High-resolution carbonate isotopic study of the Mural Formation (Cerro Pimas section), Sonora, México: Implications for early Albian oceanic anoxic events

Madhavaraju, J.,Lee, Yong Il,Scott, R.W.,Gonzá,lez-Leó,n, C.M.,Jenkyns, H.C.,Saucedo-Samaniego, J.C.,Ramasamy, S. Elsevier 2018 Journal of South American earth sciences Vol.82 No.-

<P><B>Abstract</B></P> <P>The 420-m thick stratigraphic section of the Mural Formation that is exposed in the Cerro Pimas area of northern Sonora, Mexico, is composed of limestone lithofacies ranging from bioclastic wackestone to boundstone, whose biota is characterized by low diversity. Prominent age-diagnostic fossils are benthic foraminifera and long-ranging calcareous algae that indicate the Aptian/Albian boundary is close to the base of the Los Coyotes Member. The carbonates of this formation have negative to positive δ<SUP>13</SUP>C values (−4.63 to +2.6‰) and highly depleted δ<SUP>18</SUP>O values that range from −12.74 to −8.34‰. The absence of correlation between δ<SUP>13</SUP>C and δ<SUP>18</SUP>O values supports a primary marine origin for the δ<SUP>13</SUP>C values of these limestones.</P> <P>The carbon-isotopic curve of the Cerro Pimas stratigraphic section has well-defined δ<SUP>13</SUP>C segments (C8 – C15) that compare with published curves of similar age. In the lower part of the early Albian Los Coyotes Member, the presence of OAE 1b is indicated by an increase followed by a decrease in δ<SUP>13</SUP>C values, suggesting correlation with the Kilian Event. The middle part of the Los Coyotes Member has a significant negative carbon-isotope excursion correlated with the globally recognizable early Albian Paquier event. Moreover, another significant negative carbon-isotope shift is observed in the upper part of the Los Coyotes Member, which can be correlated with the Leenhardt Event. The occurrence of the Kilian, Paquier and Leenhardt Events (OAE 1b cluster) in the Cerro Pimas stratigraphy confirms the global nature of these early Albian disturbances of the carbon cycle.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Benthic foraminifera and calcareous algae that indicate the Aptian/Albian boundary. </LI> <LI> The Aptian–Albian boundary is placed at the base of the Los Coyotes Member. </LI> <LI> High-resolution carbon-isotope curves of the Cerro Pimas are divided into seven well-defined δ<SUP>13</SUP>C segments. </LI> <LI> The upper Aptian-lower Albian Cerro Pimas section of the Mural Formation records the impact of OAE 1b. </LI> <LI> The occurrences of Kilian, Paquier and Leenhardt Events (OAE 1b clusters) are documented in the Cerro Pimas section. </LI> </UL> </P>

Mineralogy and geochemistry of clastic sediments of the Terani Formation, Cauvery Basin, southern India: implications for paleoweathering, provenance and tectonic setting

Jayagopal Madhavaraju,Subin Prakash Rajendra,이용일,Erik Ramirez Montoya,Sooriamuthu Ramasamy,Rufino Lozano SantaCruz 한국지질과학협의회 2020 Geosciences Journal Vol.24 No.6

Mineralogical and geochemical (major, trace and rare earth elements) studies were carried out on the clay samples of the Terani Formation, South India to investigate the paleoweathering, source rocks characteristics and tectonic setting. The chemical index of alteration (CIA), plagioclase index of alteration (PIA) values and A-CN-K diagram indicate that clays were generated from source rocks of the upper continental crust affected by intense chemical weathering. The chondrite-normalized REE patterns show considerable LREE enrichment, HREE depletion with significant negative Eu anomalies. The REE patterns, elemental ratios like Al2O3/TiO2, Cr/Ni, Eu/Eu*, (La/Lu)cn, La/Sc, Th/Sc, La/Co, Th/Co, and Cr/Th, discriminant function diagram, various bivariate and ternary plots indicate the contribution of sediments from felsic and intermediate source rocks. The discriminant-function-based tectonic setting diagrams reveal passive margin setting for the source area of the Terani Formation.

Carbon, oxygen and strontium isotopic signatures in Maastrichtian-Danian limestones of the Cauvery Basin, South India

Jayagopal Madhavaraju,Alcides N. Sial,Reghunathan Rakhinath,Sooriamuthu Ramasamy,이용일,Ariputhiran Ramachandran 한국지질과학협의회 2015 Geosciences Journal Vol.19 No.2

