Holocene reef growth in Torres Strait

The platform and fringing reefs of Torres Strait are morphologically similar to reefs of the northern Great Barrier Reef to the south, except that several are elongated in the direction of the strong tidal currents between the Coral Sea and the Gulf of Carpentaria. Surface and subsurface investigations and radiocarbon dating on Yam, Warraber and Hammond Islands reveal that the initiation and mode of Holocene reef growth reflect antecedent topography and sea-level history. On the granitic Yam Island, fringing reefs have established in some places over a Pleistocene limestone at about 6 m depth around 7000 years BP. Emergent Holocene microatolls of Porites sp. indicate that the reefs have prograded seawards while sea level has fallen gradually from at least 0.8 m above present about 5800 years BP. On the Warraber Island reef platform drilling near the centre indicated a Pleistocene limestone foundation at a depth of about 6 m over which reefs established around 6700 years BP. Reef growth lagged behind that on Yam Island. Microatolls on the mature reef flat indicate that the reef reached sea level around 5300 years BP when the sea was around 0.8–1.0 m above present. On the reef flat on the western side of Hammond Island bedrock was encountered at 7–8 m depth, overlain by terrigenous mud. A progradational reef sequence of only 1–2 m thickness has built seaward over these muds, as sea level has fallen over the past 5800 years. Reef-flat progradation on these reefs is interpreted to have occurred by a series of stepwise buildouts marked by lines of microatolls parallel to the reef crest, marking individual coalescing coral heads. Detrital infill has occurred between these. This pattern of reef progradation is consistent with the radiocarbon dating results from these reefs, and with seismic investigations on the Torres Reefs.     

福建沿岸6000年来的海平面波动

本文通过35个~(14)C测年数据进行评价,建立一条福建省沿岸过去6000年海平面变化曲线,该线表明海平面在现代位置上下呈振荡性变化,最高和最低海平面分别出现距今5000年前和4000年前左右,海平面高度分别为约+2m,-2m。     

Holocene sea-level changes on Jersey

Stratigraphic, sedimentological, palaeontological and survey techniques, accompanied by radiocarbon dating, have been used to establish the pattern of Holocene sea-level changes around Jersey. Prior to ca. 6000 years bp, the proposed sequence of sea-level movements parallels those demonstrated for adjacent parts of France and the United Kingdom. Most data from the latter areas indicate that subsequently, sea-level has not attained a height in excess of that of the present day. Around Jersey (and on the western coast of the Cotentin Peninsula to its east), Holocene sea-level rose to its maximum height around 4500-4000 years bp. This high sea-level was maintained around Jersey for about 2000 years, since then it has fallen to the present level. Such a discrepancy may be explicable by differential crustal movement during the Holocene.     

Subantarctic macrotidal flats, cheniers and beaches in San Sebastian Bay, Tierra Del Fuego, Argentina

San Sebastian Bay is a large, semicircular coastal embayment situated on the Atlantic coast of Tierra del Fuego, Argentina. It is a high-energy, subantarctic environment with a tidal range of 10.4 m, influenced by large waves of Atlantic and local origin and swept by constant, strong westerly winds. A 17 km long gravel spit protects the Northern part of the Bay giving rise to a gradient in sedimentary processes. From south to north, are seven distinct sedimentary environments. Coastal sedimentation started at least 5200 years before present (BP) and a rapid progradation related to a relative sea-level drop has infilled about 6 kilometres of the Bay with a sedimentary sequence 10–11 m thick. 14-C dating of unabraded shells in the Chenier ridges of the relict part of the complex allows for a precise reconstruction of the stages of the progradation, that has slowed from 2.35 m/year at 5000 years BP to 0.6 m/year at present. The possible causes of the sea-level drop are discussed.     

