Sonostratigraphy of tropical Indian Ocean giant piston cores: toward a rapid and high-resolution tool for tracking dissolution cycles in Pleistocene carbonate sediments

During the seymama expedition of the French R/V Marion Dufresne in the equatorial Indian Ocean, we retrieved giant piston cores (30–53 m long) as part of a high resolution palaeo-oceanographic and stratigraphic study of Pliocene-Pleistocene pelagic carbonates. Major changes in the compressional wave (P wave) velocity profiles recorded in these cores appear to be correlatable from the Madingley Rise (western equatorial Indian Ocean) to the southeast of the Maldives archipelago (central equatorial Indian Ocean), about 1700 km away, thus emphasizing the stratigraphic potential of acoustic records in uncemented pelagic carbonates.

As expected in deep-sea carbonate deposits, changes in P-wave velocity parallel past changes in coarse fraction content (> 63 μm). Changes in grain size appear to be mainly controlled by carbonate dissolution, as evidenced by a strong relationship between sand content and a foraminifer preservation index. Thus, in uncemented pelagic carbonates, P-wave velocities provide quick and easy to obtain qualitative information on carbonate dissolution pulses. As diagenesis takes place, however, compaction and cementation change the dynamic rigidity (μ) of the sediments and may conceal the original grain size signal.

Due to the strong positive relationship between P-wave velocity and coarse fraction content in uncemented pelagic carbonates, P-wave velocity profiles can be tied to a precise chronologic framework by correlating them to the composite grain size index curve (CGSI) established by Bassinot et al. for the tropical Indian Ocean [1,2]. This composite curve has been constructed by stacking the normalized coarse fraction records from ODP Site 722 (Owen Ridge, Arabian Sea [3]) and ODP Site 758 (Ninetyeast Ridge, central equatorial Indian Ocean [4]). In these two sites, detailed δ¹⁸O records provide the basis for precise inter-site correlations. They ensure the accuracy of the stacking procedure, which tends to reduce most of the local grain size signals and enhances the regional signal related to carbonate dissolution pulses [1,2]. A detailed chronostratigraphy of CGSI curve was developed by correlating the δ¹⁸O records of Sites 722 and 758 to the orbital chronology recently developed from ODP Site 677 [5]. The CGSI may be used as a reference curve for developing a sonostratigraphy in the tropical Indian Ocean.     

Neogene tectonic evolution of the Gibraltar Arc: New paleomagnetic constrains from the Betic chain

New paleomagnetic results from Neogene sedimentary sequences from the Betic chain (Spain) are here presented. Sedimentary basins located in different areas were selected in order to obtain paleomagnetic data from structural domains that experienced different tectonic evolution during the Neogene. Whereas no rotations have been evidenced in the Late Tortonian sediments in the Guadalquivir foreland basin, clockwise vertical axis rotations have been measured in sedimentary basins located in the central part of the Betics: the Aquitanian to Messinian sediments in the Alcalà la Real basin and the Tortonian and Messinian sediments in the Granada basin. Moreover, counterclockwise vertical axis rotations, associated to left lateral strike-slip faults have been locally measured from sedimetary basins in the eastern Betics: the Middle Miocene to Lower Pliocene sites from the Lorca and Vera basins and, locally, the Tortonian units of the Huercal-Overa basin. Our results show that, conversely from what was believed up to now, paleomagnetic rotations continued in the Betics after Late Miocene, enhancing the role of vertical axis rotations in the recent tectonic evolution of the Gibraltar Arc.     

A rapid screening-level method to optimize location of infiltration ponds

A rapid-screening technique was developed to identify lithologies that best disperse artificial recharge via surface infiltration and minimize effects on ground water chemistry. The technique prospectively evaluates basin infiltration rates and water chemistry influences by integrating geotechnical, hydraulic, and water quality data with column test data and numerical modeling. The technique was validated using field data collected from surface infiltration basins designed to recharge ground water pumped from the Pipeline pit gold mine in Nevada. Observed recharge rates at these infiltration sites correlated most significantly with depth to groundwater, with basins in coarse-grained lithologies performing better (0.45 to 0.85 m/day) than those with fine-grained layers (< 0.30 m/day). Observed water quality resulting from leaching of the previously unsaturated vadose zone showed a transitory (< six months) increase in solute concentrations followed by a decrease to baseline conditions, a phenomenon also observed in column tests that leached native soils with local ground water. Leaching of fine-grained soils with evaporites resulted in greater solute concentrations (TDS > 2000 mg/L) than coarse-grained soils (< 1200 mg/L). The results of HYDRUS_2D simulations using the accumulated data as input were in agreement with observed ground water chemistry downgradient of the infiltration basins for a variety of lithologies. Sites for infiltration basins can be rapidly screened to include areas with greatest depth to groundwater and in coarsest alluvial sediments, and impact to ground water chemistry can be reliably predicted using computer modeling and column test results.     

