River To The North Sea 4 Letters

River To The North Sea 4 Letters – The beginning of the Quaternary (2.58 Ma) corresponds to significant palaeoenvironmental events, such as the intensification and southward extension of the Northern Hemisphere glaciation. A significant Late Cenozoic succession has been identified in the North Sea Basin as a high-resolution archive of palaeoenvironmental changes during the Pliocene and Pleistocene. However, identification of the base of the Quaternary has been a long-standing problem due to the lack of stratigraphic calibration. This study incorporates continuous regional 3D seismic data with high-quality chronostratigraphic markers to map the base Quaternary surface in high resolution across the North Sea. Depth conversion, backstripping, seismic geomorphology and sedimentation rate calculations are integrated to analyze the paleogeographic evolution of the North Sea basin and its filling from c. 83 × 10

From marine to deltaic sediments prograding towards the north. The basin is 600 km long from SSE to NNW and is located largely above the residual topography of the Mesozoic graben system. During the earliest Quaternary (2.58 – 2.35 Ma) paleo-water depths were c. 300 ± 50 m and solid sedimentation rates (calculated from 0% porosity) c. 32 km

River To The North Sea 4 Letters

. The Quaternary base provides an important marker for further studies of the changing Quaternary environment of northwestern Europe, as well as for the analysis of shallow geological resources and hazards.

Cross Border Stratigraphy Of The Northern, Central And Southern North Sea: A Comparative Tectono Stratigraphic Megasequence Synthesis

The onsets of cooling and widespread glaciation of the Northern Hemisphere at the Plio–Pleistocene transition are important markers for palaeoclimate and palaeoenvironmental studies worldwide ( Raymo 1994 ; Lisiecki & Raymo 2007 ). Climatic records often vary greatly with latitude, and cooling trends such as the Plio-Pleistocene transition are often better preserved in mid- to high-latitude basins (Mudelsee and Raymo 2005; Rohling et al. 2012). In the North Sea Basin, a mid-latitude epicontinental basin, understanding the nature and extent of early Pleistocene cooling has previously been difficult due to poor definition and identification of the base Quaternary boundary. A considerable thickness (ca. 1 km) of Quaternary deposits has long been known to exist in the central North Sea (Holmes 1977; Cameron et al. 1987; Gatliff et al. 1994). However, discrepancies between inconsistent lithostratigraphic and chronostratigraphic studies in the five bordering countries, combined with spatiotemporal changes in climate and sediment supply (Huuse 2002) and strong glacial overprint, have prevented precise definition of the basal Quaternary ( 2.58 Ma). across the basin (Cameron et al. 1987).

Regional 3D seismic data acquired for deeper oil exploration have previously been used for local- and subregional-scale glacial geomorphological studies (e.g., Praeg 1996, 2003; Kuhlmann and Wong 2008; Stewart and Lonergan 2011; Kristensen and Huuse 2012; Stewart et al. 2012, 2013; Moreau and Huuse 2014). The improved seismic resolution provided by these data has allowed a previously hidden view of the structure and stratigraphy of the late Cenozoic succession. This study documents the shape and evolution of the early Quaternary North Sea basin (2.58 – 2.35 Ma) by integrating continuous 3D regional seismic data with recent biostratigraphic studies of the southern North Sea. The Plio-Pleistocene boundary and sediment distribution patterns are accurately mapped across the central and southern North Sea for the first time. The newly mapped basin contains an expanded and largely complete record of paleoclimatological studies of the onset and history of glaciation in the Northern Hemisphere and will further contribute to a better understanding of the geological hazards and resources constituted by deposits of shallow gas

The present-day North Sea is an epicontinental sea reaching an average water depth of 100 m (outside the Norway Channel) and borders the continental masses of northwestern Europe, Scandinavia and Britain. The North Sea basin originated during episodic extensional rifting related to the breakup of the Atlantic from the Paleozoic to early Cretaceous (Ziegler 1992). Rifting was followed by continuous subsidence throughout the Late Cretaceous and Cenozoic marked by episodes of basin inversion during the Paleogene (Ziegler 1992; White & Lovell 1997; Stoker et al. 2005). The role of continued regional and local tectonic activity in the late Cenozoic is still debated. Most evidence favors a model of passive thermal subsidence enhanced by sediment loading in the central North Sea and marginal uplift due to denudation and unloading of the Norwegian landmass (Huuse 2002; Nielsen et al. 2009 ; Anell et al. 2010; Goledowski et al. 2012).

In previous studies of the central North Sea, early Quaternary stratigraphy in the North Sea has been mapped as a unit, the Aberdeen Onshore Formation, of pro-deltaic to marine sediments (Gatliff et al. 1994; Stoker et al. al. 2011). The sediment comes mainly from the Rhine-Meuse and Baltic river systems of northern Europe and Scandinavia (Bijlsma 1981; Overeem et al. 2001; Busschers et al. 2007). The timing of the onset of Quaternary glaciation remains unclear, although there is increasing evidence for several ice sheet advances during the Middle and Late Pleistocene from the UK and Scandinavian landmasses (Graham et al. 2011), and even evidence of iceberg accretion. in the southern North Sea basin since the beginning of the Quaternary (Kuhlmann et al. 2006; Stuart & Huuse 2012; Dowdeswell & Ottesen 2013; Ottesen et al. 2014).

