Part of the Earth Sciences CommonsThis Article is brought to you for free and open access by the Earth and Atmospheric Sciences, Department of at DigitalCommons@University of Nebraska -Lincoln. It has been accepted for inclusion in Papers in the Earth and Atmospheric Sciences by an authorized administrator of DigitalCommons@University of Nebraska -Lincoln. AbstractSequence stratigraphy emphasizes facies relationships and stratal architecture within a chronological framework. Despite its wide use, sequence stratigraphy has yet to be included in any stratigraphic code or guide. This lack of standardization reflects the existence of competing approaches (or models) and confusing or even conflicting terminology. Standardization of sequence stratigraphy requires the definition of the fundamental model-independent concepts, units, bounding surfaces and workflow that outline the foundation of the method. A standardized scheme needs to be sufficiently broad to encompass all possible choices of approach, rather than being limited to a single approach or model.A sequence stratigraphic framework includes genetic units that result from the interplay of accommodation and sedimentation (i.e., forced regressive, lowstand and highstand normal regressive, and transgressive), which are bounded by "sequence stratigraphic" surfaces. Each genetic unit is defined by specific stratal stacking patterns and bounding surfaces, and consists of a tract of correlatable depositional systems (i.e., a "systems tract"). The mappability of systems tracts and sequence stratigraphic surfaces depends on depositional setting and the types of data available for analysis. It is this high degree of variability in the precise expression of sequence stratigraphic units and bounding surfaces that requires the adoption of a methodology that is sufficiently flexible that it can accommodate the range of likely expressions. The integration of outcrop, core, well-log and seismic data affords the optimal approach to the application of sequence stratigraphy. Missing insights from one set of data or another may limit the "resolution" of the sequence stratigraphic interpretation. 1 2 c a t u n e a n u e t a l . i n e a r t h -science r e v i e w s 92 (2009)

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The Sistan region in southeast Iran is considered as one of the most active dust source regions in South west Asia. The strong "Levar" winds in summer favor the uplift of large quantities of dust from the Hamoun basin, which is located in the northern part of Sistan. After a dry period at the end of the 1999s, and due to land-use change and desiccation of the Hamoun lakes, the frequency and severity of dust storms have been significantly increased. Within this framework, this study analyses the aerosol characteristics, dust loading and air quality over the Sistan region. The dust loading was measured using dust traps up to four and eight meters height (with a one meter distance between the traps) at two locations near the Hamoun basin during the period August 2009 to July 2010. The results show large quantities of transported dust that strongly dependent on the duration of the dust events, and secondarily, on the wind 2 speed and distance from the source region. The grain size distribution of the dusts reveals that the coarser calibers are found at the station nearer to Hamoun, while the large differences in the grain-size distribution found between the two stations indicate significant spatio-temporal variation in dust characteristics. Furthermore, to assess the air quality, Particulate Matter (PM 10 ) concentrations were measured over Zabol city during September 2010 to July 2011, and the Air Quality Index (AQI) was obtained. Daily PM 10 levels during intense dust storms rise up to 2000 gm -3 , even reaching to 3094 gm -3 , while the monthly mean PM 10 variationshows extreme values (>500 gm -3 ) for the period June to October. Analysis of the AQI shows that 61% of the days are associated with a high health risk, while 30.1% are even identified as hazardous.