Sedimentology and depositional environment of the Late Eocene marine siliciclastic to evaporite transition in the Sivas Basin (Turkey)

Abstract

Sivas foreland basin in Turkey recorded a salinity crisis during the Late Eocene resulting in evaporite accumulations thick enough to trigger intense halokinesis during the Oligo-Miocene. The salinity crisis is studied thanks to three sedimentological sections crossing the transition from the last marine deposits (Bözbel Formation) to the overlying evaporitic facies (Tuzhisar Formation) preserved from halokinetic deformations. The top of the Bözbel Formation presents flood-generated hyperpycnites developed in pro-delta to delta front settings. In the central part of the basin, such facies become increasingly sediment-starved with azoic calcareous facies interlayered with organic-rich shales. Such facies are ultimately capped by thick accumulations of gypsiferous turbiditic lobe deposits. Southward, the foredeep was partly isolated from the central domain due to the propagation of an anticline. There, the basal siliciclastic turbidites become increasingly gypsum-rich and are capped by a 45 m-thick mass-transport deposit enclosing olistoliths of gypsum and of ophiolitic rocks. Such gravity collapse deposits evolve upward to the same gypsiferous turbiditic lobes observed northward. Both transitional facies record the progressive confinement of the basin from the sea, likely due to the northward propagation of the fold-and-thrust belt located farther south. The evaporites started to precipitate in piggy-back evaporitic basins, along the highs of the fold-and-thrust belt, before being reworked gravitationally in the foredeep to the north, producing the high to low density gypsum turbidites. Finally, from north to south, the reworked evaporites are extensively covered by a >100 m thick, chaotic, prismatic gypsum mass likely resulting from the hydration of anhydrite grains left as a residual phase after the leaching of a significant amount of halite. The latter formed in a hypersaline marine-fed basin and have lately allowed mini-basin salt tectonics during Oligo-Miocene times.

Successive phases of serpentinization and carbonation recorded in the Sivas ophiolite (Turkey), from oceanic crust accretion to post-obduction alteration

“…Therefore, the formation of S2 occurred simultaneously with the deposition of Bartonian evaporites (Pichat, 2017;Pichat et al, 2021). If confirmed by other analyses, this finding favors a possible causal relationship between serpentine and evaporite formation, through water pumping and dehydration of the foreland basin.…”

“…It is covered by sedimentary successions consisting of Maastrichtian to Thanetian shallow-water platform carbonates (Tecer Formation; İnan and İnan, 1990;Legeay et al, 2019), changing northward to middle Eocene transgressive marine facies of the Çerpaçindere Formation (Aktı̇mur et al, 1990). The late Eocene "Bartonian" regressive phase resulted in deposition of the Tuzhisar evaporite (Pichat, 2017;Pichat et al, 2021). A first generation of continental mini-basins were formed and subsequently infilled by sediments of the Selimiye Formation.…”

Stratigraphy, Paleogeography and Depositional Setting of the K–Mg Salts in the Zechstein Group of Netherlands—Implications for the Development of Salt Caverns

“…Considering the deep water setting during the deposition of the Z2H1, it also seems very likely that part of the anhydrite beds reported in the offshore domain mark turbiditic lobe deposits derived from the dismembering of the marginal anhydrite platform (Z2A, e.g., [87][88][89]. Indeed, several studies have already documented these types of basinal deposits in the Zechstein Basin, but only during the development of the Z1, Z2 or Z3 sulfate platforms [42,90,91].…”

C20-C21-C23 tricyclic terpanes abundance patterns: Origin and application to depositional environment identification

“…Reconstruction of paleo-depositional environment is critical in oil-gas exploration, paleoclimatic and paleoenvironmental studies. Conventional methods for environmental reconstruction mostly rely on sedimentary, petrological and/or mineralogical characterizations (e.g., Oskay et al, 2019;Pichat et al, 2021), paleontological record (e.g., Heard et al, 2020), and/or geochemical tracing (e.g., Govind et al, 2021). For example, lithology, sedimentary/biogenic structures, rock fabrics and texture in sedimentary rocks have been used to reconstruct sedimentary microfacies, which is further used to infer depositional environments (e.g., El-Sabbagh et al, 2017;Mtelela et al, 2017;Barrera et al, 2020).…”