New conceptual fold-fracture model including prefolding fractures, based on Fuyang-Lin’an anticline, Zhejiang Province

Abstract

Field observations of the crossing relationships of fractures have been used to explain the sequence of fractures. Based on field observations from Fuyang-Lin’an anticline, located near Hangzhou, Zhejiang Province, this paper proposes that the formation of synfolding fractures was influenced dominantly by one fracture set, which developed prior to folding and the orientation was nearly parallel to the bedding. The length of the prefolding fractures is longer than the synfolding fractures. These prefolding fractures cut thicker strata into small pieces and form a dense network of fractures in thicker strata. Most synfolding fractures, which are oblique to the bedding, are truncated by prefolding fractures in thicker strata. The synfolding fractures, which result from local stress, are inferred to form during folding. Here, the mechanism of truncation was analyzed using finite-element models. The approach was based on the idea that natural fractures can be interpreted or inferred from stress distribution. The presence or absence of prefolding fractures is shown to strongly control the distribution of stress, and this control has an important implication for interpreting the fracture truncation mechanism from geomechanical models.

Keywords

folding / fracturing / sequence / model / finite-element

References

[1] Angelier J. Neotectonique de L’Arc Egeen. Rev. Geol. Dyn. Géogr. Phys., 1979, 21(1): 67-92.

[2] Bartlett W L, Friedman M, Logan J M. Experimental Folding and Faulting of Rocks under Confining Pressure. Part IX. Wrench Faults in Limestone Layers. Tectonophysics, 1981, 79: 255-277.

[3] Bergbauer S, Pollard D D. A New Conceptual Fold-Fracture Model Including Prefolding Joints, Based on the Emigrant Gap Anticline, Wyoming. Geological Society of America, 2004, 116(3–4): 294-307.

[4] Colmenares L B, Zoback M D. A Statistical Evaluation of Intact Rock Failure Criteria Constrained by Polyaxial Test Data for Five Different Rocks. International Journal of Rock Mechanics and Mining Sciences, 2002, 39: 695-729.

[5] Dong Y, Yan Y, Xiao A, . The Constraints of Bed Thickness on the Development of Oblique Structural Fractures in the Sandstones. Geotectonica et Metallogenia, 2013, 37(3): 384-392.

[6] Engelder T. Atkinson B K. Joints and Shear Fractures in Rock. Fracture Mechanics of Rock, 1987 London: Academic Press, 27-29.

[7] Griggs D T, Handin J. Observations on Fracture and an Hypothesis of Earthquakes in Boulder, Colorado. Geological Society of America Memoir, 1960, 79: 264-347.

[8] Gross M R, Fisher M P, Engelder T, . Factors Controlling Joint Spacing in Interbedded Sedimentary Rocks: Integrating Numerical Models with Field Observations from the Monterey Formation, USA. Fractography, Fracture Topography as a Tool in Fracture Mechanics and Stress Analysis. Geological Society, London, Special Publications, 1995, 92: 215-233.

[9] Hou G. Fractal Characterization of Reservoir’s Varieties. Geological Science and Technology Information, 1993, 12(3): 78-81.

[10] Hou G. Fractal Analysis of Fractures. Jounal of Basis Science and Engineering, 1994, 2(4): 299-305.

[11] Ismat Z, Mitra G. Folding by Cataclastic Flow at Shallow Crustal Levels in the Canyon Range, Sevier Orogenic Belt, West-Central Utah. Journal of Structural Geology, 2001, 23(2): 355-378.

[12] Lacazette A. Paleostress Analysis from Image Logs Using Pinnate Joints as Slip Indicators. AAPG Bulletin, 2009, 93(11): 1489-1501.

[13] Manda A K, Mabee S B, Wise D U. Influence of Rock Fabric on Fracture Attribute Distribution and Implications for Groundwater Flow in the Nashoba Terrane, Eastern Massachusetts. Journal of Structural Geology, 2008, 30(4): 464-477.

[14] Meng Q, Hou G, Pan W, . Layer Thickness Controls on Surface Density and Fractal Dimension of Structural Fractures in Carbonate Strata. Geological Journal of China Universities, 2011, 17(3): 462-468.

[15] Mitra S. Fold-Accommodation Faults. AAPG Bulletin, 2002, 86(4): 671-693.

[16] Narr W, Suppe J. Joint Spacing in Sedimentary Rocks. Journal of Structural Geology, 1991, 13: 1037-1048.

[17] Price R A. Flathead Map Area, British Columbia. Geological Society of Canada Memoir, 1965, 336 221.

[18] Schöpfer M P J, Arslan A, Walsh J J, . Reconciliation of Contrasting Theories for Fracture Spacing in Layered Rocks. Journal of Structural Geology, 2011, 33(4): 551-565.

[19] Smart K J, Ferrill D A, Morris A P. Impact of Interlayer Slip on Fracture Prediction from Geomechanical Models of Fault-Related Folds. AAPG Bulletin, 2009, 93(11): 1447-1458.

[20] Stearns D W. Riecker R E. Certain Aspects of Fractures in Naturally Deformed Rocks. Rock Mechanics Seminar, 1968 Bedford: Terrestrial Sciences Laboratory, 97-118.

[21] Xia Z. Tectonic Evolution and Hydrocarbon Exploration Prospects in Central Iran Basin: [Dissertation], 2008 Chengdu: Chengdu Uiniversity of Technology

[22] Xu K, Zhu Z. Structural Geology, 1993 Beijing: Geological Publishing House

[23] Zhang L. The Study of Reservoir Fractures in Chinese Northern Typical Low-Permeability Oilfield: [Dissertation], 2001 Xi’an: Northwest University

[24] Zhang Q, Hou G, Pan W, . Fractal Study on Structural Fracture. Jounal of Basic Science and Engineering, 2011, 19(6): 853-861.

[25] Zhu G, Xu J W, Liu G S, . Tectonic Pattern and Dynamic Mechanism of the Foreland Deformation in the Lower Yangtze Region. Regional and Geology of China, 1999, 18(1): 73-79.