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Paleozoic Carbonates in Foreland Basin Settings: Northern Pricaspian Basin (Kazakhstan) and Cantabrian Zone (Spain)*

Jeroen A. M. Kenter1 and Paul M. (Mitch) Harris1

 

Search and Discovery Article #30070 (2008)

Posted October 31, 2008

 

*Adapted from oral presentation at AAPG International Conference and Exhibition, Cape Town, South Africa, October 26-29, 2008.
Click to view list of articles adapted from presentations by P.M. (Mitch) Harris or by his co-workers and him at AAPG meetings from 2000 to 2008.

 

1 Chevron Energy and Technology Company, 6001 Bollinger Canyon Road, San Ramon, CA 94583-2324, USA ([email protected]; [email protected])

 

Abstract

Tengiz field is an isolated carbonate buildup in the southeastern Pricaspian basin, containing a complete Late Famennian to Early Bashkirian platform succession that was deposited in a relatively stable but rapidly subsiding foreland basin setting facing a thrust belt to the south. Since the Famennian, the platform aggraded and periodically back stepped resulting in approximately 800 m (2625 ft) of relief above the Famennian platform, followed by up to 2 km (1.2 miles) of Serpukhovian progradation. Vertical trends in relative shoaling and deepening, recorded exposure and/or erosional events, and biostratigraphy provide a relative sea level record of punctuated sea level falls and rises that are made up of 2nd and 3rd order sequences which are superimposed by higher (4-5th order) frequency platform cycles.

Though several of the observed sea level low stands correspond to 3rd order eustatic sequences on the EPR curve, the influence of rapid changes in the paleobathymetry of the foreland basin, which caused significant thickening of sequences and drowning in the Late Devonian elsewhere in the basin, appears to have a strong influence on the regional sequence stratigraphic framework. This presentation addresses the interplay between subsidence and recorded sequences in such foreland basin settings and compares the Pricaspian Basin evolution with that of a nearly age-equivalent foreland basin in Northern Spain.

 

uAbstract

uFigures

uRationale

uCaspian Basin

uCantabrian zone

uInternal vs. External zones

uFrontal basins & thrust-top platforms

uSummary

uReferences

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

uAbstract

uFigures

uRationale

uCaspian Basin

uCantabrian zone

uInternal vs. External zones

uFrontal basins & thrust-top platforms

uSummary

uReferences

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

uAbstract

uFigures

uRationale

uCaspian Basin

uCantabrian zone

uInternal vs. External zones

uFrontal basins & thrust-top platforms

uSummary

uReferences

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

uAbstract

uFigures

uRationale

uCaspian Basin

uCantabrian zone

uInternal vs. External zones

uFrontal basins & thrust-top platforms

uSummary

uReferences

 

Rationale

  • Sedimentation in tectonically active settings controlled by 1) structural grain, 2) timing and rate of deformation, and 3) eustacy.
  • Many carbonate hydrocarbon reservoir systems formed in foreland basin settings.
  • Generally difficult to extract geometry and timing from outcrop, BUT
  • Outcrop analog from northern Spain shows variation of depositional style in time and space.
  • May assist understanding/interpretation of carbonate system evolution in such tectonic regimes and in Pricaspian, in particular.

Caspian Basin - Background

  • Produces oil from subsalt Devonian-Carboniferous carbonate platforms.
  • Pricaspian Basin holds 46 BBOE (56% gas).
  • Four supergiant carbonate fields: Tengiz, Karachaganak, Astrakhan and Kashagan
  • Complex tectonic history of:
    • Thermal subsidence and rifting until Late Carboniferous.
    • Collision and thrusting starting in Permian.
    • Separation from Tethys Ocean and formation of salt basin in Kungurian.

Cantabrian Zone: Marine Foreland Basin

  • Complex arc-shaped collision/deformation system.
  • Nucleation of Serpukhovian to Moscovian isolated platforms in foreland basin.
  • Highly variable subsidence rates caused by advancing thrust belt.
  • As a result, local drowning of buildups and variable depositional styles and internal geometries across basin.
  • Development of local basins at - and on top of - frontal part of thrust belt.
  • Filled by (Moscovian-Ghzelian) alternating clastics and carbonate ramps and low relief platforms.
  • Angular unconformities and thickness variations reflect tectonic deformation rates, but 3rd order (and higher) eustatic SL signal preserved.

(Merino-Tomé et al., in press)

Internal (Proximal) vs. External (Distal) Zones

Bashkirian

Internal Zone: Evolution low-to high angle and high relief progradation (>10 km); no basinal input –starved.
External Zone: Low relief platforms and ramps.

Bashkirian—Moscovian Transition

Internal Zone: Clastics partially fill starved basin modifying progradation from horizontal to climbing.
External Zone:Clastics draping low relief ramp.

Moscovian

Internal Zone: General aggradational growth style with minor progradational pulses.
External Zone:Formation of buildups; high rates (> 2 km/Ma) of platform progradation.

Late Moscovian — Early Kasimovian

Internal Zone: Migration of thrust front towards the foreland incorporates carbonate platforms. Rapidly subsiding basins develop in front and on top of the thrust wedge (thrust-top platforms).
External zone: Carbonate sedimentation continuous.

Frontal Basins and Thrust-top Platforms

Mid-late Myachkovskian (late Moscovian)

External Zone: Active platform growth.
Basins developed at the frontal part of the thrust wedge.
Internal Zone: Deformation and uplifting of the carbonate shelf.

Early Krevyakian(early Kasimovian)

External Zone: Active platform growth.
Flexural warping generated subsiding basins developed on top of the frontal part of the thrust wedge.
Internal Zone: Continued thrusting.

Summary and Conclusions

  • Northern Pricaspian has 46 BBOE and 4 supergiant isolated platforms in Paleozoic foreland basin settings.
  • Highly complex and variable system.
  • Both undeformed and deformed isolated buildups and thrust-top platforms have reservoir potential.
  • Cantabrian Zone (Spain) provides well-studied outcrop analogs of arc-shaped system.
  • Spain provides mosaic of carbonate buildup styles in space and time and as a result of tectonic deformation and eustatic sea level.

References

Bosence, D.W.J., 2005, A new, genetic classification of carbonate platforms based on their basinal and tectonic setting in the Cenozoic: Sedimentary Geology, v. 175, p. 49-72.

Merino-Tomé, Bahamonde, Fernandez and Colmenero, 2008, in press.

 

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