bluuebunny/crossref_metadata_2025_split huggingface dataset:
Is the oceanic Moho a serpentinization front?
Authors: Minshull T. A. , Muller M. R. , Robinson C. J. , White R. S. , Bickle M. J. 
Published: April 2008

Abstract

Our main constraint on the volume of melt coming out of the mantle at mid-ocean ridges is the thickness of oceanic crust determined by seismic methods. The recovery of serpentinized peridotites in the rift valleys of slow-spreading ridges has led recently to a revival of the suggestion that the seismically defined lower oceanic crust may include partially serpentinized peridotite. Both seismic and geochemical data from a recent experiment on the very slow-spreading Southwest Indian Ridge indicate that, away from the fracture zone valley, a total melt thickness of ∼4 km is being generated. However, in one region, around Ocean Drilling Program (ODP) hole 735B, where ∼2 km of the upper crust is estimated to have been removed, the seismic data indicate a crustal thickness of 5 km. Here, the seismically determined Moho is interpreted as a serpentinization front. Serpentinization is facilitated if there are readily available pathways for seawater to reach the upper mantle, and if the upper mantle is cool. These conditions frequently are met at fracture zones on slow-spreading ridges, in the ocean-continent transition zone at non-volcanic rifted margins, and at the axes of extinct rifts. In all these locations, serpentinization sufficient to lower mantle velocities to normal oceanic crustal velocities does not reach a depth of more than 5 km beneath the seabed, and commonly normal mantle velocities of ∼8 km s
−1
are also reached at shallow depths. Therefore, although in some anomalous locations the seismically defined crustal thickness can only be used as an upper limit on the melt supply, for normal oceanic crust, where the seismically defined crustal thickness is ∼7 km, the Moho is probably not a serpentinization front, but rather a petrological boundary between mafic rocks above and ultramafic rocks below.
Precipitation of hydrothermal sediments on the active TAG mound: implications for ochre formation
Authors: Goulding H. C. , Mills R. A. , Nesbitt R. W. 
Published: April 2008

Abstract

Submersible and drilling studies of the active TAG hydrothermal mound (26°N, Mid-Atlantic Ridge) have led to new models of fluid flow and evolution within an active mineral deposit which has implications for Fe-oxide and ochre precipitation. Metalliferous sediments from the top of the hydrothermal mound accumulate from a combination of processes including slumping and oxidation of chimney material and
in situ
precipitation of low-temperature phases from fluids that percolate through the mound. Geochemical proxies of hydrothermal processes allow identification of the mode of formation of one sediment core from the southeastern periphery of the TAG mound. The Fe rich sediment is capped with a ∼5 cm thick kaolinite, illite, chlorite, smectite layer which formed from alteration and replacement of basalt and diagenetic reactions within the hydrothermal sediment. Underlying this layer is a ∼10 cm thick zone of Mn, Cu, Zn and Pb enrichment which is controlled by the sharp redox gradients in the core. The base of the core is characterized by Mn-poor, Fe-rich oxide that is dominated by goethite, haematite and amorphous Fe oxides equivalent to ochreous and gossan material. Rare earth element (REE) patterns from the different layers within the core allow interpretation of the modes of formation of sediment in the light of existing fluid flow models for TAG. The basal layer is dominated by
in situ
precipitation of Fe oxide phases from evolved fluids that result from significant within-mound anhydrite precipitation. The REE data for the upper part of the core demonstrate mixing with sea water which provides the oxidizing conditions for Mn precipitation along with Cu, Zn and Pb enrichment from the evolved fluid. Sea water ingress results in higher V/Fe and P/Fe ratios in the upper part of the core but no enhanced U/Fe ratio. The uppermost clay-rich layer hosts the majority of the REE inventory for the core and the significant positive Eu anomaly indicates recrystallisation of the phyllosilicate phases from the ochreous material during diagenesis. REE data from land-based ochre and gossan sediments demonstrate that the TAG model may be applicable to a wide variety of sites throughout the geological record.
Oxygen-isotope correlation of marine terraces and uplift of the Mesa hills, Santa Barbara, California, USA
Authors: Trecker M. A. , Gurrola L. D. , Keller E. A. 
Published: April 2008