A petrographic, carbon, oxygen and strontium study of the carbonate succession of the shallow marine Kallankurichchi and Niniyur formations of the Cauvery Basin, Tamil Nadu, India was conducted to understand the isotopic variations in seawater during Maastrichtian-Danian. The limestones from both the Kallankurichchi and Niniyur formations show large variations in Mn and Sr concentrations and high Mn/Sr ratios indicate alterations of primary isotopic signatures during shallow burial diagenesis. The limestones of both the Kallankurichchi and Niniyur formations show negative δ13C (‒4.73 to ‒0.49‰ VPDB; ‒5.63 to ‒1.87‰ VPDB; respectively) and δ18O values (‒8.89 to ‒3.66‰ VPDB; ‒8.56 to ‒5.41‰ VPDB; respectively). The carbon and oxygen isotope composition, δ13C vs. δ18O plot and Mn/Sr ratio suggest that the measured δ13C and δ18O values have been significantly altered during diagenesis. The limestones from both the Kallankurichchi and Niniyur formations show large variations in 87Sr/86Sr values (0.709310 to 0.711962; 0.708280 to 0.708398, respectively) which are higher than 87Sr/86Sr ratios of the contemporary Lower Maastrichtian (87Sr/86Sr: 0.707760) and Danian (0.707819 to 0.707833) seawaters. The elevated 87Sr/86Sr ratios in the limestones of the Kallankurichchi Formation suggest that these limestones were significantly modified by pore fluids during meteoric diagenesis. The observed large fluctuations in 87Sr/86Sr ratios in the Niniyur Formation resulted from variations in riverine input. One sample from the Niniyur Formation exhibits an unaltered 87Sr/86Sr ratio (0.707828) which is interpreted to indicate an age of 65.02 Ma.

Microtextures on detrital quartz grains of upper Maastrichtian-Danian rocks of the Cauvery Basin, Southeastern India: implications for provenance and depositional environments

J. Madhavaraju,Yong Il Lee,J.S. Armstrong-Altrin,S.M. Hussain 한국지질과학협의회 2006 Geosciences Journal Vol.10 No.1

Quartz grains from the Kallamedu (late Maastrich-tian) and lower Niniyur (Danian) Formations, Cauvery Basin,Southeast India were examined under a scanning electron microscope,and twenty three distinct microtextures were observed. Thesemechanical (thirteen features), mechanical and/or chemical (fivefeatures) and chemical (five features) origins. Quartz grains fromthe Kallamedu and lower Niniyur Formations show conchoidalfractures, straight steps and arcuate steps which are the charac-teristic microtextures of quartz grains derived from crystallinesource rocks. Quartz grains from the upper Kallamedu and lowerNiniyur Formations show angular to subangular outline, whereasthose from the lower Kallamedu Formation show subangular torounded outline. The dominance of angular to subangular grainsand the presence of straight and arcuate steps suggest that theseclastic sediments were undergone short transportation and rapidKallamedu Formation suggests that significant amounts of quartzgrains are of recycled origin. Vs, straight scratches and curvedscratches, the characteristic features of marine environment, are com-mon on the quartz grains from the lower Niniyur Formation, whichis consistent with the previous interpretation. However, quartz grainsfrom the lower Kallamedu Formation exhibit very low frequency ofthese features, whereas they are moderately present in the upperKallamedu Formation, suggestive of a change in depositional con-ditions with time. The lower Kallamedu Formation exhibits planarenvironment. The unfossiliferous upper Kallamedu Formation containsappreciable amount of illite and mixed-layer (illite/smectite) clayminerals, which suggests that the saline conditions prevailed dur-ing its deposition. Microtextures on the quartz grains coupled withdominant clay mineral types suggest the deltaic depositional envi-ronments for the upper Kallamedu Formation.

Geochemistry of Neoproterozoic limestones of the Shahabad Formation, Bhima Basin, Karnataka, southern India

Ramasamy Nagarajan,Jayagopal Madhavaraju,John S. Armstrong-Altrin,Raghavendra Nagendra 한국지질과학협의회 2011 Geosciences Journal Vol.15 No.1

Major, trace and rare earth element (REE) geochemistry of carbonate rocks of the Neoproterozoic Shahabad Formation, southern India were studied in order to investigate the depositional environment and source for the REEs. The PAAS (Post Archaean Australian Shale) normalized REE + Y pattern of Shahabad limestones have consistent seawater-like pattern i.e., i) LREE depletion (average (Nd/Yb)_(SN) = 0.64 ± 0.08), ii) negative Ce anomaly, iii) positive Gd anomaly (average Gd_(SN)/Gd^* = 1.05 ± 0.16), iv) superchondritic Y/Ho ratio (average Y/Ho = 38.13 ± 21.35). The depletion of LREE and enrichment of HREE are clearly indicated by the (La/Yb)_(SN), (Dy/Yb)_(SN) and (Nd/Yb)_(SN) ratios, which suggest the retention of seawater characteristics in these limestones. The negative Ce anomaly reflects the incorporation of REE directly from seawater or from the pore water under oxic condition, and also reveals the mixing of two-component systems with terrigenous clay (detrital) in the marine sediments. The terrigenous input in these limestones is confirmed by positive correlation of REE with Al_2O_3, negative correlation of REE with CaO and differences in Y/Ho ratios. V, Cr, and Sc, are positively correlated with Ti, and strong positive correlation of REE with Fe_2O_3, Ni, Cr, Sc, and Y also indicate the presence of terrigenous materials in the Shahabad limestones.