the amplitudes characteristics (Figs. 3 and 4). Correlation with core data isobath map of BH in Fig. 6. The lateral continuity of the estuarine units is indicates that these facies are composed of fluvial gravels and coarse interrupted by basement high (BH) generating positive estuarine sands (Fig. 8 and Table 1). bottom morphologies and characterized by a free positive response SH1 is the first seismic interface showing lateral continuity and and highly irregular relief. The internal characteristics of BU are sub- deepens in general downstream throughout the study area (see Fig. 6, parallel seismic reflectors of which lateral continuity is often interrupted isobath map of SH1), from 35 m in the north to 60 m in the south by uneven contorted reflectors of moderately high-amplitude (Feng (Figs. 3–5, and 8). It is a moderate-amplitude to high-amplitude et al., 1996; Long, 1997). reflector amalgamating with younger horizons near BH (Fig. 4).

Fig. 4. GeoPulse seismic proﬁle (A) and interpretation (B) in the middle part of the estuary. The core NZ2 from GMGS was on the seismic proﬁle (for seismic line and core location see Fig. 1, 2). Low-angle retrogradation patterns can be seen internally within SU2. The numbers beside the core show C14 dating age of the corresponding sample layer. The core's description and legend also are shown on Fig. 7. S8 C. Tang et al. / Journal of Marine Systems 82 (2010) S3–S16

4.1.3. SU2 SU2 is bounded by seismic horizons SH2 and SH3, of which has internal subparallel and laterally continuous reflectors. Low-angle seaward stepping internal reflectors are identified on the erosive Erosion Unconformity surface surface Sequence surface surfaces SH2 (Figs. 4 and 8). SU2 is normally 6–8 m thick and it shows a variable thickness that is determined by underlying topography. Two deposit epicenters are shown one to the northern and the other ). MFS: Maximum Flooding to the southern part of the island in the middle of the PRE (see Fig. 6, TSTTST LST TRS HST Sequence HST MFS Sequence stratigraphy isopach map of SU2). SH2 is the most distinct high-amplitude reflector identified in

Davis, 1999 seismic profiles, representing subaerial exposure and erosion during SU3 SH3 SU2 SH2 SU1 SH1 SU4 SH4 unit BU BH LST ? Base surface the sea level fall between SU1 to SU2. Locally SH2 can be subhorizontal, especially in the southern sector (Fig. 8), where its depth increases downstream up to 40 m below the sea bottom (see Fig. 6, isobath map of SH2). ectors, ective fl fl ectors, moderately 4.1.4. SU3 fl ectors at re fl ) and Hong Kong waters ( sponse, generally fl SU3 is generally bounded by horizons SH3 and SH4. It shows a generally low-amplitude, and locally semi-transparent or transparent

ectors, high amplitude reﬂectors. Internal low-angle progradation patterns are observed in ﬂ

ectors fi fi fl most pro les. SU3 displays the most signi cant thickness in the southern sector is up to 12 m (Fig. 8) and towards the river mouth is ective acoustic re fl Huang et al., 1982 4–6 m (see Fig. 6, isopach map of SU3).

ope Stage. SH3 is an erosional surface and can be traced mostly in the estuary. In the northern sector it is generally located at depths of less to low lateral continuity, high-amplitudes lacks internal re Seismically transparent and internal subparallel and laterally continuous re acoustic response located generally at topographic elevations overlying SU3, upper boundary isestuarine present-day bottom, moderately re Seismic unit characteristics Seismic Variable chaotic re erosional surfaces, part of toplocally boundaries cut are by channels than 20 m (Fig. 6). Locally, SH3 marks erosional scours and channels of 5–10 m deep cutting into the lower transgressive SU2 deposit

— (Fig. 8).

4.1.5. SU4 The lower and upper boundaries of SU4 are seismic horizons SH4 and Formation Strata division from HK Hang Hau Formation Characterized by extensive Formation seaﬂoor. SU4 is characterized by aggradationally stacked reﬂectors and is distinguished by a sequence of more monotonous low-amplitude sub

from ﬂ –

— parallel succeeded re ections with average of 8 12 m thickness (see Fig. 6, isopach map of SU4). Seaward-progradational patterns with high lateral continuity are identiﬁed in the middle PRE (Fig. 5). SH4 is generally subhorizontal, with erosional scours 3–4 m deep Xinan Formation Highly irregular, incoherent re Huang, 1982 Formation Shipai Formation Chek Lap Kok and channels up to 7 m deep and 300 m wide (see Fig. 6, isobath map of SH4). It is subhorizontal in the nearshore area, and gradually slopes offshore, and deepens progressively seaward (Fig. 8). 5 stage, – 6ka HenglanFormation Highlyre 30 ka – – 4.2. Borehole analysis 5 ka Denglongsha 40 ka, older MIS 3 25 C14 Dating Strata division b N than MIS 5

