Reduced sediment accumulation rate enhances early marine diagenesis of periplatform sediments

Increased sediment loads over coral reefs in Saint Lucia in relation to land use change in contributing watersheds

Sediments of Ocean Drilling Program's hole 625B (northeastern Gulf of Mexico, south flank of DeSoto Canyon) represent a virtually continuous record of Pleistocene paleoceanographic development associated with the Florida Loop Current. Using relative abundances of the Globorotalia menardii complex. G. inflata, and left-coiling and right-coiling varieties of G. truncatulinoides, the authors have subdivided the pre-zone W Pleistocene of hole 625B into 17 subzones, resulting in an average duration of approximately 100,000 yr per unit. This is substantially better resolution than for the previous workers' zones, which are based on the G. menardii complex alone (average duration {approx} 300,000 yr per unit). The subzones can be recognized in Eureka Core E67135 from the north margin of DeSoto Canyon, as well as in cores 502B (Colombia Basin, Caribbean Sea) and V16205 (tropical Atlantic). The Globorotalia inflata and G. truncatulinoides parts of the biostratigraphic signals are damped in the tropical cores (V16205 and 502B) but amplified in the subtropical Gulf of Mexico (625B). Subzonal boundaries are largely coeval between sites based on graphic correlation of paleomagnetic, biostratigraphic, and oxygen isotope datums. The subzonation reveals relatively subtle changes in sediment accumulation rate not readily apparent from visual inspection of isotopic stages. In some cases,more » accumulation rate changes correspond to core breaks. The subzonal scheme is useful in identifying biostratigraphic tops whose position is affected by changes in sediment accumulation rate.« less

Research Article| May 01, 2013 Synchronizing Holocene lacustrine and marine sediment records using paleomagnetic secular variation Sædís Ólafsdóttir; Sædís Ólafsdóttir 1Institute of Earth Sciences, University of Iceland, IS-101 Reykjavík, Iceland Search for other works by this author on: GSW Google Scholar Áslaug Geirsdóttir; Áslaug Geirsdóttir 1Institute of Earth Sciences, University of Iceland, IS-101 Reykjavík, Iceland Search for other works by this author on: GSW Google Scholar Gifford H. Miller; Gifford H. Miller 1Institute of Earth Sciences, University of Iceland, IS-101 Reykjavík, Iceland2Institute of Arctic and Alpine Research, and Department of Geology, University of Colorado, Boulder, Colorado 80303, USA Search for other works by this author on: GSW Google Scholar Joseph S. Stoner; Joseph S. Stoner 3College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA Search for other works by this author on: GSW Google Scholar James E.T. Channell James E.T. Channell 4Department of Geological Sciences, University of Florida, Gainesville, Florida 32611, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Sædís Ólafsdóttir 1Institute of Earth Sciences, University of Iceland, IS-101 Reykjavík, Iceland Áslaug Geirsdóttir 1Institute of Earth Sciences, University of Iceland, IS-101 Reykjavík, Iceland Gifford H. Miller 1Institute of Earth Sciences, University of Iceland, IS-101 Reykjavík, Iceland2Institute of Arctic and Alpine Research, and Department of Geology, University of Colorado, Boulder, Colorado 80303, USA Joseph S. Stoner 3College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA James E.T. Channell 4Department of Geological Sciences, University of Florida, Gainesville, Florida 32611, USA Publisher: Geological Society of America Received: 13 Aug 2012 Revision Received: 15 Nov 2012 Accepted: 20 Nov 2012 First Online: 09 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 © 2013 Geological Society of America Geology (2013) 41 (5): 535–538. https://doi.org/10.1130/G33946.1 Article history Received: 13 Aug 2012 Revision Received: 15 Nov 2012 Accepted: 20 Nov 2012 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Sædís Ólafsdóttir, Áslaug Geirsdóttir, Gifford H. Miller, Joseph S. Stoner, James E.T. Channell; Synchronizing Holocene lacustrine and marine sediment records using paleomagnetic secular variation. Geology 2013;; 41 (5): 535–538. doi: https://doi.org/10.1130/G33946.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract High sediment accumulation rates in lacustrine and shallow-marine archives around Iceland offer the potential to compare high-resolution paleoclimatic reconstructions from terrestrial and marine archives; however, direct comparisons are hampered by difficulties in stratigraphic correlation and in deriving accurate age models for lacustrine archives. Icelandic paleomagnetic secular variation (PSV) has the potential to synchronize these records. Here we compare Holocene PSV from a well-dated marine core on the North Iceland shelf with PSV from two lacustrine archives with comparable sediment-accumulation rates, HVT03–1A, a glacier-dominated lake, and HAK03–1B, in a nonglacial catchment. Geochemically characterized tephra layers combined with unique high-amplitude structures in the PSV records provide secure tie points every ∼200 yr. Once the records are synchronized, the chronology from the marine core can be reliably transferred to the two lacustrine records. The resultant lacustrine age models reveal large changes in sediment accumulation rate at submillennial scales that escape detection in conventional age models with independent dates every ∼1 k.y. Sediment accumulation rate changes occur at similar times in both lakes, despite very different catchment properties. Low and regular accumulation rates during the Holocene thermal maximum suggest regionally stable, vegetated catchments, followed by a stepped landscape destabilization during the transition into neoglaciation, culminating with maximum sedimentation rates during the Little Ice Age. PSV allows synchronization between multiple records from nearby marine and lacustrine archives, providing improved age models and a means of assessing leads and lags between marine and terrestrial environments. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Using sediment accumulation rates in floodplain paleochannel lakes to reconstruct climate-flood relationships on the lower Ohio River