Seismic and sequence stratigraphy of the central western continental margin of India: late-Quaternary evolution

Seismic and sequence stratigraphic architecture of the central western continental margin of India (between Coondapur and south of Mangalore) has been investigated with shallow seismic data. Seismic stratigraphic analysis defined nine seismic units, that are configured in a major type-1 depositional sequence possibly related to fourth-order eustatic sea-level changes, comprising regressive, lowstand, transgressive and highstand systems tracts. The late-Quaternary evolution of the continental margin took place under the influence of an asymmetric relative fourth-order sea-level cycle punctuated by higher frequency cycles. These cycles of minor order were characterised by rapid sea-level rises and gradual sea-level falls that generated depositional sequences spanning different time scales. During the regressive periods, dipping strata were developed, while erosional surfaces and incised valleys were formed during the lowstands of sea level. Terraces, v-shaped depressions, lagoon-like structures observed on the outer continental shelf are the result of the transgressive period. In the study area we have recognised a complex erosional surface that records a long time span during the relative sea-level fall (regressive period) and the following sea-level lowstand and has been reworked during the last transgression. We also infer that sedimentation processes changed from siliciclastic sedimentation to carbonate sedimentation and again to siliciclastic sedimentation, marking an important phase in the late-Quaternary evolution of the western continental shelf of India. We attribute this to an abrupt climate change at the end of the oxygen isotope stage 2, between the Last Glacial Maximum and the Bølling-Allerod event (14?000 yr BP). This sensitive climate change (warming) favoured the formation of reefs at various depths on the shelf, besides the development of Fifty Fathom Flat, a carbonate platform on the outer shelf off Bombay developed prior to 8300 yr BP. The highstand systems tracts were deposited after the sea level reached its present position.     

An inflection in the rate of early mid-Holocene eustatic sea-level rise: A new sea-level curve from Singapore

This study presents a sea-level curve from 9500 to 6500 cal BP for the farfield location of Singapore, on the Sunda Shelf in southeast Asia. The curve is based on more than 50 radiocarbon dates from elevations of +1.43 m to −15.09 m representing sea-level index points in intertidal mangrove and shallow marine sediments deposited by sea-level rise accompanying deglaciation. The results indicate that mean sea level rose rapidly from around −17 m at 9500 cal BP to around −3 m by 8000 cal BP. After this time, the data suggest (but do not unequivocally prove) that the rate of sea-rise slowed for a period of 300–500 years centred on 7700 cal BP, shortly after the cessation of meltwater input to the oceans from the northern hemisphere. Renewed sea-level rise amounting to 3–5 m began around 7400 cal BP and was complete by 7000 cal BP. The existence of an inflection in the rate of sea-level rise, with a slow-down centred on 7700 cal BP, is broadly consistent with other available sea-level curves over this interval and is supported by evidence of stable shorelines and delta initiation elsewhere at this time, as well as evidence of comparatively rapid retreat of the West Antarctic ice sheet beginning around 7500 cal BP. ‘Stepped’ sea-level rise occurring shortly after 7500 cal BP and also earlier during deglaciation may have served to focus significant post-glacial episodes of human maritime/coastal dispersal, into comparatively narrow time intervals.     

Facies architecture of the mixed carbonate/siliciclastic inner continental shelf of west-central Florida: implications for Holocene barrier development

Sediment vibracores and surface samples were collected from the mixed carbonate/siliciclastic inner shelf of west–central Florida in an effort to determine the three-dimensional facies architecture and Holocene geologic development of the coastal barrier-island and adjacent shallow marine environments. The unconsolidated sediment veneer is thin (generally <3 m), with a patchy distribution. Nine facies are identified representing Miocene platform deposits (limestone gravel and blue–green clay facies), Pleistocene restricted marine deposits (lime mud facies), and Holocene back-barrier (organic muddy sand, olive-gray mud, and muddy sand facies) and open marine (well-sorted quartz sand, shelly sand, and black sand facies) deposits. Holocene back-barrier facies are separated from overlying open marine facies by a ravinement surface formed during the late Holocene rise in sea level. Facies associations are naturally divided into four discrete types. The pattern of distribution and ages of facies suggest that barrier islands developed approximately 8200 yr BP and in excess of 20 km seaward of the present coastline in the north, and more recently and nearer to their present position in the south. No barrier-island development prior to approximately 8200 yr BP is indicated. Initiation of barrier-island development is most likely due to a slowing in the Holocene sea-level rise ca. 8000 yr BP, coupled with the intersection of the coast with quartz sand deposits formed during Pleistocene sea-level highstands. This study is an example of a mixed carbonate/siliciclastic shallow marine depositional system that is tightly constrained in both time and sea-level position. It provides a useful analog for the study of other, similar depositional systems in both the modern and ancient rock record.     

