Sample# 9, Lagoinhas, Santa Maria (subunit B1) (Pleistocene of Portugal)

Where: Portugal (37.0° N, 25.1° W: paleocoordinates 37.0° N, 25.1° W)

• coordinate based on nearby landmark

• outcrop-level geographic resolution

When: Late/Upper Pleistocene (0.1 - 0.0 Ma)

• STRATIGRAPHIC RELATIONS: From unnamed Late Quaternary marine deposits. AGE: early Late Pleistocene. Dated on the basis of U series. recently, Ávila et al. (2008a) dated the basal conglomerate of the Prainha outcrop (subunit A1 of Ávila et al., 2002) as Marine Isotopic Substage 5.5 (MIS 5.5), based on U/Th ages on shells of Patella spp. As explained by Ávila et al. (2008a), due to taphonomic problems and the wet climatic conditions prevailing on the island, the U-series measurements from their fossilized remains can only help constrain the age of the uranium taken up diagenetically. U-series data from Santa Maria Island indicate. an open system, providing mean 230Th ages that are much younger than the true age of the unit. They suggest relatively steady, more or less continuous, diagenetic U-uptake by the fossils since their deposition in the Pleistocene. Thus, accepting an age of 130–120 ka for the deposits, Ávila et al. (2008a) estimated that within the embedded biogenic carbonates U-uptake rates varied from c. 2.5 to 5 μg g CaCO−31 kyr−1. This was based on 230Th-ages in the 60–70 ka range, for shells that would have started accumulating diagenetic U some 130–120 ka ago (i.e. during the MIS 5.5) (Ávila et al., 2008a). STRATIGRAPHIC POSITION: Succession comprises cemented and bored carbonate sands, overlaind by 0.5 m beach sands with concentrations of shell debris.

• bed-level stratigraphic resolution

Environment/lithology: foreshore; unlithified, shelly/skeletal, yellow sandstone

• ENVIRONMENT: Sediments correspond to beach foreshore (intertidal) facies and show marked similarities to the recent beach sands both in grain size and composition.
• SPECIFIC LITHOLOGY: Yellow uncemented lithic sands (dominated by the 250–500 μm [Lagoinhas] fraction), apart from the volcanogenic grains consisting almost exclusively of small mollusc fragments (carbonate contents ranging from 56.2 to 67.3% in the samples investigated). LITHIFICATION: Unlithified, as described in text.

Size class: macrofossils

• In some of the valves of E. castanea, and in a lesser extent, of Lucinella divaricata, predatory borings assigned to the ichnogenus Oichnus Bromley, 1981, are present. These borings were also found, although rarely, in shells of Cantharus variegatus, Trachypollia nodulosa and Natica prietoi Hidalgo, 1873 (Fig. 10).

Preservation: original aragonite

Collected by Ávila et al in 2003

Collection methods: bulk, sieve,

• COLLECTOR: S. Ávila and others, Febuary 17, 2003. REPOSITORY: Not stated in text, but presumably the Universidade dos Açores. METHODS: Ten bulk samples of approximately 1 kg each were collected from the sand facies of the Lagoinhas deposit in a standardised sample spacing (about 50 cm laterally between contiguous samples). Sampling was restricted to fresh material, obtained from in-situ deposits after removal of weathered residues. Samples were disaggregated by short ultrasonic treatment and gentle wet-sieving. A mesh width of 0.250 mm was chosen, allowing the retrieval of almost all determinable remains of the macrobenthos (including fragments). Molluscs were the most abundant group recovered, accompanied by rare brachiopods and echinoderm debris.

Primary reference: S. P. Ávila, P. Madeira, C. Zazo, A. Kroh, M. Kirby, C. Marques Silva, M. Cachao and A. M. Frias Martins. 2009. Palaeoecology of the Pleistocene (MIS 5) outcrops of Santa Maria Island (Azores) in a complex oceanic tectonic setting. Palaeogeography, Palaeoclimatology, Palaeoecology 274:18-31 [W. Kiessling/U. Merkel/S. Ávila]more details

Purpose of describing collection: paleoecologic analysis

PaleoDB collection 122291: authorized by Austin Hendy, entered by Austin Hendy on 20.12.2011

Creative Commons license: CC BY (attribution)

Taxonomic list

• COVERAGE: Exhaustive faunal list for gastropods. Bivalves omitted from sample faunal lists. NOMENCLATURE: Not an authoritative publication, but with modern nomenclature and species-resolution identifications.
unclassified
  -
Gastropoda
 Heterostropha - Pyramidellidae
Odostomia sp. Fleming 1817 snail
 Sorbeoconcha - Littorinidae
"Melarhaphe neritoides" = Littorina neritoides
"Melarhaphe neritoides" = Littorina neritoides Linnaeus 1758 periwinkle
 Sorbeoconcha - Rissoidae
 Neogastropoda - Muricidae
Ocenebra sp. Leach in Gray 1847 murex snail
 Neogastropoda - Horaiclavidae
Haedropleura septangularis Montagu 1803 snail
 Neogastropoda - Mitromorphidae
 Neogastropoda - Columbellidae
 Sorbeoconcha - Naticidae
 Sorbeoconcha - Cerithiopsidae
Cerithiopsis sp. Hanley 1849 snail
 Sorbeoconcha - Triphoridae
Triphoridae indet. Gray 1847 snail
 Cerithioidea - Planaxidae
Fossarus ambiguus Linnaeus 1758 snail
 Cerithioidea - Cerithiidae
Bittium latreillii cerith snail
 Trochoidea - Trochidae
 Patellogastropoda - Patellidae
Patella sp. Linnaeus 1758 limpet