Mixed Carbonate-siliciclastic Succession Research Articles

Significance of Middle Cambrian mixed carbonate-siliciclastic units for global correlation: southern Nevada, USA

Sequence-stratigraphic analysis of the Middle Cambrian Highland Peak, Bonanza King, Swasey, and Wheeler formations in the Great Basin refines platform-to-basin correlations and distinguishes local tectonic events from eustasy. This analysis provides a reliable sea-level history through the Ptychagnostus gibbus and Ptychagnostus atavus trilobite intervals and confirms that the Global Stratotype Section and Point (GSSP) at the first appearance datum (FAD) of P. atavus was deposited during an overall sea-level rise. Deposition during the Middle Cambrian Ehmaniella/ Bolaspidella biozones in the western U.S. is represented by two lithologically distinct successions: (1) a poorly fossiliferous, shallow-water, mixed carbonate-siliciclastic succession that is widespread across southern Nevada and southeastern California and (2) a highly fossiliferous, deeper water, fine-grained, siliciclastic succession in central Nevada and western Utah. The deeper water succession was deposited within the fault-controlled House Range Embayment and contains the P. atavus GSSP. Correlation of these disparate successions had been hampered by a lack of high-resolution biostratigraphic data, and limited chemostratigraphy and sequence stratigraphy. In this study, sequence-stratigraphic analysis indicates that the Condor Member of the Highland Peak Formation and the “mixed unit” of the Bonanza King Formation are the shallow-water platform equivalents of the basal Wheeler Formation encompassing the P. gibbus and lower P. atavus zones. The deepening event that is recorded in the P. gibbus Zone represents a major flooding surface that may be used as an important event marker for regional and global correlation. The overlying P. atavus GSSP, however, is within the later stage of transgression and may represent a globally synchronous event that can be correlated from platform to basin.

Anatomy of a submarine channel system and related fan in a foramol/rhodalgal carbonate sedimentary setting: a case history from the Miocene syn-rift Sardinia Basin, Italy

During Aquitanian–Burdigalian times, thick mixed carbonate–siliciclastic successions were deposited in basins located on the grabens and half-grabens along the Oligo-Miocene Sardinia Rift Basin. Locally active tectonics, sea level variations and ecological factors combined to control the development and distribution of foramol carbonate factories as well as the remobilisation and the redeposition of carbonate sediments into the adjacent deeper areas. In the Isili Basin, foramol/rhodalgal carbonate factories developed on submerged structural highs which resulted from pre- and syn-sedimentary tectonics. These carbonate factories were periodically shaved mainly during negative sea level oscillations and the sediments removed were funnelled towards the basin through a complex submarine channel network which included a tributary belt, one main channel (Isili Channel) and the related fan. The Isili Channel is up to 1 km wide, 60–100 m deep and includes two stacked channel complexes each built up by several minor-order channel units. Complex strata geometries characterise the Isili Channel and its related architectural elements (e.g., overbank, levee, margin and channel thalweg) which also include up to 15 m high bedforms. Individual channel complexes were temporally related to individual fan systems whose spatial distribution and internal geometry were strongly controlled by the type and rate of sediment accumulation and, in turn, by relative sea level oscillations. Facies associations include sandy to cobble-sized gravity flow and bottom current deposits as well as megabreccias characterised by impressive displaced and tilted blocks which resulted from major channel margin collapses. Detailed analysis has led to the reconstruction of the internal geometry and depositional architecture of these carbonate bodies and to the determination of the main controlling factors. The dimension and distribution of channel and channel-related depositional bodies have been accurately determined. This information provides a useful tool to analyse less extensively exposed analogues and to model foramol shelf to basin transitions and related channel and fan systems.

Sedimentology of the Upper Triassic Charlie Lake, Baldonnel and Pardonet formations from outcrop exposures in the southern Trutch region, northeastern British Columbia

