Subaqueous sediment gravity flow deposits: practical criteria for their field description and classification

Abstract

A new method for the description and classification of subaqueous sediment gravity flow deposits is proposed. The classification scheme employs a convenient letter code and divides deposits (individual beds) into descriptive categories of two hierarchical levels: facies and subfacies. Facies, as the higher rank categories, are distinguished chiefly on the basis of sediment type (i.e. bed grain size/texture). A total of 13 facies have been distinguished: G= gravel; GS = gravel‐sand couplet; GyS = gravelly sand; S = sand; SM = sand—mud couplet; MS = mud—sand couplet; TM = silt—mud couplet; MT = mud—silt couplet; M = mud; MyS = muddy sand; SyM = sandy mud; MyG = muddy gravel; GyM = gravelly mud. Subfacies, as the lower rank categories, are distinguished within the individual facies on the basis of the bed's internal structures. The number of subfacies is unlimited, and their labelling code includes particular facies symbols (see above) preceded by lower—case letters denoting specific sedimentary structures and their vertical arrangement. Subfacies thus refer to the bed's intervals, or divisions, which are labelled as follows: m = massive (unstratified and ungraded); g = graded (unstratified and graded); s = plane‐stratified; x=cross‐stratified; 1 = parallel– and/or cross‐laminated; q = liquefied. For example, subfacies gsG (graded to plane‐stratified gravel) are gravel beds that have a lower graded interval and an upper plane‐stratified interval; subfacies xG (cross‐stratified gravel) are gravel beds that are cross‐stratified throughout; subfacies slS (plane‐stratified to laminated sand) are sand beds that have a lower plane‐stratified interval and an upper laminated (parallel‐ and/or cross‐laminated) interval.

Late Cretaceous - Early Palaeogene sandy-to-gravelly debris flows and their sediments in the Silesian Basin of the Alpine Tethys (Western Outer Carpathians, Istebna Formation)

“…The ab bre vi a tions of lithofacies ap plied cor re spond with the first let ters of lithological terms in Eng lish, for in stance, CSsandy con glom er ate (see e.g., Ghibaudo, 1992;Słomka, 1995;Strzeboński, 2005). Due to the scar city of di rec tional sed i mentary struc tures in sand stone-to-con glom er ate debrites, the direc tions of sed i men tary palaeotransportation were de fined on the ba sis of the imbrication of clasts, flame struc tures, the arrange ment of long clast axes or the di rec tion of wash-outs and ero sional chan nels (chutes) axes.…”

“…For the pur pose of de scrib ing the Istebna For ma tion of the Beskid Śląski Mts., sev eral ba sic sed i men tary lithofacies types have been dis tin guished (see : Ghibaudo, 1992;Słomka, 1995;Strzeboński, 2005): -con glom er ate (C) -vol u met ric prev a lence of grain compo nents coarser than 2 mm (i.e., gravel frame work), frequently me dium-grained (4-32 mm; -mudstone-sand stone cou plet (MS) -M>S, sim i lar el ements as in SM only in dif fer ent pro por tions (Fig. 3B, the low est part of the photo); -grav elly mudstone (MG) (sensu peb bly mudstone; Dżułyński and Radomski, 1955;Crowell, 1957) -mudstone con tain ing ran domly scat tered gran ules, pebbles, cob bles, boul ders, lo cally with a higher con cen tration of grav elly com po nents in the basal part of the bed or out sized clasts at the top (see Strzeboński, 2005).…”

Sedimentary indicators of a deep sea environment, in the sandstones of rocky forms, from the Ciężkowice-Rożnów Landscape Park (Outer Carpathians, Poland)

“…Płaszczo-wina śląska: 1 -warstwy cieszyńskie, 2 -warstwy grodziskie, 3 -warstwy lgockie, 4 -łupki pstre (Cr), 5 -warstwy godulskie, 6 -warstwy istebniańskie, 7 -warstwy ciężkowickie, 8 -warstwy hieroglifowe, 9 -warstwy menilitowe, 10 -warstwy krośnieńskie. Płaszczowina magurska: 11 -warstwy inoceramowe, 12 -łupki pstre (Pg); 13 -utwory mioceńskie, 14 -uskoki, 15 -nasunięcia A lithofacies of sandstones with intercalated mudstones occurs sporadically (see Ghibaudo, 1992). Such a sequence of lithofacies is typical of deposits developing within this part of the fan.…”

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“…Por sus características se corresponden con la facies «G» (<<gravel beds») de Ghibaudo (1992). Unicamente en sus partes más distales exhiben una pobremente definida estratificación discontinua, marcada por superficies de erosión irregulares que limitan secuencias granocrecientes hacia el techo.…”