The sediments cores (Fig. 7) got in the PRE can generally be divided into 5 stratigraphic sections with a concern of previous studies. There is a very good agreement with depth between the

ll of the Pearl River Estuarine surrounding area with comparison to Pearl River Delta ( ﬁ ﬁ boundaries of the ve depositional units and corresponding seismic Alluvial facies 20 10 kaMainly marine facies Paleo Pearl River Sanjiao Formation Sham Wat Marine facies 8.5 facies facies alluvial deposit boundaries.

4.2.1. Section P Section P corresponds to the seismic unit BU directly over the granite weathering crust. It is composed mainly of coarse sediments which are identiﬁed as paleo Pearl River deposits in an alluvial environment which are shown in core L2 (Chen et al., 1994; Wen et al., 1997) and core NZ2 (see Fig. 7). There is no age model for this section, (1) sea level descend quickly; (2) transgression start transgression, sea level fall in general Regression sea level descend Transgression stage, transit to highstand but a minimum age is thought to be prior to ca. 40 k cal yr BP by comparing with cores dated on the delta (Huang et al., 1982; Lan, 1991; Xu and Feng, 1997, see Table 1.)

4.2.2. Section A This section corresponds to SU1, which is composed of mainly medium-coarse sand silty sand gravel, clayey silt bunch of shell Core description Sea level change Sedimentary marine muddy silt and clay with C14 dating between 36∼20 ka BP in core L2 (Chen et al., 1994). Such a fact is supported by evidence in core NZ2 that section A is prior to 20 ka BP. This time period was almost equal to Marine Isotope Stage (MIS) 3 stage, which is widely BA Mottled silt clay, P Silty clay, muddy silt, Fine-coarse sand, C Clayey silt, mud with Core stratigraphy D Clay, muddy clay Stable seal level Mainly marine Baserock Surface; TRS: Tidal Ravinement Surface; HST: Highstand System Tract; TST: Transgressive System Tract; LST: Lowstand System Tract, MIS: Marine Isot Table 1 Summary of main evolutionary steps recorded in the sedimentary in considered as a stage of transgression on the delta in Late Pleistocene C. Tang et al. / Journal of Marine Systems 82 (2010) S3–S16 S9

Fig. 5. GeoPulse seismic proﬁle (A) and interpretation (B) in the middle part of the estuary, the core L2 (Chen et al., 1994) is on the seismic proﬁle (for seismic line and core location see Fig. 1 and 2), the numbers beside the core show C14 dating age of the corresponding sample layer, and the core descriptions and legends are also shown on Fig. 7.

(Huang et al., 1982; Lan, 1991; Long, 1997). However, there are still Chappell, 2001). Yim (1999) suggested that Pre-Holocene radiocarbon many arguments about the transgression age, because the global sea dates exceeding some 8100 a BP show a young age bias which may be level was about 40–60 m below present in MIS3 (Lambeck and attributed mainly to the post-depositional introduction of ‘young’ S10 C. Tang et al. / Journal of Marine Systems 82 (2010) S3–S16 C. Tang et al. / Journal of Marine Systems 82 (2010) S3–S16 S11