Abstract Upper Triassic strata in the Trutch (94 G) NTS map area consist of the Charlie Lake, Baldonnel and Pardonet formations. These units comprise a mixed siliciclastic-carbonate succession, approximately 350 to 400 m thick. Sediments accumulated along a low gradient continental ramp deposited on the northwestern margin of Pangaea. Twenty-two lithofacies, deposited in distal offshore through supratidal settings are documented. Seven recurrent facies associations are identified in these strata; four reflecting deposition in continental to marginal marine settings, and three reflecting shallow to deep water marine deposition. Facies association 1 (FA1) consists of interbedded dolomitic mudstone/siltstone and dolomitic sandstone that was deposited in an intertidal flat depositional setting. Facies association 2 (FA2) consists of normally graded, trough cross-bedded to current ripple-laminated lenticular beds of mudclast-rich fine- to medium-grained sandstone, and was deposited by a series of small tidal channels. Facies association 3 (FA3) consists of well-sorted fine-grained sandstone beds characterized by high-angle tabular to wedge-shaped cross-beds, low-angle planar cross-beds, low-relief, translatent ripples and inversely graded lamina sets. FA3 is interpreted to represent deposition by a series of elongate, shore-parallel aeolian dunes. Facies association 4 (FA4) consists of a heterogeneous succession of solution collapse breccias, rooted, pedogenically-altered mudstone and siltstone, and wave-rippled very fine- to fine-grained sandstone. It is interpreted as ephemeral lacustrine and/or supratidal sabkha. Facies association 5 (FA5) consists of variably bioclastic quartzose sandstone, crinoidal packstone-grainstone and bivalve-dominated packstone beds. It is interpreted as a wave-dominated shoreface to foreshore on a shallow (inner) ramp. Facies association 6 (FA6) is dominated by very fine-grained calcareous sandstone and thin to thick-bedded bivalve-dominated wackestone, packstone and grainstone. It is interpreted as medial ramp (i.e., offshore transition to proximal offshore). Facies association 7 (FA7) consists primarily of organic-rich calcareous siltstone and mudstone (commonly with abundant carbonate concretions) and variably thick tightly packed bivalve packstone/grainstone beds. It is interpreted as outer ramp (proximal to distal offshore). Siliciclastic sediment in the study area was derived from a variety of sources, including fluvial input from the east-northeast, longshore drift from the north, and aeolian input sourced from marginal marine dune fields. Carbonate sediment in the study interval consists primarily of bioclastic detritus, although non-skeletal grains, particularly faecal pellets, and ooids are locally common. Skeletal carbonate material is dominated by disarticulated mollusc valves and crinoid skeletal debris but also includes ammonoids, articulate brachiopods, gastropods. Vertebrates (fish and reptiles) are also common.

Carbon isotope stratigraphy of the Neoproterozoic-Cambrian transition: An introduction

Carbonate units deposited during the Precambrian-Cambrian transition records a unique δ13C profile that is useful for chemostratigraphic correlation. However, the Precambrian-Cambrian boundary is currently defined within siliciclastic units where δ13C data are not available. The mixed siliciclastic-carbonate succession from the southern Great Basin, USA, records the appropriate fossils in the siliciclastic strata interbedded with carbonate strata that record the appropriate shifts in δ13C to facilitate correlation between the lithologic end-members. Ultimately, the integrated dataset demonstrates that vertical burrowing and the onset of widespread biomineralization was essentially synchronous.

Lithostratigraphy of the Neoproterozoic Chattisgarh Sequence, its Bearing on the Tectonics and Palaeogeography

The Neoproterozoic Purana succession in the eastern part of Chattisgarh basin around Sarangarh has been classified into a conglomerate-sandstone-shale dominated proximal assemblage, and a lithographic limestone-shale dominated distal assemblage. The proximal assemblage constitutes the Chandarpur Group, and unconformably overlies the Archean crystalline basement complex. The Chandarpur succession has been classified into three formations that were deposited in fan-fan delta, deep water prodelta and storm- tide dominated prograding shelf environments. The distal assemblage, the Raipur Group, conformably overlies the Chandarpur Group, and may be subdivided into two shale-dominated formations separated by a limestone-dominated formation. The limestone sequence, the Sarangarh Limestone, comprises a lower member of mixed carbonate-siliciclastic succession deposited in a storm dominated shallow water platform, and an upper member of pelagic limestone that grades upward into a deep water shale, the Gunderdehi Shale. The rapid transition from shallow water platformal succession to deep-water pelagic limestone and shale points to abrupt deepening of the basin and drowning of the craton. The peak of transgression is represented by a persistent horizon of black limestone, a product of basin wide anoxia. Disposition of facies belts in proximal and distal assemblages and palaeocurrent directions measured from different facies belts point to a north-northwesterly palaeoslope of the basin. Signatures of intense storm and tidal currents in different litho-units collectively point to an open marine circulation condition. It has been inferred that the basin was connected to a major seaway that skirted the northern and north-western margin of the craton. Development of thick fan-delta sequence at the base of the succession, occurrence of felsic welded tuff within the Gunderdehi Shale, thick sandstone-mudstone cyclothems in the Chandarpur Group, and abrupt drowning of the carbonate platform leading to pelagic sedimentation collectively point to major tectonic control on basin evolution. The basin developed as a cratonic rift and evolved into a deeply subsiding one, without any major stratigraphic hiatus, through episodic tectonic pulses.

Sedimentology, Paleontology, and Sequence Stratigraphy of Early Permian Estuarine Deposits, South-Central New Mexico, USA

Abstract The Lower Permian (Wolfcampian) Hueco Formation in the Dona Ana Mountains of south-central New Mexico contains a 30-m-thick, mixed siliciclastic-carbonate succession exposed for up to 1 km perpendicular to regional paleoslope. The succession was deposited in shallow-marine, wave- and tide-dominated estuarine, and fluvial environments, and is arranged into three fourth-order sequences. The lower two sequence boundaries incise marine fossiliferous packstone and offshore to lower-shoreface mudstone-siltstone and are overlain by fluvial sediment comprising the lowstand systems tract. Fluvial-channel sedimentation above the lower two sequence boundaries changed from vertical to lateral accretion in response to decreasing gradient in the incised valley. The transgressive systems tract of the lower two sequences begins with a tidal ravinement surface, which is mantled locally by a pebble–cobble lag of rip-up clasts and fossils. The tidal ravinement surface cuts channels up to 4 m deep, locally removing ...