A quantitative analysis of the desiccation and re-filling of the Mediterranean during the Messinian Salinity Crisis

Notwithstanding the great deal of attention that the Messinian evaporites of the Mediterranean region have received from an observational point of view, there is, to date, no consensus as to their mechanism of formation. We aim to contribute to the investigation through a quantitative analysis of the processes of desiccation and re-filling. These processes are thought to have played a role in particular during the deposition of the upper part of the evaporite sequence. We calculate the evolution of sea level and average salinity based on both the present-day geometry and a paleogeographic reconstruction and assess the sensitivity to variations in the freshwater budget. Our results support previous inferences that desiccation and re-filling are fast; desiccation occurs on a time scale of 3-8 kyr, re-filling probably even faster. Equilibrium sea levels imply that most water has gone from the western basin while a significant water column remains in the eastern basin. Whether or not the eastern basin reaches the level of halite saturation depends critically on, in particular, the freshwater budget. The fast rate of desiccation and re-filling imply that temporal differences in the onset of salt precipitation between western and eastern basin and between marginal basins and basin centres are below the resolution of (astronomical) dating. Also, when Atlantic sea level periodically varied from below to above the level of the intervening sill, the Mediterranean basin will have responded with repeated desiccation and re-filling. Fast re-filling is found to require only a small connection to the Atlantic Ocean. This, in combination with the previous results, suggests the Mediterranean is unlikely to attain stable intermediate water levels.     

Cenozoic stratigraphy and sedimentation history of the northern Philippine Sea based on multichannel seismic reflection data

Abstract To clarify the regional distribution and characteristics of the sedimentary deposits in the northern part of the Philippine Sea, multichannel seismic reflection surveys of 26 864 km in total length were performed. The seismic reflection data were interpreted and correlated with available Deep Sea Drilling Project/Ocean Drilling Program (DSDP/ODP) data and a general stratigraphic framework of the area was established. The sedimentary deposits in this area were divided into five layers; Units I, II, III, IV and V in ascending order. Their approximate geological ages are the Early Eocene, Middle to Late Eocene, Oligocene, Miocene and Pliocene‐Pleistocene, respectively. Seismic records were classified into three seismic facies, Facies A, B and C, on the basis of their characteristics. They were judged to represent pelagic and hemipelagic sediments of non‐volcanic origin, fine pyroclastic sediments and coarse pyroclastic or volcanic sediments, respectively, by comparing them with lithological data in the DSDP/ODP holes. From the thickness and facies distributions of these sediments, a sedimentary history in the area was reconstructed as follows. The oldest sediments in the study area, Unit I, interfinger with some parts of the Daito Ridge (acoustic basement) in the Minami Daito Basin. The geological age of the unit is estimated by microfossils in the sediment and supports the idea that this part of the Daito Ridge is composed of the Early Eocene oceanic basalt. Later, a fair amount of sediments were deposited in the Minami Daito Basin in the Middle to Late Eocene age. A large volume of volcanic materials was supplied from the Paleo‐Kyushu‐Palau Ridge in the Kita Daito Basin in the Eocene and Oligocene ages. The eastern part of the Shikoku and Parece Vela basins is characterized by volcanic sediments supplied from the Nishi Shichito and West Mariana Ridges in the Miocene age. However, pelagic and hemipelagic sediments prevail in the northern part of the Shikoku Basin in the Miocene or later. In short, the area of principal sedimentation has generally shifted from west to east through geological time, reflecting the evolution of the island arc systems with the same trend in the northern Philippine Sea.     