Fig. 7. Longitudinal, lithological stratigraphic section across the Pearl River Estuary. The white line on the right bottom shows the profile with core SX97 from Yu et al. (2003), core 90_L2 from Chen et al. (1994), core NZ2, NNZ1, NNZ2 from GMGS (2003, 2004). Numbers beside the cores show the C14 dating ages to the corresponding sample layers. MFS: Maximum flooding Surface; TRS: Tidal Ravinement Surface. carbon into the sample. The transgression layer in the Hong Kong to the sample dating position on the boundary of the seismic profile waters could belong to the MIS 5 stage or even older (Yim et al., 2002). SU3, see Fig. 8). The Holocene transgression has been considered to In contrast, studies in the PRE have shown the earliest transgression start at 12 ka BP and the sea reached higher levels during 9∼5.8 ka BP layer might have occurred since 50 ka BP that has been covered in the (Huang et al., 1982; Wen et al., 1997; Wu and Zhou, 2001). A general PRE and along the coast of China, The confirmed sediments of littoral view of the highest sea level was formed about 6 ka BP (Li et al., 1991; facies has been almost continuous since 45 ka BP in the core ZK1 on the Yim, 1999; Wu and Zhou, 2001), but highstand indicators are still in PRD (Xu and Feng, 1997). Such an age model was also consistent in discussion (Huang et al., 1982; Davis et al., 2000; Yim and Huang, other studies (Huang et al., 1982; Long, 1997). A possible explanation 2002; Zong, 2004). Taking the AMS C14 ages of the ZK1 corresponding is that the PRD/PRE is bedrock controlled estuarine valley (Wu and layer and stratigraphic correlation with cores in the PRE (Fig. 7) into Zhou, 2001), in the MIS3 stage, part of its base elevation is lower than account, it is concluded that section C could be formed between 10 the sea level and causes highstand deposits. This phenomenon was and 6 ka BP, an estuarine environment resulting from the Holocene also observed in the Guadiana estuary and on the Gulf of Cadiz shelf transgression with tidal influence. (Lobo et al., 2003). 4.2.5. Section D 4.2.3. Section B This section corresponds to SU4, which is composed of mainly gray, This section corresponding to SU2, yellow-brown fine-medium yellow gray mud and muddy clay. Water content of ZK1 in section D sands mixed with clay of typical alluvial deposit of fine-medium shows a clear increase in trend. Thus, the distribution of moisture sands, representing a significant stage of regression. A mottled silty content is a useful method in identifying stratigraphic boundaries clay and clayey silt layer was generally covered on the top of this (Yim et al., 2002). SU4 is interpreted as estuarine environment under section as a boundary between the Late Pleistocene and Holocene the sea level highstand of the last 6 ka. It is believed that there exists a (Huang et al., 1982; Chen et al., 1994). In core L2, this section of small regression about 2.5 cal ka BP (Huang et al., 1982). Cor- deposited terrestrial alluvial layer has been weathered during responding evidence is also found in core SX97 (Yu et al., 2003)of 20∼12 ka BP (Wen et al., 1997). The stage of regression could be which a peak value of element V is consistent with a sea level rise about linked to the last glacial period and the sea level fall (Huang, et al., 3500 yr BP. The water content in the ZK1 shows a variation between 1982). is evidently not present in the part of Hong Kong waters which 4.9 and 3.9 cal ka BP may also be an environment change proof (Fig. 8), may depend on whether or not alluvial deposition occurred during but we could not find a correspondence for this layer in our seismic low sea level stands of the glacial periods (Davis, 1999). data, similar report also from Hong Kong waters. For credibility, we briefly compare the identified sedimentary 4.2.4. Section C cycles with the local Pearl River Delta stratigraphic system in Table 1 This section corresponds to SU3, of which is composed of mainly (Huang et al., 1982; Lan, 1991; Chen et al., 1994). The section C gray muddy silt represent a new stage of transgression. The age shows corresponds to the Early Holocene late transgressive Henglan this transgression occurred between 9.6 and 4.1 cal ka BP (according Formation and the section D corresponds to Late Holocene regressive

Fig. 6. Isobath maps of seismic horizons (SHs) under present sea level and isopach maps of seismic units (SUs) in the Pearl River Estuary. Depth and thickness values are given in meters. The coordinate systems are deﬁned by UTM, WGS-84 Zone 49 N, northing and easting meter coordinates. S12 C. Tang et al. / Journal of Marine Systems 82 (2010) S3–S16

Fig. 8. Sequence stratigraphic framework of seismic profile based on the correlation between estuarine seismic units and the stratigraphic borehole sections subdivided by the water content analysis of core ZK1. The core ZK1 was fixed on the seismic profile by GPS, see the location in Fig. 2. The numbers beside the core show 14 C dating age of the corresponding sample layer. The core descriptions and legend are also shown on Fig. 7. HST: Highstand Systems tract; TS: Transgressive Surface; MFS, Maximum flooding Surface; TRS: Tidal Ravinement Surface.

