bluuebunny/crossref_metadata_2025_split huggingface dataset:
Salt diapirism with simultaneous brittle faulting and viscous flow
Authors: Poliakov Alexei N. B. , Podladchikov Yuri Yu. , Dawson Ethan Ch. , Talbot Christopher J. 
Published: April 2008

Abstract

In this paper we show for the first time how sedimentary rocks above a salt diapir can deform in either a brittle or a viscous way depending on the stress state and strain rates. Most existing models for salt tectonics incorporate only one or other of these deformation mechanisms resulting in different conclusions. Taking as an example the controversial problem of buoyant salt diapirism, we demonstrate how diapirs can grow in an overburden which may deform by both creep and faulting. We argue that salt movement can take place under low differential stresses because sediments may deform by pressure-solution creep. These zones of diffuse deformation co-exist with faults where differential stresses are high enough to reach the yield limit at which sediments fail. We demonstrate two conditions under which buoyant diapirs can cause substantial faulting in their overburden without the application of tectonic forces. Buoyant diapirs can fault overburdens with high viscosity contrast (μ
overburden
/μ
salt
> 10
2
) if the topographic relief they induce in the surface is removed by rapid erosion.
A summary of Paleogene sequence stratigraphy in northwest Europe and the North Sea
Authors: Neal J. E. 
Published: April 2008

Abstract
Sequence stratigraphic analysis of Paleogene central North Sea well-log, seismic and biostratigraphic data recognizes patterns of cyclic sedimentation seen in the physical stratigraphy and biostratigraphy. Numerous authors have documented cyclic sedimentation resulting from relative changes in sea level in northwest Europe, but interregional integration of these observations with North Sea subsurface data is lacking in the literature. Presented here is a chronostratigraphic correlation framework for the Paleogene of northwest Europe, built by integrating subsurface and outcrop data using sequence stratigraphic first principles. Biostratigraphic data from many sources is ordered with the composite standard method. Graphic correlation of this data documents certain correlations and helps suggest previously unrecognized ties.
Paleogene North Sea sediments record five major regressions and their intervening major transgressions. Overprinting this low frequency signal are 19 higher frequency sequence cycles that control lithofacies distribution. In northwest Europe, western basins (London-Hampshire, Paris and Belgian) have shallow marine to non-marine settings which reveal basinward and landward facies shifts that indicate sea level changes. The biostratigraphy of these shallow water deposits is linked to deep water central North Sea biostratigraphy by correlating through deeper water deposits outcropping in Denmark that have been tied to western basin stratigraphy. Using this biostratigraphic framework, key bounding surfaces are correlated between basins using sequence stratigraphic principles. Depositional sequences are recognized onshore that are completely sediment starved in the North Sea. The mixing of low and high frequency sea level signals requires that all of northwest Europe be studied to recognize the ‘true’ signal. Final correlations resolve 30 depositional sequences with five long-term sea-level changes that can vary from one sub-basin to another.
Forward and reverse stratigraphic modelling of Cretaceous-Tertiary post-rift subsidence and Paleogene uplift in the Outer Moray Firth Basin, central North Sea
Authors: Nadin P. A. , Kusznir N. J. 
Published: April 2008

