Quaternary Sea-level Changes Research Articles

Geomorphic controls and transition zones in the lower Sabine River

AbstractInstream flow science and management requires identification of characteristic hydrological, ecological, and geomorphological attributes of stream reaches. This study approaches this problem by identifying geomorphic transition zones along the lower Sabine River, Texas and Louisiana. Boundaries were delineated along the lower Sabine River valley based on surficial geology, valley width, valley confinement, network characteristics (divergent versus convergent), sinuousity, slope, paleomeanders, and point bars. The coincidence of multiple boundaries reveals five key transition zones separating six reaches of distinct hydrological and geomorphological characteristics. Geologic controls and gross valley morphology play a major role as geomorphic controls, as does an upstream‐to‐downstream gradient in the importance of pulsed dam releases, and a down‐to‐upstream gradient in coastal backwater effects. Geomorphic history, both in the sense of the legacy of Quaternary sea level changes, and the effects of specific events such as avulsions and captures, are also critical. The transition zones delineate reaches with distinct hydrological characteristics in terms of the relative importance of dam releases and coastal backwater effects, single versus multi‐channel flow patterns, frequency of overbank flow, and channel‐floodplain connectivity. The transitional areas also represent sensitive zones which can be expected to be bellwethers in terms of responses to future environmental changes. Copyright © 2007 John Wiley & Sons, Ltd.

Late Quaternary Sea Level Changes on Brock and Prince Patrick Islands, Western Canadian Arctic Archipelago

Emerged shorelines are few and poorly defined on Prince Patrick and Brock islands. The sparse radiocarbon dates show emergence of only 10 m through the Holocene on the Arctic Ocean coast, increasing to 20 m 100 km to the east. Hence, from Brock Island, representative of westernmost coasts, the sea level curve since the latest Pleistocene has a very low gradient, whereas on eastern Prince Patrick Island the curve takes the more typical exponential form. A decline in isobases towards the west is thus registered. Drowned estuaries, breached lakes, and coastal barriers, particularly in southwest Prince Patrick Island, suggest that the sea is now transgressing at a rate that decreases towards the north end of the island, hence there is also a component of tilt to the south. Delevelling is assumed to result from undefined ice loads, but may have a tectonic component. The sole prominent raised marine deposit is a ridge probably built in a period of more mobile sea ice, possibly at a time of stable or slightly rising sea level in the middle or early Holocene. It winds discontinuously along several hundred of kilometres of the shores of the Arctic Ocean and connecting channels, declining to the south.

Publisher's Note

Quaternary glacial stratigraphy and relative sea-level changes reveal at least four expansions of the Kara Sea ice sheet over the Severnaya Zemlya Archipelago at 79 degrees N in the Russian Arctic, as indicated from tills interbedded with marine sediments, exposed in stratigraphic superposition, and from raised-beach sequences that occur at altitudes up to 140 m a.s.l. Chronologic control is provided by AMS C-14, electron-spin resonance, green-stimulated luminescence, and aspartic-acid geochronology. Major glaciations followed by deglaciation and marine inundation occurred during MIS 10-9, MIS 8-7, MIS 6-5e and MIS 5d-3. The MIS 6-5e event, associated with the high marine limit, implies ice-sheet thickness of >2000m only 200km from the deep Arctic Ocean, consistent with published evidence of ice grounding at similar to 1000m water depth in the central Arctic Ocean. Till fabrics and glacial tectonics record repeated expansions of local ice caps exclusively, suggesting wet-based ice cap advance followed by cold-based regional ice-sheet expansion. Local ice caps over highland sites along the perimeter of the shallow Kara Sea, including the Byrranga Mountains, appear to have repeatedly fostered initiation of a large Kara Sea ice sheet, with exception of the Last Glacial Maximum (MIS 2), when Kara Sea ice did not impact Severnaya Zemlya and barely graced northernmost Taymyr Peninsula. (c) 2007 Elsevier Ltd. All rights reserved.

