The Stratigraphy Machine

ABSTRACT There is a significant difference between the average sedimentation rate of a lengthy stratigraphic section spanning many millions of years, and the rate that can be calculated from any short segment within such a section, such segments typically yielding rates several orders of magnitude more rapid than the overall rate. Stratigraphic successions contain numerous surfaces of nondeposition and erosion representing time spans from minutes to many millions of years, which collectively may account for as much as 90% of the total elapsed time that the succession represents. The stratigraphic record is constructed by a range of geological processes that operate over all time scales from seconds to billions of years, and at rates that vary by ten orders of magnitude. The generation of the stratigraphic record can be conceptualized in the form of a mechanical device, which we term the “Stratigraphy Machine.”

Separating Climate Variability and Non-Climate Noise in Proxy Records - A case study on replicate marine sediment records

<p>To describe earth’s former and predict the expected future climate in a general way we need to understand at least two basic characteristics of the distribution of earth’s temperature, its mean state and its temporal and spatial variance of temperature. There is some confidence in the projection of the mean state but the characteristics and changes of climate variability, especially on multi-decadal and longer time-scales are less known.</p><p>To characterize climate variability on these time scales, the instrumental record is too short. Climate proxies such as oxygen isotopes from foraminifera retrieved from marine sediments provide long records but do not exclusively carry information about the climate signal of interest. The decomposition of proxy time series into climate and non-climate components is challenging and depends on the adequate representation of the major involved biological and physical processes influencing the record. But even with a reasonable representation of the combined processes as fluctuations in proxy seasonality, bioturbation and errors in the age model, a proxy record still appears as the combination of these effects.</p><p>As a proxy record is only a single representation of this sum of effects we work on replicate measurements as a tool to characterize and separate the variability components. We therefore analysed oxygen isotopes and Mg/Ca in replicated measurements from the same sample, in replicated samples from the same sediment layer and in nearby sediment cores spanning the Holocene.  <br>If we compare two records the relation of them will determine the commonness of the underlaying processes. As records for example come from the same core or from cores of nearby located sites, they share the same climate signal. In the case they are from the same core they also share the errors in the age model and the time uncertainty introduced by bioturbation. Combining different types of replicates allows us the analyse the effect of different combinations of shared and independent errors.</p><p>The first two cores that we work on come from about 10 km apart located sites in the Indonesian Sea. GeoB 10054-4 was drilled in a water depths of 1076 meters, at longitude of 112°40.10’E and latitude 8°40.90’S and its average sedimentation rate was estimated as 20 cm/kyears. GeoB 100537 was drilled in a water depths of 1372 meters, at longitude 112°52.30’E and at latitude 8°40.56’S and its average sedimentation rate is estimated as 45cm/kyears.</p><p>In the presentations we will show first results of the analysis of intra core and inter core variability.</p>

Influences of sea level on depositional environment during the last 1000 years in the southwestern Bengal delta, Bangladesh

This study illustrates the influences of sea-level on the depositional process during the last 1000 years of the southwestern delta, Bangladesh. Sediments of eight litho-sections from landward in upper delta plain to seaward in lower delta plain along the Rupsa-Pasur river were studied. Sedimentary facies, total organic carbon, total nitrogen, δ13C value, diatom assemblages, and radiocarbon dating of deposits were carried out to determine the paleoenvironments that were influenced by the relative sea-level (RSL) change over time. During the 850–1300 AD, RSL was reached up to +80 cm higher than the present level where tidal-influenced bioturbated light yellow to gray mud deposited in the upper delta plain area. RSL was dropped up to −110 cm during 1300–1850 AD, organic-rich bluish-gray mud, mangrove peat, and terrestrial influenced yellowish-gray mud were deposited successively in the lower delta plain area, and the terrace was formed at landward due to the lowering of the base level. RSL started to rise after the period 1850 AD where tidal-influenced sediments gradually increased and deposited in the upper part at seaward and terrestrial flood sediment deposited over the erosional surface at the landward part. The estimated average sedimentation rate (1.96–2.89 mm/year) is not enough to offset the effect of subsidence and present sea-level rise over the study area. The rising trend of the sea creates inundation in the lower delta plain area, also hinders upstream water flow. For that, terrestrial flood sediments settle over the erosional surface in landward, and tidal-influenced sediment gradually onlap upon it from seaward.