On the continental shelves of the northern Mediterranean basin, the late Holocene highstand systems tract (HST) prograded un- der the influence of major rivers, after the attainment of the present sea-level highstand (about 5.5 cal kyr BP). On the Adriatic shelf, the thickness distribution of the late Holocene HST reflects the location of major deltas on the western side of the basin and the geostrophic cir- culation, which prevents a more uniform sediment dispersal toward the center of the basin. Very high sediment accumulation rates (1 to 10 cm/year) resulted in the construction of a HST depocenter up to 35 m thick. This shore-parallel depocenter is affected by failure of limited displacement over as much as 40% of its extent. Gas impregnation is common in the topset region and occurs at very shallow levels (a few meters) below the sea floor. Five areas are characterized by a variety of sea-floor and subsurface crenulations. Although locally some of these crenulations have an intriguingly regular geometry, sediment failure is the most plausible mechanism for their formation. Sediment failure better explains the large variety of geometries that characterizes the coastal mud prism of the late Holocene HST. Furthermore, we observe that these crenulations occur only where the downlap surface at the base of the HST is disrupted and affected by geometries that are con- sistent with fluid escape processes. This relationship suggests that the basal surface acts as a weak layer for sediment failure. Failure occurred in variable water depths from the northern slope of the modern Po prodelta (10-20 m water depth) to the narrow shelf offshore Bari (40-110 m water depth). In all these areas the proximal part of the HST prodelta wedge is intensely gas-charged. The thickness and age of the sediment sections affected by failure are slightly differ- ent from place to place but appear everywhere younger than 5.5 cal kyr BP. Where failure affects the entire HST the detachment occurs on the downlap surface at its base. Failure geometries characterize the head region whereas compressional features, such as pressure ridges and mud diapirs, dominate in the toe region, ranging in depth between 70 and 110 m. Where failure is limited to the upper few meters of the HST, there is a clear lithologic change (decrease in carbonate fraction and grain size) across the basal surface. This lithological change reflects a switch in sediment supply from local Apennine rivers (below) to Po- derived mud; this change occurred at the onset of the Little Ice Age, documenting the indirect control of short-term climate change and hu- man impact on sediment architecture. The deformations affecting the late Holocene HST in the various areas show differences in internal geometry, but appear everywhere to be characterized by limited downward displacement and can be attri- buted to shear-dominated retrogressive failure. It is suggested that some degree of consolidation occurred immediately after mobilization, possibly induced by the escape of fluids. Nowhere has failure evolved into disintegration and flow, likely because the type of cyclic loading that triggered it was not prolonged over a long enough interval. Short-lived radionuclides in the uppermost stratigraphic layers, which postdate the failure in the area offshore Ortona, allowed us to quantify systematic changes in sediment accumulation rates as a func- tion of the underlying deformed sea floor. In areas of wavy sea floor, troughs show sediment accumulation rates of greater than 16 mm/yr, a figure that is fourfold the rate measured on the flanks of the troughs.