Population structure of Hypochaeris salzmanniana DC. (Asteraceae), an endemic species to the Atlantic coast on both sides of the Strait of Gibraltar, in relation to Quaternary sea level changes

To detect potential Pleistocene refugia and colonization routes along the Atlantic coast, we analysed amplified fragment length polymorphisms (AFLPs) in 140 individuals from 14 populations of Hypochaeris salzmanniana (Asteraceae), an annual species endemic to the southwestern European and northwestern African coastal areas. Samples covered the total distributional range of the species, with eight populations in southwestern Spain and six populations in northwestern Morocco. Using nine primer combinations, we obtained 546 fragments in H. salzmanniana and its sister species H. arachnoidea of which 487 (89.2%) were polymorphic. The neighbour-joining tree shows that the populations south of the Loukos river in Morocco are clearly differentiated, having more polymorphic, private, and rare fragments, and higher genetic diversity, than all the other populations. The southernmost populations in Morocco, south of the river Sebou, form a large panmictic population. They are probably the oldest populations that have been relatively unaffected by stochastic processes resulting from Pleistocene glaciations. Northward migration of populations during this period may have resulted in loss of genetic diversity in specific regions, perhaps due to bottlenecks caused by rise in sea level during interglacial periods, and, in some cases, by changes in the breeding system.

Late Quaternary sedimentation and tectonics in the submarine Şarköy Canyon, western Marmara Sea (Turkey)

Abstract Influences of tectonics and late Quaternary sea-level changes on sedimentation in the submarine Şarköy Canyon, western Marmara Sea (Turkey) were investigated using a total of 37 seismic reflection profiles and 12 gravity sediment cores (with 63–435 cm thicknesses), which were collected at water depths ranging from 62 to 245 m. 14 C ages of base sections in three cores (11.585, 11.845 and 24.915 ka bp ) and upward fining of grain size in the cores suggest that these sediments must have been deposited since the sea-level lowstand at about 12 ka bp, when the conditions in the Marmara Sea began to change from lacustrine to the present marine phase. With some exceptions, siliciclastic mud (silt+clay >90%) with low carbonate contents (<15% CaCO 3 ) is the dominant sediment type covering the floor of the canyon. The high organic carbon contents (1–2%) with slight downcore-increasing tendencies reflect higher primary organic productivities towards the early Holocene. Faults, sedimentation deformation structures, and submarine slides or slumps observed on seismic profiles, varying elevations of dated lowstand palaeoshores and low water contents (19–25%) of sediments at some sites together strongly indicate the important effect of neotectonics on sedimentation in this canyon. On the seismic profiles at least four stratigraphic units were recognized overlying the pre-Miocene basement, which indicate not only the effects of faulting and folding but also changing conditions and related depositional environments in and around the canyon. Geological evolution and thus the sea-floor morphology of the Şarköy Canyon is controlled by both regional Plio-Quaternary tectonics and global Quaternary sea-level changes.

Comment on “Record of MIS 5 sea-level highstands based on U/Th dated coral terraces of Haiti” by Dumas et al. [Quaternary International 2006 106–118

The opening sentence of the introduction [Dumas, B., Hoang, C.-T., Raffy, J., 2006. Record of MIS 5 sea-level highstands based on dated coral terraces of Haiti. Quaternary International 145–146, 106–118] “Quaternary sea-level changes are mainly deduced from the study of raised coral terraces” involves a flawed premise. As two undefined variables operate simultaneously (sea-level changes and vertical tectonic motion; both perhaps having up and down components) to produce a succession of terraces, it is impossible to solve the equation without supplying real numbers for either variable. Hence, to deduce sea-level history, either largely unprovable assumption about constant uplift and/or featureless sea-level histories are required, or a model of sea level must be imported from regions that have not experienced tectonic displacement. Furthermore, coral reefs are less than ideal monitors of sea-level change; rather, they might be preferred as monitors of sea level stability, as their response time and depositional tempo may be measured in hundreds or thousands of years. Reefs may grow and flourish during slow rise of sea level. Once accommodation space is filled, vertical growth ceases, and only erosion and diagenesis of the reef occurs, until sea level changes once more. Major intervals of sea-level change may thus be lost or never recorded in the rocks.

