Liviu Giosan | Woods Hole Oceanographic Institution (original) (raw)

Papers by Liviu Giosan

During the 2006 National Gas Hydrate program of India's Expedition 1 (NGHP-01), 30 holes ... more During the 2006 National Gas Hydrate program of India's Expedition 1 (NGHP-01), 30 holes at 21 sites were drilled and cored to study gas hydrate occurrences at four regions along the peninsular Indian continental margins and in the Andaman accretionary wedge. In order to characterize the host sedimentary environment for gas hydrate at these sites we investigate the source and

Visual-domain diffuse reflectance data collected aboard the JOIDES Resolution with the Minolta sp... more Visual-domain diffuse reflectance data collected aboard the JOIDES Resolution with the Minolta spectrometer CM-2002 during Ocean Drill-ing Program Leg 172 have been used to estimate successfully the car-bonate content of sediments. Calibration equations were developed for each site and for each lithostratigraphic unit (or subunit at Site 1063) using multiple linear regression on raw as well as pretreated reflectance spectra (i.e., first-order derivation and squaring of raw reflectance spec-tra) for a total of 4141 direct carbonate measurements. The root-mean-square errors of 4% to 7% are within the range of previous estimates us-ing diffuse reflectance data and are acceptable for the general extensive range of carbonate contents (i.e., 0–70 wt%) that characterize sedimen-tation at Leg 172 sites.

In addition to archaeological and geological investigation of submerged prehistoric settlements i... more In addition to archaeological and geological investigation of submerged prehistoric settlements in the harbour of Sozopol (southern Bulgarian Black Sea coast), two cores were analyzed for pollen and spores, dinoflagellate cysts, non-pollen palynomorphs, and micro-charcoal. The cores provide detailed information about the vegetation and climate of periods with abundant archaeological evidence. Four local pollen assemblage zones based on arboreal pollen/non-arboreal pollen (AP/NAP) ratios are distinguished. A detailed reconstruction of the past vegetation reveals the extent of anthropogenic influence on the area. Three AMS radiocarbon determinations show that the palaeoecological record starts at c. 4139 cal BC.The palynological and geoarchaeological data confi rm the existence of anthropogenic activity and settlement during the fi nal stage of the Late Eneolithic (c. 4100–3850 cal BC) and the second phase of the Early Bronze Age (c. 3500–2650 cal BC). These two archaeological cultura...

During the 2006 National Gas Hydrate program of India's Expedition 1 (NGHP-01), 30 holes at 2... more During the 2006 National Gas Hydrate program of India's Expedition 1 (NGHP-01), 30 holes at 21 sites were drilled and cored to study gas hydrate occurrences along the peninsular Indian continental margins and in the Andaman accretionary wedge. During coring at sites NGHP-01-12A and -10D, located on the eastern Indian continental margin in the Krishna-Godavari Basin, an abundant occurrence of intact and broken clam and mussel shells and authigenic carbonate nodules at ~16 mbsf was recovered. These occurrences are coincident with the measured SMI (sulfate methane interface), lie above significant accumulations of gas hydrate, and are suggestive of a paleo-seep/chemosynthetic biological community (CBC). Recent radiocarbon dating and carbon isotope measurement at Sites 12A and 10D and recently published results by Mazumdar et al. (2009) from a piston core collected ~10 m away help constrain the timing and confirm the origin of this paleo-seep/CBC. Using the combined data sets from t...

The Indus River/Delta system is highly dynamic, reflecting the impacts of monsoonal-driven floods... more The Indus River/Delta system is highly dynamic, reflecting the impacts of monsoonal-driven floods and cyclone-induced storm surges, earthquakes ranging up to Mw = 7.8, and inundations from tsunamis. 19th century Indus discharge was likely larger than today, but upstream seasonal spillways limited the maximum flood discharge. Upstream avulsions during the 2010 flood similarly reduced the downstream discharge, so that only 43% of the floodwaters reached the delta. The present-day Indus River is wider with larger meander wavelengths (∼13 km) compared to the 4 km to 8 km meander wavelengths for the super-elevated historical channel deposits. The Indus River is presently affected by: 1) artificial flood levees, 2) barrages and their irrigation canals, 3) sediment impoundment behind upstream reservoirs, and 4) inter-basin diversion. This silt-dominated river formerly transported 270+ Mt/y of sediment to its delta; the now-transformed river carries little water or sediment (currently ∼13 M...