Denglongsha Formation. The Xinan Formation corresponds to Late 1999; Zong, 2004), which reflect a complex history of Holocene sea Pleistocene transgressive deposits of section A. The last glacial level. However, the pre-Holocene depositional history around river maximum deposits of section B corresponds to the Sanjiao formation. mouth is generally poorly known. As the depositional facies might be The correlation is difficult because radiometric ages backing the PRE secondarily altered and the sedimentary records might have been stratigraphic system are sparse to absent and available lithologic reduced by repeated ravinement, long-term subaerial exposure, and columns are rather generalized. extensive soil formation during periods with low sea levels (Hanebuth et al., 2006). In such circumstances, to reconstruct sea 5. Discussion level changes since the Last Glacier Maximum (LGM), the dating of as many samples as possible immediately above the Holocene–Pleisto- 5.1. Sea level curve for Late Pleistocene–Holocene in the PRE cene hiatus from a range of water depths down to about 130 m below present sea level is deemed to be necessary (Yim et al., 2006). Fig. 9 Various sea level curves have been proposed for the PRD region in shows the sea level curve for the PRE region over the past 15 ka. The the past two decades (Huang et al., 1982, 1987; Li et al., 1991; Yim, sea level curve was constructed from a combination data including C. Tang et al. / Journal of Marine Systems 82 (2010) S3–S16 S13 those for the offshore of Northern South China Sea continental shelf tracts. Fig. 10 shows the recognition and interpretation of estuarine (Yim et al., 2006), the Sunda shelf of Southeast Asia (Hanebuth and systems sedimentary infill stages in detail. Distinctive sequence Stattegger, 2004), the Vietnam shelf and surrounding areas (Schi- stratigraphic features of the Pearl River Estuary sedimentary fill are manski and Stattegger, 2005), the Pearl River Delta region (Huang et described below. al., 1982; Zong, 2004), the Pearl River Estuary (Chen et al., 1994; Yu et al., 2003), and the Bonaparte Gulf of Australia (Yokoyama et al., 2000) 5.2.1. Stage I: Late Pleistocene Highstand deposit (MIS 3/5) as a reference. It is noted that any sediment compaction effects were Lower units of valley infills representing fluvial deposits at the base neglected by the curve. of estuarine successions are characterized by discontinuous, con- Additionally, the δ18O record of the Ocean Drilling Program (ODP) torted, and moderately high-amplitude reflectors inside. Meanwhile, Leg 184 site 1144 in the Northern shelf of South China Sea shown in the SH1 is considered as a clear facies transition from a predominantly Fig. 9 may help to discover the relationship between the Relative Sea incoherent facies patterns of BU to semi-transparent facies of SU1. The Level (RSL) change and the detailed high resolution stable isotope core data corresponding to this layer shows sediments are mainly stratigraphy. The site 1144 Holocene δ18O record displays a high- composed of littoral clay and silt clay and generally 14C dating links to amplitude internal variability reaching 0.6–0.8‰. The planktonic Marine Isotope Stages (MIS) 3 highstands (Chen et al, 1994; Long, Holocene to LGM δ18O shift amounts to approximately Δ1.8‰, with 1997). Analogous to the record presented in the nearby Hong Kong maximum differences of 2.4‰ between short term extremes in the waters. It was proposed that this transgression layer was generated by Holocene and LGM. The ice volume effect on the δ18O for the most MIS 5, and not by MIS 3 due to a young age bias (Yim, 1999). recent glacial–interglacial transition (MIS 1–2) is estimated to be Although there still exist many discussions about whether there is 1.2‰, assuming that 10 m of sea level rise is equivalent to 0.11‰ MIS 3 or MIS 5 age for the late Pleistocene highstand, the Late change in δ18O(Buehring et al., 2004). Fig. 9 shows that the PRE could Quaternary sea level changes considered as a band between maximum experience a rapid RSL rise around 11–10 ka BP and 8–6 ka BP which and minimum estimates (Bard et al., 1990; Lambeck and Chappell, was also proposed by Zong (2005), and could reach its maximum 2001) in the MIS3–5 stage is in favor of such highstand deposit landward extent around 6 ka BP (Huang et al., 1987; Li et al., 1991; (Fig. 10). Zong, 2005), followed by a period of deltaic sedimentation infilling the accommodation space. 5.2.2. Stage II: Early deglacial period deposit (20–10 ka BP) The strong seismic signature, the common occurrence of depressed 5.2. Sequence stratigraphic model for the PRE morphologies, and the highly irregular and erosional pattern of SH2 are taken as diagnostic criteria indicating subaerial exposure and The variation of a general estuarine sequence locally depends on erosion during the sea level fall and lowstand of MIS stage 2, in many factors including the specific physiography, sediment supply agreement with the views made by numerous authors (Huang et al., and hydrology of the estuarine system as well. To reconstruct the 1982; Chen et al., 1994; Feng et al., 1996; Long, 1997; Huang, 2000). postglacial depositional history in the study area, it is necessary to rely During this period, the sea level change includes 2 intervals: (1) sea on the dating ages, sedimentary characteristics of the core sediments level fall and Wuermiam lowstand (MIS stage 2) forming a mottled and the seismic signatures of the deposits, in conjunction with the sea clay layer widely distributed in the PRE/PRD (Huang et al., 1982; Chen level changes during the latest Pleistocene and Holocene (Liu et al., et al., 1994); and (2) sea level rise during the post glacial transgression 2007). By applying the sequence stratigraphic approach, the deposi- (Fig. 10, stage II). Thus, formation of widespread mottled clay in the tional structures of PRE could then be defined as part of four systems subaerial part during the LGM, together with underlying deposits