Geomorphic expression of late Quaternary sea level changes along the southern Saurashtra coast, western India

Geomorphic expression of land-sea interaction is preserved in the form of abandoned cliffs, marine terraces, shore platforms and marine notches along the southern Saurashtra coast. These features have been used to ascertain the magnitude of sea level changes during late Quaternary. Notch morphology and associated biological encrustation have been used to estimate the magnitude and duration of palaeo-sea strands. Marine notches and other erosive features occurring between 12 and 15 m above the present Biological Mean Sea Level (BMSL) are attributed to the last interglacial corresponding to the Marine Isotopic Stage 5 (MIS-5). However, 6 to 9 m upliftment of the coastal fringe is attributed to this sea level. The second major high sea strand was identified during the mid-Holocene when the sea rose 2 m above the present level. Notches corresponding to this high sea level are recorded 4 to 5 m above the present BMSL.

Contrasting patterns of genetic structure in two species of the coral trout Plectropomus (Serranidae) from east and west Australia: Introgressive hybridisation or ancestral polymorphisms

Inter-specific genetic relationships among regional populations of two species of grouper ( Plectropomus maculatus and Plectropomus leopardus) were examined using mitochondrial and nuclear markers. mtDNA revealed contrasting regional inter-specific patterns whilst nuclear markers revealed contrasting patterns among markers, irrespective of region. In eastern Australia (EA) the species form a single mtDNA lineage, but the two species are reciprocally monophyletic in Western Australia (WA). This supports previous evidence for hybridisation between these species on the east coast. WA P. leopardus forms a sister relationship with the EA P. leopardus-maculatus clade while WA P. maculatus is more basal and sister to the P. leopardus lineages, indicating mtDNA does not suffer from incomplete lineage sorting for these species. In contrast, one of three nuclear markers (locus 7-90TG) differentiated the species into two reciprocally monophyletic clades, with no evidence of hybridisation or ancestral polymorphism. The remaining two nuclear markers (2-22 and ETS-2) did not separate these two species, while distinguishing other plectropomid species, suggesting incomplete lineage sorting at these nuclear loci. These results together with coalescence analyses suggest that P. leopardus females have hybridised historically with P. maculatus males and that P. maculatus mitochondria were displaced through introgressive hybridisation and fixation in the P. maculatus founder population on the Great Barrier Reef. The contrasting regional patterns of mtDNA structure may be attributed to Quaternary sea-level changes and shelf width differences driving different reef configurations on each coast. These reef configurations have provided opportunities for local scale interaction and reproduction among species on the narrower EA continental shelves, but not on the broader WA continental shelves.

Should Quaternary sea-level changes be used to correct glacier ELAs, vegetation belt altitudes and sea level temperatures for inferring climate changes?

Changes in the altitudes of glacier snowlines (ELAs) and the altitudes of montane vegetation belts (VBAs) measure Quaternary climatic change. An accepted ‘correction’ to such changes by deducting the amount of contemporary sea level fall is wrong, since the air displaced by the ice sheets approximately fills the space left by the falling sea level and so there is no overall downward movement of the troposphere. This also causes a reduced cooling at the lowered sea level relative to that at the former inter-glacial sea level, about 1°C at the Las Glacial Maximum, which reduces the discrepancies previously noted by others between terrestrial and marine estimates of sea-level cooling. The change in temperature is indicated by the product of the ELA or VBA lowering and the environmental lapse rate (ELR). Prior estimates of ΔELA (−900 ± 135 m) and ELR (−6° ± 0.1°C km −1) would indicate a cooling of −5.4°C at interglacial sea level and −4.4°C at glacial sea level, although glacial-period ELRs are not known reliably. Established ELA corrections for local epeirogenic uplift or subsidence are appropriate.