Deciphering relationships between the Nicobar and Bengal submarine fans, Indian Ocean

Sediments of Ocean Drilling Program's hole 625B (northeast Gulf of Mexico) represent a virtually continuous record of Pleistocene paleoceanographic development associated with the Florida Loop Current. Utilizing relative abundances of the Globorotalia menardii complex and G. inflata, supplemented by left‐ and right‐coiling varieties of G. truncatulinoides, we have subdivided the prezone W Pleistocene of core 625B into 17 subzones, resulting in an average duration of approximately 100,000 years per unit. This is substantially better resolution than for the Ericson and Wollin [1968] zones alone (average duration ∼300,000 years per unit). The subzones recognized in core 625B can be recognized in Eureka core E67‐135 (northeast Gulf of Mexico) and extended to cores 502B (Colombia Basin, Caribbean Sea) and V16‐205 (tropical Atlantic). Subzonal boundaries are largely coeval between sites based on graphic correlation of paleomagnetic, biostratigraphic, and oxygen isotope datums. The subzonation reveals relatively abrupt changes in sediment accumulation rate which probably decrease the signal to noise ratio in spectral analysis and tuning of oxygen isotope curves. In some cases, accumulation rate changes correspond to core breaks. Abundances of Globorotalia inflata and G. truncatulinoides are damped in the tropical cores (V16‐205 and 502B) but amplified in the subtropical Gulf of Mexico (625B), an observation which is consistent with previously published biogeographic models.

Relationship between δ15N values of bulk sediments and total organic carbon concentration in response to orbital-scale biogenic opal production in the Bering slope area over the last 600 kyrs

This study was undertaken to determine whether recent anthropogenic changes in the Nile basin have affected the modern rate of sediment accumulation in the Nile delta. Excess 210Pb, 137Cs, and 239,240Pu were used to develop a sediment chronology for a core from central Manzala lagoon, the delta sector which has had the highest average rate of sediment accumulation during the Holocene (to about 0.7 cm year–1). Excess 210Pb was detected in the top 32 cm of the core, yielding an accumulation rate of 1.2 cm year–1, higher than the mean rate for the Holocene. A high 137Cs/239,240Pu ratio requires a reactor source (possibly Chernobyl) for these nuclides. Low concentrations of excess 210Pb and weapons-fallout nuclides precluded recognition of changes in sediment accumulation rate in Manzala lagoon during this century and may limit the use of tracer radionuclides for modern sediment chronology in the Nile delta.

Stable isotope ratios of oxygen (δ18O) and carbon (δ13C) in tests ofGloborotalia menardii from samples at 25 cm intervals of top 900 cm cores, representing different thicknesses of the Pleistocene, from DSDP Sites 219, 220 and 241 in the northern Indian Ocean have been measured. Based on the δ18O stratigraphy, glacial and interglacial phases during the Pleistocene have been recognized, which are in good agreement with the standard Quaternary planktonic foraminiferal/climatic zones i.e., Ericson zones at these sites, based onG. menardii abundances. The GIA (glacial interglacial amplitude) at Sites 241, 219 and 220 are of the order of 1·2, 1·4 and 1·9‰ respectively. The last glacial and interglacial maxima (18 ka BP and 125 ka BP respectively) could be identified in DSDP Cores 241, and 219 with some precision. ‘Isotopic ages’ could be assigned to the different levels of these core sections based on the correlation of δ18O record from these sites with the SPECMAP record (Imbrieet al 1984). Changes in sediment accumulation rates at different levels of the Pleistocene have been worked out on the basis of changes in oxygen isotopic ratio.Oscillations in δ13C stratigraphy at Site 241 indicated southwest monsoon induced increase in upwelling and productivity during warmer periods. At Sites 219 and 220, variations in the δ13C record were due to the mixing of bottom water.