Abstract

The Paleogene stratigraphy in the Outer Moray Firth is part of the North Sea post-rift sedimentary sequence that was deposited in a thermally subsiding basin following Late Jurassic rifting. Previous studies have drawn attention to anomalous uplift and departure from the McKenzie (1978,
Earth Planetary Science Letters
,
40
, 25–32) post-rift subsidence trend in the early Paleocene followed by an accelerated phase of basin subsidence in the early Eocene before returning to the normal post-rift subsidence. 2D forward and reverse stratigraphic modelling incorporating first-order global sea-level variations have been used to determine the timing and magnitude of departures from McKenzie post-rift thermal subsidence in the early Paleogene for the Outer Moray Firth. Reverse post-rift modelling, consisting of flexural backstripping, decompaction and reverse thermal subsidence, has been used to produce restored post-rift sections from present-day stratigraphy, which have been constrained by palaeobathymetric data. Forward syn-rift and post-rift structural and stratigraphic modelling uses the flexural cantilever model of rift basin formation and has been constrained by syn-rift structural data, present-day stratigraphy and palaeobathymetric markers. Forward and reverse modelling show that observed Cretaceous and Tertiary stratigraphy of the Outer Moray Firth was generated by the combined effects of inherited Late Jurassic syn-rift accommodation space, post-Jurassic rift thermal subsidence, sediment supply, long-term eustasy and an additional transient uplift event in the Paleocene. The much thicker Tertiary compared with Cretaceous can be explained by sediment infilling of starved Cretaceous palaeobathymetry. Reverse and forward post-rift modelling predict regional Paleocene uplift in the Outer Moray Firth of the order of 375–390 m (375 m reverse modelling, 390 m forward modelling), followed by
c.
160 m of rapid Eocene subsidence, both superimposed on post-rift thermal subsidence following Late Jurassic rifting. Regional Paleocene uplift in the Outer Moray Firth is attributed to dynamic uplift associated with the development of the Iceland plume.
Early Paleogene offshore igneous activity to the northwest of the UK and its relationship to the North Atlantic Igneous Province
Authors: Ritchie J. D. , Hitchen K. 
Published: April 2008

Abstract
Offshore occurrences of Early Tertiary igneous rocks to the northwest of Britain are allocated to seven major categories using criteria such as geographical location, structure, age and genetic relationship. The categories are: (1) Faeroe Plateau Lava Group; (2) North Rockall Trough-Hebrides Lava Group; (3) central igneous complexes; (4) volcaniclastic rocks; (5) Faeroe-Shetland Intrusive Complex; (6) the Minch; and (7) Wyville-Thomson Ridge. An igneous chronology is presented based on radiometric age dating (mainly K-Ar whole rock), biostratigraphical data and seismic relationships.
Most landward central complexes (i.e. Skye, Rhum, Ardnamurchan, Mull, Arran) pre-date those which are more oceanward (i.e. Erlend, Darwin, St Kilda, Rockall). Exceptions to this trend (i.e. Rosemary Bank, Anton Dohrn, Hebrides Terrace) are probably genetically linked to crustal thinning in the Rockall Trough. The age of the Faeroe Plateau Lava Group, and especially the contiguous Rockall Trough-Hebrides Lava Group, are not particularly well constrained.
The main intrusive phase on, and to the southeast of, the Faeroe Islands (i.e. Faeroe-Shetland Intrusive Complex) was a relatively late stage magmatic event, coeval with the opening of the North Atlantic between Greenland and NW Europe.
An integrated stratigraphy for the Paleocene and Eocene of the North Sea
Authors: Mudge David C. , Bujak Jonathan P. 
Published: April 2008

Abstract
A high-resolution sequence stratigraphy has been developed for the Paleocene and Eocene rocks of the North Sea Basin, using electric log data and biostratigraphy. A total of nine stratigraphic sequences has been defined, together with a further 11 subsequences. The sequences are bounded by high-gamma log markers representing maximum condensation surfaces that can be readily correlated over the whole basin. Biostratigraphic analysis has allowed the recognition of 37 last occurrence or top abundance dinocyst bioevents that have also been correlated with the microfaunal succession. Integration of the sequence stratigraphy and biostratigraphy demonstrates that a consistent relationship exists between individual sequence boundaries and bioevents, suggesting that these surfaces are time lines.
The usefulness of developing an accurate stratigraphic framework is illustrated by a series of maps showing the lithofacies distribution for individual sequences on a regional scale. At the prospect or field level, it can be used in conjunction with seismic data to map the more subtle Tertiary hydrocarbon plays in the North Sea Basin.
An integrated palynological-palynofacies approach to the zonation of the Paleogene in the Forties-Montrose Ridge area, central North Sea
Authors: Wood Susan E. , Tyson Richard V. 
Published: April 2008