Holocene environmental change and the accumulation–erosion balance of sheltered river-mouth sediments, Göteborg, SW Sweden

Holocene sedimentological change was investigated in 15 sediment piston cores (250 cm long) from the mouth of the Göta älv River, outside of Göteborg, which is sheltered by an archipelago. The main objective was to interpret recent, natural and human-induced influences upon the accumulation–erosion balance and the sedimentary environment from Holocene sediment units. The five main units are: consolidated glaciomarine clay (Facies gC) lowermost, consolidated estuarine clay (Facies dC), soft sub-recent sediment (Facies omC and Facies C) uppermost and dumped sediment (Facies D) in some parts of the study area. The sediment facies are divided by two major hiatuses: (a) the early Holocene hiatus between Facies gC and dC involves a time gap of at least 7000 years, ending at ca. 4000 BP and (b) the late Holocene hiatus between the consolidated clays (Facies gC and dC) and Facies omC spans 1000 years and ends ca. 50 BP (i.e. 100 years ago). Both hiatuses probably relate to the effects of isostatic land uplift. Surface sediments consist mainly of an organic-matter-rich clay facies, suggesting changes in the trophic state of the estuary during the last 100 years. Together with human-induced increased river erosion and loss of accommodation space in the estuary, this caused the onset of sedimentation in the estuary. The recent sediments are contaminated with heavy metals (Cu, Zn, Pb, Hg), with highest concentrations in the lower part of Facies omC.     

Mid-Holocene evolution and paleoenvironments of the shoreface–offshore transition, north-eastern Argentina: New evidence based on benthic microfauna

A sedimentary record spanning 5792–5511 cal yr BP and 3188–2854 cal yr BP was recovered at 36° 45′ 43″ S–56 ° 37′ 13″ W, south-west South Atlantic. The sedimentological features and micropaleontological (benthic foraminifera and ostracoda) content were analyzed in order to reconstruct paleoenvironmental conditions. Considerable environmental fluctuations are indicated by all these proxies. Five different stages were distinguished: Stage 1 (ca. 5800–5000 cal yr BP) consists of muddy sand with abundant microfossils. In this interval, species typical for inner marine shelf environments maintained a high abundance. Stage 2 consists of plastic light greenish grey clays barren of microfossils, and probably represents fluvial input from the de la Plata River to the shelf contemporaneous of a lowering of sea level. Stage 3 is composed of brownish yellow sandy silts, and represents increasing marine conditions in the area as reflected by higher faunal diversity and typical foraminifera of inner shelf environments. Stage 4 is made of homogeneous mud, barren of microfossil, which represents a new pulse of fluvial input to the shelf in consequence of a new fall in sea level. The final part of the core (Stage 5) is a coarsening upward sequence, grading from greeny brown clayey sandy silts to coarse shelly sands and represents the modern sedimentation in the area. This interpretation strengthens the stepped model of late-Holocene sea-level fall between 5511–5792 cal yr BP and 2854–3188 cal yr BP in Buenos Aires coast, and agrees with the relative sea-level history previously proposed by some authors from western South Atlantic coasts.     

