Multiple controls on rift basin sedimentation in volcanic settings: Insights from the anatomy of a small Early Cretaceous basin in the Yanshan belt, northern North China

Abstract

This paper deals with a small continental rift basin in a volcanic setting and tries to decipher potential controls on its synrift sedimentation. The Luanping basin, which is a well-exposed Early Cretaceous rift basin in the Yanshan belt on the northern periphery of the North China block, was chosen as a case study. We show that extensive and vigorous volcanism took place just prior to the onset of basin formation and continued into a synrift period. Basin fi lls consist predominantly of lacustrine, fan-delta, braid-delta, and volcaniclastic deposits. Lacustrine facies are composed mostly of deep-lake deposits that appear to have been established soon after basin initiation. Fan-delta systems developed along two high-angle border faults, the master northern Hongqi fault and the secondary western Xiaobaiqi fault. Fan-delta fronts were built up primarily by gravelly and sandy debrites and turbidites. Braiddelta deposits are restricted to the eastern corner of the basin and are characterized by an aggregation of braid-plain conglomeratic deposits. Underwater extrusions of magma and pyroclastic fl ows are inferred from the presence of volcanic breccias, ignimbrites, andesitic pillows, and peperites, which are enclosed by host lacustrine deposits. Deep-lake and fan-delta systems persisted throughout the synrift period, indicating a rapid subsidence rate, with both adequate sediment and water supply. The high-angle border faults are thought to have played a critical role in creating large accommodation space, and simultaneous displacements of the Hongqi and Xiaobaiqi faults led to the localization of a major depocenter in the western part of the basin. One-dimensional backstripping analysis of three stratigraphic sections shows that the Luanping basin experienced marked synrift tectonic subsidence up to 2 km at a subsidence rate close to 0.2 mm yr -1 . We propose that the high rate of basin subsidence might have been caused mainly by left-lateral transtensional faulting and was enhanced by the superposition of basement downsag induced by underlying magma withdrawal. A predominance of volcanic particles in both debrites and sandstones suggests that source areas were erodible volcanic edifi ces. A humid paleoclimate is inferred, which not only provided enough water supply, but also promoted weathering of volcanic rocks in source areas, thus maintaining both the deeplake environment and sediment infl ux. We conclude that relatively small and isolated rift basins in volcanic settings can experience both rapid subsidence and receive thick lacus trine deposits if they are under the combined control of favorable structure, climate, and magmatism. The model proposed here is believed to be applicable to other rift basins in similar volcano-tectonic settings.

Did the Paleo‐Asian Ocean between North China Block and Mongolia Block exist during the late Paleozoic? First paleomagnetic evidence from central‐eastern Inner Mongolia, China

“…The corresponding poles of these remagnetized sites are compatible with the Early Cretaceous poles of NCB, MOB, and SIB [ Halim et al ., ; Kravchinsky et al ., ; Cogné et al ., ; Charles et al ., ]. Meanwhile, East Asia, including MOB, IMB, and NCB, experienced Mesozoic extensional tectonics, characterized by abundant extensional half‐graben basins and emplacement of numerous magmatic massifs [e.g., Webb et al ., ; Graham et al ., ; Ren et al ., ; Liu et al ., ; Wu et al ., ; Charles et al ., ; Wei et al ., ; Daoudene et al ., ]. The magmatic event, which may induce thermal remagnetization, started in Late Jurassic and reached the peak in the Early Cretaceous (127 Ma, Figure b).…”

Cretaceous anomalous subsidence and its response to dynamic topography in the Songliao Basin, Northeast China

“…According to recent isotopic dating of syn-rift volcanic rocks, several Cretaceous rift basins in the Yanshan belt, including the LuanPing Basin and Chengde Basin, simultaneously formed during the Early Cretaceous by basement rifting with the Songliao basin (Niu et al, 2003;Liu et al, 2003;Cope, 2003;Niu et al, 2004;Wei et al, 2012) (Fig. 1).…”

“…1). Importantly, these basins in the Yanshan belt were only filled by syn-rift subsidence, which was controlled by master basement faults without overlying post-rift subsidence (Davis et al, 2001;Cope, 2003;Wei et al, 2012), in contrast with the Songliao Basin. The deposits associated with thermal subsidence should overlie the syn-rift subsidence that is driven by earlier lithospheric thinning.…”

“…To investigate the theoretical thermal subsidence in these basins, we chose the Luanping Basin as a case study. The Luanping basin is a well-exposed Early Cretaceous rift basin in the Yanshan belt on the northern periphery, and the tectonic subsidence data from three sections of this basin (Wei et al, 2012) was calculated using a 1D strain rate inversion model. Because of the lacuna in the post-rift strata in the Luanping Basin, we set the top interface of the syn-rift strata (approximately 120 Ma) as the boundary between the syn-rift and post-rift stages (Wei et al, 2012).…”

“…The grey shaded areas represent the Cretaceous basins in Northeast Asian and small Cretaceous rift basins in the Yanshan belt including Luanping Basin(LB), Chengde Basin(CB), etc. (Faure et al, 2012;Wei et al, 2012). In this paper, we apply the backstripping method and 1D strain rate inversion modeling (Song et al, 2010) methods on data from seismic sections and wells in the Songliao Basin. By analyzing these results, we separate the post-rift anomalous subsidence from the tectonic subsidence and investigate the spatial and temporal patterns of anomalous subsidence in the Songliao Basin.…”