The Middle Pleistocene To Early Holocene Subsurface Geology Of The Norderney Tidal Basin: New Insights From Core Data And High Resolution Sub Bottom Profiling (central Wadden Sea, Southern North Sea)

This study uses seismic stratigraphic and seismic geomorphological techniques ( Mitchum et al. 1977a , b ; Posamentier et al. 2007 ) to analyze a basin-scale 3D seismic dataset covering 128 000 km.

Of the center and south of the North Sea. The study uses the continuous 3D Central and Southern PGS Seismic MegaSurveys with a sub-sampling size of 50 m and a sampling rate of 4 ms two-way travel time (TWT) to map the deepest part of the basin of the Quaternary North Sea ( Fig. 1). In areas not covered by the MegaSurvey, regional 2D seismic lines were used to resolve the basin shape. At the upper 1.5 s TWT, the vertical resolution of the MegaSurveys is 8 – 16 m, while the vertical resolution of the 2D lines is between 10 and 18 m with variable spacing between 1 and 15 km. Lithological descriptions, gamma-ray logs and depth-time calibration curves were accessed from a regional database of public and private domain data provided by TNO and TGS respectively.

Fig. 1. Location map and datasets. The data shown are the Central North Sea and Southern North Sea 3D Seismic MegaSurveys, TGS North Sea Renaissance 2D lines and the Josephine-1 and A15-03 well locations used for the basal Pleistocene dating. Bathymetry and topography data from Ryan et al. (2009). The location of the seismic sections in Figures 2 and 6 is indicated.

The Quaternary base stratigraphic surface, taken as 2.58 Ma, was correlated with a well-defined, continuous seismic reflection channel using well A15-03 in the Dutch North Sea, for which bio- and magnetostratigraphic dating is available very detailed in the public domain. (Kuhlmann et al. 2006; see discussion below). The horizon was picked at the well link and then mapped to the depositional dip of the clinoforms in the basin, which minimized correlation errors to about half the dominant wavelength (20 – 35 m), using a decreasing grid size (200 m then 100 m). then 50 m), which then propagated in three dimensions ( Hart 1999 ). The base Quaternary was correlated and compared with the biostratigraphic record from the Josephine-1 well (Knudsen and Asbjörnsdóttir 1991), which is commonly used as a reference point for Quaternary studies of the United Kingdom Continental Shelf (UKCS) ( Fig. 2), as well as the Cenozoic studies of the southern North Sea, including those of Thöle et al. (2014) for the German sector and Nielsen et al. (2008) for the Danish sector (Table 1). The mapped horizon was converted to a gridded surface at 100 m spacing, and seismic attributes such as instantaneous root mean square (RMS) amplitudes at the horizon were extracted to investigate evidence of paleogeographic context using seismic geomorphology. To convert TWT surface to depth, calibrated TWT depth data from 1122 UK and Norwegian North Sea wells were plotted to find a simple but robust depth conversion equation (Equation (1)) with a variability of data defined (Fig. 3). :

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Subsidence due to differential loading and compaction leads to exaggeration of clinoform slopes, as maximum deposition occurs on the slope rather than on top. Therefore, time-depth conversion or thickness maps alone cannot accurately estimate paleowater depth. To provide realistic estimates of water depth from buried clinoforms, they must be back-rotated so that their topsets are approximately horizontal and their height is uncompacted (Pekar et al. 2000; Patruno et al. 2014).

Fig. 2. Interpretation of seismic section and line, with 75× vertical exaggeration, showing the location of the Josephine-1 and A15-03 wells plus surfaces for the middle Miocene (c. 17 – 14 Ma), 2.58 Ma (base Quaternary) , 2.35, 1.9 and 1.1 Ma (base-Jaramillo paleomagnetic event). The key biostratigraphic events of Josephine-1 well identified after Knudsen and Asbjörnsdóttir (1991) with errors range from depth conversion. The location is shown in Figure 1. FCO, usual first appearance; LCO, last common occurrence; LOD, last occurrence data. Data courtesy of PGS.

Fig. 3. Calibrated depth plotted against TWT for 1.5 s of top TWT in 1122 wells from the UK and Norway sectors of the Central North Sea MegaSurvey with regression line and R

Table 1. Comparison of chronostratigraphic calibrations from five sectors of the North Sea, used in this study to identify the basal Quaternary surface

The Early Quaternary North Sea Basin

Studies include Knudsen & Asbjörnsdóttir (1991); Kuhlmann et al. (2006); Nielsen et al. (2008); Buckley (2012, 2017); Ottesen et al. (2014) and Thöle et al. (2014). mbsf, meters below the seabed; n.a., not analyzed.

In this study, a series