Human impacts overwhelm the effects of sea-level rise on Basque coastal habitats (N Spain) between 1954 and 2004

According to coastal measurements, global mean sea-level has risen at a rate of 1.8 mm yr⁻¹ between 1950 and 2000, with large spatial variability at regional scales. Within the Bay of Biscay, trends computed from coastal tide gauges records have revealed that sea-level rise is accelerating over this period of time; this is in agreement with rates obtained from satellite imagery in the open ocean since 1993. The objectives of the present study are: (1) to assess the evidence of the relative sea-level rise on coastal morphology and habitats in the Gipuzkoan littoral zone (Basque coast, northern Spain) for the period 1954–2004, and (2) to evaluate the relative contribution of local anthropogenic versus sea-level rise impacts for explaining inter-supratidal habitat changes. A high-resolution airborne laser altimetry data (LIDAR) has been used to derive a Digital Terrain Model (DTM) of 15-cm vertical resolution. Coastal habitats were mapped for two periods, using historic airborne photography (1954) and high-resolution imagery (2004). Analysis of tide gauge records from Santander (northern Spain) has revealed that relative mean sea-level has been rising at a rate of 2.08 ± 0.33 mm yr⁻¹ from 1943 to 2004; this is consistent with sea-level trends from other measurements within the area (St. Jean de Luz and Bilbao), obtained over shorter periods of time, and with previous results obtained in the Bay of Biscay. Based upon this sea-level trend and by means of a LIDAR-based DTM, the results have indicated that the predicted change along the Gipuzkoan coast due to sea-level rise was of 11.1 ha within the 50-yr period. In contrast, comparison of historical and recent orthophotography has detected only 2.95 ha of change, originated possibly from sea-level rise, and 98 ha transformed by anthropogenic impacts. Hence, coastal changes due to sea-level rise might be overwhelmed by excessive human impacts, at the spatial and temporal scales of the analysis. This work highlights that local anthropogenic impact is the major threat to Basque coastal and estuarine habitats, compared with natural erosive processes and global climate change driving forces over recent times.     

Storms and shoreline retreat in the southern Gulf of St. Lawrence

Storms play a major role in shoreline recession on transgressive coasts. In the southern Gulf of St. Lawrence (GSL), southeastern Canada, long-term relative sea-level rise off the North Shore of Prince Edward Island has averaged 0.3 m/century over the past 6000 years (>0.2 m/century over 2000 years). This has driven long-term coastal retreat at mean rates >0.5 m/a but the variance and details of coastal profile response remain poorly understood. Despite extensive sandy shores, sediment supply is limited and sand is transferred landward into multidecadal to century-scale storage in coastal dunes, barrier washover deposits, and flood-tidal delta sinks. Charlottetown tide-gauge records show mean relative sea-level rise of 3.2 mm/a (0.32 m/century) since 1911. A further rise of 0.7±0.4 m is projected over the next 100 years. When differenced from tidal predictions, the water-level data provide a 90-year record of storm-surge occurrence. Combined with wind, wave hindcast, and sea-ice data, this provides a catalogue of potentially significant coastal storms. We also document coastal impacts from three recent storms of great severity in January and October 2000 and November 2001. Digital photogrammetry (1935–1990) and shore-zone surveys (1989–2001) show large spatial and temporal variance in coastal recession rates, weakly correlated with the storm record, in part because of wave suppression or coastal protection by sea ice. Large storms cause rapid erosion from which recovery depends in part on local sand supply, but barrier volume may be conserved by washover deposition. Barrier shores with dunes show high longshore and interdecadal variance, with extensive multidecadal healing of former inlet and overwash gaps. This reflects recovery from an episode of widespread overwash prior to 1935, possibly initiated by intense storms or groups of storms in the latter half of the 19th century. With evidence from the storms of 2000–2001, this points to the importance of storm clustering on scales of weeks to years in determining erosion vulnerability, as well as the need for a long-term, large-scale perspective in assessing coastal stability. The expected acceleration in relative sea-level rise, together with projections of increasing storm intensity and greatly diminished winter ice cover in the southern GSL, implies a significant increase in coastal erosion hazards in future.     

