ASOCIACIONES DE OSTRÁCODOS DEL MIOCENO TEMPRANO–MEDIO DE LOMA NEGRA (BARDENAS REALES DE NAVARRA, CUENCA DEL EBRO): EVOLUCIÓN PALEOAMBIENTAL DE UN MEDIO LACUSTRE

Blanca Martínez-Garcia, Oier Suarez-Hernando, Aitziber Suárez-Bilbao, Ana Pascual, Amaia Ordiales, Juan Cruz Larrasoaña, Xabier Murelaga, Francisco Javier Ruiz-Sánchez

Abstract


The palaeoenvironmental evolution of the
Loma Negra section (Bardenas Reales de Navarra, Ebro Basin) during the lower–middle Miocene, is studied for the first time. The paleoenvironmental
interpretation
is based on the recovered
ostracod assemblages and the sedimentology.
The
lower
part
of this section
is composed
by
red,
yellow
and grey
mudstones, and with Paralimnocythere
sp. as the most abundant ostracod taxon. The lithological features and the faunistic
assemblage allows
the interpretation
of a paleoenvironment
with the development
of shallow
water bodies with stagnant, warm
and
fresh
to oligohaline waters in distal alluvial flood plains for this section. The
presence
of some sandstone levels
where
the most
abundant ostracod
species is Cyclocypris
laevis (Müller)
marks
punctual higher energy events
inside this alluvial system and the presence
of more
saline
waters.
The
upper part
of the section is formed by
grey
limestones with interbedded fine grey
mudstones. In
this interval,
Pseudocandona
parallela
Müller is the most abundant ostracod species, indicating the development of a stable lacustrine system with water currents, and temperate
to cold and oligohaline to mesohaline waters. The
transition between
the alluvial and the lacustrine systems shows
a gradual
evolution.

Keywords


Miocene; Bardenas Reales de Navarra; Ostracods; Palaeoenvironmental evolution; Palaeolimnology

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DOI: http://dx.doi.org/10.5710/AMGH.14.08.2014.2745