Quaternary Research

We employed X-ray diffraction methods to quantify clay mineral assemblages in the Indus Delta and... more We employed X-ray diffraction methods to quantify clay mineral assemblages in the Indus Delta and flood plains since similar to 14 ka, spanning a period of strong climatic change. Assemblages are dominated by smectite and illite, with minor chlorite and kaolinite. Delta sediments integrate clays from across the basin and show increasing smectite input between 13 and 7.5 lea, indicating stronger chemical weathering as the summer monsoon intensified. Changes in clay mineralogy postdate changes in climate by 5-3 ka, reflecting the time needed for new clay minerals to form and be transported to the delta. Samples from the flood plains in Punjab show evidence for increased chemical weathering towards the top of the sections (6-<4 ka), counter to the trend in the delta, at a time of monsoon weakening. Clay mineral assemblages within sandy floodplain sediment have higher smectite/(illite + chlorite) values than interbedded mudstones, suggestive of either stronger weathering or more sedi...

Geological Society London Special Publications

The Indus Delta is constructed of sediment eroded from the western Himalaya and since 20 ka has b... more The Indus Delta is constructed of sediment eroded from the western Himalaya and since 20 ka has been subjected to strong variations in monsoon intensity. Provenance changes rapidly at 12–8 ka, although bulk and heavy mineral content remains relatively unchanged. Bulk sediment analyses shows more negative 1 Nd and higher 87 Sr/ 86 Sr values, peaking around 8 –9 ka. Apatite fission track ages and biotite Ar–Ar ages show younger grains ages at 8– 9 ka compared to at the Last Glacial Maximum (LGM). At the same time d 13 C climbs from – 23 to – 20‰, suggestive of a shift from terrestrial to more marine organic carbon as Early Holocene sea level rose. U–Pb zircon ages suggest enhanced erosion of the Lesser Himalaya and a relative reduction in erosion from the Transhimalaya and Karakoram since the LGM. The shift in erosion to the south correlates with those regions now affected by the heaviest summer monsoon rains. The focused erosion along the southern edge of Tibet required by current te...

Geology

Climate is one of the principal controls setting rates of continental erosion. Here we present th... more Climate is one of the principal controls setting rates of continental erosion. Here we present the results of a provenance analysis of Holocene sediments from the Indus delta in order to assess climatic controls on erosion over millennial time scales. Bulk sediment Nd isotope analysis reveals a number of changes during the late Pleistocene and early Holocene (at 14?20, 11?12 and 8?9 ka) away from erosion of the Karakoram and toward more sediment flux from the Himalaya. Radiometric Ar-Ar dating of muscovite and U-Pb dating of zircon sand grains indicate that the Lesser Himalaya eroded relatively more strongly than the Greater Himalaya as global climate warmed and the summer monsoon intensified after 14 ka. Monsoon rains appear to be the primary force controlling erosion across the western Himalaya, at least over millennial time scales. This variation is preserved with no apparent lag in sediments from the delta, but not in the deep Arabian Sea, due to sediment buffering on the contin...

The growth of Chilia deltaic lobes reflects a drastic reorganization of the Danube delta that acc... more The growth of Chilia deltaic lobes reflects a drastic reorganization of the Danube delta that accompanied its rapid expansion in the late Holocene. Using new cores collected at the apices of the two older Chilia lobes together with historical maps and satellite photos, we find that a partial avulsion since ∼1500 years BP led to a gradual rejuvenation of the Chilia distributary, which successively infilled a lake, a lagoon, and then constructed an open coast lobe at the Black Sea coast. The Chilia branch became the largest Danube distributary reaching its maximum sediment load in the last 300 years as the southernmost St. George branch lost its previous dominance. Here we propose that the intensive deforestation of Danube's lower watershed leading to this delta reorganization has historical cultural causes: an increase in sheep and timber demand associated to the Ottoman Empire expansion in Eastern Europe followed by the adoption of maize agriculture as a result of the Columbian ...

