FAILURE MODES IN TURBIDITES OF THE MAGALLANES BASIN, CHILEAN PATAGONIA: A PRELIMINARY ANALYSIS Atilla Aydin and Joseph Gonzales Department of Geological and Environmental Sciences, Stanford University, Stanford, CA 94305

marks the beginning of the development of the Abstract Magallanes Basin as a foreland basin (Figure 1C). Deposition within this tectonic context continued with We investigated failure modes in Upper the Cerro Toro Formation (Figure 1C). The depocenter Cretaceous, deep water turbidites in the Magallanes of the foreland basin was initially located immediately foreland basin in and around the Torres del Paine to the east of the Cordillera and has shifted National Park in Chilean Patagonia with the goal of progressively further eastward as the contractional providing an analog to the mechanisms of deformation deformation has propagated to the east (Winslow, of deep water turbidite reservoirs. A wide variety of 1981). The maximum sediment thickness within the fundamental failure structures are present. Among basin is as great as 7 km (Biddle et al., 1986) and the these are sharp, shear fractures with a normal sense of water depth at deposition is estimated to have been 1 to motion, oriented at about 300 to bedding and 2.5 km (Fildani and Hessler, 2005). representing the earliest failure events in the mudstone- dominated lower Cerro Toro Formation. Cleavage fractures also occur in the mudstone intervals, especially within folds and fault zones. Opening-mode failure is very common in all lithologies, producing networks of joints. Bedding interfaces, marked by mudstone of various thicknesses, prove to be prone to bed-parallel slip. The joints form the bases for sheared- joint mechanism and the strike-slip faulting which is prominent in course-grained units. Faults at low angle to bedding are common in all scales. The most complex faults are associated with coupled processes of folding and faulting. These faults form broad zones with high Figure 1. Geographic and tectonic settings of the degrees of anisotropy. These preliminary results are Magallanes Foreland Basin in southern Chile. (A) promising for identifying the distribution of the Location map and boundaries of the basin (from fundamental failure modes in various lithological units Biddle at al., 1986). (B) Early Cretaceous back-arc basin setting represented by the Tobifera and of deep water turbidites and their impact on faulting Zapata formations. (C) Late Creataceous foreland mechanisms and the resulting fault architecture. basin represented by the Punta Barrosa, Cerro Toro and Tres Pasos (not shown). (B) and (C) from Introduction Wilson, 1991 modified by Fildani and Hessler, 2005, and Crane, 2004. The Magallanes Basin is located at the southern end of South America and covers most of Chilean and The Magallanes basin contains thick sequences of Argentinean Patagonia (Figure 1A). The basin’s Upper Cretaceous, deep water turbidites (Figure 2 and western boundary is demarcated by the Andean 3A) with spectacular outcrops in and around the Torres Mountain belt and the subsidence and ensuing del Paine National Park (Chilean Patagonia). Three contraction of the basin is linked to the rise of the formations (from oldest to youngest), the Punta proto-Andean Cordillera and the convergence beneath, Barrosa, Cerro Toro, and Tres Pasos formations (Figure across the Andean subduction zone (Winslow, 1981; 2 and 3A-the Tres Pasos not shown) record both the Wilson, 1991; Fildani and Hessler, 2005). The sedimentological and structural evolution of the Andean Magallanes Basin deposits rest upon relatively shallow Fold and Thrust belt and provide an excellent analog marin rocks of Late Jurassic/Early Cretaceous age (the for deformation of deep water turbidites. In this paper, Zapata and Tobifera formations in Figure 2A), which we report our preliminary results concerning the failure have been inferred to have been deposited in a back-arc modes of various lithological packages in the older two extensional basin environment (the Rocas Verdes back- formations with an emphasis on the impact of each arc basin in Figure 1B). The arrival of the sediments of failure mode on fault initiation and development, as the Punta Barrosa Formation in the Late Cretaceous well as the resulting fault architecture.

