Allan Gil Fernando

Prevailing oxic environments in the Pacific Ocean during the mid-Cretaceous Oceanic Anoxic Event 2

The occurrence of Oceanic Anoxic Event 2 (OAE2) 94 million years ago is considered to be one of the largest carbon cycle perturbations in the Earths history. The marked increase in the spatial extent of the anoxic conditions in the worlds oceans associated with OAE2 resulted in the mass accumulation of organic-rich sediments. Although extensive oceanographic studies of OAE2 have been undertaken in the Atlantic Ocean, the Tethys Sea, and the epicontinental seas of Europe and America, little is known about OAE2 in the Pacific Ocean. Here, we present high-resolution carbon-isotope and degree of pyritization (DOP) data from marine sequences that formed along the continental margins of North America and Asia below the northeastern and northwestern Pacific Ocean. The predominance of low DOP values in these areas revealed that the continental margins of the Pacific Ocean were oxic for most of the OAE2 interval.

A new cerithioidean genus Megistocerithium (Gastropoda; Mollusca) from the Miocene of Southeast Asia: a possible relict of Mesozoic "Eustomatidae"

Abstract. Based upon large cerithiform gastropod specimens from the middle Miocene beds of Java, Indonesia and the Philippines, a new genus and new species, Megistocerithium magoi, is described herein. Ten fragmentary specimens from the lower and upper Miocene beds of the Philippines are tentatively referred to this species. M. magoi Kase sp. nov. is amongst the largest fossil cerithioidean gastropods (except for Turritellidae). It was a dweller in intertidal sandy mudflats, probably in close proximity to mangrove forests. No species considered to be congeneric with this species have been found in the Cenozoic. On the other hand, M. magoi Kase gen. et sp. nov. shares apertural characters with the Middle Jurassic species Eustoma tuberculosa, the type species of a genus belonging to the yet to be well-recognized family Eustomatidae. M. magoi Kase gen.et sp. nov. is possibly a relict of the Mesozoic Eustomatidae. It is assumed to have been a grazer on mangrove litter like the potamidid genera Terebralia and Telescopium in modern mangrove swamps.