Deposition of climbing‐ripple beds: a flume simulation

Abstract

Thirteen runs were made in a small recirculating flume to simulate the deposition of the climbing‐ripple sequences commonly present in fine‐grained facies of fluvial and deltaic deposits. These sequences consist of intergradational climbing‐ripple cross laminae and draped laminae. The experiments were based on the assumption that stratification type depends mainly on near‐bottom flow structure and uniform sediment fallout from an overloaded flow. Various combinations of curves of velocity versus time and of sediment feed versus time in runs lasting from 45 to 840 min were used in an exploratory program; conditions for each run were selected on the basis of experience in previous runs. The runs verified that Type A (erosional‐stoss) climbing ripples are produced by aggradation rates that are small relative to ripple migration rate, and Type B (depositional‐stoss) climbing ripples are produced by aggradation rates that are large relative to ripple migration rate. Draped lamination results from continued fallout of sediment from suspension after ripple migration ceases or almost ceases. Comparison of geometric details of the ripple stratification produced in the flume runs with that in natural sequences, supplemented by considerations on maximum and minimum migration rates of ripples, suggests times of no more than a few tens of hours for the deposition of the climbing‐ripple portions of sequences 10‐20 cm thick. Runs in which deposition of a 20 cm sequence took more than 10 h produced such atypical features of ripple geometry as sharp crests, planar lee‐side laminae, and angular toeset‐foreset contacts.

Evidences for a Paleocene marine incursion in southern Amazonia (Madre de Dios Sub-Andean Zone, Peru)

“…Climbing-ripple cross-stratification is 430 a common feature in a wide range of depositional environments in which suspension exceeds 431 the rate of traction transport (Jopling and Walker, 1968;Allen, 1970;Ashley et al, 1982). 432 However, sigmoidal cross-bedding associated with the presence of brackish-water fossils 433 (benthic foraminifer, see Table 1) suggests deposition within a tide-influenced environment.…”

“…Climbing-ripple cross-stratification is 430 a common feature in a wide range of depositional environments in which suspension exceeds 431 the rate of traction transport (Jopling and Walker, 1968;Allen, 1970;Ashley et al, 1982). 432…”

Sulfate-Rich Eolian and Wet Interdune Deposits, Erebus Crater, Meridiani Planum, Mars

“…The thicknesses of wavy lamination observed thus far are , 20-30 cm thick, which could be formed by supercritically climbing ripples. If the wavy lamination was formed by supercritically climbing ripples, then the flow which deposited them would have had to maintain high sediment aggradation rates relative to the ripple migration rates (Ashley et al 1982).…”

Analisis estratigrafico secuencial de las formaciones Anacleto y Allen (Cretacico Tardio) en el borde nororiental de Cuenca Neuquina, Argentina

“…El suministro de carga en suspensión se incrementa a medida que decrece la velocidad de la corriente (Ashley et al, 1982), así, las óndulas de tipo I y tipo II, con un ángulo de trepada menor que el de la pendiente erosiva ('stoss'), se asocian con flujos 'subcríticos tabulares' mientras que las óndulas de tipo III con relaciones angulares inversas corresponden a flujos supercríticos (Allen, 1983). Esta litofacies es característica de depósitos de canales menores dentro de una planicie de marea de un estuario o desbordes ('crevasse splay') de un 'lagoon' influenciado por mareas (Yokokawa et al, 1995).…”