Abstract

Resolving the chronology of marine terrace sequences is critical for determining uplift rates along tectonically active coastlines. Unfortunately, lack of suitable dating materials often makes this difficult. We present here oxygen isotopic data from 21 shells of
Olivella biplicata
from four marine terraces in the Santa Barbara and Ventura area located in southern California, USA. Terraces U-series dated at 47 ± 0.5 ka
BP
at Isla Vista and 70 ± 2 ka
BP
at Santa Barbara City College (SBCC) provide age control for the isotopic data. Shells from the Isla Vista and SBCC terraces yield average values of 1.117‰ and 0.627‰. respectively, and shells from a non-U-series dated terrace at Punta Gorda and an undated terrace at Santa Barbara Point yield average values of 1.010‰ and 0.751‰, respectively. The data indicate that stable oxygen isotopic signatures preserved in marine terrace molluscs provide a useful tool for correlating undated terraces with those of known age. Furthermore, we are able to correlate samples collected from offset fragments of the Punta Gorda terrace on either side of the Red Mountain fault, demonstrating the utility of this method for correlating terraces across structural features. Using oxygen isotopic data coupled with the U-series dated wave-cut platform at SBCC we calculate a rate of uplift ranging from 0.62 ± 0.03 mm/year (where the elevation of the first emergent terrace is 41 m) to 0.54 ± 0.05 mm/year (where the elevation of the first emergent terrace is 36 m) for marine terrace flights preserved on the Mesa hills anticline located in the city of Santa Barbara, California.
Deformation of the 125 ka marine terrace in Italy: tectonic implications
Authors: Bordoni Paola , Valensise Gianluca 
Published: April 2008

Abstract
In peninsular Italy, marine terraces and shorelines created during oxygen-isotope substage 5e, known historically as the Tyrrhenian highstand, provide a reliable and homogeneous datum of vertical motions during the past 125 000 years. Published accounts of 121 locations on the Tyrrhenian inner edge were reinterpreted and used to calculate both local and regional uplift rates. The data show arching of southern Italy between the Tyrrhenian and the Adriatic coasts and of the Calabrian Arc between the Sangineto and the Longi-Taormina tectonic lineaments at rates of up to 1.2 mm/year for the past 125 000 years. They also suggest that the present configuration of the southern Apennines is the product of post-Early Pleistocene regional uplift superimposed on Tortonian to Early Pleistocene thrusting. Uplift patterns are characterized by different wavelengths in different geodynamic settings, suggesting a close link with the depth of the causative tectonic sources.
Archaeological evidence for vertical movement on the continental shelf during the Palaeolithic, Neolithic and Bronze Age periods
Authors: Flemming N. C. 
Published: April 2008

Abstract
Submarine archaeological sites of human occupation on the continental shelf provide evidence of palaeo-shorelines during the last 50 000 years, with possibly longer periods of accessible data. Sites are widely distributed globally, and provide a rich source of peripheral information on landscapes, climate, water supply, sediment transport, and soil types, which are relevant to coastal tectonics and processes, in addition to location, elevation, and date. More than 500 sites have been discovered world-wide where there are the remains of human occupation under the sea. Artefacts embedded in a few metres of sediments can survive multiple marine transgression, given local topography that creates suitable wave and current conditions. The raw data have been analysed to separate glacial eustatic fluctuations of global sea level and local or regional tectonic processes. The number of sites in the Mediterranean permits the detection of regional vertical tectonic displacement with a spatial resolution of a few tens of kilometres in many regions. In other parts of the world the density of sites is not yet sufficient to achieve this, but indicators of vertical movements, or lack of vertical movement, provide valuable point data. Continuing discovery of new sites indicates that the technique will provide data with improved spatial resolution, and outside the Americas, over a timescale extending to hundreds of millennia, and possibly one million years
Late Quaternary tectonism along the Pacific coast of the Californias: a contrast in style
Authors: Orme Antony R. 
Published: April 2008