Long extending the record on continental margins Quaternary stratigraphy

Thick sedimentary successions on continental margins preserve a high-resolution record of environmental change on the adjacent continent. Commonly, the stratigraphic succession is well-imaged by seismic-reflection profiles but lacks direct sampling by wells or boreholes. The well-dated 100 ka cyclicity of later Quaternary sea-level change can in many situations be used to infer a chronology for continental margin sediment successions that are not directly sampled. This paper presents a series of case studies that illustrate the successes and limitations of such techniques. Extreme lowstands of sea level that result in coastal or deltaic progradation, the cutting of gullies of the slope, or the incision of river valleys across the shelf are the most useful chronological markers.

Palaeoenvironmental control on sediment composition and provenance in the late Quaternary deltaic successions: a case study from the Po delta area (Northern Italy)

Accumulation of continental, deltaic and shallow-marine sediments in the Po River coastal plain preserves a record of the Late Quaternary sea-level changes and shoreline migrations. The palaeoenvironmental evolution of this area and the changes in composition and provenance of sediments have been investigated through integrated sedimentological, micropalaeontological (mainly foraminifers) and geochemical analyses of core S1, from the southern part of the Po River delta, within a chronological framework supported by radiocarbon dating and correlations with adjacent core sequences. Eleven lithofacies, grouped into five facies associations, and four palaeontological assemblages provide the basis to define the palaeoenvironmental reconstruction of this succession consisting, from the base to the top, of: (i) continental sediments accumulated during the Late Pleistocene; (ii) back-barrier sediments marking the onset of Holocene sea-level rise; (iii) transgressive sands deposited during the rapid landward migration of a barrier-lagoon system; (iv) shallow-marine and prodelta sediments with faunal associations indicating a gradual approach to the Po River mouth; and (v) sub-recent delta front sands that form a considerable portion of the present coastal plain. Bulk chemical composition of sediments shows remarkable relationships with palaeoenvironments and locally improves facies characterizations. For example, they reveal carbonate leaching that emphasizes the occurrence of palaeosols in continental deposits or record enrichments in loss on ignition, S and Br, diagnostic of organic-rich layers in back-shore sediments. Selected geochemical elements (e.g. Mg and Ni) are particularly effective for the recognition of sediment provenances from the three main source areas observed in the subsurface deposits of the Po River coastal plain (e.g. Apenninic rivers, North Adriatic rivers and Po River). An Apenninic provenance is observed in continental and back-barrier sediments. A North Adriatic provenance characterizes the transgressive sands and the shallow-marine deposits; a significant Po River provenance is recorded in sediments related to the onset of the prodelta environment, confirmed by foraminiferal assemblages indicating remarkable increase in fluvial influxes. Copyright © 2006 John Wiley & Sons, Ltd.

Genesis and Dispersal of Carbonate Mud Relative to Late Quaternary Sea-Level Change Along a Distally-Steepened Carbonate Ramp (Northwestern Shelf, Western Australia): Erratum

Genesis and Dispersal of Carbonate Mud Relative to Late Quaternary Sea-Level Change Along a Distally-Steepened Carbonate Ramp (Northwestern Shelf, Western Australia): Erratum

Genesis and Dispersal of Carbonate Mud Relative to Late Quaternary Sea-Level Change Along a Distally-Steepened Carbonate Ramp (Northwestern Shelf, Western Australia)

