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Scanning electron microscopic images of Inoceramus shells from Sierra del Toro (SdT), the Silla Syncline (SS) and Cerro Castillo (CC). No secondary cement is observed between individual prisms.
Source publication
The details of how narrow, orogen-parallel ocean basins are filled with
sediment by large axial submarine channels is important to understand
because these depositional systems commonly form in through-like basins
in various tectonic settings. The Magallanes foreland basin is an
excellent location to study an orogen-parallel deep-marine system.
Con...
Contexts in source publication
Context 1
... (Fig. 7) were separated from the encasing mudstone and broken into millimeter-sized frag- ments. The best-preserved columnar prisms of the inoc- eramid shells were hand-selected with the aid of a binocular microscope. Examination of the samples by SEM revealed that no trace impurities or calcite cement was deposited between the calcite prisms ( Fig. 8). Inocer- amids appear to be well preserved showing distinct interprism boundaries and relatively sharp prism edges (Fig. 8). However, close-ups of the prism show slightly uneven surfaces that may be signs of dissolution that may signal post-growth interaction with fluids (Fig. ...
Context 2
... prisms of the inoc- eramid shells were hand-selected with the aid of a binocular microscope. Examination of the samples by SEM revealed that no trace impurities or calcite cement was deposited between the calcite prisms ( Fig. 8). Inocer- amids appear to be well preserved showing distinct interprism boundaries and relatively sharp prism edges (Fig. 8). However, close-ups of the prism show slightly uneven surfaces that may be signs of dissolution that may signal post-growth interaction with fluids (Fig. ...
Context 3
... or calcite cement was deposited between the calcite prisms ( Fig. 8). Inocer- amids appear to be well preserved showing distinct interprism boundaries and relatively sharp prism edges (Fig. 8). However, close-ups of the prism show slightly uneven surfaces that may be signs of dissolution that may signal post-growth interaction with fluids (Fig. ...
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Citations
... The ancient deep-water succession in southern Chile was deposited within the Magallanes retroarc foreland basin, which formed in response to Andean orogenesis during the Late Cretaceous (Wilson, 1991; Fildani et al., 2003; Fildani and Hessler, 2005; Fosdick et al., 2011). The foredeep succession includes >4000 m of deep-water sedimentary strata that were deposited over ~20 Myr (Katz, 1963; Romans et al., 2010; Bernhardt et al., 2012). The final stage of deep-marine basin infill is recorded by the southward progradation of high relief (>1000 m) clinoform systems (Hubbard et al., 2010). ...
Constructing geologically accurate reservoir models of deep-water strata is challenging due to the reliance on incomplete or limited resolution datasets. Connecting areas of high-certainty across areas where data is sparse or non-existent (e.g., between wellbores) is difficult and requires numerous interpretations and assumptions. In this study, morphometric data from the Lucia Chica Channel System, offshore California, provides high-resolution 3-D information that is used to constrain correlation and characterization of ancient submarine channel fill deposits.
A statistical relationship between cross-sectional asymmetry and planform morphology in sinuous submarine channels is determined from bathymetric data. Submarine channel cross-sectional asymmetry was quantified by calculating the ratio between the distance from the inner bend margin to the thalweg by the entire channel width. This metric was calculated for 243 cross-sections, from 27 channel bends ranging in sinuosity from 1.0 to 3.0. Three distinct channel geometries are classified based on their thalweg position; normal asymmetrical, symmetrical and inverse asymmetrical. Straight channel segments (sinuosities 1.0-1.05) exhibit the most symmetrical cross-sectional morphologies. Low (sinuosities 1.05-1.2) and high sinuosity (sinuosities >1.2) channel bends exhibit maximum cross-sectional asymmetries at bend apexes, with symmetrical cross-sectional morphologies at inflection points. As expected, asymmetry values systematically increase from straight to high sinuosity channel segments; however, the most significant increase occurs at the threshold from straight to low sinuosity channel segments, which suggests that even minor deviation from straight channels promotes development of asymmetrical cross-sectional morphologies. Defined relationships are utilized to inform correlation of channelform surfaces between two well-exposed outcrops of a sinuous deep-water channel system that are ~ 1 km apart (Cretaceous Tres Pasos Formation, southern Chile). The developed methodology can be applied in the subsurface to model realistic channelform sedimentary bodies guided by channel planform interpretations from limited-resolution 3-D seismic data, augmented by well data.
... Many stratigraphic and provenance studies have focused upon the Upper Cretaceous Patagonian Magallanes basin strata (e.g. Katz, 1963;Macellari et al., 1989;Biddle et al., 1986;Wilson, 1991;Fildani et al., 2003;Fildani & Hessler, 2005;Romans et al., 2010;Bernhardt et al., 2011;McAtamney et al., 2011) that have demonstrated sustained sedimentary connectivity between the southern Patagonian batholith (Herv e et al., 2007b) and the age-equivalent thrust belt and marine foredeep in the Patagonian Andes. Throughout the Late Cretaceous, sediment dispersal systems provided a remarkably continuous supply of batholith-sourced zircon to the basin (Fig. 2). ...