Tectonically controlled sedimentation in marginal basins

Recent sedimentary facies in marginal basins which are isolated from terrigenous sedimentation have been analysed in relation to their tectonic environment to generate a general evolutionary model for sedimentation in marginal basins of this type. Marginal basins are assumed to open symmetrically, while the sedimentation pattern is asymmetric. A volcaniclastic apron forms as a large submarine fan complex adjacent to the volcanic chain; beyond the distal end of the apron pelagic brown clay with a high content of montmorillonite, glass and phenocrysts accumulates. Pelagic oozes with high contents of CaCO₃ are deposited in distal parts of the basin. The volcaniclastic apron migrates toward the remnant arc, prograding over older pelagic sediments. Cessation of spreading has little effect on the sedimentation pattern if volcanism is still active. When volcanic activity ceases, the dominant sediment sources are biogenous and wind-blown pelagics. Most basins by this time have subsided below the carbonate compensation depth (CCD) and these brown clays accumulate at rates near 2.5 m/m.y. No simple pattern of sedimentation emerges from the available data in marginal basins adjacent to continents or to major sources of terrigenous material.     

Sedimentary evidence for an archaean shallow-water volcanic-sedimentary facies,Eastern Pilbara Block,Western Australia

Sedimentological studies of the dominantly volcanic, ca. 3.5 b.y. Warrawoona Group, eastern Pilbara Block, Western Australia, indicate widespread shallow-water deposition. Many cherty metasediments within the ultramafic-mafic sequence represent silicified carbonate mud, sand, breccia and conglomerate, and show cross-lamination, ripple marks, scour-and-fill structures, and evidence of reworking. At North Pole, some cherty metasediments appear to be silicified and baritized gypsiferous evaporites, and contain microfossils. Felsic volcaniclastic rocks include pyroclastic deposits, cross-laminated tuffaceous metasediments and conglomerate. Subaerial volcanism apparently increased as deposition proceeded.The depositional basin was large, volcanically active and apparently shallow with subdued marginal relief. Felsic volcanoes formed topographic highs within the basin from which sheets of volcanically derived sediments interfingered with ultramafic-mafic volcanics. The Onverwacht Group of the Barberton Mountain Land, South Africa, is of similar age to the Warrawoona Group and probably represents a similar environment, but other greenstone belts may have formed in contrasting basins, possibly under differing tectonic regimes.     

Effects of the Santorini (Thera) eruption on manganese behavior in Holocene sediments of the eastern Mediterranean

The explosive eruption on the island of Santorini in ∼1630 B.C. in Minoan times had a large environmental impact over the eastern Mediterranean region. It has even been suggested that the Mn-enriched layer (the “Marker Bed”) above the most recent sapropel (S1) in sediments of a crestal area of the Mediterranean Ridge gained Mn from a hydrothermal source related to the Santorini eruption. Radiocarbon dating of two cores from this area sampled at high resolution demonstrate that this large Mn peak in fact pre-dates the Santorini event by ∼2.8 ky and forms part of a pattern seen in Mn profiles from all over the eastern Mediterranean. This same Mn profile shape is altered in areas that experienced substantial deposits of either the tephra layer emitted by the Santorini eruption or the turbidites that were triggered by it. Evidence of both of these perturbations is readily identified from compositional element/Al and Sr/Ca profiles that are distinct from those of the enclosing sediments. In one core with a 37 cm thick Santorini ash layer an oxidation front succeeded in penetrating the whole ash layer after emplacement to form a Mn peak but is now retreating. In cores where thin (< 15 cm) Santorini turbidites or ash layers lie above S1, oxidation fronts initially form additional Mn peaks on top of the turbidites and subsequently alter the characteristic double peaked Mn profile shape usually observed above sapropel S1.     

Basin evolution associated to curved thrusts: The Prerif Ridges in the Volubilis area (Rif Cordillera,Morocco)

The Volubilis Basin is located between two structural arcs formed by the Prerif Ridges that developed during and after sedimentation. The arcs correspond with W- to WSW-verging anticline culminations, limited, to the north by a NE-SW strike-slip lateral ramp. Sedimentary infill took place during two stages of ridge formation and propagation. The first stage occurred in the Middle Miocene-early Tortonian and was determined by the deposition of the Nappe Prérifaine in the northern part of the basin, and continental and marine sediments over the Prerif Ridges. The second one, Late Miocene in age (Tortonian–Messinian), corresponds to the sedimentation of calcarenites and bioclastic limestones at the basin edges, with a lateral transition to white and blue marls toward the center of the basin. There is clear evidence of synsedimentary deformation, suggesting the interaction of sedimentation and tectonics. Geophysical data allow us to characterize the stratigraphic architecture of the Volubilis Basin and the geometry of the top of the Paleozoic basement. An approximately N–S Tortonian–Messinian asymmetric depocenter is located close to the front of the eastern arc. This research illustrates the nucleation, progressive thrust bending and segmentation, and the propagation of folds interacting with sedimentation. Thrust nucleation agrees with Paleozoic basement highs under the detachment surface. The progressive development of these tectonic structures conditioned the formation, segmentation and final continentalization of the Volubilis Basin, which can be considered as a piggy-back basin.     