Late Pleistocene glaciolacustrine MIS 3 record at Fagnano Lake, Central Tierra del Fuego, southern Argentina

A late Pleistocene glaciolacustrine record was studied at Fagnano Lake (54°35´S, 67°20´W), central Isla Grande de Tierra del Fuego, southernmost South America. Two profiles from the Río Valdéz outcrop were collected for isotopic, geochemical, sedimentological, and geophysical analyses. The sedimentological characteristics, such as rhythmites, presence of dropstones, absence of fossil record, and scarce presence of organic matter, suggest deposition in an ice-contact lake, possibly dammed by the Fagnano paleoglacier. Organic matter of C3 plant origin suggests certain cold and wet conditions. A chronology of the late Pleistocene outcrop was obtained from five 14C ages resulting in an age-depth model. The time span covered 49.01 cal ka BP to 32.14 cal ka BP. Based on the thickness of the deposit and the calculated average sedimentation rate, the glacial environment could have been present in the study area prior to the last glacial maximum, in agreement with the Inútil-San Sebastián paleoglacier. Both glaciers flowed from the same mountain ice sheet in the Darwin Cordillera, which makes it possible to infer a different behavior of this ice cap from those of the Patagonian Andes, perhaps forced by different atmospheric dynamics and proximity to the wet and cold subantarctic air masses.

Proterozoic–Paleozoic Sedimentary Rocks and Mesozoic–Cenozoic Landscapes of the Cape Mountains Across the Kango Complex Reveal ‘More Gaps Than Record’ from Rodinia and Gondwana to Africa

