Carbonate concretions in Miocene mudrocks in NW Algeria: types, geochemistry, and origins

Journal article
(Online publication)


Publication Details

Author(s): Nemra A, Ouali Mehadji A, Munnecke A, Belkhedim S, Belkebir L
Journal: Facies
Publication year: 2019
Volume: 65
Journal issue: 17
ISSN: 0172-9179
Language: English


Abstract

Carbonate concretions have been recorded in many recent and ancient
marine sediments around the world. The Middle Miocene marl of the Tenes
area, situated in the northeast of the Lower Chelif Basin in NW-Algeria,
contains such carbonate concretions but with a variety of different
structures and morphologies. Three different basic types are
distinguished: nodular (spheroidal, ellipsoidal, disc, and irregular),
stratiform, and tubular concretions, the last locally have a central
conduit. The close association between carbonate concretions and
synsedimentary deformation structures (synsedimentary faults, slumps)
and normal faults, pronounced in the Ounsour Anhas outcrop, indicates
synsedimentary instability related to upward fluid movement. The
concretions were formed by precipitation of micritic carbonate within
the host marl at shallow burial depth, probably in the active microbial
methanogenesis zone. Strongly varying δ13C values (− 9.82 to + 5.85‰ PDB) are interpreted as the result of the balance between 13C-enriched (residual CO2 from methanogenesis) and 13C-depleted (microbial organic matter decomposition) CO2 added to the pore solutions. δ18O
values (− 2.39 to + 1.71‰ PDB) indicate that carbonate concretion
growth occurred during early diagenesis conditions, from marine-derived
pore-water.


FAU Authors / FAU Editors

Belkhedim, Salim
Lehrstuhl für Paläoumwelt
Munnecke, Axel Prof. Dr.
Professur für Paläontologie (Schwerpunkt Faziesanalyse)


How to cite

APA:
Nemra, A., Ouali Mehadji, A., Munnecke, A., Belkhedim, S., & Belkebir, L. (2019). Carbonate concretions in Miocene mudrocks in NW Algeria: types, geochemistry, and origins. Facies, 65(17). https://dx.doi.org/0.1007/s10347-019-0559-2

MLA:
Nemra, Abdelkrim, et al. "Carbonate concretions in Miocene mudrocks in NW Algeria: types, geochemistry, and origins." Facies 65.17 (2019).

BibTeX: 

Last updated on 2019-29-03 at 17:23