Abstract Accumulation of carbonate mud is minor on the Northwest Shelf (Western Australia), a broad (< 200–300 km wide), distally steepened, tropical carbonate ramp. It is negligible along most of the inner ramp (0 to 50 m water depth) owing to siliciclastic (riverine) input. It is also negligible along the mid (from 50 to 120 m) ramp, and where the entire ramp narrows to < 100 km, owing to constant reworking by storm waves and ocean swell. In these areas, carbonate mud is derived mostly from mechanical degradation of skeletal fragments, but this does not include calcified remains of calcareous green algae (e.g., Halimeda) although these plants grow locally. Only along the outer (120 to 200 m water depth) ramp and slope is there any relatively abundant accumulation of carbonate mud. Here the sediment consists of modern pelagic (foraminifer, pteropod, and nannoplantkon) ooze and aragonitic needle-rich (< 2 μm) micrite, the latter having an age (based on AMS 14C) of ~ 19 ka. Distribution of aragonite micrite defines an extensive (5.0 × 104 km2), yet relatively narrow (< 40 km), tract running ~ 600 km along the platform margin. Crystal morphology, mineralogy, and isotope (C, O) composition identify the micrite to be a seawater precipitate, its production and seaward export having occurred during the Last Glacial Maximum, when lowered sea level transformed the otherwise broad platform into a narrow epicontinental shelf margin, now the modern distal slope. Today, this sediment body lies stranded in deep water, about 200–300 km seaward of the shallow inner ramp. The volume of micrite produced appears equal to the present-day production potential of the Great Bahama Bank. Rapid postglacial rise in sea level, and change in platform geometry, climate, and oceanography, were very influential factors, in addition to water depth and area of submergence, in the production and distribution of aragonite micrite along the Northwest Shelf. In general: (1) epicontinental carbonate platforms can lack substantial micrite accumulation when oceanic current and wave energies sweep unimpeded across a platform, and coastal clastics and absence of shoal barriers prevent development of protective lagoons and carbonate tidal flats; (2) not all highstand carbonate systems are associated with significant amounts of micrite in shallow water environments, nor do they necessarily export large volumes of micrite to the periplatform realm; and (3) some lowstand systems can produce and export volumes of carbonate mud that rival highstand systems.

Late Quaternary sea-level change, sedimentation and neotectonics of the Gulf of Gökova: Southeastern Aegean Sea

The sedimentary and tectonic Late Quaternary evolution of the Gulf of Gökova located at the southwest Anatolia–southeastern Aegean Sea region has been interpreted from 800 line km of 3.5 kHz and single channel airgun seismic reflection profiles. The older part of the Gökova basin is formed by mainly E–W trending faults and filled by the latest Miocene–Pliocene–Quaternary hemipelagic sediments with thickness up to 2.5 km. The Lycian Nappes, which primarily cover extreme southwestern Anatolia, represent the basement rocks for the Gökova region. Younger active faulting so-called Gökova Transfer Fault (GTF), which has not been previously discussed in the literature, trends NE in the central part of the Gulf of Gökova basin and records sinistral strike-slip motion broadly parallel to the convergence direction of the Aegean–Anatolian and African plates. The continental shelf of the northeastern Gulf of Gökova is mostly formed by numerous superimposed deltaic successions (depositional sequences), separated by major erosional unconformities. During times of lowered sea-level associated with late Quaternary glaciations, deltas prograded more than 40 km seaward from their present positions. Foreset progradation terminated with the rise of sea level in interglacial and post-glacial times and deltas were relocated far inland. These major transgressions resulted in unconformities that are correlated with the beginning of oxygen isotope stages 9, 7, 5 and 1, and provide chronostratigraphic markers for a detailed analysis of sedimentation patterns in the late Quaternary. All seismic lines show that the topset to foreset transition of the youngest Pleistocene delta system developed around 145–150 ms below present sea-level. Thus, the maximum Pleistocene sea-level lowering (18 000 years BP) was about −110 m. The positions of maximum regression for isotopic stages 6, 8 and 10 were found as 160, 190 and 215 m below present sea-level, respectively. Paleo shoreline positions during isotopic stages 2, 6 and 8 suggest an overall gradual subsidence of Gökova basin, during the last 0.5 Ma in the southeastern Aegean Sea. The seismic sedimentary chronology suggests that the Gökova Basin is subsiding at 0.3–0.4 mm/year. Three bathymetric low and E–W, WNW–ESE directed two main ridges in the gulf area are noticeable from the bathymetric data and are well correlated to the seismic data. While the main orientation of the gulf is E–W, more recent ENE–WSW and WNW–ESE structures are remarkable in the western and the mid-eastern part of the gulf respectively. Subsidence rates are greatest in the southern center of the basin and decrease northward, so that the northern area is being tilted southward.