Abstract

A palynological and palynofacies study of late Paleocene and early Eocene sediments of the central North Sea has been undertaken using 467 core samples from 11 wells on the Forties-Montrose Ridge. Conventional dinoflagellate cyst (dinocyst) biostratigraphy gives poor precision within the narrow (
c.
2.5 million years) time interval studied. Furthermore, dinocysts are often present in only very low numbers and are frequently poorly preserved. An alternative local zonation scheme is proposed on the basis of downwell variations in quantitative palynofacies and palynomorph occurrence data, and on angiosperm pollen ratios. Integration of these three sets of data indicates a potential sevenfold subdivision of the mid-Sele Formation (S2) to upper Lista Formation (L3) interval in this area, with up to five divisions within the Forties Sandstone Member. This composite zonation scheme appears to work reasonably well for the studied wells, and preliminary comparisons with independent biostratigraphic data from two of our wells indicate a partial correlation with the dinocyst zones.
Chronostratigraphic framework for the Thanetian and lower Ypresian deposits of southern England
Authors: Ali Jason R. , Jolley David W. 
Published: April 2008

Abstract

Magnetostratigraphic and palynomorph data are used to assess the timing and nature of the late Paleocene-earliest Eocene depositioanl sequences of SE England. Ormesby Clay Formation mudstones in east Norfolk are the oldest upper Paleocene deposits (C26r) of southern England. The base of the type Thanet Sand Formation (= start of the Thanetian Stage) is
c.
0.65 million years younger (C26n). A subaerial erosion surface separates the Thanet-Ormesby package from the Lambeth Group sediments. The duration of the hiatus (>0.5 million years) separating the two units can be calculated from the magnetostratigraphic data; C25n is missing from the stratigraphic record across almost all of southern England. However, the Upnor Formation in central London contains a record of C25n. A hiatus of
c.
0.4 million years separates the late Paleocene Lambeth Group from the early Eocene Harwich Formation. The Lambeth Group, Harwich Formation and lower London Clay Formation were all deposited during C24r. The start of Chron C24n.3n is positioned at the base of Division B of the London Clay Formation.
Upper Paleocene-Lower Eocene dinoflagellate cyst sequence biostratigraphy of southeast England
Authors: Powell A. J. , Brinkhuis H. , Bujak J. P. 
Published: April 2008

Abstract

Detailed study of the aquatic palynomorph assemblages, particularly dinoflagellate cysts, from the type-Thanetian and related sections in southeast England has enabled a detailed biostratigraphic and sequence biostratigraphic analysis to be carried out. The base of the Thanetian Stage at Pegwell Bay lies above the base of the
Alisocysta margarita
(Ama) biozone; the overlying type-Thanetian is assigned to the
Apectodinium hyperacanthum
(Ahy) and
Apectodinium augustum
(Aau) biozones. The base of the Ypresian succession is drawn at the base of the Harwich Formation at Lower Upnor corresponding to the base of the
Glaphyrocysta ordinata
(Gor) biozone. The
Wetzeliella astra
(Was) biozone is characteristic of the lower London Clay Formation at Herne Bay. Five Thanetian and three Ypresian sequences are identified through consideration of dinoflagellate cyst palaeoecology and sedimentological evidence. Deepening and shallowing trends enable transgressive and highstand systems tracts to be identified. The maximum flooding surfaces are identified and correlated into the North Sea Basin (Central Graben) as a series of eight primary condensed sections, two of which (characterized by the
Areoligera
and
Apectodinium
acmes) are of a second-order scale (the other six are third-order). Lowstand system tracts are represented onshore by a series of seven unconformities (type 1 sequence boundaries) with the amount of missing time below biozonal resolution. A single type 2 sequence boundary is also evident in the Ypresian succession at Wrabness. The unconformities may be correlated into more distal locations in the North Sea Basin where lowstand sandstone deposition is characteristic.
Recognition of Chron C25n in the upper Paleocene Upnor Formation of the London Basin, UK
Authors: Ellison Richard A. , Ali Jason R. , Hine Nicolette M. , Jolley David W. 
Published: April 2008