Stanford Rock Fracture Project Vol. 18, 2006 J-1 (Figure 4) with a maximum thickness of about 1000m (thinning eastward before pinching out; Wilson, 1991). It shows an overall upward increase in grain size and bed thickness (Katz, 1963; Wilson, 1991; Fildani and Hessler, 2005). The mud/sand ratio is higher in the lower part of the formation (Figure 4A) than in the upper part. Bed thickness in the sandstone packages ranges between 40-150cm (Wilson, 1991; Fildani and Hessler, 2005), although amalgamated composite beds up to 9m thick also exist (Wilson, 1991). From a structural perspective, it is important to note the alternating beds of sandstone and shale (see detailed sections in Figure 4 (B) and (C), which are crucial for the proposed mechanical behavior of the formation. In addition, the formation underwent a very low-grade metamorphism (Fildani and Hessler (2005), perhaps

due to anomalously high temperature introduced by Figure 2. Geological map of the Torres del Paine nearby intrusions and high overburden pressure. National Park and its vicinity. Locations of major Although the porosity of the sandstone beds in this study sites, Park Highway, Tyndall Bridge road cut, formation has not been determined, it is thought to be Lago Grey road cut along with Park Headquarter are low. also marked.

Figure 3. (A) Upper Jurassic to Upper Cretaceous rocks stratigraphy of the Magallanes Basin. (B) The Cerro Toro section at the Silla Syncline. (C) Figure 4. (A) Stratigraphic column of the Punta Heirarchical packages within the Cerro Toro Fm. (D) Barrosa Fm. (the lower 400m) and (B) and (C) detail Detailed section at the lower part of the formation packaging of sandstone/mudstone sequences. (A) across the western limb of the Syncline. (A) From From Wilson, 1991; and (B) and (C) from Fildani and Wilson, 1991; and (B) to (D) from Crane, 2004. Hessler, 2005.

Upper Cretaceous turbidites Cerro Toro Formation The Punta Barrosa Formation is capped by the Punta Barrosa Formation mud-rich turbidites of the Cerro Toro Formation, which This formation marks the initial sediment arrival suggests a paleobathymetry of approximately 2000 m into the Magallanes foreland basin associated with the (Fildani and Hessler, 2005). The thickness of this Andean Orogeny (Wilson, 1991; Fildani et al. 2003). formation is estimated to be 1100 to 2500 m (Katz, Recent detrital zircon analyses by Fildani et al. (2003) 1963; Wilson, 1991; Crane 2004). The age of the Cerro indicate that the age of the Punta Barrosa Formation is Toro Formation, based on fossil evidence, has been about 92-95 Ma (Turonian). The formation is made up established as middle-to-upper Senonian (Katz, 1963), of alternating sandstone and mudstone turbidites but it might be younger, based on recent zircon analysis

Stanford Rock Fracture Project Vol. 18, 2006 J-2 of the underlying Punta Barrosa Formation. The road cut”, the “Park Highway at the Silla Syncline”, lithology of the Cerro Toro Formation is predominantly and the “Lago Grey road cut” (Figure 2). mudstone and thin-bedded, fine-grained sandstone turbidites, intercalated with coarse-grained sandstone and conglomerate units (Crane, 2004). Crane identified three intervals of matrix- and clast-supported conglomerate and coarse-grained sandstone (Figure 3B and C), classifying them as the 4th order depositional architectural elements. He interpreted these elements as channel systems, located in incised submarine valleys. The mudstone units, interspersed with thin beds of siltstone and fine-grained sandstone, between the coarser elements of the 4th order, have thicknesses ranging from 100 to 350 m. The top mudstone- dominated unit has been eroded in the study area. Crane (2004) interpreted the mudstone-dominated intervals as late-stage channel filling or deposition from unconfined, low density turbidity currents. A detailed, measured section by Crane (Figure 3D) illustrates Figure 5. (A) and (B) Summary of the Cerro Toro and packaging within the lower part of the Cerro Toro Punta Barrosa formations and the fundamental Formation, west of the Silla Syncline. The Tres Pasos lithological elements making up these formations. Formation represents the third and youngest unit of (C) and (D) Fundamental failure modes and deep water turbidite deposition in the Magallanes properties of the faults developed from the failure Basin, which is not being considered in this study. structures.