Oscillating Quaternary water levels of the Marmara Sea and vigorous outflow into the Aegean Sea from the Marmara Sea–Black Sea drainage corridor

Detailed interpretation of single-channel air-gun and deep-tow boomer profiles demonstrates that the Marmara Sea, Turkey, experienced small-amplitude (∼70 m) fluctuations in sea level during the later Quaternary, limited in magnitude by the sill depth of the Strait of Dardanelles. Moderate subsidence along the southern shelf and Quaternary glacio-eustatic sea-level variations created several stacked deltaic successions, separated by major shelf-crossing unconformities, which developed during the transitions from global glacial to interglacial periods. Near the Strait of Dardanelles, a series of sand-prone deposits are identified beneath an uppermost (Holocene) transparent mud drape. The sandy deposits thicken into mounds with the morphology and cross-sectional geometries of barrier islands, sand waves, and current-generated marine bars. All cross-stratification indicates unidirectional flow towards the Dardanelles prior to the deposition of the transparent drape which began ∼7000 years BP, in strong support of the notion that the Marmara Sea flowed westwards into the Aegean Sea through the Dardanelles at times of deglaciation in northern Europe. The global sea-level curve shows that, at ∼11,000 and ∼9500 years BP, sea level rose to the sill depths of the Straits of Dardanelles and Bosphorus, respectively. The effect from ∼11,000 to ∼9500 years BP was seawater incursion into the Marmara Sea, drowning and formation of algal-serpulid bioherms atop lowstand barrier islands, and transgression of shelves and lowstand deltas. At ∼9500 years BP, glacial meltwater temporarily stored in the Black Sea lake, developed into a vigorous southward flow toward the Aegean Sea, forming west-directed sandy bedforms in the western Marmara Sea and initiating deposition of sapropel S1 in the Aegean Sea. This strong outflow persisted until ∼7000 years BP, after which a mud drape began to accumulate in the Marmara Sea and euryhaline Mediterranean mollusks successfully migrated into a progressively more saline Black Sea where sapropel deposition began. Most eastern Mediterranean sapropels from S1 to S11 appear to correlate with periods of rising sea level and breaching, or near-breaching, of the Bosphorus sill. These events are believed to coincide with times of vigorous outflow of low-salinity (?fresh) surface waters transiting the Black Sea–Marmara Sea corridor, and ultimately derived from melting of northern European ice sheets.     

Evolution of late Quaternary mud deposits and recent sediment budget in the southeastern Yellow Sea

Analysis of high-resolution seismic reflection profiles and sediment samples has revealed the evolution and sediment budget of the southeastern Yellow Sea mud belt (SEYSM) along the southwestern Korean Peninsula. The SEYSM, up to 50 m thick, over 250 km long and 20–55 km wide, can be divided into three stratigraphic units (A1, A2, and B, from oldest to youngest). Unit A1, overlying the acoustic basement, comprises the northern part of the SEYSM. Unit A2 comprises the southern part of the SEYSM; much of unit A2 is exposed at the seafloor. Unit B completely covers unit A1 and pinches out southward.

¹⁴C data suggest that evolution of each unit is closely related to the postglacial sea-level changes. Unit A1 consists of estuarine/deltaic or shallow-water muds deposited during the early to middle stage of postglacial sea-level rise (ca. 14,000–7000 yr B.P.). Unit A2 corresponds to relict muds deposited during the last, deceleration stage of sea-level rise (ca. 7000–3.500 yr B.P.). Unit B consists of shelf muds deposited during the recent sea-level highstand (ca. <3500 yr B.P.).

Very low background activities of ²¹⁰Pb of the surface sediment of unit A2 suggest that the present-day sediment accumulation is negligible in the southern SEYSM. On the other hand, ²¹⁰Pb excess activity profiles in unit B yield an average sediment accumulation rate of 3.9 mm/yr, indicating active sediment accumulation in the northern SEYSM. The annual sink (3.0×10⁷ tons/yr) of fine-grained sediment in unit B is about an order of magnitude greater than can be explained by the sediment input from the Korean rivers alone. We propose that reworking of unit A2 has provided large volumes of muds to unit B, resulting in excessive sediment accumulation in the northern SEYSM. Much of unit A2, in turn, is likely to have originated from erosion of unit A1 in the north. This rather unique erosional/depositional regime of the SEYSM is probably owing to the tidal and regional currents characteristic in the southeastern Yellow Sea.     