Fig. 9. Relative sea level curves reconstructed from the core ZK1 and other cores in the South China Sea area and Bonaparte Gulf of Australia as references. The δ18O curve was got from the ODP leg 184 site 1144 in Northern South China Sea (after Buehring et al., 2004). S14 C. Tang et al. / Journal of Marine Systems 82 (2010) S3–S16

Fig. 10. Model for the Holocene Pearl River estuary sedimentary infill history: (I) MIS 3/5 stage highstand deposit in the late Quaternary; (II) Paleo Pearl River channel were incised during the exposure of the shelf prior and during the last glacial maximum; (III) Rising sea level flooded the estuary with marginal sea environmental deposit. The age of transgression started was about 8.5 ka, and the maximum flooding highstand was about 5–6 ka; (IV) Progradation started after the Holocene maximum highstand. The last glacio- eustatic cycle is after Lambeck and Chappell (2001). below the sequence boundary (SB, see Table 1) described a picture for wave action and shoreface erosion in the estuary because of specific the lowstand system tract (LST). bedrock control geomorphology (Wu and Zhou, 2001), resulting in The seismic horizon SH2 represents a transgressive surface (TS) the significant preservation of the marine mud sedimentation. and is related to a boundary dividing two periods: the formation of regressive, lowstand deposits and deposition of transgressive bodies 5.2.4. Stage IV: Holocene highstand deposit (6 ka BP–present) (see Fig. 8). In the PRE, sea level reached its present position at approximately 6kaB.P. (Huang et al., 1982; Li et al., 1991). The hydrodynamic 5.2.3. Stage III: Late Pleistocene–middle Holocene transgression deposit environment changed from a strong tidal-current field to a situation (10–6 ka BP) similar to the modern circulation, resulting in a significant decrease of The transgression system tract (TST) commences in the upper part the transgression and reworking of the antecedent sediments in the of SU2, which was correlated with the ZK1 about 10 ka BP. A paleo Pearl River. Meanwhile, the HST depositional pattern also changed progradational stacking pattern and fore-stepping configuration of from progradation to aggradation. The estuary received large amounts the seismic units are depicted by the TST, which records the upper of fine-grained sediments from the Pearl River which resulting in thick part of the postglacial transgression depicts. On the one hand, SH3 accumulation of mud deposition (Zong, 2004). The seismic character- shows the presence of channel cutting onto the lower transgressive istics of SU4 enable a suggestion that it was deposited during successive muddy deposit. On the other, SH3 is considered as a tidal ravinement depositional phases in a stillstand environment. Therefore, SH4 surface (TRS), formed by shoreline erosion that shifts landward representing the Maximum Flooding Surface (MFS), highlights a during the postglacial transgression because of its strong, continuous transition from a retrogradational phase, in which the transgressive reflectivity (Figs. 3–5, and 8). depostional systems were formed, to a progradational phase of the The estuarine flooding commenced in the upper part of postglacial highstand depositional system characterized by a non-erosional surface transgression after 8 ka according to the sea level curve (Fig. 9). After of strong continuous reflectivity (Fig. 10, stage IV). that the accelerated estuarine infilling developed a mud dominated basin facies. In the eastern part of the estuary, a depositional epicenter 6. Conclusions particularly near the river mouth was developed when sea level rose quickly (Fig. 10, stage III). This may have been influenced by (1) the Overall, the sedimentary evolution of the PRE in the Holocene is influence of neotectonics (Chen et al., 2002), generating medium- complex and has been effected by a multiple of factors including scale depressions where highstand deposits preferentially accumu- sediment supply from the Pearl River, transgressive sea level in the lated in an effective tidal ravinement; and (2) limited influence of PRE, the Holocene sea level rise, and hydrographic change. The C. Tang et al. / Journal of Marine Systems 82 (2010) S3–S16 S15 sedimentary infilling of the Pearl River estuarine is composed of five Feng, Z.Q., Feng, W.K., Xue, W.J., Liu, Z.H., Chen, J.Z., Li, W.F., 1996. Evaluation of marine geologic hazards and engineering geological conditions in the northern South depositional sequences based on the high resolution shallow seismic China Sea. Hehai University Publish (In Chinese), NanJing. profiles and cores in the PRE. It is made up of 5 depositional sections: Hanebuth, T.J.J., Stattegger, K., 2004. Depositonal sequences on a late Pleistocene– P, A, B, C and D in ascending order, corresponding respectively to 5 Holocene tropical siliciclastic shelf (Sunda Shelf, southeast Asia). Journal of Asian Earth Sciences 23, 