Evolution of a mixed siliciclastic-carbonate deep-marine system on an unstable margin: the Cretaceous of the Eastern Greater Caucasus, Azerbaijan

Abstract

Mixed siliciclastic-carbonate deep-marine systems, herein termed ‘mixed systems’, are less well documented than their siliciclastic-dominated counterparts, but may be common globally and misinterpreted as transient transition zones between carbonate and siliciclastic deposition. The well-exposed Upper Cretaceous mixed-system of the Buduq Trough, Eastern Greater Caucasus (EGC), Azerbaijan, provides an opportunity to study the interaction between contemporaneous siliciclastic and carbonate deep-marine deposition. The Buduq Trough represents a sub-basin formed within the larger unstable post-rift margin of the EGC. Qualitative and quantitative facies analysis reveals that Upper Cretaceous stratigraphy of the Buduq Trough comprises a Cenomanian-Turonian siliciclastic submarine channel complex, which abruptly transitions into a Coniacian-Maastrichtian mixed-lobe succession. The Cenomanian – Turonian channels are shown to be entrenched in lows on the palaeo-seafloor, with the sequence entirely absent 10 km toward the west, where a Lower Cretaceous submarine landslide complex is suggested to have acted as a topographic barrier to deposition. By the Campanian this topography was largely healed, allowing deposition of the mixed-lobe succession across the Buduq Trough. Evidence for topography remains recorded through opposing palaeocurrents and frequent submarine landslides. The overall sequence is interpreted to represent abrupt Cenomanian-Turonian siliciclastic progradation, followed by ~Coniacian retrogradation, before a more gradual progradation in the Santonian-Maastrichtian. This deep-marine siliciclastic system interfingers with a calcareous system from the Coniacian onwards. These mixed lobe systems are different to siliciclastic-dominated systems in that they contain both siliciclastic and calcareous depositional elements, making classification of distal and proximal difficult using conventional terminology and complicating palaeogeographic interpretations. Modulation and remobilisation also occurs between the two contemporaneous systems, making stacking patterns difficult to decipher. The Buduq Trough is analogous in many ways to offshore The Gambia, NW Africa, and could be a suitable analogue for mixed deep-marine systems globally.

Interactions between deep-water gravity flows and active salt tectonics

“…Seafloor topography is generated by a variety of geological processes, including relief above mass-transport deposits (MTDs) (e.g., Ortiz-Karpf et al 2015Soutter et al 2018;Cumberpatch et al 2021), syndepositional tectonic deformation (e.g., Hodgson and Haughton 2004;Kane et al 2010) and salt diapirism (Fig. 1; e.g., Hodgson et al 1992;Prather et al 2012;Oluboyo et al 2014).…”

Diverse Deformation Mechanisms and Lithologic Controls in an Active Orogenic Wedge: Structural Geology and Thermochronometry of the Eastern Greater Caucasus

“…The eastern Greater Caucasus mountains exclusively expose Middle Jurassic and younger sedimentary rocks (Figures 2b and 3; Alizadeh et al., 2016; Azizbekov, 1968; Bairamov et al., 2008; Nalivkin, 1976). Three broad stratigraphic packages crop out across the range: (a) a northern flank succession of thinly bedded sandstone and shale with massive carbonate intervals (Alizadeh et al., 2016; Bairamov et al., 2008; Cumberpatch et al., 2021; Nalivkin, 1976; Figure 3a); (b) a range‐core succession of thinly bedded sandstone, shale, and carbonate (Alizadeh et al., 2016; Bairamov et al., 2008; Nalivkin, 1976; Figure 3b); and (c) located at the southern toe of the orogen, the Vandam Zone succession, which comprises volcaniclastic sandstone and conglomerate, volcanic tuff and flows, sandstone, shale, and carbonate (Alizadeh et al., 2016; Bairamov et al., 2008; Kopp, 1985; Nalivkin, 1976; Figure 3c). A buried fourth succession has been revealed by deep drilling in the Kura foreland basin to the south, comprising volcanic, volcaniclastic, siliciclastic, and carbonate strata (Alizadeh et al., 2016; Figure 3d), similar to strata exposed within the Vandam Zone.…”

“…The sedimentary facies of the northern flank succession and range‐core succession (Figures 3a and 3b) suggest deposition in continental shelf, slope, and deep marine environments (Alizadeh et al., 2016; Cumberpatch et al., 2021; Gavrilov, 2018). Stratigraphic architecture suggests that these strata were deposited offshore of a south‐facing continental margin (Cumberpatch et al., 2021; Gavrilov, 2018). Detrital zircon U‐Pb age distributions with peaks at ca.…”

Tectonic controls on the evolution of mixed carbonate‐siliciclastic systems: Insights from the late Palaeozoic Ouachita‐Marathon Foreland, United States

“…Sea‐level change is commonly interpreted as the primary driver for alternating carbonate and siliciclastic deposition (Chiarella et al., 2012; Cumberpatch et al., 2020; D'agostini et al., 2015; Hentz & Ambrose, 2019; Hurd et al., 2018; Miller & Heller, 1994; Rankey & Lehrmann, 1996; Yose & Heller, 1989; Zecchin & Catuneanu, 2017), although other drivers controlling mixed deposition, such as tectonics, reefal buildups, hydrodynamic factors and shelf width are also reported (Chiarella et al., 2019; Ćosović et al., 2018; Le Roy et al., 2019; Vieira et al., 2019). Although a few cases of highstand siliciclastics are reported (Brachert et al., 2003; Hentz et al., 2017), in the sea‐level driven model, carbonate sediment is typically deposited during transgressive/highstand eustatic conditions, whereas siliciclastic sediment is deposited during lowstand conditions, a phenomenon known as ‘reciprocal sedimentation’ (Van Siclen & Merriam, 1964).…”