Методът на съвременните аналози (МСА) дава възможност за палеоклиматични реконструкции, в основат... more Методът на съвременните аналози (МСА) дава възможност за палеоклиматични реконструкции, в основата на които стоят данните от спорово-поленовия анализ. За разлика от класическите качествени интерпретации на поленовите спектри, чрез МСА може да се направи количествена палеоклиматична оценка и да се изведат точни данни за параметрите на климата. Целта на настоящото изследване е на базата на съвременните климатични данни да се възстановят определени климатични параметри (средногодишна температура, средна температура на студеното полугодие, средна температура на топлото полугодие и средногодишна сума на валежите) за района на Варненско-Белославския езерен комплекс през последните 6200 години чрез спорово-поленов анализ и с използването на метода на съвременните аналози. Анализирано е съдържанието на спори и полен в седиментите от Сондаж 3, прокаран в близост до северния бряг на Варненското езеро в райо-на на кея Трансстрой при дълбочина на водния слой 6 m. Дължината на сондажа е 995 cm, ...

Wave-influenced deltas are shaped by wave-driven transport of river-borne sediments. Near the riv... more Wave-influenced deltas are shaped by wave-driven transport of river-borne sediments. Near the river mouth, combined jet and wave dynamics, along with morphodynamic feedbacks, control the fraction of sediment transported alongshore by littoral currents that can bypass the river channel. Here we study how different bypassing rates influence large-scale delta evolution and examine the effect of waves and the river mouth jet on alongshore sediment bypassing. First, we use a modified version of the Coastline Evolution Model (CEM) to look at the effects of wave climate, fluvial sediment supply, and alongshore sediment bypassing rates on channel orientation. This modified version of CEM progrades the channel in a direction perpendicular to the local shoreline orientation at the river mouth, allowing feedbacks between alongshore sediment transport and fluvial sediment delivery to steer the river channel. Additionally, we allow a prescribed fraction of littoral sediment to bypass the river m...

Journal of Geophysical Research: Biogeosciences

Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are analyzed in different lakes of the M... more Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are analyzed in different lakes of the Mackenzie (Canadian Arctic) and Kolyma (Siberian Arctic) River basins to evaluate their sources and the implications for brGDGT-based paleothermometry in high latitude lakes. Comparison of brGDGT distributions and concentrations in the lakes with those in river suspended particulate matter (SPM), riverbank sediments, and permafrost material indicates that brGDGTs in Arctic lake sediments have mixed sources. In contrast to global observations, distributional offsets between brGDGTs in Arctic lakes and elsewhere in the catchment are minor, likely due to the extreme seasonality and short window of biological production at high latitudes. Consequently, both soil and lake calibrated brGDGT-based temperature proxies return sensible temperature estimates, even though the mean air temperature (MAT) in the Arctic is below the calibration range. The original soil-calibrated MBT-CBT (methylation of ...

Ключови думи: полен, климатични реконструкции, палеоекология, съвременен калибрационен сет.

ABSTRACT Hydrate Ridge, a gas hydrate-bearing thrust anticline located on the lower slope of the ... more ABSTRACT Hydrate Ridge, a gas hydrate-bearing thrust anticline located on the lower slope of the Cascadia accretionary wedge, was the site of Ocean Drilling Program (ODP) Leg 204 drilling in 2002. Drill sites were focused along transects over the southern summit of the ridge and into the adjoining eastern slope basin. 3-D seismic data, obtained in 2000, provide the high-resolution structural and stratigraphic context for each of the drill sites and detailed lithologic description, multi-sensor track (MST) logging, and logging while drilling (LWD) data characterize the sedimentology of the recovered cores and of the in situ stratigraphy. Sedimentological description and interpretation of the cores reveals a history of sedimentation dominated by turbidites and occasional debris flows, as well as intermittent volcanic glass emplacement, either as air fall ash or detrital glass in turbidites. Downhole variability in the micropaleontology data and abrupt changes in stratal geometry in the 3-D seismic data also suggest a history punctuated by both depositional hiatuses and erosion. Post-depositional compaction, biologic activity, deformation, dewatering, and diagenesis have overprinted the stratigraphy with bioturbation, iron-sulfide and authigenic carbonate precipitation, glauconite occurrences, and gas hydrate. Turbidite sands and silts and zones with concentrated volcanic glass shards provide the greatest porosity in the section and commonly contain overpressured gas and gas hydrate. Gas hydrate was also observed in the microfractures of some clay-rich sediments as well. Initial stratigraphic correlation across sites is encouraging, however, further integration of the lithologic, MST, LWD, and 3-D seismic data across the region will be presented and help to better decipher the geologic history of this region and to quantify the stratigraphic, structural, and sedimentological framework within which the gas hydrate system on Hydrate Ridge exists.

NCK-days 2012 : Crossing borders in coastal research : jubilee conference proceedings, 2012