Prelithification and synlithification tectonic foliation development in a clastic sedimentary sequence

Meere, Patrick; Mulchrone, Kieran F.; McCarthy, David; Timmerman, Martin J.; Dewey, John

doi:10.1130/g37587.1

Cited by 7 publications

(7 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…

Using observations from a single locality (Wine Strand) in the Glashabeg Formation (Dingle Group) of the Dingle Peninsula, southwest Ireland, Meere et al (2016) conclude that more than 50% shortening of these strata was accomplished during the mid Devonian Acadian event, before lithification was complete. That the late Silurian to Emsian Dingle Group was deformed during the Acadian is not disputed (Todd, 2015, and references therein).

…”

mentioning

confidence: 99%

Prelithification and synlithification tectonic foliation development in a clastic sedimentary sequence: COMMENT

Todd¹

2016

Geology

View full text Add to dashboard Cite

Using observations from a single locality (Wine Strand) in the Glashabeg Formation (Dingle Group) of the Dingle Peninsula, southwest Ireland, Meere et al. (2016) conclude that more than 50% shortening of these strata was accomplished during the mid Devonian Acadian event, before lithification was complete. That the late Silurian to Emsian Dingle Group was deformed during the Acadian is not disputed (Todd, 2015, and references therein). Rather, it is the conclusion that the single tectonic foliation is Acadian and was generated before lithification was complete is refuted by several factors, not covered by Meere et al., but which are evident from assessment of the entire area (Todd, 2015).(1) The entire Palaeozoic of the area was affected by the endCarboniferous Variscan orogenic shortening. Structural observations indicate that Old Red Sandstone (ORS) rocks demonstrably younger than the Acadian unconformity have experienced ~14% shortening by folding and faulting and a R s yz strain of ~2.5 (or 40% shortening). The strain is associated with a cleavage that is axial planar to the folds in plan and occurs in symmetrical fans on the axial plane in cross section (Todd, 2015). In the west of the peninsula, this Variscan deformation is evidenced by steeply dipping and cleaved Late Devonian ORS on the north coast and inferred from the substantial uplift of the Acadian unconformity above regional. Any interpretation of shortening in the Dingle Group must take account of this overprint.(2) Dingle Group folding is Acadian in age but the single tectonic fabric is a younger overprint. The folding and faulting of the Dingle Group clearly accomplishes more shortening (~40%) than is evidenced by Variscan-only folds (~14%) above the Acadian unconformity (Todd, 2015). However, when strain data from the entire area are considered, there is a smaller difference in the R s yz strains in mudrocks above (~2.5) and below (~2.8) the Acadian unconformity (Todd, 2015). In other words, as much 88% of the total bulk strain in the Dingle Group is likely due to Variscan shortening, not Acadian. The cleavage transects the axial planes of the Dingle Group folds in both plan and section, commensurate with Variscan overprinting of preexisting and gently tightened Acadian folds and hence is not a product of Acadian transpression (Todd, 2015). (3) Strain patterns are highly dependent on bedding orientation and lithology and fabric of the sediments. At Wine Strand, and other locations where strata are sub-horizontal, mudrocks, when pedogenic calcrete is absent or weakly developed, are typically deformed by constant volume flattening strain with a component of vertical stretching (Meere and Mulchrone, 2006). In coarser lithologies, the calculated R s yz strains are markedly lower and instead some bulk strain occurred by volume loss along the spaced cleavage folia (Fig. 1A). The cleavage folia in the coarser units become more prominent on depositional fabrics like intraclasts, gutter casts, and channel margins that have formed preferential planes of ...

show abstract

“…

…”

mentioning

confidence: 99%

Prelithification and synlithification tectonic foliation development in a clastic sedimentary sequence: COMMENT

Todd¹

2016

Geology

View full text Add to dashboard Cite

show abstract

“…It is important to note that the beds above and below this slumped horizon do not display such a fabric. Axial planar cleavage is now interpreted to form during slumping (see discussion in Alsop and Marco, 2014) as well as in other soft-sediment settings (see also Alterman 1973;Beutner et al 1977;Dykstra 2005;Meere et al 2016).…”

Section: Axial Planar Cleavage In Slump Foldsmentioning

confidence: 97%

Sub-seismic scale folding and thrusting within an exposed mass transport deposit: A case study from NW Argentina

Sobiesiak

Alsop

Kneller

et al. 2017

Journal of Structural Geology

View full text Add to dashboard Cite

While imaging of mass transport deposits (MTDs) by seismic reflection techniques commonly reveals thrusts and large blocks that affect entire deposits, associated systems of folds are generally less apparent as they are typically below the limits of seismic resolution. However, such sub-seismic scale structures are important as they permit the direction of emplacement, gross kinematics and internal strain within MTDs to be determined. Here we present a rigorous description of two outcropscale MTDs exposed in La Peña gorge, northwestern Argentina. These Carboniferous MTDs enable us to illustrate structural changes from a compressional domain, marked by sets of imbricated sandstone layers, into an extensional domain, characterized by sheared blocks of sandstone embedded in a finer matrix. Folds may be progressively modified during slump translation, resulting in asymmetric folds, which undergo subsequent deformation leading to sheared fold limbs together with detached and rotated fold hinges. In order to constrain transport directions within the MTDs, we measured fold hinges, mud clast alignment, and thrust planes as kinematic indicators. We propose emplacement models for both MTDs based on the overall deformational behaviour of sandstone beds Sobiesiak_et_al_ JSG_manuscript Click here to view linked References during translation. The first model is based on the internal geometries and structures of a faultdominated MTD, and the second model is based on layer-normal shearing in a fold-dominated MTD.

show abstract

“…To compare cleavage related crustal shortening below and above the Acadian unconformity strain analysis needs to be carried out on similar lithologies in similar structural positions. Strain in a steeply dipping mudstone adjacent to a fault cannot be compared to the strain Meere et al (2016) report in a sub-horizontal mudstone. Horizontal layers normal to the direction of maximum compression take up the same strain whereas in dipping layers oblique to compression are subject to strain refraction with weak mudstones exhibiting anomalously high strains (Mulchrone and Meere, 2007).…”

mentioning

confidence: 93%

“…We thank Todd (2015) for highlighting the possibility that a late Carboniferous Variscan overprint was responsible for the development of the pervasive fabric seen in the Glashabeg Formation at Wine Strand, southwest Ireland and not the mid-Devonian Acadian event as postulated by Meere and Mulchrone (2006) and Meere et al (2016). We will address each of Todd's comments in turn.…”

mentioning

confidence: 96%

Prelithification and synlithification tectonic foliation development in a clastic sedimentary sequence: REPLY

Meere¹,

Mulchrone²,

McCarthy³

et al. 2016

Geology

Self Cite

View full text Add to dashboard Cite

Prelithification and synlithification tectonic foliation development in a clastic sedimentary sequence

Cited by 7 publications

References 32 publications

Prelithification and synlithification tectonic foliation development in a clastic sedimentary sequence: COMMENT

Prelithification and synlithification tectonic foliation development in a clastic sedimentary sequence: COMMENT

Sub-seismic scale folding and thrusting within an exposed mass transport deposit: A case study from NW Argentina

Prelithification and synlithification tectonic foliation development in a clastic sedimentary sequence: REPLY

Contact Info

Product

Resources

About