The Kango (Cango) region flanks the northern margins of the Klein Karoo and the Cape Mountains across the Western Cape Province of South Africa. It preserves a condensed Proterozoic–Paleozoic stratigraphy exposed via a Mesozoic–Cenozoic morphology with a present Alpine-like topography. Its rocks and landscapes have been repeatedly mapped and documented for the past 150 years. Over the last 25 years, we remapped and dated a central-eastern section of this region. The subvertically bedded and cleaved rocks reveal an 8–10 km thick stratigraphy covering more than 700 million years between ca. 1200 and 500 Ma with several unconformities and disconformities. At ca. 252 Ma, during the Cape orogeny, this Kango Complex was deformed along thrusts and sub-isoclinal folds producing steeply dipping phyllites and slates. It was uplifted by 3–5 km during the Kalahari epeirogeny between 140 and 60 Ma while eroding at ca. 100–200 m/m.y. (120–80 Ma). During the Cenozoic, the rate of uplift decreased by an order of magnitude and today is ca. 0.4–0.7 m/m.y. across steep slopes and canyons in contrast to the Himalayas where erosion rates are about hundred times faster. A recent publication about this central-eastern section of the Kango region disputes the existence of regional isoclinal folds and suggests that deposition of the oldest sedimentary successions, including carbonate rocks of the Cango Caves (limestone-marble with enigmatic microfossils) was simple, continuous and restricted to between ca. 700 and 500 Ma, decreasing earlier estimates of the stratigraphic age range by 60–80%. Similarly, recent interpretations of the complex landscapes link the northern contact between the Kango and Table Mountain rock sequences to Quaternary faults. We present a new geological database, mapped between 1:500 and 1:10,000 scales, and twelve stratigraphic sections with younging directions linked to structural and isotopic data that support repetitions along regional isoclinal folds and thrust zones of the Kango sequences during the Permo–Triassic Cape orogeny, and geomorphic data that link the origin of its landscapes to weathering and erosion during the Cretaceous–Cenozoic Kalahari epeirogeny. During its evolution, the Kango Basin directly flanked both Grenvillian and Pan-African Mountain systems. But, at an average sedimentation rate of ca. 1 mm/70 years (0.014 mm/year) and with present low erosion rates (0.005 mm/year), there is likely more time missing than preserved of the tectono-erosion across these different regions of Rodinia and Gondwana before Africa emerged. To further evaluate the geodynamic significance of these time gaps requires more field mapping linked to new transdisciplinary geosciences. RÉSUMÉLa région du Kango (Cango) flanque les marges nord du petit Karoo et des montagnes du Cap dans la province du Western Cape en Afrique du Sud. Elle préserve une stratigraphie condensée protérozoïque–paléozoïque exposée via une morphologie mésozoïque–cénozoïque avec une topographie actuelle de type alpin. Ses roches et ses paysages ont été cartographiés et documentés durant les 150 dernières années. Au cours des 25 dernières années, nous avons re-cartographié et daté une section du centre-est de cette région. Les roches litées de manière subverticale et clivées révèlent une stratigraphie de 8 à 10 km d'épaisseur couvrant plus de 700 millions d'années entre environ 1200 et 500 Ma avec plusieurs non-conformités et disconformités. À 252 Ma, au cours de l'orogenèse du Cap, ce Complexe du Kango s'est déformé le long de chevauchements et de plis isoclinaux produisant des schistes à fort pendage. Il a été soulevé de 3 à 5 km au cours de l'épirogenèse du Kalahari entre 140 et 60 Ma, tout en s'érodant à 100–200 m/m.a. (120–80 Ma). Pendant le Cénozoïque, le taux de soulèvement a diminué d'un ordre de grandeur et il est aujourd'hui d'environ 0,4 à 0,7 m/m.a. à travers des pentes abruptes et des canyons, contrairement à l'Himalaya où les taux d'érosion sont environ cent fois plus rapides. Une publication récente sur cette section du centre-est de la région du Kango conteste l'existence de plis isoclinaux régionaux et suggère que le dépôt des plus anciennes successions sédimentaires, y compris les roches carbonatées des Grottes du Cango (marbre calcaire avec des microfossiles énigmatiques) était simple, continu et limité entre environ 700 et 500 Ma, diminuant les estimations antérieures de la tranche d'âge stratigraphique de 60-80%. De même, des interprétations récentes des paysages complexes relient le contact nord entre les séquences rocheuses du Kango et de Table Mountain à des failles quaternaires. Nous présentons une nouvelle base de données géologiques, cartographiée à des échelles entre 1:500 et 1:10,000, et douze coupes stratigraphiques avec des directions de superposition liées à des données structurales et isotopiques qui concordent avec les répétitions le long des plis isoclinaux régionaux et des zones de chevauchement des séquences du Kango pendant l’orogenèse permo–triassique du Cap, et des données géomorphiques qui relient l'origine de ses paysages à l’altération et à l'érosion au cours de l'épirogenèse du Kalahari au Crétacé–Cénozoïque. Au cours de son évolution, le bassin du Kango flanquait les systèmes montagneux grenvillien et panafricain. Mais, à un taux de sédimentation moyen d’environ 1 mm/70 ans (0,014 mm/an) et avec les faibles taux d'érosion actuels (0,005 mm/an), il manque probablement plus d’enregistrements de la tectonique et érosion de ces différentes régions de Rodinia et Gondwana avant l'émergence de l'Afrique que ce qui est actuellement préservé. Pour évaluer la signification géodynamique de ces intervalles de temps manquant, il faut d’avantage de cartographie de terrain associée à de nouvelles géosciences transdisciplinaires.

Investigating glacial/interglacial cyclicity from downhole logging data and mineralogical composition: an example from the ICDP drilling project Lake Junín, Peru

