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13 - The Pliocene–Pleistocene transition in the Iberian Peninsula
- Edited by John A. Van Couvering, American Museum of Natural History, New York
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- Book:
- The Pleistocene Boundary and the Beginning of the Quaternary
- Published online:
- 10 November 2009
- Print publication:
- 28 December 1996, pp 169-177
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Summary
Introduction
The transition from the late Neogene to the Pleistocene in the Iberian Peninsula was characterized by widespread erosion on the Meseta and its margins because of structural deformation associated with subsidence over wide areas, both along the Mediterranean shorelands and in the intramontane basins along the Betic front. Marine deposition was rare and was restricted to littoral fringes. Volcanic activity in the southeast, and also in the southern Meseta, decreased after the end of the Miocene. The paleomagnetic record is extremely limited. However, there are significant sites in continental environments with both small and large vertebrates (Figure 13.1) that provide the material for interregional correlations.
Stratigraphic sequences
Bay of Cádiz
The Bay of Cádiz, in the area between the Guadalquivir depression and the western margin of the Subbetic realm, was first inundated during the late Miocene Tortonian transgression. The subsidence of the bay was related to the advance of the Subbetic olistostrome to the north-northwest, and its present configuration was influenced by a normal fault along an east-northeast axis.
Torre del Puerco section. This section (36°19′20″N; 2°29′45″W) begins with marls and marly limestones of the TP-1 (Torre Puerco Unit 1) containing Globorotalia margaritae, overlain by TP-2 marly sands and bioturbated offshore horizons with G. crassaformis. Near its top, G. margaritae, G. crassaformis, and Turborotalia puncticulata disappear, but Globigerinoides extremus and Turborotalia humerosa are still present. The TP-3 shallow conglomerates that close this cycle yield abundant rhodoliths of Lithotamniaeae, with Flabellipecten planomedius, Pseudoamussium calcatur, Pecten jacobaeus, and Ostrea lamellosa. The top of the series is continentally karstified, and it disconformably underlies a lower to early middle Pleistocene terrace with Olduwan-like pebble tools.
9 - Plio–Pleistocene mammal faunas: an overview
- Edited by John A. Van Couvering, American Museum of Natural History, New York
-
- Book:
- The Pleistocene Boundary and the Beginning of the Quaternary
- Published online:
- 10 November 2009
- Print publication:
- 28 December 1996, pp 114-128
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Summary
Introduction
The evidence from mammalian biostratigraphy with regard to the boundary between the Neogene and the Quaternary, or, more precisely, the base of the Pleistocene, can be analyzed in various ways. Long-established regional biostratigraphic scales are still widely used, although for the most part they are based on uneven, inadequate evidence and thus are subject to differing and unreliable interpretations. In seeking for greater reliability, vertebrate paleontologists in the past few decades have attempted to subdivide the geological time scale into probabilistic mammal ages and mammal zones, such as the MN (Mammal Neogene) zones of Mein. That approach is equally subject to imprecision and subjective bias (De Bruijn et al., 1992; Fahlbusch, 1991), and scholars may, consciously or unconsciously, constrain the paleofaunal changes to coincide with a particular magnetic reversal, a climate event, or any other significant, even preselected, level.
The objective approach is to begin with the ages of local faunal horizons that are directly based on radiometric dates or paleomagnetic analysis and build a biochronologic framework on this ground (e.g., Lindsay et al., 1987). Interpolations are legitimate, as are correlations based on faunal similarities, when the limits of probable error are realistically included. In cases where a local fauna presents many first appearances or last appearances, it is reasonable to suspect a lack of information in the preceding or following time interval, respectively. When the sampling factor is corrected, if unusual numbers of earliest and latest occurrences are still seen at one level, a genuine faunal overturn can be inferred.
10 - Human evolution in the Plio–Pleistocene interval
- Edited by John A. Van Couvering, American Museum of Natural History, New York
-
- Book:
- The Pleistocene Boundary and the Beginning of the Quaternary
- Published online:
- 10 November 2009
- Print publication:
- 28 December 1996, pp 129-138
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- Chapter
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Summary
Introduction
For many years, the main problem in relating the Pliocene–Pleistocene boundary to human evolution has been the controversy over “Tertiary man.” For some, this has had serious philosophical implications arising from the definition of the Quaternary period in anthropological terms. The development of modern stratigraphical standards, however, makes this a merely nominal question, because such boundaries are now based entirely on geological principles. At the same time, the terms “Tertiary” and “Quaternary,” having been drawn from primitive concepts of stratigraphy that once also distinguished a “Primary” and a “Secondary,” have been called into question. Nevertheless, the chronology of early humans is pertinent to the goal of this project, for other than merely historical reasons.
The search for fossil Hominidae in the past three decades has produced an immense amount of geological and paleontological evidence. In Africa, particularly, well-exposed and relatively thick Plio–Pleistocene sections yielding abundant remains of Hominidae and a wide diversity of other fossils have been very well characterized in terms of biochronology, and also with reference to magnetostratigraphy and isotopic dates. Similar data, if not so well developed, have been recovered from other areas as a direct result of paleoanthropological studies.
It is now clear that key events in human evolution occurred within the time interval that also encompassed the Pliocene–Pleistocene boundary (i.e., within the limits of the Matuyama paleomagnetic chron, from 2.6 to 0.8 Ma) (Figure 10.1). It was during that time that the genus Homo first appeared in Africa, giving rise to the key species Homo habilis Leakey, Tobias, and Napier, at about 1.8 Ma, almost exactly coincident with the beginning of the Pleistocene.
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