MULTIPROXY CHARACTERIZATION OF THE LOWER VALANGINIAN - LOWER APTIAN SUCCESSION AT THE LA LATA QUARRY, SIERRA DE LOS ORGANOS, AND ITS RECORD OF OCEANIC ANOXIC EVENTS IN THE PROTO CARIBBEAN

A 30-meter sedimentary succession at Peña Blanca, near Pons, Sierra de los Órganos, Western Cuba, comprises two lithologic units: Unit 1 (0-4 m) consists of biomicritic limestones (TIC > 70%; TOC ~2.3%) alternating with chert-bearing marlstones (TIC: 32.2 - 69.6%; TOC: 2.8 -10.8%). Calcareous nannofossils reveal the late Valanginian nannofossil subzone NK3A-B while calpionellids (Tintinnopsella cf. carpathica, Calpionellites cf. darderi) and strontium isotope values (⁸⁷Sr/⁸⁶Sr: 0.707447-0.707465) extend its chronology to the Hauterivian (NC4A). Key findings include a δ¹³C_org profile averaging -27.0‰ with a peak of -25.6‰ and δ¹³C_carb of 3‰ correlated with the "Weissert" Event [1,2,3] between 0.9 and 1.48 meters.

Unit 2 (4-30 m) consists of biomicritic limestones (~74% TIC, ~3% TOC), marlstones, and siliceous layers. Index taxa in the upper part include planktic foraminifera (Leupoldina cf.cabri, Globigerinelloides ferreolensis, G. blowi, Praehedbergella spp.) and coccolithophores (Zeugrhabdotus embergeri, Nannoconus steinmannii, N. kamptneri) indicating that the section encompasses the Aptian, which is consistent with previous correlations extending to the Albian[4,5]. A prominent carbon isotope excursion (CIE) at 10 m (~3.8‰) is hypothesized to correspond to the Faraoni event [6,7], followed by ~3.9‰ CIE between 24.1m and 27 m) coeval with OAE1a.

Geochemical correlations between aluminum (Al) and lithium (Li) (r = 0.98) and phosphorus (P) and titanium (Ti) (r = 0.99) suggest the influence of terrigenous source. A negative correlation between silicon (Si) and TIC (r = -0.64) indicates divergent sedimentary sources. Rock Eval pyrolysis highlights oxidized terrestrial organic matter and enhanced redox-sensitive trace elements (Mo, V, TL, U) imply dysoxic conditions favoring organic matter preservation. The section reveals that conditions in the Proto-Caribbean Basin also played a significant role during the Early Cretaceous carbon sink.

1) Weissert et al (1979) Ocean. Geol.7, 147-151; 2) Weissert (1989) Surv. Geophys. 10, 1–61; 3) Orihuela et al (2023) Abstr.14 RSP, Bucharest 14 – 15 Sept. 90 – 91 ; 4) Pszczółkowski (1978) Acta Geologica Polonica 28 (1), 1-96 ; 5) Pszczółkowski et al (2013) X Congreso Cubana Geología. ISSN 2307-499X; 6) Cecca et al (1994a) Riv. It. Paleont. Strat. 99, 4, 551-568; 7) Baudin et al (1999) Bull. Soc. géol. France, l70, 4, 487- 498.