Late Creataceous Research Papers - Academia.edu (original) (raw)

La Breccia di Slivia, affiorante circa 2 km a nord di Aurisina (Trieste), rappresenta la registrazione stratigrafica di un'importante fase tettonica verificatasi nell'area del Carso triestino durante il Campaniano... more

La Breccia di Slivia, affiorante circa 2 km a nord di Aurisina (Trieste), rappresenta la registrazione stratigrafica di un'importante fase tettonica verificatasi nell'area del Carso triestino durante il Campaniano superiore-Maastrichtiano. In tale periodo si è originata una depressione strutturale nei calcari di piattaforma di età santoniano-coniaciana, riempita da imponenti corpi di breccia derivati da smantellamenti e frane dei calcari incassanti. Questi depositi sono coevi alle facies schizoaline "liburniche" affioranti, con discreti spessori, nel Carso triestino meridionale e nel Carso goriziano settentrionale, mentre lungo la vicina fascia costiera il "Liburnico" è molto ridotto od assente e comunque generalmente limitato a termini basali del Paleocene. Infine, la depressione tettonica contenente la breccia è verosimilmente associata ad un significativo lineamento strutturale che sblocca e ripete la successione di piattaforma coniaciano-santoniana tra Slivia e S. Pelagio (a NE) ed Aurisina (a SW).

Reliable reconstructions of atmospheric carbon dioxide concentrations (pCO2) are required at higher resolution than currently available to help resolve the relationship between mass extinctions and changes in palaeo-pCO2 levels. Such... more

Reliable reconstructions of atmospheric carbon dioxide concentrations (pCO2) are required at higher resolution than currently available to help resolve the relationship between mass extinctions and changes in palaeo-pCO2 levels. Such reconstructions are needed: 1, at a high temporal resolution for constraining the pre- and post-extinction atmospheres; and 2, at a sufficient spatial resolution to constrain potential inter-hemispheric differences. Here we estimate pCO2 based on fossil Lauraceae leaf cuticle specimens derived from three localities with strata spanning the latest Cretaceous to the mid-Paleocene, including a new Cretaceous–Paleogene boundary (K–Pg) locality, in New Zealand. We use two independent methods of stomatal density-based pCO2 reconstructions; a transfer function calibrated using herbarium material and the stomatal ratio method, producing three calibration sets. Our results based on the mean values of each of the three calibration methods indicate pCO2 ranging between ca. 460 and 650 ppm during the latest Cretaceous, falling precipitously to average values between ca. 360 and 430 ppm across the K–Pg boundary, and further to ca. 305–320 ppm in the mid-Paleocene. A ‘spike’ of extremely high pCO2 at the K–Pg could not be confirmed, but our results are, nonetheless, consistent with previously published pCO2 records from the Northern Hemisphere, and show that stomatal density worldwide was responding to significant changes in pCO2 across the K–Pg.

Permineralized palm stems and adventitious roots are classified under specific organ-type genera (Palmoxylon or Rhizopalmoxylon) without affinities below the family level. Fragments of vegetative basal axes provide an incomplete picture... more

Permineralized palm stems and adventitious roots are classified under specific organ-type genera (Palmoxylon or Rhizopalmoxylon) without affinities below the family level. Fragments of vegetative basal axes provide an incomplete picture of histological changes due to axial and radial differences in cell growth. However, stem and root anatomical descriptors were previously reported based on general and consistent internal structural features. Two root specimens from the Tarahumara Formation and six stem specimens from the Olmos Formation are included as terminals in a previously reported family-wide morphological and molecular character matrix at the genus level enriched with stem and root anatomical descriptors to elucidate their systematic relationships. Late Cretaceous vegetative basal axes from northern Mexico have systematic affinities to subfamily Coryphoideae. The root system of Palmoxylon polymorphum is included in its original stem description and this fossil species is inferred to have a sister relationship to Cryosophileae. Circumscription of Rhizopalmoxylon huepaciense is emended to include former R. teguachiense, and a systematic affinity to the syncarpous clade is inferred. Circumscription of Palmoxylon longum is also emended, to include former P. commune, P. enochii, P. fibrosum and P. kikaapoa, and a systematic affinity to tribe Borasseae is inferred. These findings highlight the utility of cladistic analyses for reconstructing fossil fragments of palm vegetative basal axes and for inferring their systematic relationships. They also support a Late Cretaceous divergence of Coryphoideae and raise questions about its biogeographic history.