Reconstruction of late Quaternary sea-level change in southwestern British Columbia from sediments in isolation basins

Reconstruction of late Quaternary sea-level change in southwestern British Columbia from sediments in isolation basins

Reconstruction of late Quaternary sea‐level change in southwestern British Columbia from sediments in isolation basins

Bracketing ages on marine—freshwater transitions in isolation basins extending from sea level to 100 m elevation on Lasqueti Island, and data from shallow marine cores and outcrops on eastern Vancouver Island, constrain late Pleistocene and Holocene sea‐level change in the central Strait of Georgia. Relative sea level fell from 150 m elevation to about —15 m from 14000 cal. yr BP to 11 500 cal. yr BP. Basins at higher elevations exhibit abrupt changes in diatom assemblages at the marine‐freshwater transition. At lower elevations an intervening brackish phase suggests slower rates of uplift. Relative sea level rose to about +1 m about 9000 cal. yr BP to 8500 cal. yr BP, and then slowly fell to the modern datum. The mean rate of glacio‐isostatic rebound in the first millennium after deglaciation was about 0.11 in a ‐1, similar to the peak rate at the centres of the former Laurentide and Fennoscandian ice complexes. The latter feature smooth, exponential‐style declines in sea level up to the present day, whereas in the study area the uplift rate dropped to less than one‐tenth of its initial value in only about 2500 years. Slower, more deeply seated isostatic recovery generated residual uplift rates of &lt;0.01 m a‐1 in the early Holocene after the late‐Pleistocene wasting of the Cordilleran ice sheet.

Architecture and evolution of a fjord‐head delta, western Vancouver Island, British Columbia

AbstractThe architectural framework and Holocene evolution of the Zeballos fjord‐head delta on west‐central Vancouver Island was established through a multidisciplinary field‐based study. The Zeballos delta is a composite feature, consisting of an elevated, incised, late Pleistocene delta and an inset Holocene delta graded to present sea level. Both deltas have a classic Gilbert‐type tripartite architecture, with nearly flat topset and bottomset units and an inclined foreset unit. Time domain electromagnetic (TDEM) and ground‐penetrating radar (GPR) surveys, borehole data, and gravel pit exposures provided information on the internal form, lithologies and substrate of both deltas. Both sets of deltaic deposits coarsen upward from silt in the bottomset unit to gravel in the topset unit. The TDEM survey revealed a highly irregular, buried bedrock surface, ranging from 20 m to 190 m in depth, and it delineated saltwater intrusion into the deltaic sediments.Late Quaternary sea‐level change at Zeballos was inferred from delta morphology and the GPR survey. The elevated, late Pleistocene delta was constructed when the sea was about 21 m higher relative to the land than it is today. It was dissected when sea‐level fell rapidly as a result of glacio‐isostatic rebound. Relative sea‐level reached a position about 20 m below the present datum during the early Holocene. Foreset beds that overlap and progressively climb in a seaward direction and topset beds that thicken to 26 m landward imply that the delta aggraded and prograded into Zeballos Inlet during the middle and late Holocene transgression. Sea‐level may have risen above the present datum during the middle Holocene, creating a delta plain at about 4 m a.s.l. Remnants of this surface are preserved along the valley margins. Copyright © 2004 John Wiley &amp; Sons, Ltd.

215-ka History of sea-level oscillations from marine and continental layers in Argentarola Cave speleothems (Italy)

Several Quaternary sea-level changes are recorded by speleothems in the Argentarola Cave (Italy), which is currently flooded by the Mediterranean Sea. Speleothems with a sequence of continental layers and marine biogenic overgrowths (serpulid colonies), all presently covered by living serpulids, were sampled at water depths between −3.5 and −21.7 m. The composite sequence contains five marine and four continental layers, formed over the last 215 ka. The Mediterranean Sea flooded the cave during two short periods of MIS 7 (7.3 and 7.1), as well as during an episode at the end of MIS 6 and during MIS 5, when a thick biogenic overgrowth grew during MIS 5.2 and 5.4. Thin continental layers also formed during the LGM. This final speleothem layer was interrupted during the Holocene sea-level rise, but at different times in each speleothem. A Holocene sea-level curve has been constructed from this same layer. A thin marine layer, found only in the deeper stalagmites at −21.5 and −21.7 m, is tentatively related to the short marine transgression of Termination II, after 145 ka BP and before MIS 5.5. The island of Argentarola lies in a tectonically stable area and our data generally agree with the results obtained by other authors on speleothems from the Bahamas. The data presented here are compared with the SPECMAP curve and other recently published sea-level curves.