Shear wave constraints on crustal structure of the pole abyssal plain

A study of the crustal structure in the Pole Abyssal Plain of the Arctic Ocean was carried out using P-waves constrained with converted shear waves. The data, recorded with a single ocean bottom seismometer (O.B.S.) on three channels, were modelled for travel time and amplitude variations with WKBJ synthetic seismograms. The study confirms that converted shear waves can be usefully employed to place limits on P-wave data.Shear wave velocities of sediments ranging from 0.3 km/s on the sea bed to 0.9 km/s at the sediment-basement interface with corresponding P-wave velocities of 1.6 to 2.1 km/s were obtained. The resulting Poisson's ratios for the sediments varies between 0.48 and 0.39, and indicate a poorly consolidated sedimentary layer. Well determined P- and S-wave velocities from the PPP and PSP phases give a Poisson's ratio of 0.31 for the lower crust in agreement with results from other studies.The models developed lead to the conclusion that there is considerable lateral heterogeneity in structure, and that the thickness of the crust (layers 2 and 3) under the Pole Abyssal Plain varies between 3.2 km and 4.1 km. The crust here is therefore much thinner than average oceanic crust, a thinning which may be related to the slow spreading rate at the Arctic Mid-Ocean Ridge.     

Pb in the western Indian Ocean: distribution, disequilibrium, and partitioning between dissolved and particulate phases

²²⁶Ra profiles have been measured in the western Indian Ocean as part of the 1977–1978 Indian Ocean GEOSECS program. These profiles show a general increase in deep and bottom water Ra concentration from the Circumpolar region to the Arabian Sea. A deep Ra maximum which originates in the Arabian Sea and in the Somali basin at about 3000 m depth spreads southward into the Mascarene basin and remains discernible in the Madagascar and Crozet basins. In the western Indian Ocean, the cold Antarctic Bottom Water spreads northward under the possibly southward-flowing deep water, forming a clear benthic front along the Crozet basin across the Southwest Indian Ridge into the Madagascar and Mascarene basins. The Antarctic Bottom Water continues to spread farther north to the Somali basin through the Amirante Passage at 10°S as a western boundary current. The benthic front and other characteristic features in the western Indian Ocean are quite similar to those observed in the western Pacific where the benthic front as a distinctive feature was first described by Craig et al. [15]. Across the Mid-Indian Ridge toward the Ceylon abyssal plain near the triple junction, Ra profiles display a layered structure, reflecting the topographic effect of the mid-ocean ridge system on the mixing and circulation of the deep and bottom waters. Both Ra and Si show a deep maximum north of the Madagascar basin. Linear relationships between these two elements are observed in the deep and bottom water with slopes increasing northward. This suggests a preferential input of Ra over Si from the bottom sediments of the Arabian Sea and also from the flank sediments of the Somali basin.     

Vestiges of an Iapetan rift basin in the New Jersey Highlands: implications for the Neoproterozoic Laurentian margin

Thin, discontinuous remnants of Neoproterozoic intracratonic rift-basin deposits of the Chestnut Hill Formation occur in the western New Jersey Highlands. These deposits form an important link between well-documented Iapetan rift-basins in both the northern and southern Appalachians. The close spatial relations of Chestnut Hill rocks to Paleozoic sedimentary rocks open the possibility that additional Iapetan rift-basins could be concealed beneath the rocks of the Valley and Ridge Province to the west indicating a much broader zone of rifting than has been previously proposed. The Chestnut Hill Formation is intermittently exposed along a 100 km-long band that extends northeast from Pennsylvania nearly to New York State. The lower part of the Chestnut Hill Formation is composed of interbedded lithic pebble- to boulder-conglomerate and feldspathic sandstone grading upward into interbedded phyllite, feldspathic and quartz sandstone, local paleosaprolite, quartz-pebble conglomerate, thin limestone lenses, volcanic, and volcaniclasic rocks, abundant bedded ironstone (hematite ore), and ultimately into diamictites that are interpreted as possible tilloids and containing rounded intra and extrabasinal clasts of the other lithologies. Extensive soft-sediment deformation, cross bedding, and clastic dikes are common in all but the lowest and upper facies. Banded hematite layers occur preferentially in fine-grained tuffs and tuffaceous sediments, but hematitization has affected most lithologies. Volcanic rocks consist of altered rhyolitic tuffs and lapilli tuffs that are interbedded with sediments. The Chestnut Hill Formation is interpreted to have been deposited in early alluvial, and later a complex of fluvial, lacustrine and deltaic environments. Provenance studies based upon petrographic and geochemical analysis of clastic rocks indicate that the sediments are predominantly immature and reflect derivation from local uplifted felsic basement sources in a rifted-margin tectonic setting. Low to moderate weathering of the source rocks is indicated by the geochemistry of most samples, as is the locally intense effect of hydrothermal alteration. Most occurrences of the Chestnut Hill Formation are associated with major faults that exhibit normal movement of apparent Neoproterozoic age. Rocks from the Morgan Hill fault near Easton, Pennsylvania display consistent normal shear sense and vary from low temperature S-C mylonites to breccia that contains deformed pieces of Chestnut Hill Formation.     