Timing and magnitude of deformation Shear fractures The development of a fold and thrust belt is The most conspicuous type of failure structures generally considered to be contemporaneous with are sharp (very thin), inclined slip surfaces with deposition. See Contribution K (in this volume) for a beautifully striated and polished surface markers. These detailed analysis of the relationship between the sharp discontinuities occur predominantly in the deposition and structural deformation of the Cerro Toro mudstone packages of the lower Cerro Toro Formation Formation. Here, we note only that the overall (Figure 6A) and are limited in size. contraction reflected by the folds and reverse/thrust faults in the region is enormous. Winslow (1981) estimated it at 30 to 160 km, while Kraemer (2003) estimated it at 110 km at lat 50° S and 300 to 600 km at lat 56° S.

Failure modes The diagrams in Figure 5 summarize the major lithological elements making up the Punta Barrosa and Cerro Toro formations and their packaging patterns (5A and B). Also identified in the figure are the failure modes within each lithological unit or assemblage of units (Figure 5C). In this section, we will briefly describe each failure mode and related fault development, as well as the geometric and physical characteristics of the structural products (Figure 5D). We will also briefly assess the potential impact of these Figure 6. (A) and (B) Apparent shear fractures in modes on fluid flow across the units in which they mudstone units of the lower Cerro Toro Formation occur. Although extensive observations have been cropping out on a road cut immediately east of the Tyndall Bridge, southeast of the Park Headquarters. made throughout the Torres del Paine area, the data Notice Curved geometry of the slip surfaces presented here come primarily from three locations. (convex side up) and the well developed striation These are informally referred to as the “Tyndall Bridge slightly fanning towards the bottom of the surface in (B).

Stanford Rock Fracture Project Vol. 18, 2006 J-3 In some cases, the surfaces of the discontinuities are deformation is pronounced within tight folds and fault noticeably curved with the convex sides up and zones, as will be described later. curvilinear striation lines fanning out slightly towards the bottoms of the surfaces (Figure 6B). Generally, it is Bedding plane shear fractures difficult to determine the offset across these slip Bedding interfaces, especially in intervals with surfaces, partly because the structures are within the mudstone intercalation, provide weaknesses along mudstone packages and partly because their slip which slip can occur. Figure 9A shows an outcrop in magnitudes are small, on the order of a few mm to a the western limb of the Silla Syncline across from the few cm. However, in a few cases, a normal sense of Hosteria Pehoe (a well-known motel just west of the movement across them can be inferred, thanks to calcite Syncline). An intrusive dike (light colored in the precipitation across dilational asperities (jogs) along the photograph) is being offset by a bedding plane fault in surfaces. the coarse-grained sandstones of the Cerro Toro Formation. Figure 9B shows another example, a striated Opening mode fractures surface on the east side of an anticline in the uppermost All sandstones and conglomerates of the Punta Barrosa part of the Punta Barrosa Formation, located near the and Cerro Toro formations are characterized by a Tyndall Bridge, southeast of the Park Headquarters. failure mode in the form of opening mode fractures leading to well-defined joint patterns. Figures 7A and B show examples of these in the matrix-supported Sheared-joint based faults conglomerates and coarse sandstones of the Cerro Toro The shearing of joints and the consequent Formation (A) and in the fine-to-medium sandstones of formation of splay joints and their shearing, is the the Punta Barrosa Formation (B). Notice that in (A), the typical mechanism for fault development in the circular or elliptical cross sections of the clasts within sandstone and conglomerate intervals of the Cerro Toro the conglomerate on the joint surface indicate fractures and Punta Barrosa formations. Figure 10 shows two cutting across the clasts, while in (B), multiple sets of examples in the conglomerate of the Cerro Toro joints stop at the thin mudstones between the sandstone Formation: (A) shows morphology of a fault with ~40 layers. m offset and (B) shows an increasing fracture concentration adjacent to another fault with ~5m slip. This mechanism results in the development of two sets Closing mode fractures of strike-slip faults in apparent conjugate patterns, Closing mode fractures, in the form of cleavages similar to that described by Myers and Aydin (2004) due to mineral realignment and planar anisotropy, occur and Flodin and Aydin (2004). in the mudstone units of both the Punta Barrosa and Cerro Toro formations (Figure 8). This mode of

