Decay in Upper Cretaceous Normapolles Exines

Abstract

Three different types of decay have been observed in exines of Normapolles type from anther 143 A 3, found in a clayey sand in the Upper Cretaceous fluviolacustrine sediments at Åsen. The outer exine layer (tectum) is penetrated by numerous radial needlepores, interpreted as widened microchannels. The tectum and, in some cases, also the infratectal layer and the foot layer (solum) may be penetrated by irregular, tunnels (>500 nm in diameter), sometimes branching into finer tunnels (50–100 nm) at the transition to the infratectal layer. Still finer holes (15–40 nm) have been observed in all exine layers. They occur as a rule in zones, separated by about 200 nanometer from the surfaces of the exine layers, needle-pores and tunnels. No indisputable evidence of the agents responsible for these types of decay has as yet been recognized.