AbstractMarine terraces and associated features are examined along 1500 km of coast at the seaward margin of that part of the North American plate that has been captured by the Pacific plate. This coast embraces parts of three morphotectonic provinces, each with its own distinctive tectonic style, namely the southern Coast Ranges, western Transverse Ranges, and northern Peninsular Ranges. Based primarily on the 125 ka shoreline, four magnitudes of late Quaternary deformation are recognized: (1) high uplift rates exceeding 1.0 m per 1000 years; (2) moderate uplift rates between 1.0 and 0.1 m per 1000 years; (3) low uplift rates less than 0.1 m per 1000 years; and (4) variable net subsidence. The highest rates of uplift and subsidence are associated with the intense fold-thrust tectonics of the western Transverse Ranges nearest the Big Bend in the San Andreas fault, and diminish in magnitude to east and west. Moderate uplift rates occur in both the southern Coast Ranges and the northern Peninsular Ranges adjacent to the western Transverse Ranges, commonly associated with block uplift and subsidence between high-angle reverse faults within a broader strike-slip scenario. This suggests that compression and transpression are significant features of these areas and that the continued rotation and relative westward motion of the western Transverse Ranges, within the broader context of shear distributed across the San Andreas fault system, continue to have an impact on regions immediately to the north and south. Uplift diminishes with distance from the Transverse Ranges and is low for Baja California south of Punta Banda. The style of late Quaternary deformation is similar to that defined by earlier Quaternary marine limits, but intensity varies, most notably in the western Transverse Ranges.
Slip parameters for the Rann of Kachchh, India, 16 June 1819, earthquake, quantified from contemporary accounts
Authors: Bilham Roger 
Published: April 2008

Abstract

The 16 June 1819 Rann of Kachchh earthquake was felt throughout much of India. Although significant vertical movements of the ground caused flooding of regions near sea level, damming of a distributary of the Indus river, widespread liquefaction, and a local tsunami, the geometry of the fault plane has hitherto remained obscure. Dislocation models based on deformation data gathered 7 and 25 years after the earthquake suggest that a near-surface reverse fault slipped locally more than 11 m, and that rupture extended at least 80 km along strike. Estimates of maximum uplift and depression during the earthquake yield similar, but not identical, solutions to those based solely on a levelling profile across the zone of uplift, known as the Allah Bund. The inferred 50–70°N-dipping fault plane beneath the Allah Bund is unfavourably steep for reverse faulting, and its down-dip width (6–10 km) short for slip exceeding 10 m. Some forms of listric fault geometry are also consistent with the observed surface deformation fields, with increased fault width (15–25 km) and similar coseismic slip. A geometric moment magnitude of
M
= 7.7 ± 0.2 is obtained from the inferred slip parameters, assuming uniform along-strike slip, consistent with a magnitude estimated empirically from the intensity distribution. Although a recurrence of the Kachchh earthquake is unlikely soon because of low inferred contractional strain rates in the region, the westward continuation of the Kachchh rift zone could host future ruptures contiguous with the 1819 event, with important consequences for the city of Karachi.
Late Holocene coastal tectonics at Falasarna, western Crete: a sedimentary study
Authors: Dominey-Howes Dale , Dawson Alastair , Smith David 
Published: April 2008

Abstract

The late Holocene sedimentary record of Falasarna Harbour, western Crete, includes detailed evidence of tsunamis and serves as an independent dataset to evaluate the magnitude and timing of coastal tectonic movements in an area affected by contrasting tectonic regimes. Analysis of a foraminiferal assemblage makes it possible to identify suites of tsunami-deposited sediments within normal sedimentary sequences. The palaeo-environmental record is then complemented with a sequence of raised fossil marine notches. The transitional boundary between marine and terrestrial sedimentation indicates tectonic uplift at
c.
ad
63–75 ± 90 radiocarbon years
bp
, which is in conflict with previously published interpretations. No sedimentary evidence can be found for a tsunami believed to be associated with a large uplift event during
ad
365.
Possible tsunami deposits from the 1855 earthquake, North Island, New Zealand
Authors: Goff James R. , Crozier Michael , Sutherland Venus , Cochran Ursula , Shane Phil 
Published: April 2008