Figure 7. (A) Opening mode fractures in matrix supported conglomerate and course sandstone of the Cerro Toro Formation cropping out at the northwestern slope of Cerro Silla overlooking Lago Nordinskjol. Inset showing details of pebbles with circular and elliptical sections on the joint’s walls indicating knife-sharp cuts. (B) Opening mode fractures in sandstones of the Punta Barrosa Formation cropping out on a road cut, east of the Tyndal Bridge show well developed joint systems. Note joint truncations at thin mudstone intervals.

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Figure 10. Faults formed by sheared-joints mechanism. (A) Morphological expression of a strike-slip fault with ~40 m slip in the matrix- supported conglomerates of the Cerro Toro Fm. cropping out on the western limb of the Silla Figure 8. Closing mode fractures or cleavage Syncline across from Hosteria Pehoe. (B) fractures in the mudstone layers of the Punta Increasing joint concentration adjacent to a strike- Barrosa Fm., Lago Grey Road cut. slip fault in the Cerro Toro Fm.

A Figure 11 illustrates three examples. In (A) is a fault zone with about 40 cm of thrust slip in the Cerro Toro Formation exposed by the Park Highway road cut through the east limb of the Silla Syncline. The fault zone is surprisingly narrow (a few cm), but there is a broad zone of cleavage within the mudstone units adjacent to the fault. The photograph in (B) shows a large scale example (slip>30m) of this type of fault across Lago Sarmiento. Figure 11(C) shows an example of faulting in the Punta Barrosa Formation exposed in the Lago Grey road cut about

5km from the Hosteria Lago Grey on the Park Headquarters-Lago Grey road (see Figure 2 for location). Because the angle between the major fault and the bedding is small and the outcrop is not B accessible, it is difficult to determine the slip magnitude accurately. It appears to be on the order of a few tens of meters. Again, the individual fault zones are narrow except where folded mudstone intervals are present. The last observation provides a prelude to the description of the next category of faults, formed by a coupled folding/faulting process.

Faults/folds coupling Our observations indicate that folding and

faulting in the Upper Cretaceous turbidites in the Figure 9. Bedding plane faults. (A) In a course Magallanes Basin are intimately related. We will grain unit of the Cerro Toro Fm. On the western document this spatial relationship and will shed light limb of the Silla Syncline across from Hosteria on how complex combination of faults and folds may Pehoe. (B) Across the shale lamina of the Punta develop by considering cases from a small Barrosa Fm., east of the Tyndall Bridge. deformation to a large deformation. Figure 12(A) shows a fault zone with a relatively Faults at a low angle to the bedding small offset exposed at Lago Grey road cut. Although Faults occurring at a low angle to the bedding the intervals identified in the figure show very little (<150) are common at all scales in mudstone and integral offset, individual thrust faults with opposing fine-grained sandstone intervals. dip directions have offsets on the order of 30 to 40 cm. In places, the proto fold geometry is apparent.

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Figure 11. (A) A fault with about 40 cm slip at low angle to bedding in the fine grain units of the Cerro Toro Fm., The Park Highway location. (B) A large fault (slip>30m) at low angle to bedding in one of the fine-grained members of the Cerro Toro Fm. across from Lago Sarmiento. (C) A large thrust fault at low angle to bedding apparently juxtaposing the upper Punta Barrosa (on the left) and the lower Cerro Toro (on the right) formations (young over old), east of the Tyndall Bridge. (D) A fault at low angle to bedding in the Punta Barraso Fm., Lago Grey Road cut.

Figure 12. Coupled folding and faulting. (A) A system of faults across a fold. The integral offset is small. However, there are larger offset across the individual faults. Rotations due to folding and faulting are evident. (B) A medium size thrust fault zone (about 10m offset) developed along the steeper limb of a kink fault.

