On the road from Agost to Castalla, just above the north exit of Agost town, near km post 13, the K/T boundary crops out. The K/T boundary is marked by a 6.5 cm thick grey clay layer, underlain by a 2-3 mm thick ejecta layer (see below) (full size)

The K/T boundary layer, outcropping along the road Agost-Castalla, Province of Alicante, SE Spain.[Map] near km13, opposite the cemetery of Agost

The K/T Boundary clay layer actually consists of 2 layers: the lower layer (index finger) is the 2-3 mm thick ejecta layer (see details below) and an upper, 6.5 cm thick clay layer that represents the "Strangelove" ocean conditions following the Chicxulub impact event. The latter clay is of P0 or Guembelitria cretacea Zone, of basalmost Paleocene age. Note the homogeneous nature of the upper Maastrichtian.

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Blow-up of the K/T ejecta and boundary clay layers.
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scale in mm.

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K/T Boundary ejecta layer near Agost, Spain.

P0 Zone age boundary clay, laminated, dark, organic rich, extremely poor in planktic foraminifers. The transition from foraminifers rich (Maastrichtian) to foraminifer poor is marked by the ejecta layer. Above the ejecta layer no interval is visible that documents a gradual transition, the transition is extremely rapid

Ejecta layer, containing here 24.4 ng/g Ir. Numerous cross-sections of altered microkrystites, and a few droplets of altered tektites (brown) are visible

K/T boundary level, placed here -according to the official definition of the GSSP in Tunisia- at the base of the Ir-rich layer, above the mass-extinction level of Maastrichtian planktic foraminifers.

Uppermost Maastrichtian hemipelagic marls. The largest foraminifers are Globotruncanids (in circle). The distribution of the Foraminifers is random, and no decrease in abundance towards the ejecta layer can be observed.

relative abundance of planktic foraminifers in the Agost section.
Although the scale ranges from 10m below (=about 1 million years) to 10 m above (=about 2 million years) the K/T boundary, it is clear that the populations of Maastrichtian foraminifers remain stable below K/T, until the ejecta layer. The lack of progressive changes in the foraminiferal populations therefore indicates that these populations have no idea of their pending mass-extinction!
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Microkrystites in the Agost ejecta layer. White spherules are composed of k-spar, green spherules of smectite, and black ones contain numerous 1-20 micron sized Ni-rich spinels (magnesioferrite)

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K/T Boundary ejecta layer (red and green, details below) from Agost, Spain. The ejecta layer has the same thickness along the entire outcrop, a distance of >500m.

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move mouse over image to trace the K/T boundary in outcrop
(Enlarged images)