Planet Mars
Universidad Internacional Menéndez Pelayo
Palacio de Magdalena, Santander, Cantabria (Spain)
5th to 9th July, 2004

Fieldtrip Guide to the K/T Boundary at Santander

Fernando Ayllón & Jesús Martínez-Frías

Centro de Astrobiología (CSIC/INTA)

Associated to the NASA Astrobiology Institute
Instituto Nacional de Técnica Aeroespacial
Ctra de Ajalvir, km 4
28850 Torrejón de Ardoz, Madrid (SPAIN)
Aim of the excursion and brief description of the stratigraphic section

Spain presents two areas where the transition from the Cretaceous to the Tertiary system (K/T boundary) is very well preserved, with associated Ir anomalies which have been studied in some of the most relevant publications about meteoritic impact markers in the stratigraphic record (see references). The most representative localities of both zones are: Zumaia, in Guipúzcoa (Basque-Cantabrian Basin), and Agost and Caravaca in Levante (Betic cordillera).

Along the Cantabrian coast west of Zumaia there are several sections where the Cretaceous-Tertiary transition crops out. Regarding impact studies, these sections have not been investigated in detail due to the apparent lack of a specific clay layer of material attributed to the end Cretaceous meteoritic impact. Stratigraphical and paleontological studies point to a more gradual, ill defined, sedimentary transition for this area. In this context, at the Centro de Astrobiología we have initiated the investigation of the K/T boundary sections in Cantabria, focussing in the mineralogical, geochemical and isotopic changes that have taken place in the rocks (sand-bearing limestones and dolomites) deposited just below, along and above the boundary.

The aim of this excursion is to introduce the participants to the geology and general features of the sedimentary rock section placed along the North coast of Santander. These rocks were deposited on an open shelf, sandy carbonate succession at the time of the transition from the Cretaceous to the Tertiary period, around ± 65 Ma. As we walk westwards along the coast, the gentle dipping section evolves from relatively shallow inner platform clastic materials, deposited within fair-weather wave base (Cabo de Lata Fm), to a shallow restricted internal platform, probably emerged at times (San Juan Fm). In the three planed stops, attention will be focussed on the environments on which sedimentation took place, on the abrupt faunal decline as we progress upwards in the section and on the diagenetic processes that modified the sedimentary rocks after deposition.


Stop 1: Panteón del Inglés

Bioclastic accumulations on the Maastrichtian.

Here we have a fair view of the coast to the west. The small promontory, marked by a tombstone, is formed by sandy limestones with tempest associated deposits (tempestites). The tempestites are formed by significant accumulations of fossil fragments.

Stop 2: Cabo de Lata

Silicification of fossil fragments and formation of geodes.

At this point the sandy limestone beds present fist-sized brownish lumps, more resistant to erosion, formed by fossil fragments cemented by silica. A few meters above in the section one limestone bed presents numerous small, white and cm-sized geodes formed by amorphous silica + quartz + calcite, with relict micro-crystals of anhydrite. Both features are considered to represent early cementation (diagenetic) processes diagnostic of arid climatic conditions and supratidal coastal environments after deposition. Our results, based on a fluid inclusion study of the geode minerals, support this hypothesis.

Just ahead this bed, above a soft brown marl bed, lies the last bioclastic-rich bed of the section.

Stop 3: Bajos de Malasmañas.

Dolomitization at the K/T boundary.

In these rocky reefs the transition from the Cabo de Lata Fm to the San Juan Fm, where the K/T boundary lies, is reflected in the geomorphology. The San Juan Fm, formed by laminated dolomites with hardgrounds, shrinkage cracks and sandy lenses, is more easily eroded. This gives a rugged profile to these rocks, which lie above well bedded tabular limestones also affected by dolomitization. At this zone, very scattered foraminifera are the only fossils present. Further upwards in the San Juan Fm, gasteropods and ostracodes are also found.

Selected References

Apellaniz E, Baceta JI, Bernaola-Bilbao G, et al. (1997) Analysis of uppermost Cretaceous lowermost Tertiary hemipelagic successions in the Basque Country (western Pyrenees): evidence for a sudden extinction of more than half planktic foraminifer species at the K/T boundary. Bulletin Societé Geologique de France, 168 (6): 783-793.

Arinobu, T., Ishiwatari, R., Kaiho, K. & Lamolda, M.A. (1999) Spike of pyrosynthetic polycyclic aromatic hydrocarbons associated with an abrupt decrease in delta C-13 of a terrestrial biomarker at the Cretaceous-Tertiary boundary at Caravaca, Spain. Geology, 27 (8): 723-726.

Arz, J.A., Arenillas, I., Molina, E. & Sepulveda, R. (2000) Planktonic foraminiferal stability in the Upper Maastrichtian and the catastrophic mass extinction at the Cretaceous-Tertiary (K/T) boundary at Caravaca (Spain). Revista Geológica de Chile 27 (1): 27-47.