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A Two sets of thrust faults occurred along the core of the fold thereby displacing the limbs which became nearly sub parallel to the over all fault zone. In addition to folding-related limb rotation, a large magnitude rotation associated with faulting is also apparent. This configuration shows that once folded, one or both fold limbs may be incorporated into a deformed zone by individual faults. Figure 12(B) shows an intermediate size deformed zone with a B total thrust offset of about 8m at the same location. Here a fault zone of about 1m thick represent proto steeper limb of what appears to be a kink fold. Many course-grain beds still maintain the folding related rotation and lie at an angle to the direction of the shearing. Also three individual narrower fault zones of about 5 cm thick are localized along the fault zone, two which follow the axial planes of the kink fold. Figure 13(A) illustrates a more complex example of coupling of folding and faulting that led to a broad fault zone (about 20m wide, only 10m of which is in the frame) which underlies the east limb of the Silla Syncline along the Park Highway (see Figure 2 for location). This fault zone extends N-S for at least 1.5- 2 km and is located at the core of a major anticline, C locally preserved along the fault zone. The photograph and the map mark selected beds, faults, late joints, and sheared joints. Figures 13 (B) and (C) show the complexity of the fault zone with folds detached and truncated by shear zones which are tens of cm wide (B) as well as details of the internal architecture of one of the major shear zones with the associated structural elements (C). Both figures show localization of shearing in mudstone levels with intervening slabs of coarser beds oriented parallel to the shear direction. In two cases, central parts of detached folds are bounded by shear zones which probably represent coalesced mudstone beds at the steeper parts of the proto-fold limbs. All of the fault zones show well-developed foliation, an example of which is clearly shown in figure 13 (C). There appears to be a good correlation between the presence of thinly-bedded reddish and whitish carbonaceous layers between the layers of black mudstone and the occurrence of the complex fault zones. To illustrate the point that tight fold structures in thinly-bedded, alternating sandstone and mudstone units of the Punta Barrosa Formation lead to thrust Figure 13. A broad complex fault zone due to faults, refer to Figure 14(A) and (B). In these folding/faulting coupling in the fine-grained structures, large sections of the thrust faults follow mudstome member of the Cerro Toro Fm near the the mudstone-rich levels of the gentle, dipping limbs Park Highway site. (A) A 10 m section of the zone of the folds at various amplitudes and wavelengths. It with structural elements mapped. (B) Details of is apparent that the steeper limbs of small kink folds the western part of the zone in (A). (C) Details of the shear zone marked in (A). have been cut across by the incipient thrust faults, but the fold-fault relationship is unclear for larger structures.

