DLA 36 (Arenal) (Ordovician of Argentina)

Also known as Are 22

Where: Jujuy, Argentina (23.5° S, 65.3° W: paleocoordinates 44.8° S, 128.8° W)

• coordinate based on unpublished field data

• small collection-level geographic resolution

When: Rupasca Member (Santa Rosita Formation), Tremadocian (485.4 - 477.7 Ma)

• bed-level stratigraphic resolution

Environment/lithology: transition zone or lower shoreface; lithified, silty, sandy siliciclastic sediments and lithified, muddy siliciclastic

• Lower-shoreface deposits consist of light grey, hummocky cross-stratified, fine-

•grained sandstone forming amalgamated packages. Individual sandstone beds generally pinch out, but bedsets are laterally persistent. Thin mudstone part-

•ings are locally present. Gutter casts, load casts, ball-and-pillow structures and tool marks are common, while wrinkle marks are present locally. Physical sedimentary structures in these deposits indicate episodic storm wave activity, and wave-generated surges(Buatois & Mangano 2003; Buatois et al. 2006). High-energy oscillatory, and combined flows were the dominant processes during frequent storms. Flows were strongly erosive, and characterized by rapid

•influx of sand. Recurrent storms and continuous wave agitation during fair-weather removed most of the finer-grained particles, leaving only thin mudstone

•partings between sand units. These deposits are typified as strongly storm-dominated shorefaces (sensu MacEachern & Pemberton 1992).

Size classes: macrofossils, mesofossils

Preservation: cast, mold/impression

Collection methods: bulk,

Primary reference: D. Balseiro, B. G. Waisfeld, and L. A. Buatois. 2011. Unusual trilobite biofacies from the Lower Ordovician of the Argentine Cordillera Oriental: new insights into olenid palaeoecology. Lethaia 44:58-75 [D. Balseiro/D. Balseiro]more details

Purpose of describing collection: paleoecologic analysis

PaleoDB collection 136937: authorized by Diego Balseiro, entered by Diego Balseiro on 07.12.2012

Creative Commons license: CC BY (attribution)

Taxonomic list

Trilobita
 Asaphida - Asaphidae
Asaphellus sp. Callaway 1877 trilobite
 Ptychopariida - Olenidae
Leptoplastides sp. Raw 1908 trilobite