Seismic expression and inferred depositional environments of Plio-Pleistocene sedimentary sequences in the southwestern Caspian Sea

Eight seismic profiles from the southwestern Caspian Sea were analyzed to establish the sedimentary environments and depositional history in the South Caspian Basin since Pliocene times. Based on reflection terminations, nine sequence boundaries (S1 to S9) were identified and traced across the study area. Consequently, nine depositional sequences (S1–S9) were defined on the basis of seismic facies analysis. The results suggest a transition from non-marine sedimentation in the Lower Pliocene to marine-dominated conditions in the Upper Pliocene (S1–S4). Marine conditions then continued to the present time; however, several sea-level changes led to the formation of sequences S5 to S9. Although no local sea-level curve is available due to a lack of well data, there is good agreement between the seismic stratigraphy of the study area and a published regional sea-level curve.     

Sedimentary facies and paleoenvironmental interpretation of a Holocene marsh in the Gironde Estuary in France

1Introduction Since the last glacial maximum, the Holocenehas been marked by a rapid rise in sea level. After6 000 a BP, the present-day level was reached andthe rate of sea-level rise (SLR) decreased rapidly(Morzadec -Kerfourn, 1974; Kidson, 1986 ).These…     

Morphodynamics of a high discharge tropical delta, San Juan River, Pacific coast of Colombia

The San Juan River has one of the most extensive and best developed deltas on the Pacific coast of South America, measuring 800 km². The river drainage basin measures 16?465 km² and is located in one of the areas with the highest precipitation in the western hemisphere. The annual rainfall varies from 7000 to 11?000 mm, and as a result the San Juan River has the highest water discharge (2550 m³ s⁻¹), sediment load (16×10⁶ t yr⁻¹), and basin-wide sediment yield (1150 t km⁻² yr⁻¹) on the west coast of South America. The San Juan delta growth began approximately 5000 years BP. The structure of the delta is determined by the interactions between fluvial deposition and the effect of 1.7-m significant swells, mostly from the SW, and strong tidal currents. Analysis of delta progradation indicates that during 1848-1992 the morphology of the delta was characterized by beach ridge accretion, spit growth, narrowing of inlets, and a general advance of the delta shoreline. During the past decade processes such as rapid erosion of the delta shore, narrowing of barrier islands, and breaching of a new inlet, are the result of a long-term relative sea-level rise of 2.6 mm yr⁻¹ due to tectonically induced subsidence coupled with a eustatic rise of sea-level. The delta also experiences strong oceanographic manifestations associated with the El Niño-La Niña cycle, causing regional sea-level elevation of 20-30 cm during El Niño years. Recent coastal subsidence in the delta is evidenced by: (1) increased occurrence of non-storm washover events; (2) increased erosion of barrier islands with average loss of 11 m yr⁻¹ during 1993-1997; and (3) a relative sea-level rise of 3.4 mm yr⁻¹ during 1991-1999. The morphology and recent evolution of the San Juan delta are unique when compared to other deltas of South America because of the singular combination of extreme climatic, geologic, and oceanographic conditions under which the delta has formed and the absence of human-induced impact in the drainage basin.     

Archeological evidence of Pacific salmon distribution in northern Japan and implications for future global warming

Archeological evidence of Pacific salmon in Hokkaido is reviewed and compared with results from western North America. Salmon remains have been found at 24 sites in Hokkaido from the Early Jomon Period to the Ainu Period (6000–100 years ago). Fish remains at three archeological sites in the Kushiro River basin indicated that Pacific salmon (Oncorhynchus spp.) were distributed and utilized from 6000 years ago. The present Kushiro Wetland was formerly covered with seawater and called the Paleo Kushiro Bay 5000–6000 years ago. Based on the molluscan fossil fauna, seawater temperature at Paleo Kushiro Bay was about 5°C warmer than at present. Warmer conditions for salmon in Kushiro 5000–6000 years ago corresponded with the poor conditions for salmon in the Columbia River basin 6000–7000 years ago. If the future global warming is similar to the conditions that prevailed 5000–6000 years ago, the southern limit of salmon distribution will shift northwards and the salmon production will decrease. However, they will not disappear from either Hokkaido or southwestern North America.     