Stanford Rock Fracture Project Vol. 18, 2006 J-7 A however, all of the sandstones and conglomerates of the Magallanes turbidites failed only by opening mode fracturing and the faults in these units developed by sheared-joint mechanism. These faults, even when they have small displacement discontinuity, have broad zones of fractures that would provide ideal pathways for fluids. It is highly conspicuous that no deformation bands (Aydin et al., 2006) were found in the granular rocks of the Upper Cretaceous turbidites in the study area. We think that this is due to the internal texture of the sandstone deposits in these sequences. Figure 15 includes four photomicrographs of sandstone B samples; two from the Cerro Toro Formation (A and B from Crane, 2004) and two from the Punta Barrosa Formation (C and D from Fildani, 2004). These photomicrographs indicate that the corresponding sandstones are very tight. They all show that the grains are surrounded by a fine-grained matrix occupying about 12-15 % volume (Crane, 2004). Scott (1966) documented the same texture and Figure 14. Coupling of complex folds and faults in estimated a volume fraction slightly higher than that the thinly bedded sandstone/mudstone sequence by Crane (2004). Some samples show clear evidence of the Punta Barrosa Fm., the eastern coast of for amalgamation especially in the Punta Barrosa Lago Grey. (A) A series of kink bends and related sandstones. These textures either genuinely thrust faults. (B) One large scale thrust fault zone. depositional or diagenetic in origin resulted in very tight rocks virtually with no pore space between the Discussion and implications grains. We propose that these textures are indicative The sharp, shearing structures described in this of high grain contact strength, and in turn, increasing study are remarkable. If, in fact, they are knife sharp, skeleton stiffness thereby promoting sharp opening with shear-fracture morphologies and small shear- mode failure, rather than localized strain in the form displacement discontinuities, then they are similar to of deformation bands with a finite thickness. idealized “shear cracks”. To the best of our Bedding plane faults are easy to rationalize knowledge, this is the first time such a genuine because of the presence of shale layers or lenses prototypical shear failure of any rock has been along the bedding interfaces. However, the faults that documented. Notice that the mudstone in which these are oriented at very low angle to the bedding structures occur, later failed by opening-mode interfaces that contain mudstone are more difficult to fracturing (presumably after the sediments rationalize. It is possible that some sections of these consolidated), as evidenced by high-angle joints structures follow the mudstone layers while other cutting through both the rock and the shear fracture parts cut up section across the coarser layers, the surface morphology. This observation indicates that detail mechanism of which remains to be elucidated. the sharp shear fractures are the oldest structures in These faults may not add much to the sealing across the study area. If the initial assertion that these are the fault due to already existing, sub-parallel normal faults is correct, then we may speculate about mudstone layers. However, the impact of cleavages two scenarios for their formation. The first possibility and veins, which are common along these fault is soft sediment deformation under gravitational zones, is a worthwhile subject for further exploration. loading while the mudstone was unconsolidated. The The interaction of folding and faulting results in second is based on the conical, curved geometry and deformed zones with: slight fanning of the curvilinear striations, which are (1) Fragmented and broken pieces of stiffer reminiscent of characteristics associated with impact layers, aligned sub-parallel to the shear direction; (2) structures seen the world over. Considering that the differentiated mudstone and fine-grained materials rocks are of Upper Cretaceous age, the temporal accommodating much of the slip and; (3) detached, setting lends support for this latter scenario. tight folds displaced from their original positions. Most if not all lithologies (including those of the Thus, fault zones produced by this mechanism mudstones turbidites of the Magallanes Basin) fail by display extremely complex heterogeneity across a opening-mode fracturing at some stage. Notably, broad shear zone.

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Figure 15. (A to D) Photomicrographs of thin sections from four sandstone samples collected from the Cerro Toro (A and B, from Crane, 2004), and Punta Barraso (C and D, from Fildani, 2004) formations. Scales bars 0.5 mm. (a) and (b) are for grains whereas (c) is for the fine-grained matrix.

The thickness of such faults will probably vary news is that it may be possible to predict where, significantly as the fault transects lithological within a turbidite column, fundamental failure packages with different mechanical and geometric fractures and faults with various internal architectures characteristics. are likely to occur.

Conclusions Acknowledgements We have identified a number of interesting We thank Steve Graham, Donald Lowe, Will failure types in the Upper Cretaceous turbidites of the Crane, Andrea Fildani, and Steve Hubbard with the Magallanes Basin in Chilean Patagonia. These are: SPODDS Group at Stanford for their help. We also apparent shear fractures, likely formed when thank Ghislain de Joussineau and Ramil Ahmadov sediments were unconsolidated; closing mode for their assistance in the preparation of the paper. fractures in mudstone; opening mode fractures in most of the lithological units; and bedding-interface References shear fractures along interfaces marked by mudstone. Aydin, A., Borja, R. I., and Eichhubl, P., 2006, Geological These failure modes are likely dependent on the and Mathematical framework for failure modes in lithological content of the turbidite deposits and their granular rock. J. Structural Geology, 28, 83-98. rheological properties, as well as the driving stresses Biddle, K.T., Uliana, M.A., Mitchum Jr., R.M., Fitzgerald, at the time of the fracturing. Faults oriented at low M.G., and Wright, R.C., 1986, The stratigraphic and angle to the bedding and highly heterogeneous, broad structural evolution of the central and eastern Magallanes thrust fault zones, resulting from coupled fold and Basin, southern South America, in Allen, P.A., and fault instabilities, are complex structures which Homewood, P., eds., Foreland Basins: International remain subjects for further investigation. The good