Late Quaternary sea level and environmental changes from relic carbonate deposits of the western margin of India

Relic carbonate deposits along the western margin of India occur as dolomite crusts, aragonite sands (pelletal / oolitic) and aragonite-cemented limestones, oyster shells, corals, encrusted coralline algal and foraminiferal-dominated nodules. The petrology and mineralogy of the deposits indicate that except for aragonite sands and foraminiferal nodules, the others were formed in shallow marine conditions and serve as sea level indicators. Radiocarbon dates were measured for 62 relic deposits covering the entire margin. The age of these deposits on the continental shelf off Cape Comorin and Mangalore, between 110 and 18 m depth, ranges between 12, 61014C yr BP and 6,39014C yr BP. On the northwestern margin of India, especially on the carbonate platform (between 64 and 100 m), the age ranges from 17,250 to 6,73014C yr BP. The relic deposits of the Gulf of Kachchh at depths between 35 and 25 m are dated at 12,550–9,63014C yr BP. The age vs. depth plot of the relic deposits further indicates that the Gulf of Kachchh was inundated much early, atleast by 15 ka, after the Last Glacial Maximum, and was subjected to uplift and subsidence during the Holocene. The carbonate platform subsided during the early Holocene. Some of the relic deposits between Cape Comorin and Mangalore plot on or, closely follow the glacio-eustatic sea level curve. Despite abundant siliciclastic flux discharged by the Narmada and Tapti during the early Holocene, the platform off these rivers is largely devoid of this flux and carbonate sedimentation continued until 6,70014C yr BP. We suggest that the river-derived sediment flux diverted southwards under the influence of the SW monsoon current and, thereby, increased the turbidity on the shelf and slope southeast of the carbonate platform and facilitated the formation of deeper water foraminiferal nodules off Vengurla-Goa.

Sea level change in Italy during last 300 ka. A review

Biogeographia vol. XXIV - 2003 (Printed October, 31st 2003) Marine biogeography of the Mediterranean Sea: patterns and dynamics of biodiversity Sea level change in Italy during last 300 ka. A review FABRIZIO AN TONIOLI ENE/I, via Anguillarese 301, I—00060 Szmtzz Maria dz‘ Gzzlerizz, Roma (Italy) e—mzzil: fizbrizio. zziztonioli @m::zccz&#39;;z. men. it Key words: sea level, isostatic rebound, radiocarbon ages. SUMMARY This paper is a review about t_he sea level change in Italy during last 300 ka and the markers used to constrain the curves. In particular is underlined as it is important to distinguish between Global, Local and Predicted sea level curves. INTRODUCTION Sea level change can be reconstructed from dated fossil coral reef terraces, and these data are complemented by a compilation of global sea—level estimates based on deep—sea oxygen isotope ratios at millennial—scale resolution or higher. Because of the lack of coral reefs in the Mediterranean seas, results on late Quaternary sea—level changes have been difficult to obtain in comparison with typical sites such as Barbados, the Huon Peninsula, Tahiti and others. Otherwise, the very low tidal range of Italian seas offers a good opportunity to produce precise palaeo— sea level curves. Sea level change along the Italian coast is the sum of eustatic, glacio—hydro— isostatic, and tectonic factors. The first is time—dependent while the latter two also vary with location. This wants to say that at the same time slices, the relative sea level (the sum of 3 different movements) should be different in different coastlines. For any palaeo reconstruction of ancient coastline it is necessary to take in account all components. It is important to distinguish between Global sea level curve (s.l.c.), Local s.l.c. or Predicted s.l.c., constrained using geophysical models.