Indian summer monsoon variability during the holocene as recorded in sediments of the Arabian Sea: Timing and implications

Indian monsoon precipitation fluctuated significantly during the Holocene and a reliable reconstruction of the timing of the events and their implications is of great benefit to our understanding of the effect and response of low latitude climate systems to the forcing factors. We have carried out high-resolution terrigenous proxy studies on a laminated sediment core from the Oxygen Minimum Zone of the eastern Arabian Sea margin to reconstruct the summer monsoon-controlled precipitation changes during the Holocene. The temporal variation in the terrigenous proxy indicators of this core, in combination with other high-quality cores from the Arabian Sea, suggests several abrupt events in monsoon precipitation throughout the Holocene. The early Holocene monsoon intensification occurred in two abrupt steps at 9500 and 9100 years BP and weakened gradually thereafter, starting at 8500 years BP. A weakening in precipitation recorded at ∼7000 years BP, synchronous with similar conditions in India. One of the most significant weak monsoon periods recorded in our studies lies between 6000 and 5500 years BP. Spectral analysis of the precipitation records reveals statistically significant periodicities at 2200, 1350, 950, 750, 470, 320, 220, 156, 126, 113, 104 and 92 years. Most of these millennial-to-centennial cycles exist in various monsoon records as well as the tree ring Δ¹⁴C data and/or other solar proxy records. We suggest that throughout the Holocene, externally, small changes in solar activity controlled the Indian monsoon to a large extent, whereas internally, non-solar causes could have influenced the amplitude of decadal-to-centennial oscillations.     

Dispersal of the Zhujiang River (Pearl River) derived sediment in the Holocene

High-resolution Chirp profiling and coring reveals an elongated(ca. 400 km) Holocene Zhujiang River(Pearl River)-derived mud area(maximum thickness 20 m) extending from the Zhujiang River Delta, southwestward off the Guangdong coast, to the Leizhou Peninsula. Two depo-centers, one proximal and one distal, are identified. On the continental shelf off the west Guangdong Province, the mud is deposited in water depth shallower than 50 m; while to the southeast of the Zhujiang River Estuary, the mud area can extend to the-120 m isobath. A combined analysis with the stratigraphic sequences of other muddy deposits in the Western Pacific marginal seas(mainly Changjiang(Yangtze) and Huanghe(Yellow) Rivers derived) indicates that the initiation of the Zhujiang River muddy deposit can be further divided into two stages: Stage 1 is before the mid-Holocene sea-level highstand(ca. 7.0 cal. ka BP), the proximal mud was mostly deposited after 9.0 cal. ka BP, when the sea-level rose slowly after the Meltwater Pulse-1C; Stage 2, after the mid-Holocene sealevel highstand, clinoform developed on the continental shelf off the west Guangdong Province, extending ca. 400 km from the Zhujiang River Estuary. The proximal clinoform thins offshore, from ca. 10 m thickness around 5–10 m water depth to less than 1–2 m around 20–30 m water depth. In addition, we also find a developed distal clinoform in the east of the Leizhou Peninsula.     

Sea-level modelling: The past and the future

The development of an analytical expression to describe the natural variation of global temperature and related climatic variables over periods from a few years or less to over a billion years is shown and seen to match the variation of eustatic sea-level over similar periods. An additional anthropogenic factor to take the greenhouse effect into account is added to this natural climatic variation giving close correlation between the combined natural-plus-anthropogenic model of global temperature variation and its observed history over the past century. This provides grounds for confidence in the subsequent deterministic forecast for the combined model and its sea-level counterpart of, for instance, about 0.7m rise by 2050AD.A tentative physical explanation of the natural climate model is given invoking the possibility that the Universal Gravitational Constant (G) may, in fact, be a variable. In parallel, the anthropogenic climate model is underlined by alluding to a theoretical explanation of the population growth mechanism which largely drives it. The interactive nature of the impact of man on sea-level rise and vice versa is stressed.