Stanford Rock Fracture Project Vol. 18, 2006 J-9 Association of Sedimentologists Special Publication 8, p. Hallam, A., 1991, Relative importance or regional tectonics 41-63. and eustasy for the Mesozoic of the Andes, in Bruhn, R.L., Stern, C.R., and de Wit, M.J., 1978, Field and Macdonald, D.I.M., ed., Sedimentation, Tectonics and geochemical data bearing on the development of a Eustasy, Sea-level Changes at Active Margins: Mesozoic volcano-tectonic rift zone and back-arc basin International Association of Sedimentologists Special in southernmost South America: Earth and Planetary Publication 12, p. 189-200. Science Letters, v. 41, p. 32-46. Katz, H. R., 1963, Revision of Cretaceous stratigraphy in Crane, W.H., 2004, Depositional history of the Upper Patagonian cordillera of Ultima Esperanza, Magallanes Cretaceous Cerro Toro Formation, Silla Syncline, Province, Chile: Bulletin of the American Association of Magallanes Basin, Chile [PhD thesis]: Stanford Petroleum Geologists, v. 47, no. 3, p. 506-524. University, Stanford, California, 275 p. Kraemer, P.E., 2003, Orogenic shortening and the origin of Dott, R.H., Winn, R.D., Jr., and Smith, C.H.L., 1982, the Patagonian orocline (56°S. lat): Journal of South Relationship of late Mesozoic and Early Cenozoic American Earth Sciences, v. 15 p. 731-748. sedimentation to the tectonic evolution of the Macellari, C.E., Barrio, C.A., and Manassero, M.J., 1989, southernmost Andes and the Scotia Arc, in C. Craddock, Upper Cretaceous to Paleocene depositional sequences ed., Antarctic Geoscience: International Union of and sandstone petrography of south-western Patagonia Geological Sciences, Symposium on Antarctic Geology (Argentina and Chile): Journal of South American Earth and Geophysics, University of Wisconsin, Madison, p. Sciences, v. 2, no. 3, p. 223-239. 193-202. Myers, R; Aydin, A., 2004, The evolution of faults formed Flodin, E. A. and Aydin, A., 2004, Evolution of a strike- by shearing across joint zones in sandstone. Journal of slip fault network, Valley of Fire, southern Nevada. Structural Geology, v.26, no.5, p.947-966. Geological Society of America Bulletin, v. 116, no. 1/2, Shultz, M.R., and Hubbard, S.M., 2005, Sedimentology, p. 42-59, DOI 10.1130/B25282.1. stratigraphic architecture, and ichnology of gravity-flow Fildani, A., Cope, T.D., Graham, S.A., and Wooden, J.L., deposits partially ponded in a growth-fault-controlled 2003, Initiation of the Magallanes foreland basin: Timing slope minibasin, Tres Pasos Formation (Cretaceous), of the southernmost Patagonian Andes orogeny revised Southern Chile: Journal of Sedimentary Research, v. 75, by detrital zircon provenance analysis: Geology, v. 31, no. 3, p. 440-453. no. 12, p. 1081-1084. Wilson, T.J., 1991, Transition from back-arc to foreland Fildani, A., and Hessler, A.M., 2005, Stratigraphic record basin development in the southernmost Andes: across a retroarc basin inversion: Rocas Verdes- Stratigraphic record from the Ultima Esperanza District, Magallanes Basin, Patagonian Andes, Chile: Bulletin of Chile: Bulletin of the Geological Society of America, v. the Geological Society of America, v. 117, no. 11/12, p. 103, p. 98-115. 1596-1614. Winslow, M.A., 1981, Mechanisms for basement Gust, D.A., Biddle, K.T., Phelps, D.W., and Uliana, M.A., shortening in the Andean foreland fold belt of southern 1985, Associate Middle to Late Jurassic volcanism and South America, in McClay, K.R., and Price, N.J., eds., extension, southern South America: Tectonophysics, v. Thrust and nappe tectonics: Geological Society 116, p. 223-253. [London] Special Publication 9, p. 513-529.

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