Banca de QUALIFICAÇÃO: Thales Lúcio Santos da Silva

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
STUDENT : Thales Lúcio Santos da Silva
DATE: 26/05/2022
LOCAL: Remotamente
TITLE:
KEY WORDS:

Black Shale; Codó Formation; Ipubi Formation; Late Aptian; Paleogeog-raphy

PAGES: 162
BIG AREA: Ciências Exatas e da Terra
AREA: Geociências
SUMMARY:

The Codó (São Luís-Grajaú Basin) and Ipubi (North area of the Araripe Basin) for-mations have been correlated because of their lithological distribution and fossil con-tent. However, geochemistry research correlating both have not been made, until now, to elucidate some issues about their depositional environment, deposition age and paleogeographic setting. Thus, by using geochemistry research (organic, inorganic, and isotopic), paleoenvironment conditions (redox, climate, salinity, paleoproductivity, organic matter source), geochronology (Re-Os system) and paleogeography setting (by δ13Corg profiles) are presented herein. The black shales of Codó and Ipubi For-mations are enriched in Fe, S, V, Cu and Zn (organophilic elements) and are mostly of authigenic source due their relation between Aluminum and Avarege Shale. These rocks deposited in oxic-suboxic conditions (V/Cr < 2; COT/NT > 5; δ15Ntotal = 3.7-6.9 ‰), during hot-humid paleoclimate (Rb/Sr < 1; Sr/Cu < 5; high Fe/Mn; negative δ13Corg), with paleosalinity variation (Sr/Ba < 0.2) which made primary paleoproductivity oscillations due to stratified water body (shallow and deep water; (Al+Fe)/(Ca+Mg) = 0.1-20.7). Furthermore, the organic matter of those black shales suffered more terri-genous influence as they approach those of the Ipubi Formation - which means that these black shales have marine with terrigenous influence organic matter in the São Luís-Grajaú Basin and have terrigenous with lacustrine influence organic matter in the Araripe Basin. Moreover, it is suggested that the black shale deposition of both basins is geochronocorrelated due to the Codó Formation black shales been deposited ~123 Ma in age (by Re-Os geochronology) – same age obtained for the black shales of the Ipubi Formation in previous study (~123 Ma; Re-Os geochronology). Associated to this, it is argued that these black shales are correlated to those from Tethys Sea typical sections, since they present similar δ13Corg chemiostratigraphy profiles (negative ex-cursion and δ13Corg ~-25.5 ‰). The data here presented suggests that the marine in-gression into the Northeast basins occurred by São Luís-Grajaú Basin - coinciding with the Anoxic Oceanic Events 1a and 1b (~120 Ma and ~111 Ma, respectively). However, since the black shales of the Ipubi Formation show paleodepositional conditions differ-ent (terrigenous organic matter) than those of the Codó Formation (marine organic matter), it is suggested that the first Tethys Sea ingressions (ca. ~123 Ma) reached only the southern region of the Araripe Basin (from Sergipe-Alagoas Basin?) during those black shales’ deposition.

BANKING MEMBERS:
Presidente - 1320828 - JOAO ADAUTO DE SOUZA NETO
Externa à Instituição - JULIANA CHARÃO MARQUES - UFRGS
Interno - 1133908 - MARIO FERREIRA DE LIMA FILHO
Externo à Instituição - RENÉ RODRIGUES - UERJ
Interno - 1133907 - VIRGINIO HENRIQUE DE MIRANDA LOPES NEUMANN