Abstract
Lithostratigraphic studies of four borehole cores drilled through the late Paleocene Lambeth Group (Upnor, Woolwich and Reading Formations) and basal London Clay Formation of central London have been supplemented with palaeomagnetic, calcareous nannoplankton and palynological data. The Woolwich and Reading Formations and the lower London Clay Formation are reversely magnetized and were deposited during the early part of Chron C24r. The first record of both NP9 and Chron C25n, hitherto missing from the Paleogene record in southern England, has been identified in the Upnor Formation (formerly the Woolwich Bottom Bed). It provides a key reference marker for linking events associated with the Paleocene-Eocene boundary (positioned within Chron C24r) to the type area of the internationally recognized Thanetian and Ypresian Stages.
The ‘Oldhaven magnetozone’ in East Anglia: a revised interpretation
Authors: Ali J. R. , Hailwood E. A. , King C. 
Published: April 2008

Abstract

A palaeomagnetic study has been carried out on the type Harwich Formation and basal London Clay Formation in the Ispwich area of East Anglia. Both units were deposited during the middle part of geomagnetic Chron C24r. The normal polarity magnetization previously identified in the upper part of the Harwich Formation at Wrabness (Townsend & Hailwood 1985,
Journal of the Geological Society, London
,
142
, 1–27), and called the ‘Oldhaven magnetozone’ by these authors, is now regarded as a recent overprint. The new information is critical in linking the Paleocene-Eocene boundary to NW Europe where the internationally recognized early Eocene Ypresian stage stratotype is defined.
The earliest Eocene sediments of eastern England: an ultra-high resolution palynological correlation
Authors: Jolley David W. 
Published: April 2008

Abstract

The acritarchs, dinoflagellate cysts, algae, pollen and spores from the Harwich Formation sediments in 28 sections from southeastern England have been quantitatively studied to assist in the stratigraphic correlation of sedimentary units. Application of published zonations based on dinoflagellate cyst zonations does not enable a subdivision of the Harwich Formation to be proposed; to address this problem, quantitative palynological data has been studied to define associations which have been grouped into association sequences. Thirteen subdivisions of the Harwich Formation palynofloras have been achieved, enabling an accurate correlation of units with an
c
. 38 500 year duration across southeastern England. This correlation has identified two major depositional sequences, deposited during separate periods of rising relative sea level during the 54.5–54.0 Ma period. Application of the association sequence technique to three equivalent sections from the North Sea Basin and one from the eastern margin of the Wyville-Thompson Ridge, has allowed a comparison of the southeastern England onlap model with depositional sequence models proposed for the outer Moray Firth by other authors. Correct identification of the relationship of the deposits in southeastern England to the Dornoch, Balder and Sele Formations of the North Sea, and identification of the stratigraphic level of tephra layers −17 and +19, enables comments to be made about the position of the Paleocene-Eocene boundary in the North Sea.
The upper Paleocene-lower Eocene stratigraphic record and the Paleocene-Eocene boundary carbon isotope excursion: implications for geochronology
Authors: Aubry Marie-Pierre , Berggren William A. , Stott Lowell , Sinha Ashish 
Published: April 2008

Abstract
The late Paleocene carbon isotope excursion which was first identified at ODP Site 690, is currently regarded as the best means for an exact correlation at a specific point in space and time between deep sea and continental stratigraphies. Yet its position relative to biostratigraphic datums in several outcrop and deep sea sections is apparently inconsistent. Based on the integration of magnetostratigraphic, biostratigraphic (calcareous nannofossils and planktonic foraminifera) and carbon isotopic data from the North (DSDP Sites 549 and 550) and South (ODP Site 690) Atlantic Ocean, we show that in order to understand the temporal relationships and sequence of late Paleocene to early Eocene biotic and isotopic events, it is necessary to construct a composite reference section. We infer from this that in addition to the well documented ‘classic’ carbon isotope excursion which occurs in mid-Biozone NP9, a younger isotopic excursion, yet undocumented, occurs in lower Biozone NP10. The 55 Ma age estimate in Chron C24r (0.66) used as a calibration in the construction of the latest geomagnetic polarity time scale in DSDP Hole 550 lies at an unconformity (separating stratigraphic levels low in Zone NP9 from low in Zone NP10) with the result that the position of the NP9/NP10 zonal/chronal boundary is higher/younger in Chron 24r. Because the sections recovered from DSDP Sites 550 and 690 probably do not overlap over the upper NP9-lower NP10 zonal interval, and because the former section is unconformable at the NP9/NP10 zonal boundary, there is currently no means of establishing satisfactorily a numerical chronology for Chron C24r, which means that the age estimates for the upper Paleocene to lowermost Eocene biostratigraphic and isotopic events await documentation of bio-, magneto-, and isotopic stratigraphy in continuous stratigraphic section(s).
Early Eocene palaeoceanography and palaeoclimatology of the eastern North Atlantic: stable isotope results for DSDP Hole 550
Authors: Charisi Stella D. , Schmitz Birger 
Published: April 2008