Structural profile of the northwestern Caribbean

A seismic reflection and gravity profile across the continental margin of the Yucatan Peninsula, Yucatan Basin, Cayman Ridge, and Cayman Trough suggests that sediments in the Yucatan Basin consist of a thick succession of beds dominated by turbidites that overlie a thick but irregular sequence of beds, probably dominated by pelagic deposits. The so-called “Carib beds”, present elsewhere in the Caribbean, are not evident in the part of the basin crossed by this profile. The sedimentary section rests on a acoustic basement that probably represents the top of oceanic layer 2. A gravity model indicates that the crust beneath the Yucatan Basin is thin and therefore probably is oceanic in character. The crust thickens southward under the Cayman Ridge but thins again beneath the Cayman Trough. This local thickening is consistent with the suggestion that the Cayman Ridge is a rifted part of the Nicaraguan Rise.     

中国近海前新生代残留盆地初探

中国近海沉积盆地按形成时代可以划分为新生代盆地和前新生代盆地。新生代陆相碎屑岩断陷盆地有良好的油气前景,而古生代还有广泛海相碳酸盐岩分布地区,只要它们经受中生代挤压,改造后还能保留下来,就具有巨大的油气潜力。初步分析中国近海的油气勘探资料及大地构造演化史表明,陆内断坳盆地下伏以古生代碳酸盐岩为主的残留盆地。而陆缘盆地并不是寻找古生代残留盆地的场所。但在台西南盆地,珠江口盆地潮汕坳陷发育海相中生代盆     

利用成像测井自动判别礁滩储层沉积相和岩性

礁滩储层是我国海相碳酸盐岩油气勘探的重要目标,也是我国油气产能的重要接替领域之一。由于礁滩储层储集空间类型多样,非均质性极强,依靠常规测井判别其沉积相和岩性非常困难。成像测井能够清晰地反映礁滩储层的结构组分和沉积构造,为沉积相和岩性的判别提供了可靠的依据。在对大量礁滩储层的成像和岩心对比观察的基础上,我们提出了9种典型的成像解释模式,建立了利用成像解释模式自动判别礁滩储层沉积相和岩性的方法并研制了相应的处理软件。该方法在塔中和川东北地区礁滩储层的实际应用中取得了良好的效果。     

裂隙充填型天然气水合物的各向异性分析及饱和度估算——以印度东海岸NGHP01-10D井为例

沿裂隙发育的天然气水合物是印度深水盆地细粒沉积物中水合物的重要产出方式,水合物以结核状或脉状充填在高角度裂隙中.天然气水合物主要沿着构造主应力方向生成,由于裂隙的存在,含水合物的沉积物层呈现各向异性.利用孔隙介质中水合物呈均匀分布的速度模型计算的NGHP01-10D井水合物饱和度高达40%,而压力取芯表明水合物饱和度占孔隙空间的20%左右.为了研究水合物饱和度差异,基于层状介质的各向异性模型计算了裂隙充填型水合物的饱和度.在垂直井孔中,由于波入射角与裂隙倾角有关,考虑裂隙倾角变化,利用纵波和横波速度同时反演水合物饱和度和裂隙倾角.利用层状介质模型计算的水合物占孔隙空间的15%～25%,裂隙的倾角在60°～90°,多为高角度裂隙.在NGHP01-10D井中,纵横波速度联合计算的饱和度与压力取芯结果吻合更好.     

