|
Paleobotany
Paleobotanical research has partially
characterized the flora associated with the
amber deposits. The forests that produced
the resin that originated the amber were
composed of cheirolepids, araucariaceans,
and cypresses, while the undergrowth
consisted of ferns, cycads, ginkgos,
bennettites, caytoniales, gnetales, and a
few angiosperms. However, our research shows
a different forest composition between the
Maestrat Basin and the western part of the
Basque-Cantabrian Basin, cheirolepid-dominated,
and the eastern part of the Basque-Cantabrian
Basin, araucariacean-dominated. Furthermore,
gas chromatography–mass spectrometry (GC–MS)
of Peñacerrada I amber suggests that it had
an araucariacean origin, which is supported
by the presence of an important amount of
pollen grains with affinities to this group
of conifers. In other amber localities, like
El Soplao, additional geochemical studies
suggest the cheirolepid Frenelopsis as a
possible resin producer instead. This
hypothesis is supported by the presence of
abundant macro-remains and pollen in the
sediment associated with the amber and a few
flows of amber with imprints of this conifer.
Moreover, in all amber outcrops, Frenelopsis’
cuticles are the most abundant plant
macroremains, and pollen grains of the
related genus Classopollis are also abundant.
Study of Frenelopsis’ morphology and
stomatic recount permitted to infer the
paleoclimatological conditions for the
studied outcrops, like wet/dry season
alternation. Palynological assemblages are composed of
spikemosses, clubmosses, and fern spores, as
well as pollen grains from araucariaceans,
cupressaceans/taxodiaceans, cheirolepid,
cycadaleans, ginkgoaleans, bennettitaleans,
pteridosperms, gnetaleans, and angiosperms;
also, dinoflagellate cysts and phycomas of
prasinophycean algae have been found, which
suggest a certain marine influence in the
Basque-Cantabrian Basin outcrops. The study
of the palinomorphs from the amber-sediments
is great relevance as it allows to
accurately date the sediments in which amber
is found. In turn, the study of plant macro-remains
allows us to reconstruct the resin-producing
sources. Increase in size and vein density
of angiosperm leaves during the Albian
caused increases in easy-to-eat soft organic
matter and sugars, leading to a
diversification of insect herbivores. A
complete study of the meso- and macro-remains
from gymnosperms and angiosperms found in
the amber deposits is being undertaken. Some microorganisms have been found as amber
inclusions, especially protists and mycelia
with sporangia. Some of these protists have
been identified as ciliates, flagellates,
and amoebas, assigned to Euglenozoa,
Chlorophyceae, and Chromalveolata; however,
their relationship with the paleoecosystem
has not been investigated yet. |
