Structure Families Sergei Parnachov Gary Couples 2 Geodynamics

Structure Families Sergei Parnachov Gary Couples

2 Geodynamics Settings Salt Tectonics Fold and Thrust Belts Rifting and Passive Margins Strike-Slip Provinces Stable interior (epicontinental) basins Basement/Cover interactions

3 Salt Tectonics Salt structures in the Gulf of Mexico and adjacent areas (Seni & Jackson, 1983) Associated with large HC accumulation in many basins like US Gulf Coast, Southern Mexico, Gabon, Senegal, Canadian Arctic, North Sea, Romania, Zagros Mountain (Iran), Caspian Depression (CIS)

4 Salt Tectonics Associated with diapirs – salt intrusions known also as a “salt dome” (although other morphology distinguished –see below) May be very big Marchand-Timbalier-Caillou Island Salt Massive (Louisiana, some 500km2 with 500MMbbl of oil) salt roller salt anticline salt pillow diapiric salt wall diapiric salt stock detached diapir Twiss & Moores, 1992

5 Salt Tectonics With regional stress field near isotropic normal faults mainly developed radial pattern of faults (see Heidelberg structure plain view on the right) Note listric faults, rollover anticline, sin- and antithetic faults, grabens and half-grabens Twiss & Moores, 1992

6 Salt Tectonics Surrounded faults developed do not penetrate salt dome – faults should be mapped terminated opposite the dome Twiss & Moores, 1992 Tearpock & Bischke, 1991

7 Salt Tectonics With regional stress being more anisotropic (or salt exhibits complex growth story) faults tend to have more preferred orientation, forming subparallel peripheral faults Brown, 1999

8 Salt Tectonics HC trap types simple domal anticline, graben fault trap over the dome, porous caprock (limestone or dolostone), flank sand pinchout, traps beneath an overhang, traps against the salt itself, unconformity, fault traps downthrown the dome

9 Salt Tectonics Macbeth, 2003 Because of strata dip beneath the dome bright spots are highly visibly sometime (Gannet-C Oil & Gas Field 4D seismic survey)

10 Fold and Thrust Belts Compressional tectonic settings: Reverse and thrust faults, forming within a forearc, backarc and collision belt (accretion prism), Anticlines in hanging wall – as a: fault propagated fold, fault bend folds and duplex structures Zagros collision belt in Iran accounted 75% of the world’s fold-and-thrust belt HC production

11 Fold and Thrust Belts Wyoming-Utah backarc fold and thrust belt – almost all HC are trapped in hanging wall of Absaroka Thrust (Painter Reservoir, Whitney Canyon, Ryckman Creek, Anschutz Ranch Fields). Lamerson, 1982

12 Fold and Thrust Belts Lamerson, 1982 Most of the fields are found in asymmetric anticlinal folds with steep east limb Tearpock & Bischke, 1991

13 Fold and Thrust Belts Twiss & Moores, 1992 Note: Autochthon Allochthon Window Klippe Flat Ramp Tearpock & Bischke, 1991 Thrust fault = надвиг, шарьяж Allochton = аллохтон Autochtone = автохтон Klippe = тектонический останец Window = тектоническое окно

14 Fault-bend folds (a) form where thrust surface changes from steeper dip to shallow in a up-dip direction Fault-propagation folds (b, c) form as layers fold during propagation of a thrust through a sedimentary sequence. Fault-propagation folds may evolve aceinto fault-bend fold with displacement increasing Fold and Thrust Belts Hatcher, 1995

15 Imbricated Thrust (or Imbricated Fan) formed by the series of subparallel thrust developing – probably – from the master detachment Duplexes forms where subparallel thrusts of appr. equal displacement are separated by deformed sequence. Include Horse Blocks, Roof and Floor Thrust Fold and Thrust Belts Couples, 2003

16 Rifting and Passive Margines Mostly extensional environments: Normal Faults domination Twiss & Moores, 1992 Tarbuck & Lutgens, 1996

17 Rifting and Passive Margines Listric Faults (may be Growth Fault) Rollover Anticline Graben and Half-Graben Synthetic and Antithetic Faults Master or Detachment Fault Couples, 2003 Twiss & Moores, 1992 Note Transcurrent (or Tear) Fault – what is actually a strike-slip feature May be opposite tilting of hanging walls

18 Rifting and Passive Margines Couples, 2003 Bookshelf model: blocks rotation and new generation of normal faults Growth nature of faults

19 Rifting and Passive Margines Tearpock & Bischke, 1991 Salt Domes Normal Faults Anticlines

20 Rifting and Passive Margines Growth faults Shale and Salt diapirism Synthetic and Antithetic Normal Faults Buckle Folds (because of local compression) on the base Couples, 2003 Halbouty, 1989

21 Strike-Slip Provinces Wrench Faults (high-angle or vertical) forms under horizontal compression May have a great linear extend (were tectonic plates are involved in the motion – San Andreas fault complex) Sinistral or Dextral – depending on the motion of the relative block’s direction HC traps associated with anticlines – which may be faulted by normal or reverse faults Twiss & Moores, 1992

22 Strike-Slip Provinces Hatcher, 1995

23 Strike-Slip Provinces Different type of deformation of the adjacent blocks are very characteristic – Tear Faults Tearpock & Bischke, 1991 Twiss & Moores, 1992

24 Strike-Slip Provinces Flow (or Palm Tree) structure in Pull-Appart structure: normal or negative (транстенция) reverse or positive (транспрессия) Twiss & Moores, 1992 Pull-appart or Rhomb-graben basin

25 Strike-Slip Provinces Twiss & Moores, 1992 Strike-Slip Faults termination: plainview of extensional dextral (A) and compression sinistral (C) strike-slip faults, local extension (B) – listric fault with half-grabens, Imbricate Fan or even Duplex zone (D), formed in local compression, Horsetail splay (E) of secondary dextral strike-slip faults

26 Stable interior (epicontinental) basins No modern analogue Post-rift (past-Triassic) story of West-Siberian basin Middle and Late Cretaceous episode of North Sea Gradual basin infilling by the sediments (Chalk or clastic) From Layercake to Jigsaw architecture (from the deep to the margins) Main deformation are sedimentary-induced (isostatic subsidence, sin-sedimentary faults and folds – deltas etc.) Roberts et al., 1999

27 Basement/Cover interactions Most complex and unpredictable Mainly vertical basement movements dominate Basement faulting and cover’ rheology determine folds morphology

28 Basement/Cover interactions Most complex and unpredictable Mainly vertical movements dominate