Changes in sediment accumulation rate (SAR, cm/ky) for fifteen AMS 14C dated late Quaternary sites from along the NE margin of Canada (between 66° and 54° N) are examined. These 15 cores cover the last deglacial cycle of sediment input from the decaying Laurentide Ice Sheet, and subsequent postglacial marine sedimentation on these arctic and subarctic shelves and basins. It is shown that the spatial and temporal variability of the 15 SAR time series do not simply parallel the known glacial chronology. Deglaciation of the shelves initially occurred after Heinrich event 1 (H-1, 14.5 ka; all dates are in 14C yr). Subsequently, there were major ice advances during the Younger Dryas (YD/H-0, 10-11 ka) and the Noble Inlet glacial events (8.6 ka), with final collapse of the ice sheet ca. 8.0 ka. A total of 73 radiocarbon dates were used, which led to 58 SAR estimates. The median SAR is 69 cm/ky; however, the distribution is strongly positively skewed because of short-lived intervals of very high SAR ( 5000 cm/ky, ca. 5000 kg m-2 ky-1). On the Labrador Shelf, high SAR are associated with ice retreat from the Noble Inlet maximum (< 8.6 ka), whereas on the SE Baffin Shelf there is little response in the sediment system to this event. Conversely, during the Younger Dryas/Heinrich-0 (YD/H-0) event, high SARs occur on the SE Baffin Shelf, but along the Labrador Shelf the interval 10-11 ka is marked by modest SARS. Both the 11-10 and 8.6-8 ka rapid sediment accumulation events are marked by considerable increases in the detrital carbonate content, hence bear similarities to the major Heinrich events in the NW Labrador Sea. These unexpected spatial and temporal differences in sediment deposition probably reflect changes in sediment transport trajectories associated with differences in ice (glacial or sea-ice) extent, and atmospheric/oceanic circulations.

Holocene evolution of the wave-dominated embayed Moruya coastline, southeastern Australia: Sediment sources, transport rates and alongshore interconnectivity

&amp;lt;p&amp;gt;Sediment budgets on wave-dominated coastlines are important in understanding shoreline behaviour. Coastal sediment compartments provide a means to investigate sediment budgets over a range of time and space scales. This study reconstructs the sediment budget over the mid- to late- Holocene for a secondary coastal compartment on the New South Wales (NSW) south coast ~26 km in length and containing five adjacent but discrete barriers: Barlings Beach, Broulee Beach, Bengello Beach, Moruya Heads Beach and Pedro Beach. Building upon existing morphostratigraphic studies in this region, a new set of Optically Stimulated Luminescence (OSL) ages are reported for foredune ridge successions at previously un-dated sites. Additional Ground Penetrating Radar (GPR) transects complement earlier stratigraphic data, and topographic and bathymetric LiDAR datasets capture the morphology of subaerial coastal deposits and the inner shelf. The results demonstrate two different sediment sources promoting shoreline progradation and coastal barrier construction. A quartz-rich sand, transported onshore from the shoreface as it evolved towards equilibrium, dominates the barrier sequences. Skeletal carbonate sand augmented the quartz sand supply for the northern Barlings and Broulee beaches after ~3000 years ago. Shoreline progradation at Bengello Beach was steady throughout the mid-to late- Holocene. Bengello Beach contains the largest volume of Holocene sand and accreted at an average rate of 3.1 m&amp;lt;sup&amp;gt;3&amp;lt;/sup&amp;gt;/m/yr (for the current shoreline length). Changes in sediment accumulation rate has occurred for the other barrier systems as their shorelines prograded resulting in changes to their alongshore interconnectivity. Rapid infilling of the Pedro Beach embayment by ~4000 years ago initiated headland bypassing northwards to Moruya Heads Beach which only then commenced progradation. In contrast, as Broulee and Bengello Beaches prograded, a tombolo formed in the lee of Broulee Headland which restricted northward sand drift into the Broulee embayment. As these once continuous shorelines became two, a marked increase in skeletal carbonate content at Broulee occurred attesting to shoreline separation and independence of sediment budget. This study emphasises the importance of quantifying the long-term temporal variability in sediment budget and embayment interconnectivity in order to better understand shoreline response to contemporary anthropogenic influences and changing boundary conditions such as sea level and wave climate.&amp;lt;/p&amp;gt;