<p>Reconstructing the history of continental records covering the glacial-interglacial cycles was the main objective of the ICDP Lake Junín drilling project. Located at 4000 m above sea level, Lake Junín is characterized by a thick sediment package (>125 m) deposited with a sedimentation rate of 14-15 cm/kyr. In fact, the lake predates the maximum extent of glaciation, and is in a geomorphic position to record the waxing and waning of glaciers in the nearby Cordillera. Drilling was performed in 2015 at three sites and a suite of downhole logging measurements were applied. Downhole logging measurements were used to recognize the glacial and interglacial cycles, to reconstruct an age–depth model, to estimate sedimentation rates and to identify electrofacies. Initially, we investigate the consistency of cyclic sediment behavior and see that the interval from ~30-90 m shows a rather stable cyclicity with a wavelength of ~10 m. Natural and spectral gamma ray data were used for cyclostratigraphic analysis, and the astronomical spectral misfit (ASM) method was used to reconstruct the sedimentation rate. The results indicate a sedimentation rate of about 5-20 cm/kyr in the Lake Junín record. Furthermore, the TimeOpt method was applied to test for a fit of precession amplitude with eccentricity; it results in an average sedimentation rate of 15 cm/kyr. Both ASM and TimeOpt are astronomical testing approaches for untuned stratigraphic data in the depth domain that comprehensively evaluate a range of plausible time scales for the deposition history. This method suggests a good fit of the precession amplitude and an eccentricity filter when applying an average sedimentation rate of 14-15 cm/kyr. Based on these information on sedimentation rate, we establish a correlation of the spectral gamma ray data to the LR04 benthic isotope stack. In addition, the downhole logging data were used for cluster analysis to construct a lithological profile, called the electrofacies log.  Three major groups (carbonate-silt, peat and silt) have been identified by spectrum gamma ray, magnetic susceptibility, and p-wave velocity logs. With this method we are able to attribute the lithology in correspondence of core gaps. Finally, the properties of the clusters are analyzed and converted into lithological units according to the lithological information from the visual core description or mineralogical analysis or core material. To achieve this, 68 samples were taken in total from two core runs, in order to compare and characterize the minerals in the lake sediments at different depths. The mineralogical analyses performed by X-ray diffraction (XRD) show quartz, calcite, feldspar and clay minerals. The clay size fraction (< 2 micron) contains illite, smectite and kaolinite in different amounts. Linking the abundance and the lack of clay minerals in core samples with the downhole logging data, a relationship between geological history of the lake and climate change processes can be recognized. Consequently, the different mineralogical composition of the sediments, especially the presence or absence of smectite in the clay bulk, reflects a glacial/interglacial climate cyclicity.</p>

Geochemical Signatures of Paleoclimate Changes in the Sediment Cores from the Gloria and Snorri Drifts (Northwest Atlantic) over the Holocene-Mid Pleistocene

A multiproxy study of the sediment cores taken from the Snorri Drift, formed under the influence of the Iceland–Scotland bottom contour current, and from the Gloria Drift, located southward Greenland at the boundary of Irminger and Labrador Seas, was performed. This area undergoes a variable mixing of polar waters with the warm North Atlantic current, whose intensity and direction seemed to change dramatically with the alteration of warming and cooling periods during the six marine isotope stages MIS 1-6. The relative age of this core does not exceed 190,000 cal yr BP; the average sedimentation rate was 1.94 and 2.45 cm/kyr in the Gloria and Snorri Drifts core respectively. In both the cores, the sediment records showed the downcore co-variation of ice-rafted debris (IRD); and terrigenous elements, such as Si, Al, Ti, Cr, and Zr, were revealed; their values were clearly higher in the glacial periods (MIS 2, 4, and 6) compared to interglacials (MIS 1, 3, and 5). The downcore rhythmic distributions of these elements, as well as Al/Si, Ti/Al, Fe/Al ratios exhibit an opposite trend with that of δ18O values, biogenic components (CaCO3, BioSiO2), and Si/Fe and Mn/Fe ratios.

Suitability Conservation Types Analysis of Panglima Besar Soedirman Reservoir

Mrica Reservoir located in Banjarnegara Regency is amultipurpose reservoir. Based on the report of PT Indonesia Power UnitPembangkitan (UP) Mrica in 2016, the sediment of Mrica Reservoir hasentered the critical phase as it reached 114.25 million m3 and the value ofland-cover index of Mrica reservoir was 80% of the total watershed areawith the average sedimentation rate reaching 4.09 million m3 per year. Itis estimated that the reservoir will be full of sediment by 2021. The maincause of the high rate of sedimentation in Mrica reservoir is the changes inland use and agricultural-plantation activities in the upper river areas andalong the river flow of Serayu River, Merawu River, and Lumajang River. This study aimed to determine the appropriate type of conservation forMrica Reservoir. The method used was the Analytical Hierarchy Process(AHP), in which the determination of conservation efforts was based onsecondary data and observation. According to the current condition ofMrica Reservoir, the planned conservation efforts include two types, namely non-structural conservation and structural conservation. If theconservation begins in 2019, the total sediment in 2021 will decrease to74% and it is predicted that the sediment will be exhausted by 2056.

