Editing A sequence-stratigraphy scheme of the Late Carboniferous, southern North Sea, Anglo-Dutch sector

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==== Geometry ====
 
==== Geometry ====
  
Mapping of lake and marine-bay facies reveals an uninterrupted areal extent of several hundred square kilometres. Thickness variations suggest that the depth of lakes and bays ranged from less than 10 m to over 30 m in places.
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Mapping of lake and marine-bay facies reveals an uninterrupted areal extent of several hundred square kilometres. Thickness variations suggest that the depth of lakes and bays ranged from less than 10m to over 30m in places.
  
 
==== Wireline log characteristics ====
 
==== Wireline log characteristics ====
  
Lake and marine-bay mudstones and siltstones are characterized by high gamma-log responses of 120–>150&nbsp;API and δ''T ''values of 90–105&nbsp;µsft<sup>–1</sup>. Marine horizons commonly display particularly high gamma responses, often in excess of 150&nbsp;API. The presence of nodular beds causes a marked reduction in gamma-log response and δ''T ''values.
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Lake and marine-bay mudstones and siltstones are characterized by high gamma-log responses of 120–>150API and δ''T ''values of 90–105µsft<sup>–1</sup>. Marine horizons commonly display particularly high gamma responses, often in excess of 150 API. The presence of nodular beds causes a marked reduction in gamma-log response and δ''T ''values.
  
 
=== Facies Os – swamp/floodplain deposits ===
 
=== Facies Os – swamp/floodplain deposits ===
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==== Description ====
 
==== Description ====
  
This facies comprises coal seams and associated rootlet-disrupted mudstones, siltstones and fine-grained sandstones. Coal seams are up to 2–3&nbsp;m thick and are typically banded, whereas the associated clastic strata, also on average 2–3&nbsp;m thick, are invariably structureless, because of disturbance by rootlets. Nodules of pyrite or siderite may be developed within all these lithologies. Swamp/floodplain sediments occur mainly at the top of cyclothems overlying channel (facies Cl and Ch), distributary mouth-bar (facies Cd), crevasse-splay (facies Cl) and locally lake or marine bay (facies Ol) deposits.
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This facies comprises coal seams and associated rootlet-disrupted mudstones, siltstones and fine-grained sandstones. Coal seams are up to 2–3m thick and are typically banded, whereas the associated clastic strata, also on average 2–3m thick, are invariably structureless, because of disturbance by rootlets. Nodules of pyrite or siderite may be developed within all these lithologies. Swamp/floodplain sediments occur mainly at the top of cyclothems overlying channel (facies Cl and Ch), distributary mouth-bar (facies Cd), crevasse-splay (facies Cl) and locally lake or marine bay (facies Ol) deposits.
  
 
==== Interpretation ====
 
==== Interpretation ====

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