Although interbedded limestone–marl couplets in many hemipelagic and pelagic deposits have been commonly attributed to orbital-driven climate cycles, the driving mechanisms of these couplets remain largely controversial. This situation arises from the fact that detailed sedimentologic and petrographic facies characteristics of these fine-grained deposits have rarely been examined closely. In this study we conduct an integrated sedimentologic and petrographic analysis to disentangle causes of the limestone–marl bedding couplets in the Cenomanian–Turonian Bridge Creek Limestone Member (BCL) of the Greenhorn Formation using cores and outcrop near Pueblo, Colorado. By integrating existing geochemical datasets, each of the three general lithologies in the BCL including limestone, marl, and calcareous mudstone can be divided into two facies, a more bioturbated vs. a more laminated facies, in addition to bentonite beds. The variability in sedimentary, bioturbation, and petrographic characteristics of different sedimentary facies types, as well as constraints from the existing orbital time scale, in the BCL indicate changes in sediment accumulation rate or the amount of time recorded by different facies—the limestone, marl, and calcareous facies are interpreted to reflect increasing sedimentation rate. The sedimentary and petrographic facies variations, including but not limited to lithological alternations, in the BCL are interpreted to result from the combined influence of various processes such as bottom currents, bioturbation, early diagenesis, and episodic volcanic input, with some of the above-mentioned processes likely modulated by short-term relative changes in sea level. Results of this study highlight the need for detailed sedimentologic and petrographic studies and consideration of short-term changes in sedimentation rate to fully resolve the causes of the apparent limestone–marl bedding couplets and reliably reconstruct short-term changes in depositional and environmental conditions from the BCL and other similar successions.

Abstract. The systematic bioturbation of single particles (such as foraminifera) within deep-sea sediment archives leads to the apparent smoothing of any temporal signal as recorded by the downcore, discrete-depth mean signal. This smoothing is the result of the systematic mixing of particles from a wide range of depositional ages into the same discrete-depth interval. Previous sediment models that simulate bioturbation have specifically produced an output in the form of a downcore, discrete-depth mean signal. However, palaeoceanographers analysing the distribution of single foraminifera specimens from sediment core intervals would be assisted by a model that specifically evaluates the effect of bioturbation upon single specimens. Taking advantage of advances in computer memory, the single-specimen SEdiment AccuMUlation Simulator (SEAMUS) was created for MATLAB and Octave, allowing for the simulation of large arrays of single specimens. This model allows researchers to analyse the post-bioturbation age heterogeneity of single specimens contained within discrete-depth sediment core intervals and how this heterogeneity is influenced by changes in sediment accumulation rate (SAR), bioturbation depth (BD) and species abundance. The simulation also assigns a realistic 14C activity to each specimen, by considering the dynamic Δ14C history of the Earth and temporal changes in reservoir age. This approach allows for the quantification of possible significant artefacts arising when 14C-dating multi-specimen samples with heterogeneous 14C activity. Users may also assign additional desired carrier signals to single specimens (stable isotopes, trace elements, temperature, etc.) and consider a second species with an independent abundance. Finally, the model can simulate a virtual palaeoceanographer by randomly picking whole specimens (whereby the user can set the percentage of older, “broken” specimens) of a prescribed sample size from discrete depths, after which virtual laboratory 14C dating and 14C calibration is carried out within the model. The SEAMUS bioturbation model can ultimately be combined with other models (proxy and ecological models) to produce a full climate-to-sediment model workflow, thus shedding light on the total uncertainty involved in palaeoclimate reconstructions based on sediment archives.