Studi Perubahan Garis Pantai Berdasarkan Interpretasi Citra Satelit Landsat dan Perhitungan Rasio Lahan di Wilayah Pesisir Indramayu Jawa Barat

ABSTRAKWilayah pesisir sebagai kawasan peralihan yang menghubungkan ekosistem darat dan ekosistem laut, sangat rentan terhadap kerusakan dan perubahan yang diakibatkan oleh berbagai aktifitas manusia di darat maupun di laut. Kabupaten Indramayu merupakan salah satu wilayah di Pesisir Utara Jawa Barat yang mengalami kerusakan paling parah diantara seluruh kabupaten di wilayah pesisir Utara Jawa Barat serta memiliki penggunaan lahan pesisir yang cukup lengkap mulai dari pemukiman, persawahan, tambak, dan industri (PLTU dan MIGAS)..Besarnya perubahan garis pantai yang meliputi abrasi dan sedimentasi diturunkan dari data citra satelit Landsat wilayah pesisir Kabupaten Indramayu tahun 1994-2009 dengan metode komposit RGB 4, 5, 7 dan Metode AGSO kemudian dilakukan proses digitasi.. Luas abrasi di 11 Kecamatan Pesisir Indramayu dari tahun 1994 – 2009 sebesar 3900,41 Ha dengan laju abrasi rata-rata sebesar 23,64 Ha/ tahun dan Luas sedimentasi sebesar 650,29 Ha dengan laju sedimentasi rata-rata sebesar 4,81 Ha/tahun. Hasil perhitungan regresi terhadap rasio lahan penduduk untuk tahun 2015 sebesar 0,07 Ha/ jiwa dan menurun pada tahun 2025 menjadi 0,05 Ha/jiwa .Rasio lahan petani untuk tahun 2015 sebesar 0,66 Ha/petani dan menurun menjadi 0,55 Ha/petani di tahun 2025.Kata Kunci : Pesisir indramayu, citra satelit, abrasi dan sedimentasi, Rasio lahanABSTRACTCoastal areas as a transitional region connecting the land ecosystems and marine ecosystems, are vulnerable to damage and changes caused by various human activities on land and at sea. Indramayu regency is one of the areas in the North Coast of West Java is the most severely damaged among all districts in the northern coast of West Java and has a coastal land use complete enough from residential areas, wet rice fields, ponds, and industrial (power plant and Gas). The number of change in coastal line include erosion and sedimentation derived from Landsat satellite image data coastal areas of Indramayu district in 1994-2009 with the composite method RGB 4, 5, 7 and methods AGSO then do the digitization process. The extent of abrasion in 11 districts of the coastal Indramayu from 1994 - 2009 are 3900.41 hectares with average abrasion rate of 23.64 ha / year and sedimentation area of 650.29 hectares with an average sedimentation rate of 4.81 ha / year. Results of regression calculations to land ratio for the 2015 population of 0.07 ha / life and decreased in 2025 to 0.05 hectares /life .Rasio farmers' fields for 2015 of 0.66 ha / farmer and decreased to 0.55 Ha / farmers in 2025. Keywords: Coastal area of indramayu, satellite imagery, erosion and sedimentation, land Ratio

The history of the sedimentation processes and heavy metal pollution in the Central Danube Delta (Romania)

The aim of this study was to investigate the effects of the Iron Gates (IG) hydroelectric power station on the Danube Delta sediment dynamics, and to assess the heavy metal concentrations and pollution in a typical Central Danube Deltaic lake. Eight sediment cores were analysed. The total 210Pb content was measured with 210Po using alpha spectrometry, and the supported 210Pb (226Ra) and 137Cs were measured by gamma spectrometry. The age depth model was derived by applying the 210Pb dating method, and for the calculation of the ages and the sedimentation rates the CRS model was used. The sedimentation rates can be divided into four periods:1940–1972, 1972–1980, 1972–1989 and 1989–2013. In the case of Lake Iacob in the first period, the average sedimentation rate was 0.418 g/cm2y, while in the second it slowly decreased to 0.376 g/cm2y. In the third period, the sedimentation fell to 0.209 g/cm2y, which means the retention of 27.3% of the sediment by the IG dam. In the case of Lake Isac the changes were more visible: in the first period the average sedimentation rate was 0.446 g/cm2y, while in the second it decreased to 0.197 g/cm2y, which means a 42.35% retention of sediment. In the last period, in both cases, a high increase in the sedimentation rate is shown: 0.677 g/cm2y for Lake Iacob and 0.715 g/cm2y for Lake Isac. The heavy-metal concentrations for As, Co, Cr and Ni show decreasing and Hg increasing tendencies, while Cd and Pb show constant values of 310 ± 12 ppb and 9 ± 1 ppm respectively.