Canudo, J.I., Keller, G. & Molina, E. (1991) Cretaceous Tertiary boundary extinction pattern and faunal turnover at Agost and Caravaca, SE Spain. Marine Micropaleontology, 17 (3-4): 319-341.

Díaz-Martínez, E., Sanz, E. & Martínez-Frías, J. (2002) “Sedimentary record of impact events in Spain” Geological Society of America Special Papers, 356: 551-563.

Heredia, N., Robador, A. Rodríguez, L.R., Locutura, J., Zapardiel, J.M., Gómez G., Calderón, V., Díaz, L.A. & Peralta, M. (1990). Memoria. Mapa Geológico-Minero. Escala 1:100.000. 133p, 29 figs, 2 maps. Cantabria. Instituto Tecnológico Geominero de España-Diputación Regional de Cantabria.

Huertas, M.O., Ruiz, F.M., Palomo, I. & Chamley, H. (1995). Comparative mineralogical and geochemical clay sedimentation in the Betic-cordilleras and Basque-Cantabrian basin areas at the Cretaceous-Tertiary boundary. Sedimentary Geology, 94 (3-4): 209-227.

Izett, G.A. (1987) Authigenic spherules in K-T boundary sediments at Caravaca, Spain, and Raton Basin, Colorado and New-Mexico, may not be impact derived. Geological Society of America Bulletin, 99 (1): 78-86.

Kaiho, K. & Lamolda, M.A. (1999) Catastrophic extinction of planktonic foraminifera at the Cretaceous-Tertiary boundary evidenced by stable isotopes and foraminiferal abundance at Caravaca, Spain. Geology, 27 (4): 355-358.

Macleod, K.G. (1994) Extinction of Inoceramid bivalves in Maastrichtian strata of the Bay of Biscay region of France and Spain. Journal of Paleontology, 68 (5): 1048-1066.

Marshall, C.R. & Ward PD (1996) Sudden and gradual molluscan extinctions in the latest Cretaceous of western European Tethys. Science, 274 (5291): 1360-1363.

Martinez-Ruiz, F., Ortega-Huertas, M. & Palomo, I. (1999) Positive Eu anomaly development during diagenesis of the K/T boundary ejecta layer in the Agost section (SE Spain): implications for trace-element remobilization. Terra Nova, 11 (6): 290-296.

Mount J.F. & Ward, P. (1986) Origin of limestone/marl alternations in the Upper Maastrichtian of Zumaya, Spain. Journal of Sedimentary Petrology, 56 (2): 228-236.

Nelson B.K., Macleod, G.K. & Ward P.D. (1991) Rapid change in strontium isotopic composition of sea-water before the Cretaceous Tertiary boundary. Nature, 351 (6328): 644-647

Ortega-Huertas, M., Martinez-Ruiz, F., Palomo, I. & Chamley, H. (2002) Review of the mineralogy of the Cretaceous-Tertiary boundary clay: Evidence supporting a major extraterrestrial catastrophic event. Clay Minerals, 37 (3): 395-411.

Ortega, M., Palomo, I., Martinez, F. & Gonzalez, I. (1998) Geological factors controlling clay mineral patterns across the Cretaceous-Tertiary boundary in Mediterranean and Atlantic sections. Clay Minerals 33 (3): 483-500.

Puig, G & Sanchez, R (1888) Datos para la geología de la Provincia de Santander. Boletín de la Comisión del Mapa geológico de España, XV, p.251 - 329.

Ruiz, F.M., Huertas, M.O., Palomo, I., et al. (1992) The geochemistry and mineralogy of the Cretaceous Tertiary boundary at Agost (Southeast Spain). Chemical Geology, 95 (3-4): 265-281.

Sanz Rubio, E., Díaz Martínez, E. y Martínez-Frías, J. (2000). Search criteria and evidence for impact-induced beds in the geological record of Spain. Geotemas, 1, 199-

Smit, J. (1999) The global stratigraphy of the Cretaceous-Tertiary boundary impact ejecta. Annual Review of Earth and Planetary Sciences, 27: 75-113.

Smith, A. B., J. Gallemi, et al. (1999). "Late Cretaceous-early Tertiary echinoids from northern Spain; implications for the Cretaceous-Tertiary extinction event." Bulletin of the Natural History Museum. Geology Series, 55(2): 81-137.

Ward P.D. (1995) After the fall: Lessons and directions from the K/T debate.
Palaios, 10 (6): 530-538

Ward, P. (1990) The Cretaceous/Tertiary boundary in the marine realm: a 1990 perspective, Geological Society of America Special Papers, 247: 425-431.

Ward, P. (1995) The K/T Trial. Paleobiology, 21 (3): 245-247

Ward. P., Wiedmann, J. & Mount J.F. (1986) Maastrichtian molluscan biostratigraphy and extinction patterns in a Cretaceous Tertiary boundary section exposed at Zumaya, Spain. Geology, 14 (11): 899-903.

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