113–126. seismic units, BU, SU1, SU2, SU3 and SU4. Moreover, the most recent Hanebuth, T.J.J., Saito, Y., Tanabe, S., Vu, Q.L., Ngo, Q.T., 2006. Sea levels during late sequence is composed of TST and HST deposits and the lower marine isotope stage 3 (or older?) reported from the Red River delta (northern sequences might constitute the HST due to corresponding time for Vietnam) and adjacent regions. Quaternary International 145–146, 119–134. MIS 5/3 sedimentation. The SU2 formed in the early deglacial period Hori, K., Tanabe, S., Saito, Y., Haruyama, S., Nguyen, V., Kitamura, A., 2004. Delta initiation and Holocene sea-level change: example from the Song Hong (Red River) deposits (20–10 ka BP). The SU3 formed during Late Pleistocene– delta. Vietnam Sedimentary Geology 164, 237–249. middle Holocene transgression period (10–6 ka BP) and SU4 formed Huang, G.Q., 2000. Holocene record of storms in sediments of the Pearl River Estuary – Holocene highstand period (6 ka BP–present). and vicinity. PhD thesis, the University of Hong Kong. Hong Kong, pp. 1 33 Huang, Z.G., Li, P.R., Zhang, Z.Y., Li, K.H., Qiao, P.N., 1982. The development of Pearl River Meanwhile, the main stratigraphic surfaces inside the estuarine Delta. Science Popularization Press Guangzhou Branch, Guangzhou (in Chinese). fillings are characterized by distinct seismic attributes. The most Huang, Z., Li, P., Zhang, Z., Li, K., 1987. The geomorphological evolution of the Zhujiang readily identifiable surface is the SB (Sequence Boundary), repre- Delta, In: Gardiner, V. (Ed.), 1986, Part I. International Geomorphology. Wiley, – fl fi New York, pp. 989 997. sented by a high-amplitude re ector indicating a signi cant facies Lambeck, K., Chappell, J., 2001. Sea level change through the last glacial cycle. Science transition. The TRS is characterized by strong ravinement and tidal- 292, 679–686. channel formation in the outer estuarine zones. The MFS is identified Lan, X.H., 1991. Sedimentary characteristics and strata division of core △22 of the Zhujiang River Delta. Oceanologia et Limnologia Sinica 22, 148–154 (In Chinese by change of strata patterns and by progradation of tidal bars and with English abstract). prodelta deposits over transgressive estuary mouth sands. The BH Lericolais, G., Berne, S., Fenies, H., 2001. Seaward pinching out and internal stratigraphy isobath map suggests that the basement morphology may influence of the Gironde incised valley on the shelf (Bay of Biscay). Marine Geology 175 (1–4), 183–197. the hydrodynamic regime and the PRE sedimentary developments. Lessa, G.C., Merers, S.R., Marone, E., 1998. Holocene stratigraphy in the Paranagua bay Estuary, Southern Brazil. Journal of Sedimentary Research 68 (6), 1060–1076. Li, P.R., Qiao, P.N., Zheng, H.H., 1991. Environment changes of the Pearl River Delta since Acknowledgements 10000 years. Marine Press, Beijing. (in Chinese). Liu, J.P., Milliman, J.D., Gao, S., Cheng, P., 2004. Holocene development of the Yellow This work was completed under the framework of the project River's subaqueous delta, North Yellow Sea. Marine Geology 209, 45–67. “PECAI-Pearl River Estuary Related Sediments as Response to Liu, J., Saito, Y., Wang, H., Yang, Z., Nakashima, R., 2007. Sedimentary evolution of the Holocene subaqueous clinoform off the Shandong Peninsula in the Yellow Sea. Holocene Climate Change and Anthropogenic Impact” which was Marine Geology 236, 165–187. funded by a Sino-German cooperation project. The first author was Lobo, F.J., Dias, J.M.A., González, R., Hernández-Molina, F.J., Morales, J.A., Díazdelrío, V., funded by Chinese Academy of Sciences and Max-Planck Society 2003. High resolution seismic stratigraphy of a narrow bedrock-controlled estuary: fi the Guadiana estuarine system, SW Iberia. Journal of Sedimentary Research 73 (6), fellowships. The PECAI eld survey was done in 2001, 2004 and 2005. 973–986. We wish to express our appreciation to the Guangzhou Marine Lobo, F.J., Fernandez-Salas, L.M., Hernandez-Molina, F.J., Gonzalez, R., Dias, J.M.A., Rio, Geology Survey for providing unpublished seismic profiles and V.D., Somoza, L., 2005. Holocene highstand deposits in the Gulf of Cadiz, SW Iberian Peninsula: a high-resolution record of hierarchical environmental changes. Marine drilling core data, also appreciate to Prof. Zhang Q.M. for offering Geology 219, 109–131. the seismic data and suggestions. The authors would like to thank Long, Y.Z., 1997. Sedimentary study of Pearl River Delta. Geology Press, Beijing (in Prof. Terry Heally and an anonymous reviewer for their comments on Chinese). Lu, B., Liang, Y.B., 1995. Statistical correlation of physical parameters with sound the manuscript. Prof. Zhongyuan Chen and Dr. Yoshiki Saito are velocity in marine sediments of South and East China Seas. Science in China thanked for their valuable suggestions and discussion. (Series B) 38 (5), 613–618. Mao, Q.W., Yin, K.D., Gan, J.P., Qi, Y.Q., 2004. Tides