... In this study, we have measured combined detrital zircon U-Pb and He ages from the Maastrichtian through Middle Miocene Magallanes basin sediments to address the following questions: (1) How significant was foreland basin burial heating during Cenozoic advancement of Fildani et al., 2003;Romans et al., 2010;Bernhardt et al., 2011) in comparison to the batholith intrusive ages (shown by coloured panels). ...
... Natland et al., 1974;Wilson, 1991;Fildani & Hessler, 2005;Romans et al., 2011). Detrital zircon results from the Upper Cretaceous Patagonian Magallanes basin, summarized in the inset to Fig. 2 (Fildani et al., 2003;Romans et al., 2010), agree with other geologic evidence that collectively indicate that the Late Jurassic through Neogene plutons of the Patagonian batholith were the primary contributor of sediment to the Patagonian Magallanes basin throughout its history at this latitude (Forsythe & Allen, 1980;Herv e et al., 2003;Pankhurst et al., 2003;Fildani et al., 2003;Herv e et al. (2004); Romans et al., 2011;Bernhardt et al., 2011). Sandstone petrography and mudstone geochemistry of turbidites of the Turonian Punta Barrosa Formation deposited in the incipient foreland basin also indicate that subordinate amounts of sediment was sourced from local basement highs represented by the Rocas Verdes Basin, Palaeozoic to earliest Mesozoic metamorphic basement complexes, and the Sarmiento ophiolitic complex (Fildani & Hessler, 2005). ...
The Patagonian Magallanes retroarc foreland basin affords an excellent case study of sediment burial recycling within a thrust belt setting. We report combined detrital zircon U-Pb geochronology and (U-Th)/He thermochronology data and thermal modeling results that confirm delivery of both rapidly cooled, first-cycle volcanogenic sediments from the Patagonian magmatic arc and recycled sediment from deeply buried and exhumed Cretaceous foredeep strata to the Cenozoic depocenter of the Patagonian Magallanes basin. We have quantified the magnitude of Eocene heating with thermal models that simultaneously forward model detrital zircon (U-Th)/He dates for best-fit thermal histories. Our results indicate that 54-45 Ma burial of the Maastrichtian Dorotea Formation produced 164-180°C conditions and heating to within the zircon He partial retention zone. Such deep burial is unusual for Andean foreland basins and may have resulted from combined effects of high basal heat flow and high sediment accumulation within a rapidly subsiding foredeep that was floored by basement weakened by previous Late Jurassic rifting. In this interpretation, Cenozoic thrust-related deformation deeply eroded the Dorotea Formation from ~ 5 km burial depths and may be responsible for the development of a basin-wide Paleogene unconformity. Results from the Cenozoic Río Turbio and Santa Cruz formations confirm that they contain both Cenozoic first-cycle zircon from the Patagonian magmatic arc and highly outgassed zircon recycled from older basin strata that experienced burial histories similar to those of the Dorotea Formation.
Magallanes-Austral Basin (MAB) fill is preserved along a >1000 km north-south trending outcrop belt in the southern Patagonia region of Argentina and Chile. Although the stratigraphic evolution of the MAB has been well documented in the Chilean sector (referred to as the Magallanes Basin), its northern terminus in southern Argentina (Austral Basin) is poorly constrained. We present new stratigraphic and geochronologic analyses of the early basin fill (Aptian-Turonian) from the Argentine sector (49-51°S) of the MAB to document spatial variability in stratigraphy and timing of deposition during the initial stages of basin evolution. The initiation of the retroarc foreland basin fill is marked by the transition from mudstone to coarse-clastic deposition, which is characterised by the consistent presence of sandstone beds > ca. 20 cm thick interpreted to represent sediment gravity flows deposited in a submarine fan system. Depositional environments within the early fill of the basin range from lower to upper deep-water fan settings as well as previously undocumented slope deposits. These facies are present as far north as El Chalten, Argentina (ca. 49°S), indicating that facies-equivalent rocks can be traced along-strike for at least 5 degrees of latitude, based on correlation with strata as far south as the Cordillera Darwin (ca. 54°S). Eight new U-Pb zircon ages from ash beds reveal an overall southward younging trend in the initiation of coarse clastic deposition. Inferred depositional ages range from ca. 115 ± 1.9 Ma in the northernmost study area to not older than 92 ± 1 Ma and 89 ± 1.5 Ma in the central and southern sectors respectively. The apparent diachronous delivery of coarse detritus into the basin may reflect (1) gradual southward progradation of a deep-water fan system from a northerly point source and/or (2) orogen-parallel variations in the timing and magnitude of thrust-belt deformation and erosion that provided more local sources for sediment delivery.