AbstractHigh-resolution oxygen and carbon isotope records for benthonic and planktonic foraminifera have been established through the early Eocene at DSDP Site 550, Goban Spur in the North Atlantic. Benthonic stable isotopic records from Site 550 (estimated palaeodepthc.4000 m) represent the first documentation of actual deep water properties during the early Eocene.At Site 550 in the earliest Eocene (end of NP10 Zone), a 0.5‰ vertical δ18O (i.e. thermal) gradient between subsurface and bottom water was eliminated, probably reflecting upward displacement of subsurface water by intermediate and deep water. Thereafter vertical isothermal conditions prevailed for the rest of the early Eocene. This is consistent with earlier findings suggesting unusually low vertical and latitudinal temperature gradients in the early Eocene ocean. A comparison of the isotopic records from Site 550 and nearby DSDP Site 401 (palaeodepth 1800 m), reflecting intermediate water properties, confirms the isothermal nature of the water column in the eastern North Atlantic. This is in contrast to earlier findings for the Antarctic region (ODP Sites 689 and 690) in the early Eocene, where supposedly warm bottom waters originating in low latitudes were overlain by cooler intermediate waters originating in high latitudes. Both the oxygen and the carbon isotopic records for Sites 550 and 401 indicate that the eastern North Atlantic region was influenced by a single source of intermediate-to-deep water through most of the early Eocene. The benthonic δ18O and δ13C values for Site 550 are generally low compared with coeval sections worldwide, indicating that during most of the early Eocene the North Atlantic was dominated by warm and nutrient-enriched deep water formed in a low latitude region.The earliest stages of the long-term cooling trend, which characterizes the second part of the Paleogene, can be traced by a 2°C decrease in bottom water temperatures across the NP13–NP14 transition at both Sites 550 and 401.
High-resolution sequence stratigraphy of a mid-Cretaceous estuarine complex: the Woburn Sands of the Leighton Buzzard area, southern England
Authors: Wonham J. P. , Elliott T. 
Published: April 2008

Abstract
The Woburn Sands Formation (Aptian-Albian) is a sand-rich, tide-dominated estuarine deposit up to 120 m thick, which is extensively exposed in the Leighton Buzzard area, southern England. Previous studies have interpreted the depositional processes and environments of these strata, but have not satisfactorily resolved their lithofacies complexity. Application of sequence stratigraphical methods and concepts has identified key surfaces (sequence boundaries, tidal and wave ravinement surfaces) which provide a useful framework for correlation of the succession and for understanding the complex facies architecture.
Two regional-scale erosional surfaces identified in the succession are interpreted as erosional unconformities or sequence boundaries. These surfaces resulted from fluvial erosion during periods of relative sea-level fall, followed by extensive erosional modification by tidal currents during the early phases of relative sea-level rise. The depositional sequences defined by the erosional unconformities are dominated by the deposits of incised valleys. The valley-fills mainly comprise sand-dominated tidal current facies which occur as multistorey estuarine channel complexes. In the upper parts of the sequences thin, locally preserved units of shelf facies overlie wave ravinement surfaces. Over part of the study area the upper erosional unconformity erodes directly into the underlying incised valley-fill producing a composite sequence.