and tidal currents in the Pearl River Estuary. Continental Shelf Research 24 (16), 1797–1808. References Milia, A., Giordano, F., 2002. Holocene stratigraphy and depositional architecture of eastern Pozzuoli Bay (eastern Tyrrhenian sea margin, Italy): the influence of Allen, G.P., Posamentier, H.W., 1993. Sequence stratigraphy and facies model of an tectonics and wave-induced currents. Geo-Marine Letters 22, 42–50. incised valley fill: the Gironde Estuary, France. Journal of Sedimentary Petrology 63 Owen, R.B., 2005. Modern fine-grained sedimentation partial variability and environ- (3), 378–391. mental controls on an inner pericontinental shelf, Hong Kong. Marine Geology 214 Bard, E., Hamelin, B., Fairbanks, R.G., 1990. U–Th ages obtained by mass spectrometry in (1–3), 1–26. corals from Barbados: sea level during the past 130,000 years. Nature 346, Ridente, D., Trincardi, F., 2005. Pleistocene “muddy” forced-regression deposits on the 456–458. Adriatic shelf: a comparison with prodelta deposits of the late Holocene highstand Buehring, C., Sarnthein, M., Erlenkeuser, H., 2004. Toward a high-resolution stable mud wedge. Marine Geology 222–223, 213–233. isotope stratigraphy of the last 1.1 m.y.: site 1144, South China Sea. In: Prell, W.L., Schimanski, A., Stattegger, K., 2005. Deglacial and Holocene evolution of the Vietnam Wang, P., Blum, P., Rea, D.K., and Clemens, S.C. (Eds.), Proceedings of the Ocean shelf: stratigraphy, sediments and sea-level change. Marine Geology 214, 365–387. Drilling Program, Scientific Results, volume 184, pp. 1–29. Tanabe, S., Saito, Y., Vu, Q.L., Hanebuth, T.J.J., Ngo, Q.L., Kitamur, A., 2006. Holocene Chen, M.H., Zhao, H.T., Wen, X.S., Zhang, Q.M., Song, C.J., 1994. Quaternary foraminiferal evolution of the Song Hong (Red River) delta system northern Vietnam. group and sporopollen zones in cores L2 and L16 in the Lingdingyang Estuary. Sedimentary Geology 187, 29–61. Marine Geology & Quaternary Geology 14, 11–22 (in Chinese with English Vail, P.R., 1987. Seismic stratigraphy interpretation using sequence stratigraphy, Part 1: abstract). Seismic stratigraphy interpretation procedure, Atlas of Seismic Stratigraphy, Vol. 1: Chen, W.G., Wei, B.L., Zhao, H.M., Yu, C., 2002. The neotectonic movement in Pearl River American Association of Petroleum Geologists. Studies in Geology 27, 1–10. Delta area. South China Journal of Seismology 22, 8–18 (in Chinese with English Wen, X.S., Zhao, H.T., Zhang, Q.M., Song, C.J., 1997. Sedimentary characteristic and its abstract). environmental evolution history of the borehole in Lingding Yang estuary. Acta Dabrio, C.J., Zazo, C., Goy, J.L., Sierro, F.J., Borjaf, F., Lario, J., Gonzalez, J.A., Flores, J.A., Oceanologica Sinica 19, 121–128 (in Chinese with English abstract). 2000. Depositional history of estuarine infill during the last postglacial transgres- Wu, C.Y., Zhou, D., 2001. Evolution and long-term morpho-dynamic response in a sion (Gulf of Cadiz, Southern Spain). Marine Geology 162, 381–404. special type of estuary. Chinese Science B 44 (supp), 112–125 English edition. Dalrymple, R.W., Zaitlin, B.A., 1994. High-resolution sequence stratigrahpy of a Xia, Z., 2005. Characters of underwater topography and geomorphology in inner complex, incised valley succession, Cobequid Bay—Salmon River estuary, Bay of Lingdingyang firth of the Pearl River (Zhujiang River) Estuary. Marine Geology & Fundy, Canada. Sedimentology 41, 1069–1091. Quaternary Geology 25, 19–24 (in Chinese with English abstract). Dalrymple, R.W., Zaitlin, B.A., Boyd, R., 1992. Estuarine facies models: conceptual Xia, Z., Ma, S.Z., Shi, Y.H., 2006. Basic characteristics of submarine shallow gas in basis and stratigraphic implications. Journal of Sedimentary Petrology 62 (6), Lingdingyang firth. Quaternary Sciences 26 (3), 456–461 (in Chinese with English 1130–1146. abstract). Davis, A.M., 1999. Quaternary stratigraphy of Hong Kong coastal sediments. Journal of Xu, Q.H., Feng, Y.G., 1997. The earliest transgression layer since late Pleistocene in Asian Earth Sciences 17, 521–531. Zhongshan city of Guangdong Province and “Eustatic” sea level changes. Seismology Davis, A.M., Aitchison, J.C., Flood, P.G., Morton, B.S., Baker, R.G.V., Haworth, R.J., 2000. and Geology 19 (1), 91–95 (in Chinese with English abstract). Late Holocene higher sea level indicators from the South China coast. Marine Ye, L., Preiffer, K.D., 1990. Studies of 2D & 3D numerical simulation of Kelvin tide wave Geology 171, 1–5. in Nei Lingdingyang at Pearl River Estuary. Ocean Engineering 8 (4), 33–44. Dong, L.X., Su, J., Wong, L.A., Cao, Z., Chen, J.C., 2004. Seasonal variation and dynamics of Yim, W.W.-S., 1999. Radiocarbon dating and the reconstruction of late Quaternary sea- the Pearl River plume. Continental Shelf Research 24 (16), 1761–1777. level changes in Hong Kong. Quaternary International 55, 77–91. S16 C. Tang et al. / Journal of Marine Systems 82 (2010) S3–S16