Stratigraphic architecture of a Santonian mixed siliciclastic-carbonate succession (Catalonian Pyrenees, Spain)

At Collades de Bastus, Catalonian Pyrences, a Santonian mixed siliciclastic-carbonate succession indicates two proximal-distal gradients, and records two styles of stratigraphical development upon relative sea-level change. The succession consists of four small-scale sequences (5.1 to 5.4) within the highstand systems tract of the. “Valicarca-5” depositional sequence of Simo (1993), and is topped by a drowning sequence (small-scale sequence 5.5).

Stratigraphlc Hierarchy and Cycle Stacking, Facies Distribution, and Interwell-Scale Heterogenelty: Grayburg Formation, New Mexico: ABSTRACT

The Grayburg Formation (middle Guadaluplan) of southeastern New Mexico is a mixed carbonate-siliciclastic succession that represents predominantly shallow water sedimentation on the Northwest Shelf of the Delaware Basin. Exceptional Grayburg outcrops in the Brokeoff Mountains permit high-resolution correlation and mapping of interwell-scale facies complexity both along depositional dip and across strike. Three orders of stratigraphic hierarchy are recognized using vertical facies successions and transgressive-regressive relationships expressed along a dip cross section. This stratigraphic organization cannot be fully defined from a vertical section. Cycles (3-30 ft thick) are the smallest-scale, upward-shoaling facies successions that can be correlated across facies tracts and constitute the basic chronostratigraphic unit. Cycles are organized into transgressive-regressive cycle sets (15-40 ft thick). High-frequency sequences (100-160 ft thick) are unconformity-bound successions composed of 10 to 20 cycles arranged into transgressive and highstand systems tracts. One-dimensional cycle thickness stacking patterns do not reflect the long-term accommodation trends imposed by high-frequency sequences because most cycles did not fully aggrade to sea level. Interwell-scale heterogeneity (hundreds of ft) is high in transgressive ooid grainstones, which formed dip-elongate tidal channels and shoals. Highstand ooid grainstones formed strike-elongate shoals that are laterally continuous along dip and across strike (thousands of feet) due tomore » stacking and amalgamation of grainstone bodies in an accommodation-limited highstand setting. The well-defined relationship between stratigraphic hierarchy and facies composition and heterogeneity can be used to improve correlations and better predict lateral dimensions of reservoir facies.« less

Seismic Models of a Shelf-margin Depositional Sequence: Upper San Andres Formation, Last Chance Canyon, New Mexico

ABSTRACT The seismic resolution of stratal geometries and facies distributions observed in San Andres Formation (Permian) outcrops in Last Chance Canyon, Guadalupe Mountains, New Mexico, is studied by seismic modeling of a published, detailed stratigraphic cross section. The outcrops in Last Chance Canyon are composed of two fourth-order depositional sequences: an aggrading carbonate bank (upper San Andres 3; uSA3) followed by a strongly progradational, offlapping mixed carbonate-siliciclastic succession (upper San Andres 4; uSA4). Each sequence comprises a number of subsidiary high-frequency sequences (fifth-order). Two alternative impedance models were used: Model A, in which all facies transitions are reflecting boundaries, and Model B, in which only time-significant surfaces act as reflectors and lateral facies transitions are represented by horizontal velocity gradients. The vertical-incidence modeling technique was used to compute perfectly migrated time and depth sections with different frequencies. Using a low-frequency wavelet (25 Hz), the sequence boundary separating the two fourth-order cycles (uSA3 and uSA4) is poorly imaged. Instead, one is tempted to incorrectly interpret an onlap pattern generated by a high-frequency cycle within uSA4 as this major sequence boundary. In addition, the 25 Hz runs show toplap and downlap lap-out patterns in an overly oblique fashion, obscuring true asymptotic stratal relationships. Both at 35 Hz and 50 Hz, profiles based on Model B image the genetic structure of both uSA3 and uSA4 relatively well. At 50 Hz, Model A incorrectly shows a transition from a ramp to a rimmed margin within uSA4. The 35 Hz models are qualitatively compared with a published Exxon Production Research Co. seismic line, located approximately 50 km along depositional str ke to the northeast. Model A shows an unexpected good match with the Exxon seismic line, whereas Model B comes much closer to the depositional anatomy observed in outcrop. Our results show that the resolution of stratal geometries and facies distributions in Last Chance Canyon is strongly related to carbonate-sandstone alternations and the way impedance contrasts at carbonate-sandstone transitions are represented.

Variations in the Lithologic Expression of Sequence Boundaries in an Upper Middle Carboniferous Cyclic Mixed Carbonate-Siliciclastic Succession, Midcontinent U.S.A.

Variations in the Lithologic Expression of Sequence Boundaries in an Upper Middle Carboniferous Cyclic Mixed Carbonate-Siliciclastic Succession, Midcontinent U.S.A.