Abstract

A series of three fining-upward sequences from deposits in the Okourewa Stream bank on the south coast of the North Island, New Zealand, investigated by grain-size, diatom, radiocarbon, geochemical and macrofaunal analyses have been tentatively interpreted as the products of a tsunami. The proposed event consisted of three separate waves (the second being the largest) generated by a surface rupture of a local fault. Changes in diatom assemblages and the presence of marine shells, pumice, and beach pebbles may represent a tsunami advancing inshore over beach, freshwater channel, and coastal wetland environments. Deposition occurred between
ad
500 and 1890. The event in question may have currently the
ad
1855 rupture of the West Wairarapa fault.
A Quaternary proximal foreland ramp and its continental fringe, Arabian Gulf, UAE
Authors: Kirkham A. 
Published: April 2008

Abstract
During Quaternary time, the southern flank of the Arabian Gulf can be considered as a classic, foreland basin ramp setting in which the sedimentological processes operating changed drastically along strike. The combined effects of sea-level fluctuations and wind, which have dominated the Quaternary coastal morphology and coastal evolution, are observed at a resolution rarely achieved in the stratigraphic record of palaeoramp sequences. The facies distributions and diagenetic characteristics of the relatively thin Pleistocene-Holocene strata provide valuable insights into the complex stratigraphy that can develop within an inner ramp and its continental fringe.
In the UAE, Pleistocene sediments comprising mainly aeolian dunes overlie a deeply eroded topography of Upper Miocene strata. These sediments become increasingly carbonate rich and calcite cemented northwards towards the coast. Here they experienced severe aeolian deflation due to the later marine flooding of the aeolian sources on the formerly exposed areas lower down the ramp profile, and wind erosion along the coastal area because of a lack of sediment supply. The antecedent topography of Miocene and Pleistocene escarpments, mesas, islands, cemented seif dunes and coastal deflationary ‘Stokes surfaces’ provided a highly varied Holocene ramp margin undergoing coastal progradation (with offlap) during the 1–2 m relative sea-level fall of late Holocene time. Since then, marine carbonate deposition and evaporite diagenesis have dominated the Holocene sequence, but it is aeolian processes that largely control their ultimate distribution within the constraints of the contemporaneous sea-levels. Longshore currents, lateral and leeward accretion, infilling of stranded lagoons and deflation on a massive scale testify to the crucial role of wind in the development of this proximal ramp. The Holocene aeolian sediments, though extensive, are very different in character from the Pleistocene sediments.
Two generations of Holocene supratidal anhydrites are recognized. The earlier one was partly transgressive, but the later one is regressive. In addition to the present-day oolith factories on the ebb tidal deltas at the seaward ends of tidal channels between the barrier islands of central Abu Dhabi, oolith factories also exist on exposed beaches and tidal embayments of western Abu Dhabi. They also occurred within Pleistocene and Holocene embayments. Flat-topped and sometimes shingled hardgrounds representing isochronous events extend over very large areas. So also do commonly observed iron oxide bands formed beneath the sabkha surfaces.
Carbonate sedimentation during early foreland basin subsidence: the Eocene succession of the French Alps
Authors: Sinclair H. D. , Sayer Z. R. , Tucker M. E. 
Published: April 2008

Abstract
The Eocene Infranummulitic Formation and Nummulitic Limestones of the external chains of the French Alps in Haute Savoie and Alpes Maritimes unconformably overlie the Mesozoic passive margin succession, and were deposited during the onset of subsidence of the underfilled Alpine foreland basin. The Infranummulitic Formation represents detrital deposition in localized structural lows in braided fluvial, fan delta, coastal plain and lagoonal environments; the resultant facies record late lowstand and early transgressive sedimentation. A transgressive surface separates the fluvial-dominated conglomerates from lagoonal facies, and a ravinement surface separates lagoonal from ramp facies of the overlying Nummulitic Limestones. The combination of infilling of topographic lows by the Infranummulitic Formation, and the transgressive ravinement process, reduced local slope gradients inherited from the topography of the European foreland, thus encouraging the subsequent development of a low-angle carbonate ramp during continued transgression.