PSEUDO-DIAGRAPHIES DE VITESSE EN OFFSHORE PROFOND*

Pseudo-velocity-logs are tentative determinations of subsurface velocity variations with depth, using both information of seismic amplitude and reflection curvature. A rigorous theoretical method would consist in

• a) deconvolving the seismic traces to remove the filtering effects of the ground and of the recording equipment
• b) demultiplying the deconvolved traces by a complete desynthesization with convergence criteria
• c) computing the velocities.

While this method works with synthetic examples, it is not generally applicable to field cases, one of the reasons being the poor reliability of desynthesization in the presence of noise. The present method is a compromise between a rigorous and a practical process: the complete desynthesization is not performed; deconvolution and demultiplication are done by more classical techniques using real amplitudes; absolute velocities are determined to fit both the reflection coefficients and the rms velocities. It leads to pseudovelocity-logs, accurate enough to show lithologic variations, smoothed enough to preserve the signal/noise ratio. Examples are shown of Flexichoc profiles recorded in 2500 m (8000–9000 feet) deep areas of the Mediterranean Sea. Pseudo-velocity-logs show 1000 m (3000 feet) of a velocity-increasing-with-depth Plio-pleistocene marl formation, overlying Miocene evaporites. Intercalations of high and low-velocity layers in the evaporites seem to indicate vertical facies variations. The Pseudo-velocity-log, associated with other lithologic determination processes, should become a geological tool for deep offshore exploration.     

Authigenic gypsum found in gas hydrate-associated sediments from Hydrate Ridge, the eastern North Pacific

Hydrate Ridge is located at the second accretion-ary ridge along the Cascadia margin of Oregon in the eastern North Pacific (fig. 1). The Bottom Simulating Reflector (BSR) underlies the entire Hydrate Ridge[1]. The Ocean Drilling Program (ODP) in 1992 at Site 892 and the TECFLUX99 and 2000 showed that the gas hydrate occurs just beneath the thin sediment- covered surface and at the horizon of around 64 meter below seafloor (mbsf) on Hydrate Ridge[25]. The col-lision of the Juan de …     

祁连盆地第三纪沉积物磁性地层和岩石磁组构初步研究

祁连山山间盆地内的新生代沉积物是研究新生代以来祁连山构造演化的重要材料.本文以位于祁连山中部祁连盆地内的新生代沉积物为研究对象,利用磁性地层学方法结合碎屑颗粒裂变径迹定年方法获取其沉积时代框架,在此基础上,结合岩性变化与沉积环境变迁分析祁连山构造演化历史.野外实测剖面显示该盆地内的第三系可划分为下部砾岩组和上部砂岩组两大岩性单元.古地磁结果显示砾岩组的沉积时代约为10—14.3Ma.砾岩组沉积大约在14.3 Ma开始形成,指示祁连山14.3 Ma以来构造活动变强烈.磁组构结果显示砾石组顶部沉积形成时的受力方向与现今祁连盆地周缘断层分布所指示的应力方向一致,表明这些断层大约在10 Ma附近开始活动.我们的结果揭示祁连山中部山脉14.3 Ma以来尤其在10 Ma附近构造活动较强烈.这与过去低温热年代学所获得的祁连山山体的快速冷却年龄及祁连山两端大型盆地内的第三系所记录的构造事件发生的时间基本吻合.而砂岩组的古地磁结果并未通过褶皱检验,其古地磁记录发生了后期重磁化,无法获得地层的准确沉积年龄.     

Anthropogenic metal contamination and sapropel imprints in deep Mediterranean sediments

Sediment cores from the deep Balearic basin and the Cretan Sea provide evidence for the accumulation of Cd, Pd and Zn in the top few centimeters of the abyssal Mediterranean sea-bottom. In both cores, 206Pb/207Pb profiles confirm this anthropogenic impact with less radiogenic imprints toward surface sediments. The similarity between excess 210Pb accumulated in the top core and the 210Pb flux suggests that top core metal inventories reasonably reflect long-term atmospheric deposition to the open Mediterranean. Pb inventory in the western core for the past 100 years represents 20-30% of sediment coastal inventories, suggesting that long-term atmospheric deposition determined from coastal areas has to be used cautiously for mass balance calculations in the open Mediterranean. In the deeper section of both cores, Al normalized trace metal profiles suggest diagenetic remobilization of Fe, Mn, Cu and, to a lesser extent, Pb that likely corresponds to sapropel event S1.