Modern observations of floccule ripples: Petitcodiac River estuary, New Brunswick, Canada

Abstract

Mud floccule ripples, small mud rip‐up clasts, erosional scars and tool marks are reported for the first time from the macrotidal Petitcodiac River estuary, New Brunswick, Canada. The ripples occur on the intertidal flats and are ebb‐oriented. Observations have been conducted during the spring low tide at high‐river and low‐river discharge. Floccule ripples forming during the high‐river flow are characterized by increased silt fraction, low relief and sinuous to lunate form. The ripples forming during the low flow are clay‐dominated, have very low relief and are characterized by narrow straight ridges and patchy distribution. The preserved mud floccule ripples manifest in interbedded silt‐rich and clay‐rich deposits with parallel, wavy, lenticular and current‐ripple lamination. Presented floccule ripples are current‐generated, non‐episodic in nature and are sedimentologically characterized. The ripple origin is constrained by morphometric and grain‐size analyses, and observed hydraulic processes. It is confirmed that mud floccule ripples originate under a similar range of hydraulic parameters as documented in previous flume studies. This study confirms application of work conducted in recent decades on mud‐dominated marginal‐marine environments and helps with understanding of properties and distribution of fine‐grained sediments in tidally influenced settings.

Mud bedforms in a natural ice flume

“…In the ice flume, the suspended sediment concentration could not be measured, but appeared to be low. In consequence, water clarity, and visibility of bedforms, was excellent (in contrast to the high turbidity "sedimentology of milk" that prevails in experimental settings; Schieber, 2011), and also hinders observation in nature (Shchepetkina et al 2018). The best-developed ripples, interspersed with mud streamers, formed in water flowing at about 8-12 cm/s.…”

“…Cold water conditions may be the norm in some natural areas, such as the deep sea, and in nearshore areas subject to cold winter conditions (e.g. Shchepetkina et al 2018). Experimental sedimentologists might consider introducing a chiller in flume experiments to further explore bedform development in cold-water environments!…”

Composite Particles in Mudstones: Examples from the Late Cretaceous Tununk Shale Member of the Mancos Shale Formation

“…Micrometer-scale coccolith debris seen in the matrix of the lower calcareous interval of the Tununk Shale was likely integrated into floccules during transport due to small particle size . Although bottom-current transport of floccules and mud rip-up clasts is increasingly recognized as a key element of marine mud transport on the basis of flume experiments and the study of modern environments (Schieber et al 2007;Schieber and Southard 2009;Schieber 2011;Yawar and Schieber 2017;Shchepetkina et al 2018), to identify floccules and mud rip-up clasts in ancient rocks, such as the Tununk Shale, is very challenging because both particle types are waterrich and severely flattened and deformed during burial and compaction, as well as disrupted by bioturbating organisms (Schieber et al 2010;Schieber 2016b;Shchepetkina et al 2018). The close compositional similarity between floccules, mud rip-up clasts, and the generic mud matrix of the Tununk further complicate this task, and we therefore consider it rather challenging to identify floccules and mud rip-up clasts in the Tununk Shale matrix with confidence by either optical microscopy or SEM.…”

“…The significant role of bedload transport was further reinforced by a number of detailed petrographic studies of both ancient and modern fine-grained deposits, which show that silt-to sand-size mud-dominated composite particles constitute a significant portion (sometimes . 50%) of the overall rock volume (Plint et al 2012;Plint 2014;Schieber 2016b;Laycock et al 2017;Shchepetkina et al 2018). Instead of mud accumulating via passive settling from suspension, the common presence of silt-to sand-size composite particles implies that a wide variety of hydrodynamic processes (e.g., turbidity currents, storm-induced bottom currents, tidal currents, etc.)…”

Decoding the origins and sources of clay minerals in the Upper Cretaceous Tununk Shale of south‐central Utah: Implications for the pursuit of climate and burial histories

“…The complex sources and dispersal processes (and pathways) of fine-grained sediments in marine environments, as revealed by sedimentologic and petrographic analysis Taylor and Macquaker, 2014;Harazim and McIlroy, 2015;Lazar et al, 2015;Li et al, 2015;Wilson and Schieber, 2015;Schieber, 2016a;Li and Schieber, 2018a;DeReuil and Birgenheier, 2019), pose challenges for the interpretation of climate signals from clay mineral assemblages of ancient marine mudstone successions (Clayton et al, 1999;Thiry, 2000). The common occurrence of silt to sand-sized clay-dominated composite particles (aggregates) of multiple origins in both ancient and modern finegrained deposits (Macquaker et al, 2010;Plint et al, 2012;Schieber, 2016b;Laycock et al, 2017;Shchepetkina et al, 2018;Li and Schieber, 2018b) strongly suggests that the origin of clay minerals in fine-grained sedimentary successions is a much more complex issue than commonly presumed.…”