Deepwater dolomites and associated hiatuses in Gulf of Cadiz contourites

Zeinab Smillie, Dorrik Stow, F. J. Sierro, Montserrat Alonso Garcia, Francisco J. Jiménez-Espejo, Jim Buckman, Emmanuelle Ducassou, Adrian Joseph Boyce, Jennifer Pratscher

Research output: Contribution to conferencePaper

Abstract

Deep-marine regional unconformities are common and significant features of the contourite depositional systems in the Gulf of Cadiz. Some of these unconformities are marked by the development of fine-crystalline dolomite layers, as observed at Sites U1387 and U1391. The timing and mechanism of the dolomite formation are not fully understood.
The mineralogy and geochemistry of these dolomites and adjacent sediments were investigated. Transmitted light microscopy, SEM, X-ray tomography, XRF and stable isotope geochemistry were employed to understand the mechanisms of the dolomite formation.
Although the dolomite layers at these two sites occupy similar stratigraphic position, the associated unconformities are considerably different in duration. At Site U1391, the unconformity represents the early Pliocene discontinuity of 0.05 Ma, separating the initial drift stage below from the transition stage. The unconformity at site U1387 represents combined two hiatuses (late Pliocene and early Quaternary discontinuities) with a time gap of 1.4 Ma. This unconformity separates the initial stages of the drift (Pliocene mixed system) from the modern drift stage (mainly Pleistocene contourites), with the transitional drift stage absent at this site.
The dolomites from both sites show replacement textures with subordinate relicts of the silicate minerals. Furthermore, the dolomites at site U1387 exhibits complex zoning and geochemical pattern compared to those of U1391, indicating a complex history of formation. Low oxygen conditions were deciphered from the foraminiferal assemblage in the associated sediments. Bacterial activities in a cold seep environment may have triggered the development of the dolomites and maintained alkaline medium for a prolonged time. However, the lithostratigraphic and structural regime may have played a considerable role in the dolomitization processes.

Conference

Conference57th BSRG Annual General Meeting 2018
CountryUnited Kingdom
CityEdinburgh
Period17/12/1820/12/18

Fingerprint

contourite
dolomite
unconformity
Pliocene
discontinuity
geochemistry
cold seep
gulf
dolomitization
silicate mineral
X-ray fluorescence
sediment
microbial activity
zoning
tomography
microscopy
mineralogy
stable isotope
replacement
texture

Cite this

Smillie, Z., Stow, D., Sierro, F. J., Alonso Garcia, M., Jiménez-Espejo, F. J., Buckman, J., ... Pratscher, J. (2018). Deepwater dolomites and associated hiatuses in Gulf of Cadiz contourites. Paper presented at 57th BSRG Annual General Meeting 2018, Edinburgh, United Kingdom.
Smillie, Zeinab ; Stow, Dorrik ; Sierro, F. J. ; Alonso Garcia, Montserrat ; Jiménez-Espejo, Francisco J. ; Buckman, Jim ; Ducassou, Emmanuelle ; Boyce, Adrian Joseph ; Pratscher, Jennifer. / Deepwater dolomites and associated hiatuses in Gulf of Cadiz contourites. Paper presented at 57th BSRG Annual General Meeting 2018, Edinburgh, United Kingdom.
@conference{fcb62e9490e3484ebd21d942fa09749c,
title = "Deepwater dolomites and associated hiatuses in Gulf of Cadiz contourites",
abstract = "Deep-marine regional unconformities are common and significant features of the contourite depositional systems in the Gulf of Cadiz. Some of these unconformities are marked by the development of fine-crystalline dolomite layers, as observed at Sites U1387 and U1391. The timing and mechanism of the dolomite formation are not fully understood.The mineralogy and geochemistry of these dolomites and adjacent sediments were investigated. Transmitted light microscopy, SEM, X-ray tomography, XRF and stable isotope geochemistry were employed to understand the mechanisms of the dolomite formation. Although the dolomite layers at these two sites occupy similar stratigraphic position, the associated unconformities are considerably different in duration. At Site U1391, the unconformity represents the early Pliocene discontinuity of 0.05 Ma, separating the initial drift stage below from the transition stage. The unconformity at site U1387 represents combined two hiatuses (late Pliocene and early Quaternary discontinuities) with a time gap of 1.4 Ma. This unconformity separates the initial stages of the drift (Pliocene mixed system) from the modern drift stage (mainly Pleistocene contourites), with the transitional drift stage absent at this site. The dolomites from both sites show replacement textures with subordinate relicts of the silicate minerals. Furthermore, the dolomites at site U1387 exhibits complex zoning and geochemical pattern compared to those of U1391, indicating a complex history of formation. Low oxygen conditions were deciphered from the foraminiferal assemblage in the associated sediments. Bacterial activities in a cold seep environment may have triggered the development of the dolomites and maintained alkaline medium for a prolonged time. However, the lithostratigraphic and structural regime may have played a considerable role in the dolomitization processes.",
author = "Zeinab Smillie and Dorrik Stow and Sierro, {F. J.} and {Alonso Garcia}, Montserrat and Jim{\'e}nez-Espejo, {Francisco J.} and Jim Buckman and Emmanuelle Ducassou and Boyce, {Adrian Joseph} and Jennifer Pratscher",
year = "2018",
language = "English",
note = "57th BSRG Annual General Meeting 2018 ; Conference date: 17-12-2018 Through 20-12-2018",

}

Smillie, Z, Stow, D, Sierro, FJ, Alonso Garcia, M, Jiménez-Espejo, FJ, Buckman, J, Ducassou, E, Boyce, AJ & Pratscher, J 2018, 'Deepwater dolomites and associated hiatuses in Gulf of Cadiz contourites' Paper presented at 57th BSRG Annual General Meeting 2018, Edinburgh, United Kingdom, 17/12/18 - 20/12/18, .

