Microestructura e interrupciones en el crecimiento de las conchas de inocerámido (Bivalvia) del Maastrichtiense inferior. Cuenca Vasco-Cantábrica

Abstract

Lower Maastrichtian inoceramid shells from the Basque-Cantabrian Basin were deposited in a carbonate deep-sea environment. The referred shells show a well-developed first order prismatic microstructure formed by crystals of low magnesium calcite (LMC). Each prism, composed by several crystals, is formed by stacked crystalline tablets. Although shells have undergone burial diagenesis, it is possible to determine an important number of pairs of clear and dark growth lines (>250), more vigorous in the initial stages of growth. Occasionally, these lines can exhibit ruptures in their development of difficult interpretation, since they do not seem to be product of dramatic temperature-salinity or energy (i.e. storms) changes in the environment. The origin of the growth ruptures may be related to physiological factors without being directly associated to the stress produced by periodical spawning