The Nummulitic Limestones represent highstand sedimentation on a low-energy, wave-dominated, carbonate ramp characterized by large benthic Foraminifera. The inner ramp accumulated bioclastic banks and shoals composed of peloids, calcareous red algae and
Nummulites
. The middle ramp is recorded by wackestones with a diverse assemblage of flat Foraminifera; occasional storm events generated winnowed packstones. The outer ramp is represented by mudstones and marls with a sparse biota. The Nummulitic Limestones pass upwards into hemipelagic marls.

The drowning of the Nummulitid-rich ramp is unlikely to have been caused by flexural subsidence of the foreland plate. Possible other contributing factors to the demise of the carbonate ramp were nutrient excess from the siliciclastic-rich orogenic margin to the basin, and/or glacio-eustatic sea-level rise.
Constructional dynamics for a Lower Cretaceous carbonate ramp (Gorbea Massif, north Iberia)
Authors: Gómez-Pérez Irene , Fernández-Mendiola Pedro A. , García-Mondéjar Joaquín 
Published: April 2008

Abstract
The lower Albian distally steepened Egalezaburu carbonate ramp is composed of four stacked cycles with homogeneous characteristics throughout the section. Relative sea-level changes accounted for cycle formation and changes in facies distribution. During transgression and highstands, fossiliferous boundstones were deposited on the inner ramp, and argillaceous mudstones formed on the mid- and outer ramp. Shallow marine benthic communities flourished in open, moderate-energy environments, controlled by the depth of the photic zone. During lowstands, shallow-water sedimentation shifted basinward, and skeletal grainstones dominated shallow-water environments on the mid-ramp, controlled by the depth of the wave-base. Meanwhile megabreccias accumulated locally in oversteepened sites, at the mid- to outer ramp transition. The resulting cycles differ from the inner to the mid-ramp: shallowing-upward muddy cycles formed in the inner ramp during transgressions and highstands, as deepening-upward cycles with a basal grainy unit formed on the mid-ramp during lowstand to early highstand. Photic zone and wave-base levels, controlled by relative sea-level fluctuations, were the main controls on facies types and distribution and cycle development for the Egalezaburu ramp.
Depositional facies and sequence stratigraphy of a Lower Carboniferous bryozoan-crinoidal carbonate ramp in the Illinois Basin, mid-continent USA
Authors: Lasemi Zakaria , Norby Rodney D. , Treworgy Janis D. 
Published: April 2008

Abstract
The Lower Carboniferous Fort Payne and Ullin Formations in the Illinois Basin form the transgressive and highstand systems tracts that were deposited in a carbonate ramp setting. During deposition of the Ullin Limestone, biotic communities dominated by fenestrate bryozoans and echinoderms (primarily crinoids) proliferated, possibly in response to global tectonic, biological, and oceanographic events that affected bathymetry and nutrient supply. The Fort Payne Formation consists of a dark grey-brown, siliceous and argillaceous lime mudstone in the lower part (transgressive systems tract) and a very fine-grained wackestone to packstone with rare mud mounds in the upper part (early highstand), and was deposited in an outer ramp to basinal environment. During deposition of the lower Ullin Limestone (mostly early highstand), bryozoan-crinoidal build-ups accreted both laterally and vertically into several relatively large carbonate banks, which were partly surrounded by siliceous Fort Payne sea. Bryozoans (primarily fenestrates) were especially prevalent during the late stage of bank development and formed mud-free bioherms up to 120 m thick. In places, carbonate mud mounds also formed during the early stage of bank deposition. Bioherm development declined during deposition of the upper Ullin Limestone (late highstand), and a broad, storm-dominated carbonate ramp was established that became the site for widespread deposition of bryozoan-crinoidal sandwaves. Gradual shallowing led to ooid formation at the end of Ullin deposition. This sequence was terminated by a relative rise in sea level that resulted in deposition of the transgressive facies of the lower part of the overlying Salem Limestone. The depositional style and the nature of skeletal material of the Fort Payne and Ullin Formations are similar to those of cool-water carbonates. A deep-water setting along with upwelling of cool, nutrient-rich oceanic waters may have been responsible for the proliferation of bryozoans and crinoids at this time. The deep-water setting and abundant nutrient supply also may have restricted the formation of ooids and proliferation of shallow-water calcareous organisms.