Yim, W.W.-S., Huang, G., 2002. Middle Holocene higher sea-level indicators from the Holocene example from the Korea strait. Journal of Sedimentary Research 70, south China coast. Marine Geology 182 (3–4), 225–230. 296–309. Yim, W.W.-S., Price, D.M., Choy, A.M.S.F., 2002. Distribution of moisture contents and Yu, S.H., Zhang, Y., Yang, X.Q., Zhou, H.Y., 2003. Environmental records in the Xinmin thermoluminescence ages in an inner shelf borehole from the new Hong Kong core since the late Pleistocene in the northern coast of the Shenzhen Bay. Marine International Airport site, China. Quaternary International 92, 35–43. Geology & Quaternary Geology 23, 9–18 (in Chinese with English abstract). Yim, W.W.-S., Huang, G., Fontugne, E.M.R., Hale, R.E., Paterne, M., Pirazzoli, P.A., Zhao, H.T., 1990. The evolution of Pearl River Estuary. Ocean Press, Beijing. (in Chinese). Thomas, W.N.R., 2006. Postglacial sea-level changes in the northern South China Zong, Y., 2004. Mid-Holocene sea-level highstand along the Southeast coast of China. Sea continental shelf: evidence for a post-8200 calendar yr BP meltwater pulse. Quaternary International 117, 55–67. Quaternary International 145–146, 55–67. Zong, Y., 2005. Rapid sea-level rise in early Holocene and the onset of postglacial Yokoyama, Y., Lambeck, K., Deckker, P.D., Johnston, P., Fiﬁeld, L.K., 2000. Time of the last evolution of the Pearl River Delta. Proceedings of IGCP475/APN/CCON Delta Glacial Maximum from observed sea-level minima. Nature 406, 713–716. conference, Ho Chi Minh City, Vietnam, pp. 1–8. Yoo, D.G., Park, S.C., 2000. High-resolution seismic study as a tool for sequence stratigraphic evidence of high-frequency sea-level changes: latest Pleistocene–