Deepwater dolomites and associated hiatuses in Gulf of Cadiz contourites. / Smillie, Zeinab; Stow, Dorrik; Sierro, F. J.; Alonso Garcia, Montserrat; Jiménez-Espejo, Francisco J.; Buckman, Jim; Ducassou, Emmanuelle; Boyce, Adrian Joseph; Pratscher, Jennifer.

2018. Paper presented at 57th BSRG Annual General Meeting 2018, Edinburgh, United Kingdom.

Research output: Contribution to conferencePaper

TY - CONF

T1 - Deepwater dolomites and associated hiatuses in Gulf of Cadiz contourites

AU - Smillie, Zeinab

AU - Stow, Dorrik

AU - Sierro, F. J.

AU - Alonso Garcia, Montserrat

AU - Jiménez-Espejo, Francisco J.

AU - Buckman, Jim

AU - Ducassou, Emmanuelle

AU - Boyce, Adrian Joseph

AU - Pratscher, Jennifer

PY - 2018

Y1 - 2018

N2 - Deep-marine regional unconformities are common and significant features of the contourite depositional systems in the Gulf of Cadiz. Some of these unconformities are marked by the development of fine-crystalline dolomite layers, as observed at Sites U1387 and U1391. The timing and mechanism of the dolomite formation are not fully understood.The mineralogy and geochemistry of these dolomites and adjacent sediments were investigated. Transmitted light microscopy, SEM, X-ray tomography, XRF and stable isotope geochemistry were employed to understand the mechanisms of the dolomite formation. Although the dolomite layers at these two sites occupy similar stratigraphic position, the associated unconformities are considerably different in duration. At Site U1391, the unconformity represents the early Pliocene discontinuity of 0.05 Ma, separating the initial drift stage below from the transition stage. The unconformity at site U1387 represents combined two hiatuses (late Pliocene and early Quaternary discontinuities) with a time gap of 1.4 Ma. This unconformity separates the initial stages of the drift (Pliocene mixed system) from the modern drift stage (mainly Pleistocene contourites), with the transitional drift stage absent at this site. The dolomites from both sites show replacement textures with subordinate relicts of the silicate minerals. Furthermore, the dolomites at site U1387 exhibits complex zoning and geochemical pattern compared to those of U1391, indicating a complex history of formation. Low oxygen conditions were deciphered from the foraminiferal assemblage in the associated sediments. Bacterial activities in a cold seep environment may have triggered the development of the dolomites and maintained alkaline medium for a prolonged time. However, the lithostratigraphic and structural regime may have played a considerable role in the dolomitization processes.

AB - Deep-marine regional unconformities are common and significant features of the contourite depositional systems in the Gulf of Cadiz. Some of these unconformities are marked by the development of fine-crystalline dolomite layers, as observed at Sites U1387 and U1391. The timing and mechanism of the dolomite formation are not fully understood.The mineralogy and geochemistry of these dolomites and adjacent sediments were investigated. Transmitted light microscopy, SEM, X-ray tomography, XRF and stable isotope geochemistry were employed to understand the mechanisms of the dolomite formation. Although the dolomite layers at these two sites occupy similar stratigraphic position, the associated unconformities are considerably different in duration. At Site U1391, the unconformity represents the early Pliocene discontinuity of 0.05 Ma, separating the initial drift stage below from the transition stage. The unconformity at site U1387 represents combined two hiatuses (late Pliocene and early Quaternary discontinuities) with a time gap of 1.4 Ma. This unconformity separates the initial stages of the drift (Pliocene mixed system) from the modern drift stage (mainly Pleistocene contourites), with the transitional drift stage absent at this site. The dolomites from both sites show replacement textures with subordinate relicts of the silicate minerals. Furthermore, the dolomites at site U1387 exhibits complex zoning and geochemical pattern compared to those of U1391, indicating a complex history of formation. Low oxygen conditions were deciphered from the foraminiferal assemblage in the associated sediments. Bacterial activities in a cold seep environment may have triggered the development of the dolomites and maintained alkaline medium for a prolonged time. However, the lithostratigraphic and structural regime may have played a considerable role in the dolomitization processes.

M3 - Paper

ER -

Smillie Z, Stow D, Sierro FJ, Alonso Garcia M, Jiménez-Espejo FJ, Buckman J et al. Deepwater dolomites and associated hiatuses in Gulf of Cadiz contourites. 2018. Paper presented at 57th BSRG Annual General Meeting 2018, Edinburgh, United Kingdom.