Structural, Geomorphic, and Depositional Characteristics of Contiguous and Broken Foreland Basins: Examples from the Eastern Flanks of the Central Andes in Bolivia and NW Argentina

Abstract

In this chapter, we contrast the elements of a typical, contiguous foreland basin system in the Bolivian Andes with the broken foreland farther south in northwestern Argentina. We illustrate differences in deposition and geomorphic shape that arise from the structural conditions to which these two systems are subjected. Generally, the principal elements of foreland-basin systems result mainly from accommodation space created by the flexural response of the crust to the topographic load of a fold-and-thrust belt. This leads to the formation of four distinct depozones: the wedge-top, foredeep, forebulge, and backbulge. In contrast, broken foreland basins are formed in areas where retroarc convergence is accommodated primarily along re-activated, high-angle structures. Rather than creating a broad area of consistently sloping mean topography, rock uplift along these structures is often disparate in space and time, leading to the formation of discrete ranges of limited along-strike extent that occur far inboard of the main topographic front of the orogen. The potentially high rock-uplift rates accommodated by steep, reactivated reverse faults favors isolation of the headwater basins of such systems from the downstream fluvial network, leading to sediment ponding behind the rising mountain ranges. In addition, the limited flexural response associated with short wavelength, laterally restricted topography may fail to create large amounts of accommodation space seen in the foredeep depozone that typifies foreland basin systems. Thus, instead of the generally continuous, laterally extensive foreland basin system associated with continental-scale crustal flexure, broken foreland basins, such as in the northwestern Argentine Andes, consist of a set of variably connected, laterally restricted depocenters. These evolve behind actively rising topography or small basins that form within the limited accommodation space created around individual uplifted mountain ranges. These types of depositional systems lack many of the elements that are typical of recent foreland basins, including well-developed foredeep, forebulge, and backbulge depositional systems. Instead of applying foreland basin models to broken foreland basin systems, it is important to view these systems in the context of their distinct structural, topographic, and geodynamic circumstances.

Late Miocene-Pleistocene evolution of India-Eurasia convergence partitioning between the Bhutan Himalaya and the Shillong Plateau: New evidences from foreland basin deposits along the Dungsam Chu section, eastern Bhutan

“…What makes the Dunsgam Chu section special along the Himalayan arc is its location north of the Shillong Plateau, a unique basement‐cored uplift in the Himalayan foreland (Figure ). At the longitude of central and eastern Bhutan, the Himalayan foreland corresponds to a broken foreland basin [e.g., Jordan , ; Strecker et al ., ], rather than a classical foreland system [e.g., DeCelles and Giles , ]. In this area, the foredeep is very shallow (maybe <1 km), in contrast to areas west and east of Bhutan (depths >4 km) [ Dasgupta , ; Verma and Mukhopadhyay , ; Vernant et al ., , Figure 1b].…”

Tectonic Regimes of the Central and Southern Andes: Responses to Variations in Plate Coupling During Subduction

“…Synorogenic sedimentary basins are preserved on both orogenic flanks, including forearc basins controlled by diverse structures and retroarc hinterland and foreland basins mostly associated with shortening‐induced topographic loading and lithospheric flexure (Horton, , , ; Horton & DeCelles, ; Jordan, ; Jordan et al, ; Watts et al, ). Structural, stratigraphic, and thermochronologic results show that the locus of Late Cretaceous‐Cenozoic shortening has advanced eastward toward the South American craton (Carrapa et al, ; Carrapa & DeCelles, ; DeCelles & Horton, ; Gubbels et al, ; Elger et al, ; Ege et al, ; Horton et al, ; McQuarrie et al, , ; Strecker et al, ).…”

Synorogenic foreland rifts and transtensional basins: A review of Andean imprints on the evolution of the San Jorge Gulf, Salta Group and Taubaté Basins

“…Foreland lithosphere is sensitive to a wide variety of processes directly to indirectly related to orogenesis: lithospheric flexure, where the continental plate is forced to bend under the weight of the orogen (creating a foreland basin system), lithospheric fragmentation, where the plate breaks in response to orogenic compression (giving place to a broken foreland basin system) (DeCelles and Giles, 1996;Strecker et al, 2011) and dynamic subsidence and uplift (e.g. Braun et al, 2010).…”